U.S. Fish & Wildlife Service 

Revised Recovery Plan 

for the Mojave Population 

of the Desert Tortoise 

(Gopherus agassizii) 

©Dennis Caldwell 
Revised Recovery Plan 


for the Mojave Population of the 


Desert Tortoise (Gopherus agassizii) 


Region 8, Pacific Southwest Region 


U.S. Fish and Wildlife Service 


Sacramento, California 


Approved: 

(

Date: ( gOI ( 
 

 

 

Preamble to the Desert Tortoise Recovery Plan Revision 

The publication of the Final Desert Tortoise Recovery Plan Revision (Plan) is an exciting 

accomplishment for the U.S. Fish and Wildlife Service (Service) and an important milestone in 

recovery planning for this species. It represents many years of strategic thinking, productive 

collaboration, and careful consideration of the concerns of stakeholders. During this time, the 

Service’s Desert Tortoise Recovery Office has provided sound guidance and leadership over 

efforts to revise the Plan through both internal and external dialogue. This included the 

incorporation of information and feedback from: 

•	 The Desert Tortoise Science Advisory Committee 

•	 Four planning workshops in California and Nevada in Winter and Spring 2007 

•	 Two open houses in California and Nevada in Fall 2007 

•	 Informal internal and stakeholder reviews of the draft plan revision in 2007 

•	 Formal public comments collected following the publication of the draft plan 

revision in 2008 

•	 Formal peer review comment in 2008 

•	 Internal review from the Service’s Southwest and Mountain-Prairie Regions in 

2010 

The result is a high-quality blueprint for the recovery of the Mojave population of the desert 

tortoise. The many individuals involved in this effort, both those providing input and those 

responding to input, deserve thanks and praise for a job well-done. 

Development of the plan has been a dynamic process that has evolved over time. And 

because land use change and desert tortoise recovery implementation will continue to evolve, the 

Final Plan is being published as a living document which will similarly evolve in the future. For 

example, when Plan revision began we did not anticipate the extent to which the landscape of 

desert ecosystems in the Pacific Southwest might become modified as a result of the nation’s 

renewable energy priorities (since 2009, an emphasis on renewable energy has resulted in a large 

increase in the number of proposed utility-scale projects within the range of the desert tortoise in 

California). This relatively new emphasis is the result of Presidential, Congressional, and 

Secretarial priorities. The President has placed a priority on investing in renewable energy in 

order to put America back in the lead of the global clean energy economy, create millions of jobs 

over time, and reduce our dependence on foreign fuel. The President’s New Energy for America 

Plan sets a target of ensuring that10 percent of electricity will be generated from renewable 

sources by 2012 and 25 percent of electricity will be generated from renewable sources by 2025. 

Section 211, of the Energy Policy Act of 2005 provides that the Secretary of the Interior should, 

within 10 years of enactment of the Act, "...seek to have approved non-hydropower renewable 

energy projects located on the public lands with a generation capacity of at least 10,000 

megawatts of electricity". On February 14, 2009, Congress passed the American Recovery and 

Reinvestment Act which included more than $80 billion to generate renewable energy while 

creating new, sustainable jobs. And on March 11, 2009, Secretary Salazar issued his first 

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Secretarial Order making the production, development, and delivery of renewable energy a top 

priority for the department. 

In the Plan, renewable energy development is discussed in a number of locations. 

Discussions under “Reasons for Listing and Continuing Threats, Factor A” and “Appendix A, 

Section A8” identify the threat of large-scale energy development and the potential impacts to 

desert tortoises and their habitat. Such impacts could be realized through habitat fragmentation, 

isolation of desert tortoise conservation areas, and the subsequent possibility of restricted gene 

flow between these areas. Implementation of a number of the recommended Recovery Actions, 

as articulated throughout the Plan, would make progress towards reducing threats associated with 

energy development: 

•	 Recovery Action 2.1, Conserve intact desert tortoise habitat - Recommends that 

solar project facilities be sited outside Desert Wildlife Management Areas and 

Areas of Critical Environmental Concern, as well as the development of a 

cumulative impacts assessment to identify mitigation measures for this type of 

activity. 

•	 Recovery Action 2.9, Secure lands/habitat for conservation - Recommends 

conserving sensitive areas that would connect functional habitat or improve 

management capability of surrounding areas, such as inholdings within tortoise 

conservation areas that may be open to renewable energy development. 

•	 Recovery Action 2.11, Connect functional habitat - Recommends connecting 

blocks of desert tortoise habitat, such as tortoise conservation areas, in order to 

maintain gene flow between populations. 

•	 Recovery Action 4.3, Track changes in the quantity and quality of desert tortoise 

habitat - Recommends quantifying the loss or restoration of habitat as it relates to 

potential energy and other projects. 

•	 Recovery Action 5.5, Determine the importance of corridors and physical barriers 

to desert tortoise distribution and gene flow - This action, in part, would 

determine the effects of corridors and barriers like energy development, on desert 

tortoise movement and recovery. 

Similarly, Strategic Element 1 in the Plan’s “Recovery Strategy” specifies that activities 

of implementation teams at the local level will be coordinated with landscape and regional-level 

alternative-energy coordination efforts. 

Still, the plan does not provide a single, comprehensive strategy for addressing renewable 

energy. To more comprehensively address this threat, the Service will soon add a renewable 

energy chapter to the living Plan that will act as a blueprint to allow the Service and our partners 

to comprehensively address renewable energy development and its relationship to desert tortoise 

recovery. This supplemental chapter will focus on renewable energy in a manner that could not 

have been envisioned when Plan revision began. The supplemental renewable energy chapter 

will make clear what recovery implementation will look like in light of renewable energy 

development and will provide specific recommendations to ensure recovery and continued 

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habitat connectivity in light of such development. Given that, strategies for recovery 

implementation may be modified in the future. The chapter will reconcile recovery efforts with: 

•	 Landscape level effects of renewable energy development on the desert tortoise. 

This includes identifying how such development may contribute to tortoise habitat 

loss and/or fragmentation. 

•	 The role that desert tortoise translocation may play in mitigating potential impacts 

to desert tortoises as a result of renewable energy development. 

•	 Other ongoing conservation strategies that have run parallel to Plan development 

(for example, the Desert Renewable Energy Conservation Plan, and the Bureau of 

Land Management’s Solar Programmatic Environmental Impact Statement) to 

ensure that desert tortoise recovery moves forward in a well-coordinated manner. 

In the U.S. Fish and Wildlife Service, Pacific Southwest Region, we are firmly 

committed to ensuring that responsible renewable energy development moves forward in a 

manner that concurrently addresses both the recovery concerns of desert tortoises and the 

broader conservation of desert ecosystems in the Pacific Southwest. 

Ren Lohoefener 

Regional Director 

Pacific Southwest Region 

U.S. Fish and Wildlife Service 

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Disclaimer 

Recovery plans delineate reasonable actions that are believed to be required to recover 

and protect listed species. We, the U.S. Fish and Wildlife Service, publish recovery plans, 

sometimes with the assistance of recovery teams, contractors, State agencies, Tribal agencies, 

and other affected and interested parties. Objectives will be attained and any necessary funds 

made available subject to budgetary and other constraints affecting the parties involved, as well 

as the need to address other priorities. Recovery plans do not obligate other parties to undertake 

specific actions and may not represent the views nor the official positions or approval of any 

individuals or agencies involved in recovery plan formulation, other than our own. They 

represent our official position only after they have been signed by the Regional Director or 

Director as approved. Recovery plans are reviewed by the public and submitted to peer review 

before we adopt them as approved final documents. Approved recovery plans are subject to 

modification as dictated by new findings, changes in species status, and the completion of 

recovery actions. 

LITERATURE CITATION OF THIS DOCUMENT SHOULD READ AS FOLLOWS: 

U.S. Fish and Wildlife Service. 2011. Revised recovery plan for the Mojave population of the 

desert tortoise (Gopherus agassizii). U.S. Fish and Wildlife Service, Pacific Southwest 

Region, Sacramento, California. 222 pp. 

Additional copies may be obtained from: 

State Supervisor 

Nevada Fish and Wildlife Office 

U.S. Fish and Wildlife Service 

1340 Financial Boulevard, Suite 234 

Reno, Nevada 89502 

On-line: http://www.fws.gov/endangered/recovery/index.html#plans 

Cover illustration of Desert Tortoise used by permission of Dennis Caldwell. 

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PLAN PREPARATION 

This Recovery Plan was prepared by the Desert Tortoise Recovery Office with advice 

from the Desert Tortoise Science Advisory Committee and assistance from the Redlands Institute 

at the University of Redlands. 

Desert Tortoise Recovery Office 

Roy C. Averill-Murray, Jody Fraser, Kimberleigh Field, Linda Allison, Catherine Darst, Sandy 

Marquez 

Science Advisory Committee 

Kristin Berry, U.S. Geological Survey; Peter Hudson, Penn State University; Earl McCoy, 

University of South Florida; Katherine Ralls, Smithsonian Institution; J. Michael Reed, Tufts 

University; Robert Steidl, University of Arizona; C. Richard Tracy, University of Nevada-Reno 

Redlands Institute 

Jordan Henk, Lisa Benvenuti, Paul Burgess, Monica Hally, Thomas Leuteritz, Naicong Li, Philip 

Murphy (Infoharvest), Serene Ong, Nathan Strout 

ACKNOWLEDGMENTS 

The U.S. Institute for Environmental Conflict Resolution, the Center for Collaborative 

Policy, and two Desert Tortoise Management Oversight Group recovery planning workgroups 

provided assistance and input into the development of the revised recovery plan. 

U.S. Institute for Environmental Conflict Resolution 

Mike Eng, Joan Calcagno, Pat Lewis 

Center for Collaborative Policy, California State University-Sacramento 

Austin McInerny, Greg Bourne, Dale Schafer 

Arizona-Nevada-Utah Working Group 

Arizona Game and Fish Department: Cristina Jones 

Bureau of Land Management: Bob Douglas, Elroy Masters, Richard Spotts 

Clark County: Marci Henson, Sue Wainscott 

Lake Mead National Recreation Area: Ross Haley 

Mohave County: Buster Johnson 

Nevada Department of Wildlife: Polly Conrad, Cris Tomlinson 

Quadstate County Government Coalition: Bill Lamb 

University of Arizona: Rob Grumbles 

University of Nevada-Reno: Maria Ryan 

Southern Utah University: Nicole Frey 

U.S. Fish and Wildlife Service: Michael Burroughs, Renee Chi, Jeff Servoss 

U.S. Geological Survey: Phil Medica 

Utah Division of Wildlife Resources: Ann McLuckie 

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Washington County: Bill Mader 

California Working Group 

Bureau of Land Management: Mark Massar, Russell Scofield 

California Department of Fish and Game: Rebecca Jones 

Joshua Tree National Park: Paul DePrey 

Mojave Desert Ecosystem Program: Clarence Everly 

Mojave National Preserve: Larry Whalon 

Quadstate County Government Coalition: Gerry Hillier 

University of California-Davis: Karl MacArthur 

U.S. Fish and Wildlife Service: Brian Croft 

U.S. Geological Survey: Kristin Berry 

U.S. Marine Corps: Brian Henen, Manual Joia 

The following individuals contributed materially to one or more Science Advisory 

Committee meetings: M. Brown, University of Florida; T. Esque, L. Gass, K. Nussear, and K. 

Phillips, U.S. Geological Survey; B. Hagerty, J. Heaton, K. Hunter, and F. Sandmeier, University 

of Nevada-Reno; and B. Murphy, Royal Ontario Museum. 

In addition to previously named individuals, the following people participated in recovery 

planning workshops or otherwise contributed to previous drafts of the revised Recovery Plan. 

We also thankfully acknowledge those who provided comments on the draft plan. 

Bureau of Indian Affairs: D. Wooten 

Bureau of Land Management: S. Borchard, R. Clementsen, S. Florence, M. Herder, L. LaPré, E. 

Lorentzen, C. Ronning, A. Styles 

California Department of Fish and Game: S. Harris, S. Juarez, B. Kinney, T. Moore, D. Racine 

California Department of Transportation: A. Manee, S. Quinell 

California - Imperial, Kern, and San Bernardino counties: W. Leimgruber, D. Maben, J, 

McQuiston, B. Mitzelfelt, R. Scott 

Department of Defense: A. Bedlion, S. Collis, M. Hagan, T. Mull (Tybrin Corp.), D. Reinke, C. 

Rognan, B. Turner, R. Wood 

Kaibab Paiute Tribe: C. Bulletts, L. Skrzynski 

National Park Service: N. Darby, D. Hughson, A. Staley, M. Vamstad 

Nevada - Clark and Nye counties: L. Bice, M. Hamilton, P. Kiakopoulos, S. Kokos, M. Henson, 

T. Wheaton 

Smithsonian Institution: R. Fleischer, E. Latch, and the genetics discussion group 

Southern Nevada Water Authority: A. Bennett, C. Doyle 

U.S. Fish and Wildlife Service: R. Bransfield, D. Elam, M. Fris, P. Henson, J. Hohman, J. 

Krueger, J. McBride, L. Rabin, J. Rorabaugh, A. Salveter, S. Spangle, R. Williams 

Utah - Washington County: A. Gardner 

Private individuals and non-governmental organizations: I. Anderson, L. Belenky, M. Brower, 

M. Connor, C. Doyle, T. Egan, T. Frewin, B. Haley, B. Hughes, P. Kahn, J. McDonnell, 

M. McDonnell, J. McGarvie, J. Moore, C. Oathout, K. Ostler, J. Pantuso, E. Phillips, L. 

Rivera, D. Schaffy, M. Skuja, C. Sprofera, Y. Takagi, C. Vargas, C. Wilkerson 

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EXECUTIVE SUMMARY
 

CURRENT SPECIES STATUS
 

The Mojave population of the desert tortoise (Gopherus agassizii) (all tortoises north and 

west of the Colorado River in Arizona, Utah, Nevada, and California) was listed as Threatened 

on April 2, 1990. A recovery plan was published in June 1994 together with a supplement 

identifying proposed Desert Wildlife Management Areas. Critical habitat was also designated in 

1994 in all four states supporting the species. Based on information in this recovery plan, the 

recovery priority number is classified as 12C and is predicated upon a) a moderate degree of 

threat, which, although increased since 1994, does not place the species at imminent risk of 

extinction; b) a low potential for recovery, adjusted based on current uncertainties about various 

threats and our ability to manage them; c) listed population below the species level; and d) 

potential conflict with development or other forms of economic activity. We anticipate that 

implementation of this revised recovery plan will resolve key uncertainties about threats and 

management, thereby improving recovery potential. 

HABITAT REQUIREMENTS AND LIMITING FACTORS 

Desert tortoises occupy a variety of habitats from flats and slopes dominated by creosote 

bush scrub at lower elevations to rocky slopes in blackbrush and juniper woodland ecotones at 

higher elevations. Desert tortoises occur from below sea level to an elevation of 2,225 meters 

(7,300 feet). Throughout most of the Mojave Desert, tortoises occur most commonly on gently 

sloping terrain with sandy-gravel soils and where there is sparse cover of low-growing shrubs, 

which allows establishment of herbaceous plants. Soils must be friable enough for digging of 

burrows, but firm enough so that burrows do not collapse. Typical habitat for the desert tortoise 

in the Mojave Desert has been characterized as creosote bush scrub below 1,677 meters (5,500 

feet), where precipitation ranges from 5 to 20 centimeters (2 to 8 inches), the diversity of 

perennial plants is relatively high, and production of ephemerals is high. 

The vast majority of threats to the desert tortoise or its habitat are associated with human 

land uses. The threats identified in the 1994 Recovery Plan formed the basis for listing the 

tortoise as a threatened species and continue to affect the species today. However, despite clear 

demonstration that these threats impact individual tortoises, there are few data available to 

evaluate or quantify the effects of threats on desert tortoise populations. While current research 

results can lead to predictions about how local tortoise abundance should be affected by the 

presence of threats, quantitative estimates of the magnitude of these threats, or of their relative 

importance, have not yet been developed. Thus, a particular threat or subset of threats with 

discernable solutions that could be targeted to the exclusion of other threats has not been 

identified for the desert tortoise. In this revised recovery plan, we underscore the need to build on 

our understanding of individual threats, yet place new emphasis on understanding their multiple 

and synergistic effects due to the failure of simple threat models to inform us about tortoise 

abundance. 

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The desert tortoise requires 13 to 20 years to reach sexual maturity, has low reproductive 

rates during a long period of reproductive potential, and individuals experience relatively high 

mortality early in life. These factors make recovery of the species difficult. Even moderate 

downward fluctuations in adult survival rates can result in rapid population declines. Thus, 

high survivorship of adult desert tortoises is critical to the species’ persistence, and the slow 

growth rate of populations can leave them susceptible to extirpation events in areas where 

adult survivorship has been reduced. Another factor integral to desert tortoise recovery is 

maintaining the genetic variability of the species and sufficient ecological heterogeneity within 

and among populations to allow tortoises to adapt to changes in the environment over time. 

Because desert tortoises occupy large home ranges, the long-term persistence of extensive, 

unfragmented habitats is essential for the survival of the species. The loss or degradation of 

these habitats to urbanization, habitat conversion from frequent wildfire, or other landscapemodifying activities place the desert tortoise at increased risk of extirpation. 

RECOVERY STRATEGY 

The 1994 Recovery Plan described a strategy for recovering the desert tortoise, which 

included the identification of six recovery units, recommendations for a system of Desert 

Wildlife Management Areas within the recovery units, and development and implementation of 

specific recovery actions. Maintaining high survivorship of adult desert tortoises was identified 

as the key factor in recovery, and because the list of threats to the species remains mostly 

unchanged, the requisite management or recovery actions also remain appropriate. The most 

significant challenge in implementing the 1994 Recovery Plan was not the number or types of 

actions implemented, but rather the coordination, description, documentation, and evaluation of 

implementation of the actions. As a result, the revised strategy builds upon the foundation laid 

by the 1994 Recovery Plan by emphasizing partnerships to direct and maintain focus on 

implementing recovery actions and a system to track implementation and effectiveness of 

recovery actions. Strategic elements within a multi-faceted approach designed to improve the 

1994 Recovery Plan are: 

1.	 Develop, support, and build partnerships to facilitate recovery. 

2.	 Protect existing populations and habitat, instituting habitat restoration where necessary. 

3.	 Augment depleted populations in a strategic manner. 

4.	 Monitor progress toward recovery. 

5.	 Conduct applied research and modeling in support of recovery efforts within a strategic 

framework. 

6.	 Implement a formal adaptive management program. 

The Desert Tortoise Management Oversight Group will be the partnership (Element 1) 

responsible for providing “executive-level” support and direction for recovery implementation, 

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thus tying the entire program together. Regional Recovery Implementation Teams will include a 

member of the Desert Tortoise Recovery Office to provide guidance and coordination to 

land/wildlife managers and stakeholders on the teams, which will be responsible for developing 

step-down recovery-action plans and implementing those actions on the ground. The adaptive 

management program (Element 6) provides a formal framework through which the partnerships 

can make better, more informed, and more explicit or structured decisions. Through the 

partnership and adaptive management elements, habitat management (Element 2) and population 

augmentation (Element 3) actions will be prioritized, implemented, and reported. Aggressive 

management needs to be applied within existing tortoise conservation areas, as defined herein, or 

other important areas identified by Recovery Implementation Teams. Monitoring (Element 4) 

effects of these specific actions, as well as progress toward overall recovery, will again feed into 

the adaptive management system and inform managers on recovery progress. Finally, applied 

research and modeling (Element 5) will help us better understand desert tortoise ecology and 

refine our goals and expectations of management actions. 

RECOVERY GOALS, OBJECTIVES, AND CRITERIA 

The goals of the recovery plan are recovery and delisting of the desert tortoise. The 

recovery criteria represent our best assessment of the conditions that would most likely result in 

a determination that delisting of the desert tortoise is warranted. Recovery criteria should ideally 

include the management or elimination of threats, addressing the five statutory (de-)listing 

factors. However, even though a wide range of threats affect desert tortoises and their habitat, 

very little is known about their demographic impacts on tortoise populations or the relative 

contributions each threat makes to tortoise mortality. Therefore, specific and meaningful threatsbased recovery criteria cannot be identified at this time. In the meantime, we assume that threat 

mitigation will have been successful if the current recovery criteria have been met (taking into 

consideration any head-starting or translocation efforts). Specific recovery actions, including 

research, must be implemented to identify sets of threats that contribute to a greater number of 

mortality mechanisms or affect size structure or fecundity. As quantitative information on threats 

and tortoise mortality is obtained, more specific threats-based recovery criteria may be defined 

during future recovery plan review and revision. 

Recovery Objective 1 (Demography). Maintain self-sustaining populations of desert tortoises 

within each recovery unit into the future. 

Recovery Criterion 1. Rates of population change (λ) for desert tortoises are increasing 

(i.e., λ > 1) over at least 25 years (a single tortoise generation), as measured 

a) by extensive, range-wide monitoring across tortoise conservation areas within each 

recovery unit, and 

b) by direct monitoring and estimation of vital rates (recruitment, survival) from 

demographic study areas within each recovery unit. 

Recovery Objective 2 (Distribution). Maintain well-distributed populations of desert tortoises 

throughout each recovery unit. 

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Recovery Criterion 2. Distribution of desert tortoises throughout each tortoise 

conservation area is increasing over at least 25 years (i.e., ψ [occupancy] > 0). 

Recovery Objective 3 (Habitat). Ensure that habitat within each recovery unit is protected and 

managed to support long-term viability of desert tortoise populations. 

Recovery Criterion 3. The quantity of desert tortoise habitat within each desert tortoise 

conservation area is maintained with no net loss until tortoise population viability is 

ensured. When parameters relating habitat quality to tortoise populations are defined and 

a mechanism to track these parameters established, the condition of desert tortoise habitat 

should also be demonstrably improving. 

RECOVERY ACTIONS 

The recovery actions for each strategic element are as follows: 

1. Develop, Support, and Build Partnerships to Facilitate Recovery 

1.1.	 Establish regional, inter-organizational Recovery Implementation Teams to prioritize 

and coordinate implementation of recovery actions. 

2. Protect Existing Populations and Habitat 

2.1.	 Conserve intact desert tortoise habitat. 

2.2.	 Minimize factors contributing to disease (particularly upper respiratory tract disease). 

2.3.	 Establish/continue environmental education programs. 

2.4.	 Increase law enforcement. 

2.5.	 Restrict, designate, close, and fence roads. 

2.6.	 Restore desert tortoise habitat. 

2.7.	 Install and maintain urban or other barriers. 

2.8.	 Sign and fence boundaries of sensitive or impacted areas. 

2.9.	 Secure lands/habitat for conservation. 

2.10.	 Restrict off-highway vehicle events within desert tortoise habitat. 

2.11.	 Connect functional habitat. 

2.12.	 Limit mining and minimize its effects. 

2.13.	 Limit landfills and their effects. 

2.14.	 Minimize excessive predation on tortoises. 

2.15.	 Minimize impacts to tortoises from horses and burros. 

2.16.	 Minimize impacts to tortoises from livestock grazing. 

3. Augment Depleted Populations through a Strategic Program 

3.1.	 Develop protocols and guidelines for the population augmentation program, including 

those specific to head-starting and translocation. 

3.2.	 Identify sites at which to implement population augmentation efforts. 

3.3.	 Secure facilities and obtain tortoises for use in augmentation efforts. 

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3.4.	 Implement translocations in target areas to augment populations using a scientifically 

rigorous, research-based approach. 

4.	 Monitor Progress toward Recovery 

4.1.	 Monitor desert tortoise population growth. 

4.2.	 Monitor the extent of tortoise distribution in each recovery unit. 

4.3.	 Track changes in the quantity and quality of desert tortoise habitat. 

4.4.	 Quantify the presence and intensity of threats to the desert tortoise across the 

landscape.
 

5.	 Conduct applied research and modeling in support of recovery efforts within a strategic 

framework 

5.1.	 Determine factors that influence the distribution of desert tortoises. 

5.2.	 Conduct research on the restoration of desert tortoise habitat. 

5.3.	 Improve models of threats, threat mitigation, and desert tortoise demographics. 

5.4.	 Conduct research on desert tortoise diseases and their effects on tortoise populations. 

5.5.	 Determine the importance of corridors and physical barriers to desert tortoise
 

distribution and gene flow.
 

6.	 Implement an Adaptive Management Program 

6.1.	 Revise and continue development of a recovery decision support system. 

6.2.	 Develop/revise recovery action plans. 

6.3.	 Amend land use plans, habitat management plans, and other plans as needed to 

implement recovery actions. 

6.4.	 Incorporate scientific advice for recovery through the Science Advisory Committee. 

TOTAL ESTIMATED COST OF RECOVERY 

$159,000,000 plus additional costs that cannot be estimated at this time. 

DATE OF RECOVERY 

If recovery actions are implemented promptly and are effective, including continued 

implementation of the current monitoring program which began in 2001, recovery criteria could 

be met by approximately 2025. 

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TABLE OF CONTENTS
 

PLAN PREPARATION ............................................................................................................... v
 

ACKNOWLEDGMENTS ............................................................................................................ v
 

EXECUTIVE SUMMARY ........................................................................................................ vii
 

BACKGROUND ........................................................................................................................... 1
 

INTRODUCTION .......................................................................................................................... 1
 

The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or
 

Overutilization for Commercial, Recreational, Scientific, or Educational Purposes
 

SPECIES DESCRIPTION AND TAXONOMY .....................................................................................4
 

POPULATION TRENDS AND DISTRIBUTION ..................................................................................5
 

LIFE HISTORY AND ECOLOGY ...................................................................................................10
 

HABITAT CHARACTERISTICS.....................................................................................................11
 

CRITICAL HABITAT ...................................................................................................................13
 

REASONS FOR LISTING AND CONTINUING THREATS..................................................................14
 

Range (Factor A)..........................................................................................................15
 

(Factor B).....................................................................................................................16
 

Disease or Predation (Factor C).........................................................................................16
 

Inadequacy of Existing Regulatory Mechanisms (Factor D).............................................18
 

Other Natural or Manmade Factors Affecting its Continued Existence (Factor E)...........18
 

CONSERVATION EFFORTS ........................................................................................................ 19
 

BIOLOGICAL CONSTRAINTS AND NEEDS .................................................................................. 31
 

RECOVERY PROGRAM.......................................................................................................... 33
 

RECOVERY STRATEGY ............................................................................................................. 33
 

RECOVERY UNITS .................................................................................................................... 41
 

RECOVERY GOAL, OBJECTIVES, AND CRITERIA ....................................................................... 58
 

RECOVERY ACTIONS................................................................................................................ 65
 

IMPLEMENTATION SCHEDULE ......................................................................................... 97
 

LITERATURE CITED ............................................................................................................ 103
 

LIST OF FIGURES 

Figure 1. Desert tortoise critical habitat overlaid on the U.S. Geological Survey habitat model 12
 

Figure 2. Desert tortoise conservation areas ................................................................................ 23
 

Figure 3. Additional land designations providing conservation benefits to the desert tortoise... 24
 

Figure 4. Diagram of the adaptive management process..............................................................40
 

Figure 5. Recovery units as delineated in the 1994 Recovery Plan............................................. 42
 

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Figure 6. Ratio of rainfall in winter compared to summer in the Mojave Desert........................ 43
 

Figure 7. Revised recovery units for the Mojave population of the desert tortoise..................... 46
 

Figure 8. Upper Virgin River Recovery Unit .............................................................................. 47
 

Figure 9. Northeastern Mojave Recovery Unit............................................................................ 49
 

Figure 10. Eastern Mojave Recovery Unit .................................................................................. 50
 

Figure 11. Colorado Desert Recovery Unit ................................................................................. 52
 

Figure 12. Western Mojave Recovery Unit ................................................................................. 55
 

LIST OF TABLES 

Table 1. Summary of density estimates for each of the 1994-designated recovery units............... 9
 

Table 2. Critical habitat by state and land management in hectares............................................. 13
 

Table 3. Climatic summary for weather stations within desert tortoise recovery units................ 56
 

Table 4. Comparison of recovery actions between the 1994 and 2010 recovery plans................ 89
 

Table 5. Reference table connecting major recovery actions to listing factors and recovery
 

objectives ...................................................................................................................................... 94
 

LIST OF GLOSSARY BOXES 

Box 1. Glossary of terminology relating to desert tortoise habitat...............................................14 

Box 2. Tortoise conservation areas...............................................................................................34 

Box 3. Recovery units ..................................................................................................................41 

Box 4. Definitions according to section 3 of the Endangered Species Act ..................................58 

Box 5. Terms related to monitoring habitat..................................................................................63 

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LIST OF APPENDICES
 

Appendix A. Threats to the Mojave Population of the Desert Tortoise and its Habitat since the 

Time of Listing ............................................................................................................................125
 

Appendix B. A Decision Support System for Desert Tortoise Recovery: A Tool for Evaluating
 

Recovery Action Effectiveness....................................................................................................175
 

Appendix C. Recommended Specifications for Desert Tortoise Exclusion Fencing .................183
 

Appendix D. Comments Received on the Draft Plan .................................................................189
 

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I. BACKGROUND 

A. INTRODUCTION 

1. Listing History 

We, the United States Fish and Wildlife Service, listed the desert tortoise (Gopherus 

agassizii) on the Beaver Dam Slope in Utah as Threatened under the Endangered Species Act of 

1973, as amended, and designated critical habitat in 1980 (U.S. Fish and Wildlife Service 

[USFWS] 1980). In 1984, we were petitioned by the Defenders of Wildlife, Natural Resources 

Defense Council, and Environmental Defense Fund to list the species as Endangered. The 

following year, we determined that listing the desert tortoise as Endangered was warranted, but 

higher priorities precluded any action. 

On August 4, 1989, new information on mortality resulted in the emergency listing of 

desert tortoises north and west of the Colorado River (excluding the Beaver Dam Slope) as 

Endangered (USFWS 1989). On April 2, 1990, we listed the entire Mojave population (all 

tortoises north and west of the Colorado River in Arizona, Utah, Nevada, and California) as 

Threatened (USFWS 1990), and a recovery plan was published in June 1994 (USFWS 1994a). 

Previously, the species had a recovery priority number of 8C, which, according to the Recovery 

Priority Criteria, is based on a) moderate degree of threat, b) high potential for recovery, c) 

taxonomic classification as a species, and d) potential conflict with development or other forms 

of economic activity (USFWS 1983). Based on updated information, the recovery priority 

number has been reclassified as 12C and is predicated upon a) a moderate degree of threat, 

which, although increased since 1994, does not place the species at imminent risk of extinction; 

b) a low potential for recovery, adjusted based on current uncertainties about various threats and 

our ability to manage them; c) listed population below the species level; and d) potential conflict 

with development or other forms of economic activity (USFWS 1983). With regard to the “low 

potential for recovery” as defined in the Recovery Priority Criteria, we anticipate that 

implementation of this revised recovery plan will resolve key uncertainties about threats and 

management, thereby improving recovery potential. 

The 1994 Recovery Plan described a strategy for recovering the Mojave population of the 

desert tortoise, which included the identification of six recovery units, recommendations for a 

system of Desert Wildlife Management Areas (DWMAs) within the recovery units, and 

development and implementation of specific recovery actions, especially within DWMAs. 

Establishment of recovery units and DWMAs was intended, in part, to facilitate an ecosystem 

approach to land management and desert tortoise recovery, as stipulated by section 2(b) of the 

Endangered Species Act (USFWS 1994a). 

2. Management 

The Desert Tortoise Management Oversight Group was established in 1988 to coordinate 

agency planning and management activities affecting the desert tortoise and to implement the 

management actions in the Bureau of Land Management’s Desert Tortoise Range-wide Plan 

1
 
 

 

 

 

(Spang et al. 1988). Charter members of the Management Oversight Group included the four 

Bureau of Land Management State Directors from Arizona, California, Nevada, and Utah; the 

four State Fish and Game Directors from these States; the three Fish and Wildlife Service 

Regional Directors that share tortoise management responsibilities; and a Bureau of Land 

Management Washington Office representative. Membership was subsequently expanded to 

include representatives of the National Park Service, Biological Resources Division of the U.S. 

Geological Survey, and officials of the four branches of the military (Army, Air Force, Navy, 

and Marine Corps) that have Mojave tortoise habitat. County governments within the range of 

the desert tortoise were also included in 2007. 

The original charter of the Management Oversight Group called for it to a) standardize 

procedures for the analysis and interpretation of tortoise information, b) report on management 

actions completed for the benefit of the desert tortoise, c) recommend funding priorities, d) 

identify areas lacking sufficient information for habitat management, e) identify research needs 

to resolve management issues, f) identify threats and conflicts, g) complete annual status or 

progress reports, h) coordinate existing laws and guidance, and i) review ongoing research. 

Subsequent to the listing of the Mojave population as Threatened and following the publication 

of the 1994 Recovery Plan, the Management Oversight Group assumed a leadership role in 

coordinating agency activities directed toward recovery plan implementation. 

The California Desert Managers Group was organized to provide a forum for government 

agencies to work together to conserve and enhance the California deserts. The Desert Managers 

Group is comprised of State- and field-level managers from agencies and county governments 

with land and resource management or regulatory responsibilities in the California deserts. It also 

includes the U.S. Geological Survey, which serves in a scientific support role to the managers. 

The Group’s 5-year plan includes several topics related to desert tortoise management. 

Like the Desert Managers Group, the Southern Nevada Agency Partnership does not 

focus specifically on desert tortoise issues, but was formed as an interagency partnership to 

address various initiatives including litter clean-up, volunteerism, resource protection, recreation, 

science and research, outdoor recreation education, law enforcement, and other issues. This 

partnership is comprised of the Bureau of Land Management, National Park Service, U.S. Fish 

and Wildlife Service, and U.S. Forest Service. 

The Mojave Desert Initiative was formed among State and Federal agencies (Bureau of 

Land Management, National Park Service, U.S. Fish and Wildlife Service, Department of 

Defense, and the three State wildlife agencies) from Arizona, Nevada, and Utah in 2007 in 

response to the vast wildfires that occurred in the region in 2005 and 2006. The Mojave Desert 

Initiative is directly related to desert tortoise management because it collaboratively focuses on 

the fire and invasive species cycle and strategically restores portions of the damaged ecosystem. 

In Arizona, both the Mojave and Sonoran populations of desert tortoise are considered 

Species of Greatest Conservation Need under Arizona’s Comprehensive Wildlife Conservation 

Strategy: 2005-2015 (Arizona Game and Fish Department 2006). Desert tortoises are also 

protected under the Arizona Revised Statutes Title 17 laws and the Reptile and Amphibian 

2
 
 

 

 

 

 

Regulations, under which it has been unlawful to collect this species since 1989. In California, 

State laws have been in place since 1939 to protect the desert tortoise. The species was listed as 

Threatened under the California Endangered Species Act in 1989 and is considered a Species at 

Risk under California’s Wildlife Action Plan (Bunn et al. 2006). The California Department of 

Fish and Game manages over 19,670 hectares (48,000 acres) of land for the conservation of the 

desert tortoise, and additional lands continue to be acquired as mitigation for projects that result 

in impacts to the species. In Nevada, the desert tortoise is protected under the Nevada 

Administrative Code 503.080, wherein the species is listed as a State-protected reptile further 

classified as Threatened, and collection is prohibited under section 503.093. The desert tortoise is 

also considered a Species of Conservation Priority under the Nevada Wildlife Action Plan 

(Abele et al. 2006), which is being implemented by the Nevada Department of Wildlife. Desert 

tortoises are listed as State Endangered in Utah, where collection and importation are prohibited. 

Possession is controlled, meaning one must have a Certificate of Registration prior to possession 

of an individual animal. The species is protected under the Utah Division of Wildlife Resources 

Administrative Rule R657-53 and is considered a Species of Greatest Conservation Need under 

the Utah Comprehensive Wildlife Conservation Strategy: 2005-2015 (Gorrell et al. 2005). 

3. Recovery Plan Review and Revision 

The U.S. General Accounting Office report, Endangered Species: Research Strategy and 

Long-Term Monitoring Needed for the Mojave Desert Tortoise Recovery Program (General 

Accounting Office [GAO] 2002), found that the listing decision, critical habitat designation, and 

recommendations in the 1994 Recovery Plan were reasonable, given the available information. 

Unfortunately, the effectiveness of actions implemented by Federal agencies and others to 

benefit desert tortoises was not monitored adequately and remains largely unknown. Because 

much was unknown about the severity of specific threats to desert tortoises at the time the plan 

was written, the recommendations were made without establishing priorities that would reflect 

differences in the seriousness of the threats. The General Accounting Office report recommended 

that we develop and implement a coordinated research strategy for linking land management 

decisions with research results. Without such a strategy, recovery of the desert tortoise would be 

left to chance rather than to informed decisions based on science. In response, we initiated an indepth review of the 1994 Recovery Plan. 

In March 2003, we impaneled the Desert Tortoise Recovery Plan Assessment Committee 

to conduct a thorough review of the Recovery Plan in the context of scientific and analytical 

advances made since its publication in 1994. The assessment (Tracy et al. 2004) concluded that 

the 1994 Recovery Plan was fundamentally strong but could benefit substantially from 

modification. The assessment also identified strategies that would promote a more cohesive, 

scientifically powerful recovery program. Taking recommendations of the General Accounting 

Office report and 2004 assessment, we established the Desert Tortoise Recovery Office (DTRO) 

in 2004. The DTRO’s staff focuses solely on the desert tortoise and its recovery. The DTRO 

coordinates recovery planning and implementation, research, monitoring, and recovery 

permitting, while working closely with those Fish and Wildlife Service biologists working on 

regulatory issues. The DTRO assists in coordination among land managers, research scientists, 

the interagency Desert Tortoise Management Oversight Group, the California Desert Managers 

3
 
 

 

 

 

 

 

 

Group, and other local, state, or regional working groups. To complement the DTRO, we 

appointed a Desert Tortoise Science Advisory Committee in 2005. This committee was 

composed of seven scientists from diverse yet highly relevant backgrounds (see Plan 

Preparation) who are charged with providing recommendations relative to desert tortoise 

recovery implementation and approach, such that rigorous scientific standards are met. The 

scope of the Science Advisory Committee’s recommendations to date has included recovery 

criteria, threats assessment, effectiveness monitoring, and key research priorities. 

Based on recommendations in the recovery plan assessment, the Desert Tortoise 

Management Oversight Group recognized that the 1994 Recovery Plan should be revised with 

collaboration from scientists, managers, and stakeholders (Tracy et al. 2004), and an assessment 

of stakeholder input on recovery planning for the desert tortoise was conducted (U.S. Institute for 

Environmental Conflict Resolution and Center for Collaborative Policy 2006). To allow for 

broad participation, the Science Advisory Committee formed the base team for the scientific 

foundations, while government and non-government stakeholders were invited to participate and 

engage on management issues through various workshops, open houses, and review drafts of this 

plan. Thus, a collaborative effort resulted in this revised recovery plan for the Mojave population 

of the desert tortoise. 

B. SPECIES DESCRIPTION AND TAXONOMY 

The desert tortoise is a large, herbivorous (plant-eating) reptile that occurs in the Mojave 

and Sonoran deserts in southern California, southern Nevada, Arizona, and the southwestern tip 

of Utah in the U.S., as well as Sonora and northern Sinaloa in Mexico. The designated Mojave 

population of the desert tortoise includes those animals living north and west of the Colorado 

River in the Mojave Desert of California, Nevada, Arizona, and southwestern Utah, and in the 

Sonoran (Colorado) Desert in California (USFWS 1990; USFWS 1994a). 

The generic assignment of the desert tortoise has gone through a series of changes since 

its original description by Cooper (1863) as Xerobates agassizii. It has also been referred to in 

the literature as Scaptochelys agassizii. Currently, the accepted scientific name is Gopherus 

agassizii (Crumly 1994). Differentiation between the Mojave and Sonoran assemblages of the 

desert tortoise are supported via multiple forms of evidence, including morphology, ecology, and 

genetics (Weinstein and Berry 1987; Lamb et al. 1989; Lamb and Lydehard 1994; Berry et al. 

2002a; Van Devender 2002a,b; Murphy et al. 2007). Although fewer data are available to 

compare Sinaloan desert tortoises to the Sonoran and Mojave assemblages, the Sinaloan 

population is considerably more isolated, and differentiation in mitochondrial DNA is 

considerable (Lamb et al. 1989; Van Devender 2002b). 

Desert tortoises reach 20 to 38 centimeters (8 to 15 inches) in carapace (upper shell) 

length and 10 to 15 centimeters (4 to 6 inches) in shell height. Hatchlings emerge from eggs at 

about 5 centimeters (2 inches) in length. Adults have a domed carapace and relatively flat, 

unhinged plastrons (lower shell). Their shells are greenish-tan to dark brown in color with tan 

scute (horny plate on the shell) centers. Adult desert tortoises weigh 3.6 to 6.8 kilograms (8 to 15 

4
 
 

 

 

 

 

 

 

 

pounds). The forelimbs have heavy, claw-like scales and are flattened for digging. Hind limbs 

are more elephantine (Ernst and Lovich 2009). 

Two other tortoise species in the genus Gopherus occur in the United States, and another 

occurs in Mexico. The Texas tortoise (Gopherus berlandieri) occurs in southern Texas and 

northeastern Mexico, and the gopher tortoise (Gopherus polyphemus) occurs in southwestern 

South Carolina, Florida, Georgia, Alabama, Mississippi, Louisiana, and extreme southeastern 

Texas. The Mexican species is the Bolson tortoise (Gopherus flavomarginatus), which is found 

in a very small area in Chihuahua and Durango, Mexico. The desert tortoise is distinguished 

from the other three species by a combination of characters that are described in detail in the 

final listing rule and 1994 Recovery Plan (USFWS 1990; USFWS 1994a). For additional 

information regarding the morphological characteristics and distinguishing features of these 

species, refer to Ernst and Lovich (2009) and the references cited therein. 

Although there are significant differences genetically and ecologically, desert 

tortoises that belong to the Sonoran population could be confused visually with tortoises of 

the Mojave population. Because there are only minor visual differences between the animals 

in these populations, we determined at the time of listing that the Sonoran population also 

warranted protection as a threatened species under section 4(e) of the Endangered Species 

Act (similarity of appearance) when located outside of its natural range. This level of 

protection eliminates the need for law enforcement personnel to determine the origin of each 

individual when conducting enforcement activities under section 9 of the Endangered 

Species Act (USFWS 1990). 

C. POPULATION TRENDS AND DISTRIBUTION 

Before the 1970s, there was a limited amount of research directed at desert tortoise 

ecology, and there are correspondingly few sources of information about population sizes. Berry 

(1984a) used anecdotal accounts and interviews of long-time desert residents to portray the 

spatial distribution and relative numbers of tortoises in California during the period from 1920 to 

1960. Acknowledging that historical numbers of tortoises will remain speculative, her summary 

concluded that tortoise range had contracted in some areas and that densities had decreased in 

many areas of the California deserts. 

In the 1970s, the California desert region became the focus of more wide-spread efforts 

to describe distribution and numbers (GAO 2002; Tracy et al. 2004). The largest of these efforts 

was launched to aid Bureau of Land Management planning (Berry and Nicholson 1984a). These 

surveys were conducted using strip transects, which are also referred to in the literature as 

“triangular transects” because the total strip length is walked as an equilateral triangle. This 

became the most prevalent method for estimating tortoise numbers in local areas for the next few 

decades. 

Tortoises are rarely encountered for the large amount of effort expended, so these 

triangular transect surveys relied on counts of more prevalent accumulated tortoise sign 

(primarily burrows, scat [droppings], and shells). These sign counts were then adjusted to avoid 

5
 
 

 

 

 

 

 

 

 

overcounting evidence in those instances when more than one form of sign were found together 

(scat in a burrow, for instance). Adjusted sign counts are referred to as “total corrected sign” 

(TCS). In order to translate TCS into a number of tortoises present, the method relied on 

existence of 2.6-kilometer2 (1-mile2) plots on which the number of tortoises was estimated using 

mark-recapture techniques. Surveyors walked triangular transects in both the survey area and in 

one or more of these study plots with more closely estimated tortoise numbers. For each 

surveyor, a relationship was estimated between TCS and tortoise numbers on the study plots; this 

relationship was applied to all areas where the surveyor collected data. 

Data for the original Bureau of Land Management planning effort for the California 

Desert District came from over 1,000 such triangular transect surveys conducted between 1978 

and 1983 and were used to build a reference map based on five classes of estimated abundance 

(0-20, 21-50, 51-100, 101-250, > 250 tortoises/mile2 [tortoises/2.6 kilometer2]; Berry and 

Nicholson 1984a). The use of classes was in part an acknowledgment that the count estimates 

were very imprecise. To make efficient use of resources for the planning effort, most transects 

were placed in areas with vegetation and slope characteristics that were expected to support 

desert tortoises. Transects were spaced to cover larger areas fairly evenly, and were set away 

from dirt roads and even farther from paved roads. Study plots for estimating tortoise numbers 

more accurately were set up for the first time during this study, and a set of permanent (longterm) study plots were selected from these to be followed over the years. Whereas the original 

study plots were placed in areas expected to host tortoises (Berry and Nicholson 1984a), only 

plots in higher-density areas were considered for use as long-term study plots for surveys at 

various intervals from 1979 through the present, and work at low-density plots was discontinued 

(Berry 1984b; K. Berry, U.S. Geological Survey, pers. comm. 2003, as reported in Tracy et al. 

2004). 

A total of 31 long-term study plots were in place range-wide when the desert tortoise was 

first listed under the Endangered Species Act (Tracy et al. 2004). The first long-term plot using 

60-day mark-recapture estimation was established in 1976 and 1977 in California, but this 

technique was not implemented until later in Nevada and Utah (1981) and Arizona (1987). 

Because of the level of effort required, plots were resurveyed only every several years. While a 

substantial body of data has been collected from surveys of the original long-term study plots 

over the years, plot placement in non-representative (non-random) areas across the range is 

generally regarded as a factor limiting demographic and trend conclusions only to those specific 

areas. 

In the 1994 Recovery Plan, we recommended using sampling plots to estimate abundance 

of desert tortoises (USFWS 1994). These plots were to cover at least 5 percent of each DWMA 

and be surveyed within a 3-year timeframe, after which a new set of plots was to be randomly 

selected. Preliminary study and additional scientific input resulted in the determination that this 

method was unreliable at the range-wide level, and it was never fully implemented. Subsequent 

efforts to develop a more robust method were hampered by the lack of funding and a designated 

coordinator (GAO 2002). By the time the General Accounting Office (2002) and Tracy et al. 

(2004) assessments were published, there were 49 long-term study plots in existence, but both of 

6
 
 

 

 

 

 

 

these reports concluded that it was not appropriate to extrapolate data from these plots to serve as 

a range-wide population baseline from which to assess recovery. 

In the late 1990s, the Bureau of Land Management launched a second set of TCS surveys 

to update information from the original (Berry 1984c) description of tortoise distribution and 

abundance in California. This effort was part of preparations for its West Mojave Plan (Bureau 

of Land Management [BLM] et al. 2005) and was preceded by a set of analyses on the efficacy 

of TCS counts (BLM et al. 2005, Appendix K). The analyses concluded that although the 

predicted relationship between sign and tortoise counts was consistent, the correlation was 

relatively low and was only significant with large sample sizes. The low correlation meant that 

TCS was not reliably associated with tortoise numbers and was very likely to give an incorrect 

estimate of abundance class in a given survey. Further, the correlation between TCS and tortoise 

abundance was based primarily on burrow sign. Scat sign, which is much more common than 

burrows, was much less reliable at predicting tortoise counts, and shell counts were not 

correlated with live tortoise abundance. The analyses also noted that observers were similar in 

their reporting of burrow counts in any given study plot, whereas they usually differed in their 

counts of scat. For the above reasons, TCS data were used as an index of tortoise abundance, 

with relative sign counts assumed to reflect relative tortoise densities. For this planning effort, 

TCS were not used to estimate actual tortoise numbers. 

In addition to data from the long-term study plots, Tracy et al. (2004) considered 

evidence from TCS and line distance surveys (see below). Similar to the case of BLM et al. 

(2005), they did not use the TCS data to estimate abundance, but to describe presence/failure to 

detect. They used a single year of tortoise observations collected along 2,977 kilometers (1,850 

miles) of line distance transects in 2001 to assess the combined distribution of live and dead 

tortoises. Their preliminary spatial analyses revealed areas with higher probabilities of 

encountering both live and dead tortoises. In the western Mojave, Tracy et al. (2004) used 

logistic regression and kernel analyses (types of statistical analyses) to indicate areas with 

concentrations of dead tortoises without corresponding concentrations of live tortoises. These 

generally encompassed areas where declines had been reported in earlier studies, namely the 

northern portion of the Fremont-Kramer critical habitat unit and the northwestern part of the 

Superior-Cronese critical habitat unit. Using kernel analysis with limited data, Tracy et al. (2004) 

also described large areas where dead tortoises, but no live tortoises, were observed in the PiuteEldorado Valley and northern Coyote Springs Valley, Nevada, and in the western and southern 

portions of the Ivanpah Valley, California. All of these areas are within designated critical 

habitat. Although they were able to make qualitative conclusions (conclusions not expressed in 

terms of quantity) about population trends in individual recovery units, Tracy et al. (2004) also 

concluded that estimating accurate, historic long-term trends of desert tortoise populations, 

habitat, and/or threats across the range was not feasible based on the combined suite of existing 

data and analyses. 

Together, these data provide qualitative - not quantitative - insight into the range-wide 

status of the species and show appreciable declines at the local level in many areas (Berry 1984a, 

Luke et al. 1991; Berry 2003; Tracy et al. 2004). Tracy et al. (2004) concluded that the apparent 

downward trend in desert tortoise populations in the western portion of the range that was 

7
 
 

 

 

 

identified at the time of listing was valid and ongoing. Results from other portions of the range 

were inconclusive, but surveys of some populations found too few tortoises to produce 

population estimates (e.g., 2000 survey of the Beaver Dam Slope, Arizona), suggesting that 

declines may have occurred more broadly. 

Based on the 25-year horizon of the recovery criteria in the 1994 Recovery Plan (USFWS 

1994a), a long-term monitoring program for the desert tortoise was implemented in 2001 (1999 

in the Upper Virgin River Recovery Unit; McLuckie et al. 2002). This program was the first 

comprehensive effort undertaken to estimate densities across the range of the listed population 

(Table 1; USFWS 2006; USFWS 2009a) and continues today. The monitoring strategy uses 

annual range-wide surveys on line distance transects, with effort levels designed to detect longterm population trends. Long-term trends are expected to be relatively gradual; therefore, 

increasing trends over shorter time periods (e.g., 2001 to 2005) would not be detectable. Over 

short periods of time, only catastrophic declines or remarkable population increases would be 

noticeable. Therefore, the first five years of the long-term monitoring project provided 

information on initial densities and annual and regional (between recovery unit) variability, but 

did not describe any meaningful population trends (USFWS 2006). 

Density estimates of adult tortoises varied among recovery units and years. Over the first 

six years of range-wide monitoring (2001-2005, 2007), tortoises were least abundant in the 

Northeast Mojave Recovery Unit (1 to 3.7 tortoises per kilometer2

 [2 to 10 tortoises per mile2]; 

USFWS 2009a), and the highest reported densities occurred in the Upper Virgin River Recovery 

Unit (15 to 27 tortoises per kilometer2 [38 to 69 tortoises per mile2]; McLuckie et al. 2007). 

Considerable decreases in density were reported in 2003 in the Eastern Colorado and Western 

Mojave recovery units (USFWS 2006). However, the variability between annual estimates 

among all years (Table 1) is consistent with variability due to sampling between years; only after 

several years of consistent patterns will the range-wide approach distinguish population trends 

from the variability due to sampling. Beyond noting that no range-wide population losses or 

gains were detected, inferences as to the meaning of these first years of data would be premature. 

Please refer to The Status of the Desert Tortoise (Gopherus agassizii) in the United States 

(Berry 1984c) and the Desert Tortoise Recovery Plan Assessment (Tracy et al. 2004) for a 

detailed description of the methods and population trend and distribution analyses described 

above. In addition, Range-wide Monitoring of the Mojave Population of the Desert Tortoise: 

2007 Annual Report (USFWS 2009a) provides information regarding the current monitoring 

effort. 

8
 
 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Table 1. Summary of density estimates for each of the 1994-designated recovery units. “Adult tortoises” 

is the number of adults and subadults (midline carapace length ≥180mm). See USFWS (2006a, 2009a) for 

additional details. 

Recovery Unit Year No. of 

Transects 

Length 

(km) 

Adult 

Tortoises 

Density 

(km2

) 

Coefficient 

of Variation 

(%) 

95% Confidence 

Interval 

Low High 

Northeast Mojave 

2001 136 254.8 9 2.4 34.8 1.2 4.6 

2002 75 293.2 3 -­1 

2003 189 699.2 39 3.71 43.1 1.5 8.3 

2004 96 947.3 18 1.21 30.1 0.7 2.2 

2005 166 1754.4 40 1.8 25.8 1.1 3.0 

2007 240 2316.1 46 1.7 25.0 1.0 2.7 

Eastern Mojave 

2001 224 371.6 17 6.2 46.6 2.6 14.9 

2002 284 1120.4 56 4.1 22.1 2.6 6.2 

2003 59 215.1 11 -­1 

2004 140 1511.2 113 5.3 20.0 3.6 7.7 

2005 165 1839.5 108 7.2 20.1 4.9 10.7 

2007 76 803.9 40 5.8 25.0 3.6 9.3 

Eastern Colorado 

2001 205 328.0 54 10.1 18.3 7.0 14.4 

2002 104 416.7 42 7.7 28.8 4.4 13.4 

2003 108 431.7 32 4.0 22.7 2.6 6.3 

2004 132 1414.0 102 6.4 28.9 3.7 11.2 

2005 91 1094.3 74 7.9 26.7 4.7 13.2 

2007 100 1151.7 59 5.0 22.6 3.2 7.7 

Northern Colorado 

2001 201 321.6 39 7.2 22.6 4.6 11.2 

2002 -­1 

2003 112 445.2 54 6.3 20.6 4.2 9.3 

2004 76 835.9 79 6.9 22.8 4.5 10.8 

2005 94 1128.8 94 10.8 29.9 6.1 19.1 

2007 15 180.0 7 4.6 43.4 2.0 10.3 

Western Mojave 

2001 865 1384.0 160 5.6 13.8 4.3 7.4 

2002 547 2176.8 188 5.8 24.2 3.7 9.3 

2003 522 2083.2 218 3.8 10.6 3.0 4.6 

2004 166 1867.9 133 4.4 13.0 3.4 5.6 

2005 229 2746.6 173 6.1 17.2 4.4 8.5 

2007 97 1150.6 49 4.7 30.8 2.6 8.5 

Upper Virgin 

River2 

1999 158 306.5 168 27.3 14.8 20.4 36.5 

2000 153 301.9 170 28.1 14.2 21.2 37.1 

2001 159 313.8 169 26.8 13.4 20.6 39.9 

2003 157 309.1 97 15.6 12.8 12.1 20.1 

2005 155 304.5 151 24.7 12.6 19.3 31.7 

2007 157 308.3 92 14.9 13.7 11.3 19.5 1

In the Northeastern Mojave, there are four long-term monitoring strata. Only one stratum could be analyzed in
 

2002, while in 2003 and 2004, three of the four could be analyzed. No recovery unit estimate is provided for 2002,
 

and the 2003 and 2004 estimates are based on three of four strata. In the Eastern Mojave, only one of the three strata
 

was surveyed in 2003, so no estimate is provided for the recovery unit. The single stratum in the Northern Colorado 

Recovery Unit was not surveyed in 2002.

2

Data from McLuckie et al. (2007).
 

9 
 

 

 

 

 

 

 

D. LIFE HISTORY AND ECOLOGY 

Desert tortoises are well adapted to living in a highly variable and often harsh desert 

environment. They spend much of their lives in burrows, even during their seasons of activity. 

In late winter or early spring, they emerge from over-wintering burrows and typically remain 

active through fall. Activity decreases in summer, but tortoises often emerge after summer rain 

storms. Mating occurs during spring, summer, and fall (Black 1976; Rostal et al. 1994). During 

activity periods, desert tortoises eat a wide variety of herbaceous vegetation, particularly 

grasses and the flowers of annual plants (Berry 1974; Luckenbach 1982; Esque 1994). During 

periods of inactivity, they reduce their metabolism and water loss and consume very little food. 

Adult desert tortoises lose water at such a slow rate that they can survive for more than a year 

without access to free water of any kind and can apparently tolerate large imbalances in their 

water and energy budgets (Nagy and Medica 1986; Peterson 1996a,b; Henen et al. 1998). 

The size of desert tortoise home ranges varies with respect to location and year (Berry 

1986) and also serves as an indicator of resource availability and opportunity for reproduction 

and social interactions (O’Connor et al. 1994). Females have long-term home ranges that may be 

as little as or less than half that of the average male, which can range to 80 or more hectares (200 

acres) (Burge 1977; Berry 1986; Duda et al. 1999; Harless et al. 2009). Core areas used within 

tortoises’ larger home ranges depend on the number of burrows used within those areas (Harless 

et al. 2009). Over its lifetime, each desert tortoise may use more than 3.9 square kilometers (1.5 

square miles) of habitat and may make periodic forays of more than 11 kilometers (7 miles) at a 

time (Berry 1986). 

In drought years, the ability of tortoises to drink while surface water is available 

following rains may be crucial for survival (Nagy and Medica 1986). During unfavorable 

periods, desert tortoises decrease surface activity and remain mostly inactive or dormant 

underground (Duda et al. 1999), which reduces water loss and minimizes energy expenditures 

(Nagy and Medica 1986). Duda et al. (1999) showed that home range size, number of different 

burrows used, average distances traveled per day, and levels of surface activity were 

significantly reduced during drought years. 

Tortoises are long-lived and grow slowly, requiring 13 to 20 years to reach sexual 

maturity, and have low reproductive rates during a long period of reproductive potential (Turner 

et al. 1984; Bury 1987; Germano 1994). Growth rates are greater in wet years with higher annual 

plant production (e.g., an average of 12.3 millimeters [0.5 inches] in an El Niño year compared 

to 1.8 millimeters [0.07 inches] in a drought year in Rock Valley, Nevada; Medica et al. 1975). 

The number of eggs (1-10) as well as the number of clutches (0-3; set of eggs laid at a single 

time) that a female desert tortoise can produce in a season is dependent on a variety of factors 

including environment, habitat, availability of forage and drinking water, and physiological 

condition (Turner et al. 1986, 1987; Henen 1997; Mueller et al. 1998; McLuckie and Fridell 

2002). Success rate of clutches has proven difficult to measure, but predation appears to play an 

important role in clutch failure (Germano 1994). Bjurlin and Bissonette (2004) found that nest 

predation was highly variable. They surmised that regular presence of researchers may facilitate 

predator detection of desert tortoises and that systematic studies should be undertaken to better 

understand predator behavior as it relates to research activities (Bjurlin and Bissonette 2004). 

10
 
 

 

 

 

The most complete account of the biology, ecology, and natural history of a population 

of desert tortoises is that of Woodbury and Hardy (1948), wherein details regarding 

reproduction, growth and development, longevity, food habits, behavior, movement patterns, and 

general adaptations to desert conditions are provided for a population on the Beaver Dam Slope 

of Utah. These characteristics of tortoises do vary with changes in habitat and environment, and 

further information on the range, biology, and ecology of the desert tortoise is available in Bury 

(1982), Bury and Germano (1994), Ernst and Lovich (2009), Van Devender (2002c), and 

collected papers in Chelonian Conservation and Biology (2002, Vol. 4, No. 2), Herpetological 

Monographs (1994, No. 8), and the Desert Tortoise Council Proceedings. 

E. HABITAT CHARACTERISTICS 

The desert tortoise occurs in the broadest latitudinal range, climatic regimes, habitats, and 

biotic regions of any North American tortoise species (Auffenberg and Franz 1978; Bury 1982; 

Patterson 1982; Bury et al. 1994; Germano 1994). The species occupies a variety of habitats 

from flats and slopes typically characterized by creosote bush scrub dominated by Larrea 

tridentata (creosote bush) and Ambrosia dumosa (white bursage) at lower elevations to rocky 

slopes in blackbrush scrub and juniper woodland ecotones (transition zone) at higher elevations 

(Germano et al. 1994). Throughout most of the Mojave Desert, tortoises occur most commonly 

on gently sloping terrain with sandy-gravel soils and where there is sparse cover of low-growing 

shrubs, which allows establishment of herbaceous (non-woody) plants (Germano et al. 1994; 

USFWS 1994a). However, surveys at the Nevada Test Site revealed that tortoise sign (e.g., scat, 

burrows, tracks, shells) was more abundant on upper alluvial fans and low mountain slopes than 

on the valley bottom (Rautenstrauch and O’Farrell 1998). Soils must be friable (easily crumbled) 

enough for digging burrows, but firm enough so that burrows do not collapse (USFWS 1994a). 

During the winter, tortoises will opportunistically use burrows of various lengths, deep caves, 

rock and caliche crevices, or overhangs for cover (Bury et al. 1994). 

Records of desert tortoises range from below sea level to an elevation of 2,225 meters 

(7,300 feet) (Luckenbach 1982). Typical habitat for the desert tortoise in the Mojave Desert has 

been characterized as creosote bush scrub below 1,677 meters (5,500 feet) in which precipitation 

ranges from 5 to 20 centimeters (2 to 8 inches), where a diversity of perennial plants is relatively 

high, and production of ephemerals is high (Luckenbach 1982; Turner 1982; Turner and Brown 

1982; Bury et al. 1994; Germano et al. 1994). 

The Mojave Desert is relatively rich in winter annuals, which serve as an important food 

source for the desert tortoise. Tortoises will also forage on perennial grasses, woody perennials, 

and cacti as well as non-native species such as Bromus rubens (red brome) and Erodium 

cicutarium (red-stem filaree). Ninety percent of the precipitation that facilitates germination of 

important forage species for desert tortoise occurs in winter and sometimes in the form of snow 

(Germano et al. 1994). Tortoises in the eastern Mojave Desert are more likely to be subjected to 

freezing winter temperatures and prolonged drought than tortoises in the Sonoran Desert and 

Sinaloan region where freezing temperatures are rare and rainfall is more predictable (Germano 

1994). 

11
 
 

The U.S. Geological Survey developed a habitat model for the desert tortoise north and 

west of the Colorado River using 16 environmental variables such as precipitation, geology, 

vegetation, and slope (Figure 1) (Nussear et al. 2009). The model is based on desert tortoise 

occurrence data from sources spanning more than 80 years, especially including data from the 

2001 to 2005 range-wide monitoring surveys (USFWS 2006), using 3,753 tortoise presence 

points to develop the model and 938 points to test the model. 

The desert tortoise’s range, outside the listed Mojave population, extends into the 

Sonoran Desert, where tortoises occur in the lower Colorado River valley, Arizona uplands, 

plains of Sonora, and the central Gulf Coast; the species has not been documented in 

northeastern Baja California (Germano et al. 1994). As in the Mojave Desert, Larrea tridentata 

is a dominant species in areas occupied by tortoises, although this dominance is tempered by the 

relatively high abundance of several tree species (Turner and Brown 1982; Germano et al. 1994). 

In the Sonoran Desert, tortoises tend to inhabit bajadas (slope at the base of a mountain) and 

Figure 1. Desert tortoise critical habitat overlaid on the U.S. Geological Survey habitat model (Nussear et 

al. 2009). 

12
 
 

 

 

 

 

 

 

 

steep, rocky slopes and are not common in the valleys (Germano 1994; Van Devender 2002a; 

Averill-Murray and Averill-Murray 2005). Desert tortoises are also found in the Sinaloan 

thornscrub, which is a transitional habitat between the Sonoran Desert and Sinaloan deciduous 

forest where the vegetation is dominated by drought-resistant shrubs and deciduous trees. The 

Sinaloan deciduous forests are differentiated from the thornscrub by taller plants with larger 

leaves and fewer thorny or succulent species (Germano et al. 1994; Fritts and Jennings 1994). 

F. CRITICAL HABITAT 

Under section 3 of the Endangered Species Act, critical habitat is defined as the specific 

areas supporting those physical and biological features that are essential for the conservation of 

the species and that may require special management considerations or protection (Box 1). The 

1994 Recovery Plan identified general areas as proposed Desert Wildlife Management Areas 

where recovery efforts for the desert tortoise would be focused (Brussard et al. 1994; USFWS 

1994a; Box 1). Based on the draft recovery plan, we designated critical habitat in February 1994, 

encompassing over 2,428,114 hectares (6,000,000 acres) in portions of the Mojave and Colorado 

deserts (Figure 1; Table 2). This designation includes primarily Federal lands in southwestern 

Utah, northwestern Arizona, southern Nevada, and southern California (USFWS 1994b). 

Primary constituent elements for the desert tortoise are those physical and biological 

attributes that are necessary for the long-term survival of the species. These elements were 

identified as sufficient space to support viable populations within each of the six recovery units 

and to provide for movement, dispersal, and gene flow; sufficient quantity and quality of forage 

species and the proper soil conditions to provide for the growth of such species; suitable 

substrates for burrowing, nesting, and overwintering; burrows, caliche (hard layer of subsoil 

typically containing calcium carbonate) caves, and other shelter sites; sufficient vegetation for 

shelter from temperature extremes and predators; and habitat protected from disturbance and 

human-caused mortality (USFWS 1994b). 

Table 2. Critical habitat by state and land management in hectares (1 hectare=2.47 acres); data from the 

Mojave Desert Ecosystem Program. 

State 

Management 

Arizona California Nevada Utah 

Total 

Bureau of Land Management 116,835 1,092,675 400,243 38,041 1,647,794 

National Park Service 17,968 362,202 42,088 422,258 

U.S. Fish and Wildlife 9,308 9,308 

Bureau of Reclamation 1,350 1,350 

Department of Defense 186,564 186,564 

Department of Energy 202 202 

Tribal Land 971 971 

State Land 2,307 33,590 9,106 45,003 

Private Land 1,012 243,221 41,279 4,006 289,518 

Total 138,122 1,918,252 494,470 52,124 2,602,968 

13
 
 

 

 

 

 

Box 1. Glossary of terminology relating to desert tortoise habitat: 

Desert Wildlife Management Areas (DWMA) - General areas recommended by the 1994 Recovery 

Plan within which recovery efforts for the desert tortoise would be concentrated. DWMAs had no 

specific legal boundaries in the 1994 Recovery Plan. The Bureau of Land Management formalized the 

general DWMAs from the 1994 Recovery Plan through its planning process and administers them as 

Areas of Critical Environmental Concern (see below). 

Critical Habitat – Specific, legally defined areas that are essential for the conservation of the desert 

tortoise, that support physical and biological features essential for desert tortoise survival, and that 

may require special management considerations or protection. Critical habitat for the desert tortoise 

was designated in 1994, largely based on proposed DWMAs in the draft Recovery Plan. 

Area of Critical Environmental Concern (ACEC) – Specific, legally defined, Bureau of Land 

Management designation where special management is needed to protect and prevent irreparable 

damage to important historical, cultural, scenic values, fish and wildlife, and natural resources (in this 

case, the desert tortoise) or to protect life and safety from natural hazards. Designated critical habitat 

and ACEC boundaries generally, but not always, coincide along legal boundaries. 

G. REASONS FOR LISTING AND CONTINUING THREATS 

In determining whether to list, delist, or reclassify (change from endangered to threatened 

status, or vice versa) a taxon under the Endangered Species Act, we evaluate the role of five 

factors potentially affecting the species. These factors are: 

A) The present or threatened destruction, modification, or curtailment of its habitat or 

range; 

B) overutilization for commercial, recreational, scientific, or educational purposes; 

C) disease or predation; 

D) the inadequacy of existing regulatory mechanisms; and 

E) other natural or manmade factors affecting its continued existence. 

Documented threats to the Mojave population of the desert tortoise were described in the 

final listing rule in 1990 as they pertain to the five listing factors (USFWS 1990) and in the 1994 

Recovery Plan (USFWS 1994a). The threats identified in the 1994 Recovery Plan, and that 

formed the basis for listing the tortoise as a threatened species (GAO 2002), continue to affect 

the species today. Extensive research shows that all of these individual threats directly kill or 

indirectly affect tortoises. Research has also clarified many mechanisms by which these threats 

act on tortoises. However, despite the clear demonstration that these threats impact individual 

tortoises, there are few data available to evaluate or quantify the effects of threats on desert 

tortoise populations (Boarman 2002). While current research results can lead to predictions about 

how local tortoise abundance should be affected by the presence of threats, quantitative estimates 

14
 
 

 

 

of the magnitude of these threats, or of their relative importance, have not yet been developed. 

Thus, a particular threat or subset of threats with discernable solutions that could be targeted to 

the exclusion of other threats has not been identified for the desert tortoise. 

The assessment of the 1994 Recovery Plan emphasized the need for a greater 

appreciation of the implications of multiple, simultaneous threats facing tortoise populations and 

a better understanding of the relative contribution of multiple threats on demographic factors 

(i.e., birth rate, survivorship, fecundity, and death rate; Tracy et al. 2004). The approach of 

focusing on individual threats may not have produced expected gains toward desert tortoise 

recovery since 1994 because multiple threats act simultaneously to suppress tortoise populations 

at any given location within the species’ range. In this revised recovery plan, we underscore the 

need to build on our understanding of individual threats, yet place new emphasis on 

understanding their multiple and synergistic effects (interacting so that the combined effect is 

greater than the sum of individual effects) due to the failure of simple threat models to inform us 

about tortoise abundance. The following narrative provides a brief overview of the threats to the 

desert tortoise and its habitat as categorized by the five listing factors. A more detailed 

discussion of these threats is contained in Appendix A. 

1. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or 

Range (Factor A) 

Since the 1800s, portions of the desert southwest occupied by desert tortoises have been 

subject to a variety of impacts that cause habitat loss, fragmentation, and degradation, thereby 

threatening the long-term survival of the species (USFWS 1994a). Some of the most apparent 

threats are those that result in mortality and permanent habitat loss across large areas, such as 

urbanization, and those that fragment and degrade habitats, such as proliferation of roads and 

highways, off-highway vehicle activity, poor grazing management, and habitat invasion by nonnative invasive species (Berry et al. 1996; Avery 1997; Jennings 1997; Boarman 2002; Boarman 

and Sazaki 2006). Indirect impacts to desert tortoise populations and habitat are also known to 

occur in areas that interface with intense human activity (Berry and Burge 1984; Berry and 

Nicholson 1984b). 

Another threat that has come to the forefront is the increased frequency of wildfire due to 

the invasion of desert habitats by non-native plant species (USFWS 1994a; Brooks 1998). 

Changes in plant communities caused by non-native plants and recurrent fire can negatively 

affect the desert tortoise by altering habitat structure and species available as food plants (Brooks 

and Esque 2002). Off-highway vehicle activity, roads, livestock grazing, agricultural uses, and 

other activities contribute to the spread of non-native species (or the displacement of native 

species) and the direct loss and degradation of habitats (Brooks 1995; Avery 1998). For example, 

unmanaged livestock grazing, especially where plants are not adapted to large herbivorous 

mammals or where the non-native species are less palatable than the natives, can preferentially 

remove native vegetation, leaving non-native plants to grow under reduced competition 

(Wittenberg and Cock 2005:228). 

Landfills and other waste disposal facilities potentially affect desert tortoises and their 

habitat through fragmentation and permanent loss of habitat, spread of garbage, introduction of 

15
 
 

 

 

 

 

 

toxic chemicals, increased road kill of tortoises on access roads, and increased predator 

populations (Boarman et al. 1995; Kristan and Boarman 2003). Military operations (e.g., 

construction and operation of bases, field maneuvers) have taken place in the Mojave Desert 

since 1859 and can affect tortoises and their habitats similarly to other large human settlements 

(i.e., illegal collection of tortoises, trash dumping, increased raven (Corvus corax) populations, 

domestic predators, off-highway vehicle use, increased exposure to disease, and increased 

mortality) (USFWS 1994a; Krzysik 1998; Boarman 2002). 

As of November 2010, six solar projects in California and one in Nevada were approved 

on public lands within the range of the desert tortoise, constituting 3,037.5 megawatts (MW) on 

9,683 hectares (23,926 acres) and 430 MW on 3,173 hectares (7,840 acres), respectively. Three 

additional solar projects on private lands in California have been approved totaling 1,063 MW on 

1,686 hectares (4,165 acres). Seven solar projects on public lands were still pending, totaling 

1,450 MW on 4,314 hectares (10,659 acres) in California and 900 MW on 6,955 hectares 

(17,186 acres) in Nevada. Three wind projects within the range of the desert tortoise were also 

pending, totaling 536.5 MW on 11,775 hectares (29,096 acres) of public and private rights-ofway; one of the California projects is proposed within designated critical habitat. No applications 

have been submitted for solar or wind projects on public lands within the range of the Mojave 

population of the desert tortoise in Arizona or Utah. Dozens of project sites have been proposed, 

and the Bureau of Land Management has committed to excluding these projects from designated 

critical habitat for the desert tortoise and Desert Wildlife Management Areas. However, potential 

long-term effects of large-scale energy development fragmenting or isolating desert tortoise 

conservation areas and cutting off gene flow between these areas have not been evaluated. 

2. Overutilization for Commercial, Recreational, Scientific, or Educational Purposes 

(Factor B) 

Despite legal protection under Federal and State laws, deliberate maiming or killing of 

tortoises (previously referred to as vandalism) and collection of desert tortoises by humans for 

food or as pets were cited as potential threats to the species (USFWS 1994a). Data and anecdotal 

observations indicate that collection for personal or commercial purposes was significant in the 

past (USFWS 1994a). While illegal collection of desert tortoises still occurs and collection could 

possibly impact local populations, there is no quantitative estimate of the magnitude of this threat 

(Berry et al. 1996; Boarman 2002). 

Research projects may result in injury or loss of individuals. These activities may be 

permitted under section 10 of the Endangered Species Act, when permitted. Terms and 

conditions to minimize injury and mortality of individuals are mandatory. 

3. Disease or Predation (Factor C) 

To date the available evidence indicates that upper respiratory tract disease, as caused by 

the bacteria Mycoplasma agassizii and M. testudineum (Jacobson et al. 1991), is probably the 

most important infectious disease affecting desert tortoises. Less is known about other diseases 

that have been identified in the desert tortoise (e.g., herpesvirus, cutaneous dyskeratosis, shell 

necrosis, bacterial and fungal infections, and urolithiasis or bladder stones) (Jacobson et al. 1994; 

16
 
 

 

 

 

Homer et al. 1998; Berry et al. 2002b; Origgi et al. 2002). There is evidence that any one disease 

may predispose an animal to other diseases (Christopher et al. 2003). However, it is not known 

whether this is a cause or effect. Additional research is needed to clarify the role of disease in 

desert tortoise population dynamics relative to other threats. 

The role of environmental contaminants in directly inducing toxicosis-related diseases 

(i.e., liver diseases) and increasing susceptibility to infectious diseases has recently been 

suggested as a significant source of mortality (Homer et al. 1994, 1996; Berry 1997; Boarman 

2002; Christopher et al. 2003). Elevated mercury and arsenic levels have been associated with 

diseased tortoises in the wild (Jacobson et al. 1991; Homer et al. 1998; Seltzer and Berry 2005; 

Chaffee and Berry 2006). Necropsy and analyses of kidney, liver, and scute tissues suggested 

that tortoises from California with a variety of diseases (upper respiratory tract infection, 

urolithiasis, metabolic disease, and shell diseases) had statistically significantly higher levels of 

several potentially toxic elements as compared to healthy tortoises (Berry et al. 1997). Illegal 

dumping of hazardous wastes in the California deserts may expose tortoises to increased levels 

and possible consumption of toxic substances and affect populations on a localized level where 

these activities are concentrated (Boarman 2002). It has been postulated that elemental toxicity 

may compromise the immune system of desert tortoises or otherwise detrimentally affect 

physiological function, rendering them more susceptible to disease, but further investigation is 

needed. 

Desert tortoises, particularly hatchlings and juveniles, are preyed upon by several native 

species of mammals, reptiles, and birds. The common raven (Corvus corax) has been the most 

highly visible predator of small tortoises, while coyotes (Canis latrans) have been commonly 

implicated in deaths of adult tortoises. The population-level effects of these or other predators 

are unknown. Except for extreme predation events brought on by unusual circumstances, 

predation by native predators alone would not be expected to cause dramatic population declines. 

This reiterates the importance of combined and synergistic effects of threats. For example, 

predation pressure by ravens is increased through elevated raven populations as a result of 

resource subsidies associated with human activities. Ravens obtain food in the form of organic 

garbage from landfills and trash containers, water from sewage ponds and municipal areas, and 

nesting substrates on billboards, utility towers, bridges, and buildings (Boarman et al. 2006). 

Other avian predators of the desert tortoise include red-tailed hawks (Buteo jamaicensis), 

golden eagles (Aquila chrysaetos), loggerhead shrikes (Lanius ludovicianus), American kestrels 

(Falco sparvarius), burrowing owls (Athene cunicularia), and greater roadrunners (Geococcyx 

californianus) (Boarman 1993). Coyotes, kit foxes (Vulpes macrotis), mountain lions (Felis 

concolor), ground squirrels (Spermophilus spp.), and free-roaming dogs are some of the known 

mammalian predators (Bjurlin and Bissonette 2001; Boarman 2002; M. McDermott, Southern 

Nevada Environmental, Inc., pers. comm. 2006, K. Nagy, University of California-Los Angeles, 

pers. comm. 2006; Medica and Greger 2009). Invertebrate predators of eggs and hatchling 

tortoises include native fire ants (Nagy et al. 2007). 

17
 
 

 

 

 

 

4. Inadequacy of Existing Regulatory Mechanisms (Factor D) 

The final listing rule acknowledged that all four states within the range of the Mojave 

population of the desert tortoise have laws in place to protect the species. In addition, a great deal 

of effort has been dedicated to planning by the various land management agencies whose 

jurisdictions include desert tortoise habitat. Many of the existing plans include language specific 

to protection of the species, such as limiting off-highway vehicle use and competitive/organized 

events, grazing, vegetation harvest, and collection of desert tortoises. However, the multiple-use 

mandates under which the agencies function require a complex balance between conservation 

and use of public lands, and management agencies frequently do not have sufficient funding to 

enforce their regulations. Also, state law in Arizona, Nevada, and Utah does not regulate habitat 

degradation, making mitigation of impacts to potentially unoccupied but suitable habitat 

difficult. 

Land exchanges and transfers may result in loss of desert tortoise habitat, increased 

fragmentation, and displacement of resident desert tortoises, because habitat that is exchanged 

out of Federal ownership into the private sector is at greater risk of urban development (Sievers 

et al. 1988; but see Conservation Efforts, Land Acquisitions and Habitat Conservation Plans, 

below). Energy and mineral development and extraction also pose a significant threat to desert 

tortoises through habitat loss and fragmentation (Luke et al. 1991; Lovich and Bainbridge 1999; 

LaRue and Dougherty 1999). For example, as of November 2010, the area of approved and 

pending solar and wind-energy applications on public lands in California exceeds 100,000 

hectares (247,000 acres). 

5. Other Natural or Manmade Factors Affecting its Continued Existence (Factor E) 

Global climate change and drought are potentially important long-term considerations 

with respect to recovery of the desert tortoise. There is now sufficient evidence that recent 

climatic changes have affected a broad range of organisms with diverse geographical 

distributions (Walther et al. 2002). While little is known regarding specific direct effects of 

climate change on the desert tortoise or its habitat, predictions can be made about how global and 

regional precipitation regimes may be altered and about the consequences of these changes 

(Weltzin et al. 2003; Seager et al. 2007). 

The Intergovernmental Panel on Climate Change has suggested that increasingly reliable 

regional climate change projections are available as the result of improved modeling capabilities 

and advanced understanding of climate systems (Christensen et al. 2007). Twenty-one 

Atmosphere-Ocean General Circulation Models were run to predict regional temperature and 

precipitation across the globe in 2080 through 2099 as changed from conditions that occurred 

between 1980 and 1999. Generally, predictions for the geographic range of the desert tortoise’s 

listed population suggest a 3.5 to 4.0 degree Celsius (6.3 to 7.2 degree Fahrenheit) increase in 

annual mean temperature, with the greatest increases occurring in summer (June-July-August 

mean up to 5 degrees Celsius [9 degrees Fahrenheit] increase) (Christensen et al. 2007). 

Precipitation will likely decrease by 5 to 15 percent annually within the range of the desert 

tortoise with winter precipitation decreasing up to 20 percent (Christensen et al. 2007). Because 

germination of the tortoise’s food plants is highly dependent on cool season rains, the forage 

18
 
 

 

 

 

 

base could be reduced due to increasing temperatures and decreasing precipitation in winter. 

Smith et al. (2009) review various types of global change relative to expected effects in the 

Mojave Desert, such as elevated carbon dioxide and altered precipitation regimes facilitating 

invasive plant species, thereby increasing fire frequency. Effects of altered nitrogen dynamics on 

the Mojave Desert are less clear. For example, increased nitrogen deposition from dust in the 

vicinity of metropolitan areas could result in higher plant production, exacerbating the effects 

from carbon dioxide noted above (Smith et al. 2009). Alternatively, increased temperatures may 

release nitrogen gases from Mojave Desert soils, reducing fertility of those soils and the ability to 

support plant life (McCalley and Sparks 2009). Further predictions need to be developed 

specifically for the desert tortoise to help inform recovery efforts. 

Other activities that may impact the species include non-motorized recreation such as 

camping, hunting, target shooting, rock collecting, hiking, horseback riding, biking, and sightseeing. These activities bring with them threats associated with increased human presence, such 

as loss of habitat from development of recreational facilities, handling and disturbance of 

tortoises, increased road kill and deliberate maiming or killing of tortoises, increased raven 

predation, degradation of vegetation, and soil compaction (USFWS 1994a; Averill-Murray 

2002). Desert habitats are also disturbed by construction and maintenance of linear utility 

corridors and ancillary facilities and to some degree by vandalism and harvest of vegetation for 

personal or economic purposes (Olson 1996; LaRue and Dougherty 1999). 

Another potential threat facing the desert tortoise is the unauthorized release or escape of 

pet tortoises to the wild. Captive releases have the potential to introduce disease into wild 

populations of desert tortoises (Johnson et al. 2006; Martel et al. 2009). Tomlinson and 

Hardenbrook (1993) reported that the highest prevalence of clinical signs of upper respiratory 

tract disease was observed in tortoises removed from areas where previous releases of captive 

animals had occurred. Release or escape of captive tortoises genetically different from the 

resident population could theoretically decrease fitness (Tallmon et al. 2004). 

H. CONSERVATION EFFORTS 

While precise correlations between threats and desert tortoise populations have not been 

clearly shown, a great deal of effort has been put forth by research scientists and land managers 

to actively conserve the species. For instance, substantive datasets pertaining to disease, nonnative invasive plant species, and fire have been assembled over the years that will be used to 

inform decisions relative to recovery of the desert tortoise and its habitats. On-the-ground 

conservation actions such as land acquisitions, installing protective fencing, retiring grazing 

allotments, limiting off-highway vehicle access, and implementing restoration projects have been 

based on what we believe are threats to the desert tortoise at this time (see GAO 2002). The 

following are examples of existing guidance and strategies to further resource conservation. 

19
 
 

 

 

 

 

1. Wildlife Conservation Strategies 

In 2000, Congress enacted the State Wildlife Grants Program to fund activities that 

benefit species of concern and their habitats. To receive funding under this program, State 

wildlife agencies needed to complete a Fish and Wildlife Service-approved wildlife action plan 

(or comprehensive wildlife conservation strategy). All four states where the Mojave population 

of the desert tortoise occurs are currently implementing these strategies to guide species and 

habitat management through 2015 (Gorrell et al. 2005; Abele et al. 2006; Arizona Game and 

Fish Department 2006; Bunn et al. 2006). 

Each state has identified conservation priorities and recommendations that are both 

species- and habitat-specific. Some of these actions include, but are not limited to, the following: 

•	 improve stewardship on federally managed lands to protect wildlife diversity; 

•	 work cooperatively with landowners/permittees by providing financial and technical 

assistance (through incentive programs) for conservation projects; 

•	 work with city and county planners to incorporate wildlife values in urban/rural
 

development plans;
 

•	 promote design and construction of overpasses, underpasses, or culverts to increase 

permeability of existing or planned roads; 

•	 identify and protect key wildlife corridors for landscape connectivity; 

•	 reduce off-highway vehicle damage to wildlife habitats; 

•	 encourage revegetation and restoration of existing unauthorized roads and trails; 

•	 improve efforts and partnerships for controlling existing occurrences of invasive species 

and prevent new introductions; 

•	 rehabilitate burned and disturbed areas with native plants; 

•	 pursue projects to limit spread of disease to sensitive wildlife populations; 

•	 use fencing and/or increased law enforcement presence to reduce unauthorized use and 

access to sensitive habitats; and, 

•	 implement a statistically robust range-wide monitoring program and adaptive 

management framework that captures population trends and impacts to the species. 

2. Federal Land Management Plans 

Land use management plans provide guidance and establish a mechanism by which 

Federal agencies implement actions on lands under their purview. Throughout the range of the 

desert tortoise, multiple Federal agencies are involved in the long-term management and 

conservation of the species as part of their respective missions. These include the Bureau of Land 

Management, National Park Service, Bureau of Indian Affairs, U.S. Fish and Wildlife Service, 

Bureau of Reclamation, U.S. Forest Service, Department of Defense, and Department of Energy. 

In addition to Federal land use plans, counties and local jurisdictions draft general plans to guide 

their activities. 

Within the range of the desert tortoise, the following programmatic-level documents are 

currently in place or in preparation. Many of the respective plans include language specific to the 

protection and conservation of natural resources including desert tortoises and their habitats. 

20
 
 

 

 

 

These are often supplemented by more specific guiding documents, such as habitat management 

plans or wilderness management plans: 

Bureau of Land Management: 

•	 Arizona Strip Resource Management Plan Revision, Grand Canyon-Parashant National 

Monument Management Plan (jointly managed with the National Park Service), and 

Vermilion Cliffs National Monument Management Plan; Proposed Resource 

Management Plan/Final Environmental Impact Statement (BLM and National Park 

Service [NPS] 2007) 

•	 California Desert Conservation Plan of 1980 as amended (BLM 1999a) 

•	 Northern and Eastern Mojave Desert Management Plan (BLM 2002a) 

•	 Northern and Eastern Colorado Desert Coordinated Management Plan (BLM 2002b) 

•	 West Mojave Plan (BLM et al. 2005) 

•	 Tonopah Resource Management Plan (BLM 1997) 

•	 Las Vegas Resource Management Plan (BLM 1998a) 

•	 Red Rock Canyon National Conservation Area Resource Management Plan (BLM 2001) 

•	 Sloan Canyon National Conservation Area Resource Management Plan (BLM 2006) 

•	 Nevada Test and Training Range Resource Management Plan (BLM 2004) 

•	 Caliente Management Framework Plan (BLM 2000) 

•	 St. George Resource Management Plan (BLM 1999b) 

Fish and Wildlife Service: 

• Desert National Wildlife Refuge Comprehensive Conservation Plan (USFWS 2009b) 

National Park Service: 

•	 Joshua Tree National Park General Management Plan, as amended (NPS 2000a) 

•	 Death Valley National Park General Management Plan (NPS 2002a) 

•	 Mojave National Preserve General Management Plan (NPS 2002b) 

•	 Lake Mead National Recreation Area, Arizona and California, Strategic Plan Fiscal Year 

2001-2005 (NPS 2000b) 

U.S. Forest Service: 

•	 General Management Plan for the Spring Mountains National Recreation Area, An 

Amendment to the Land and Resource Management Plan (U.S. Forest Service 1996) 

Department of Defense: 

•	 Draft Nellis AFB and Nevada Test and Training Range Integrated Natural Resources 

Management Plan (U.S. Air Force 2007) 

•	 Marine Corps Air Ground Combat Center, Twentynine Palms, Integrated Natural
 

Resources Management Plan, Fiscal Years 2007-2011 (U.S. Marine Corps 2007)
 

•	 National Training Center at Fort Irwin Integrated Natural Resources Management Plan 

(U.S. Army 2006) 

•	 Marine Corps Logistics Base, Barstow, Integrated Natural Resources Management Plan 

(Tierra Data, Inc. 2005) 

21
 
 

 

 

 

•	 Naval Air Weapons Station, China Lake, Comprehensive Land Use Management Plan 

and Integrated Natural Resources Management Plan (Naval Air Weapons Station, China 

Lake and BLM 2004) 

•	 Edwards Air Force Base Integrated Natural Resources Management Plan (U.S. Air Force 

2001) 

•	 Yuma Training Range Complex, Arizona and California (U.S. Navy 2001) 

•	 Nevada Test Site Resource Management Plan (U.S. Department of Energy 1998) 

Among the most important recovery actions implemented pursuant to the 1994 Recovery 

Plan has been formalizing Desert Wildlife Management Areas (DWMAs; Box 1) through 

Federal land use planning processes (Figure 2). Particularly on Bureau of Land Management 

lands, DWMAs are administered and designated as Areas of Critical Environmental Concern 

(ACEC; Box 1; BLM 1998a, 1999b, 2000, 2002a, 2002b, BLM et al. 2005, BLM and NPS 

2007). These ACECs define specific management areas based on the general recommendations 

for DWMAs in the 1994 Recovery Plan. Boundaries of the ACECs were refined slightly from 

the critical habitat designation based on various management and biological considerations. The 

Bureau of Land Management DWMAs/ACECs, together with National Park Service lands, 

designated wilderness areas, other lands allocated for resource conservation, as well as restrictedaccess military lands provide an extensive network of habitats that are managed either directly or 

indirectly (e.g., wilderness areas outside desert tortoise ACECs) for desert tortoise conservation 

(Figures 2 and 3). 

A recent example of landscape-scale conservation was the Bureau of Land 

Management’s designation of ACECs and wildlife habitat areas under the Arizona Strip 

Resource Management Plan Revision and Grand Canyon-Parashant National Monument 

Management Plan (BLM and NPS 2007). On the Arizona Strip, lands managed to maintain 

wilderness characteristics were proposed on 87,100 hectares (215,345 acres) within the Grand 

Canyon-Parashant National Monument and on 14,120 hectares (34,900 acres) within the Arizona 

Strip field office’s area of responsibility. Nearly 68,800 hectares (170,000 acres) are designated 

as ACECs on the Arizona Strip, which directly benefits the desert tortoise and its habitat. The 

Resource Management Plan contains the following goals: 

•	 The Mojave population of desert tortoise would be recovered and delisted. 

•	 There would be no net loss in the quality or quantity of desert tortoise habitat within the 

ACECs or wildlife habitat areas. 

•	 Desert tortoise populations within the ACECs and DWMAs would be healthy and selfsustaining. Populations would be stable or increasing. Population declines would be 

halted. 

•	 Desert tortoise populations outside of the ACECs and wildlife habitat areas would be 

healthy and stable. Declines in the wildlife habitat areas would be minimized to the 

extent possible through mitigation. 

•	 Desert tortoise habitat would provide sufficient forage and cover attributes to support 

thriving populations of the species. 

•	 Habitat connectivity would be maintained, providing sufficiently frequent contact
 

between tortoises to maintain genetic diversity.
 

22
 
Figure 2. Desert tortoise conservation areas (see Box 2). DWMA = Desert Wildlife Management Area; 

ACEC = Areas of Critical Environmental Concern; DTCC = Desert Tortoise Conservation Center. 

23
 
 

 

 

Figure 3. Additional land designations providing conservation benefits to the desert tortoise. 

Conservation areas for other species not shown (e.g., Mohave ground squirrel [Spermophilus 

mohavensis], Mimulus mohavensis [Mojave monkeyflower]) may also provide benefit to the desert 

tortoise. 

Another example of landscape-level conservation is the withdrawal of locatable mineral 

entry within ACECs on the Southern Nevada District of the Bureau of Land Management (BLM 

2009). Locatable minerals are those that have been described as “valuable mineral deposits” and 

include metal ores such as gold, silver, copper, or lead, and certain industrial minerals such as 

gypsum, chemical-grade limestone, and diatomaceous earth. Uncommon varieties of mineral 

materials such as pumice, rock, and cinders also are regulated as locatable minerals. The BLM 

withdrew approximately 382,000 hectares (944,000 acres) of public lands from locatable mineral 

entry under the United States mining laws for a period of 20 years to protect desert tortoise 

habitat, archaeological and cultural resources, and special wildlife and riparian values on 24 

ACECs. Four of these ACECs coincide with desert tortoise critical habitat (Piute/Eldorado, 

Coyote Springs, Mormon Mesa, and Gold Butte critical habitat units). This action was included 

24
 
 

 

PECI 

as one of the most important conservation actions in the Las Vegas Resource Management Plan 

(BLM 1998a). All valid existing rights including, but not limited to, mining, recreation, and/or 

rights of way remain unaffected (BLM 2009). 

One of the most extensive land and resource management plans currently in place was 

developed for the 10,117,141-hectare (25,000,000-acre) California Desert Conservation Area. In 

1976, Congress passed the Federal Land Policy Management Act to direct the management of 

the public lands of the United States. Under that law, the California Desert Conservation Area 

was established, with 4,856,228 hectares (12,000,000 acres) of public lands administered by the 

Bureau of Land Management. The California Desert Conservation Area Plan of 1980 as 

amended provides guidance relative to the use of the public lands and resources of the California 

Desert Conservation Area, including economic, educational, scientific, and recreational uses, in a 

manner that enhances wherever possible, and does not diminish the environmental, cultural, and 

aesthetic values of the desert and its productivity. Under the California Desert Conservation Area 

Plan, all state and federally listed species and their habitats are to be managed so that the 

continued existence of each is not jeopardized. Consultation for federally listed species would be 

conducted as appropriate (BLM 1999a). 

The California Desert Conservation Area Plan was subsequently amended by regions that 

generally corresponded to the recovery units delineated in the 1994 Recovery Plan. The Northern 

and Eastern Mojave Desert Management Plan (BLM 2002a), the West Mojave Plan (BLM et al. 

2005), and the Northern and Eastern Colorado Desert Coordinated Management Plan (BLM 

2002b) all designated DWMAs/ACECs and included new management measures for desert 

tortoise conservation, including limiting various recreational activities, such as off-highway 

vehicle races, within the conservation areas. 

The California Desert Conservation Area also encompasses the 10,117-hectare (25,000­

acre) Desert Tortoise Natural Area, which was established in the western Mojave Desert in 1972. 

The Mojave National Preserve was created under the California Desert Protection Act in 1994 

for which a general management plan was drafted in 2002 (NPS 2002b). The California Desert 

Protection Act also expanded the boundaries of both Death Valley and Joshua Tree National 

Parks and designated millions of acres of wilderness, which eliminated vehicle access to these 

areas. 

Many of the actions recommended in the 1994 Recovery Plan have been incorporated 

into the land and resource management plans identified above, particularly within 

DWMAs/ACECs. Tracy et al. (2004) summarized the level of implementation of the 

management recommendations by reviewing land and wildlife managers’ responses to surveys 

asking what recovery actions had been implemented. However, the survey responses were not 

explicit enough to quantify the level of implementation for each specific recovery action; 

therefore, the results only speak to whether or not some action had been taken. In addition, 

research and monitoring have not been targeted to evaluate the effectiveness of these actions 

(Boarman and Kristan 2006), and ongoing population monitoring has been performed at a 

regional scale rather than a local implementation scale. The main conclusion was that improved 

reporting and quantification of recovery actions is necessary to more accurately assess the 

progress of desert tortoise recovery (Tracy et al. 2004). 

25
 
AL DESIGNATIONS –

 

 

 

 

 

 

3. Improved Grazing Management 

A specific example of landscape-scale conservation of desert tortoise habitat was 

improved grazing management on several allotments within designated critical habitat on public 

lands. This was identified in the 1994 Recovery Plan as an important component in the recovery 

of the species. For example, in 1995 the Desert Tortoise Preserve Committee and The Wildlands 

Conservancy bought the 550-hectare (1,360-acre) Blackwater Well Ranch in northwestern San 

Bernardino County and is managing grazing on the 19,830-hectare (49,000-acre) Pilot Knob 

cattle grazing allotment. The Bureau of Land Management removed grazing on nearly 1,214,000 

hectares (3,000,000 acres) within the California portions of the Mojave and Sonoran deserts 

(BLM 2002a,b; BLM et al. 2005; USFWS 2005, 2006b). In addition, national Bureau of Land 

Management grazing administration regulations became effective in 1996, which provided 

direction for states to develop Standards for Rangeland Health and Guidelines for Grazing 

Management on Bureau of Land Management Lands (BLM 1996). All of the states within the 

range of the desert tortoise have incorporated standards and guidelines into their management 

plans. 

Under the West Mojave Plan (BLM et al. 2005), grazing has been retired on several 

allotments mostly within designated critical habitat or DWMAs. Additional management 

improvements such as season of use and forage type (ephemeral or perennial) have also been 

instituted on some allotments within the plan area. Fort Irwin, which lies within the West Mojave 

Plan area, purchased fee lands within three cattle allotments in the Western Mojave Recovery 

Unit to partially offset the effects of its base expansion, and the Bureau of Land Management 

subsequently retired grazing on these allotments. The Bureau of Land Management has retired 

grazing from at least four other allotments in the plan area. Collectively, over 307,560 hectares 

(760,000 acres) in the West Mojave Plan area have been retired from grazing. 

Within the West Mojave Plan area, the Bureau of Land Management has identified a 

number of conservation prescriptions to be implemented within cattle and sheep allotments. The 

Northern and Eastern Mojave Desert Management Plan (BLM 2002a) instituted improved 

grazing practices on approximately 126,260 hectares (312,000 acres), which constitutes all but 

about 5,261 hectares (13,000 acres) of critical habitat in the Shadow Valley and Ivanpah Valley 

DWMAs. Grazing remains on one allotment within the Ivanpah Valley DWMA with some 

utilization restrictions, and all ephemeral (seasonal) allotments within DWMAs will be 

terminated. The Northern and Eastern Colorado Desert Coordinated Management Plan (BLM 

2002b) established two DWMAs that encompass over 647,500 hectares (1,600,000 acres). Only 

one allotment remains within designated critical habitat or a DWMA. Approximately 8,090 

hectares (20,000 acres) of this active allotment was closed to grazing due to high tortoise 

densities, and in other portions of the allotment, utilization restrictions and season of use 

requirements will be implemented. 

Under the Mojave National Preserve General Management Plan (NPS 2002b), grazing 

has been removed on nine allotments and remains active on another two (D. Hughson, NPS, 

pers. comm. 2007). The overall management goal is to remove grazing on the entire Preserve 

through voluntary relinquishment by lessees or acquisition of grazing permits and water rights by 

26
 
 

 

 

 

conservation organizations. These activities will be managed according to Bureau of Land 

Management allotment management plans and National Park Service grazing management plans, 

together with additional restrictions designed to improve resource protection (NPS 2002b). In 

Joshua Tree National Park, there are no active grazing allotments (M. Vamstad, Joshua Tree 

National Park, pers. comm. 2008). 

Since 1994, the Bureau of Land Management and U.S. Forest Service have closed 70 

ephemeral grazing allotments in Clark and southern Nye counties totaling over 2,023,400 

hectares (5,000,000 acres). Approximately 22,600 hectares (56,000 acres) currently remain 

available for grazing in five allotments in Clark and southern Nye counties (E. Masters, BLM, 

pers. comm. 2007). According to the Las Vegas Resource Management Plan, no permitted 

grazing occurs within ACECs in Clark County and southern Nye County (BLM 1998a). Under 

the Clark County Multiple Species Habitat Conservation Plan (MSHCP) and its predecessor (see 

discussion below), which lies within the Southern Nevada District of the Bureau of Land 

Management, the County has been actively purchasing the rights to permanently remove grazing 

from over 809,370 hectares (2,000,000 acres) of public lands within and outside of DWMAs (J. 

Bair, USFWS, pers. comm. 2007). 

Under the Caliente Management Framework Plan Amendment (Lincoln County, 

Nevada), all allotments or portions of allotments within ACECs were closed to livestock grazing 

(85,996 hectares [212,500 acres]). Outside ACECs, season of use on all perennial allotments was 

established through allotment evaluation and multiple-use decision processes. It was determined 

for areas outside ACECs, livestock use could occur between March 15 and October 15 provided 

forage utilization does not exceed 40 percent for key perennial grasses, forbs, and shrubs (BLM 

2000). 

Allotment closures and restrictions were also instituted on the Bureau of Land 

Management Arizona Strip District within ACECs and within the National Monuments (BLM 

1998b; BLM 2007a). Livestock grazing is authorized on portions of 11 allotments that support 

desert tortoise habitat. Improved grazing management will be implemented in these areas; 

grazing use is limited to October 15 through March 15, generally coinciding with desert tortoise 

inactivity. Ecological site inventory (basic inventory of present and potential vegetation on BLM 

rangelands) data are expected to serve as the baseline for range conditions, and utilization is not 

to exceed 45 percent of the current year’s growth. Overall, conditions must meet the Bureau of 

Land Management’s Standards for Rangeland Health and National Park Service’s Vital Sign 

Standards (BLM 2007a). 

4. Land Acquisitions and Habitat Conservation Plans (HCPs) 

Land acquisitions and transfers may negatively impact desert tortoises and their habitats 

when the intention is development. On the other hand, these transactions may result in 

conservation benefits. For instance, since 1986, California Department of Fish and Game has 

acquired over 19,670 hectares (48,000 acres) of desert tortoise habitat within critical habitat, and 

additional lands with endowment fees have been and continue to be acquired through mitigation 

for projects that impact desert tortoises. To ensure management of these lands, endowment fees 

are collected for each parcel acquired (Steele and Jones 2006). In addition, under the Southern 

27
 
 

 

 

 

Nevada Public Lands Management Act (see Appendix A: Land Acquisitions, Exchanges, and 

Transfers), approximately 1,500 hectares (3,725 acres) within occupied or suitable desert tortoise 

habitat have been purchased since 2000 through the land acquisition program for 

environmentally sensitive lands (BLM 2007b). 

In 1999, The Wildlands Conservancy facilitated the purchase of nearly 242,810 hectares 

(600,000 acres) under their California Desert Land Acquisition Project. It funded the purchase of 

over 34,425 hectares (85,000 acres) in the Mojave National Preserve, 8,100 hectares (20,000 

acres) in Joshua Tree National Park, and over 85,050 hectares (210,000 acres) in 20 Bureau of 

Land Management wilderness areas and other important areas, including designated critical 

habitat for the desert tortoise. The acquisition of these lands will ensure landscape-level 

conservation into the future and will provide habitat connectivity and reduce the potential for 

fragmentation (The Wildlands Conservancy 2009). 

The Department of the Army purchased approximately 39,285 hectares (97,000 acres) of 

lands formerly owned by the Catellus Development Corporation and fee lands within three cattle 

allotments in the Western Mojave Recovery Unit to partially offset the effects of the National 

Training Center expansion; the Bureau of Land Management subsequently retired these 

allotments on over 129,500 hectares (320,000 acres), the majority of which are within designated 

critical habitat for the desert tortoise (R. Bransfield, U.S. Fish and Wildlife Service, pers. comm. 

2009). 

Several HCPs have been developed for private lands within desert tortoise habitat that 

include provisions for acquisitions and transfers that would meet the objectives of the HCP as 

well as secure conservation lands for tortoises. However, land acquisition can be an expensive, 

time-consuming task. For example, 61 separate actions were necessary to acquire just over 3,760 

hectares (9,300 acres) within the 25,090-hectare (62,000-acre) Red Cliffs Desert Reserve, which 

was established to provide protection for the desert tortoise and its habitat under the 1996 

Washington County HCP in Utah. Approximately 2,995 hectares (7,400 acres) remain to be 

acquired within the present boundaries of the Reserve. The approximate value of the lands 

acquired stands at $87,073,000 (not adjusted for present value) (J. Crisp, BLM, pers. comm. 

2007). 

In southern Nevada, the Clark County Multiple Species Habitat Conservation Plan 

(MSHCP) was completed in 2000. The Clark County MSHCP superseded the Desert 

Conservation Plan, which was prepared in response to the Federal listing of the desert tortoise as 

a threatened species. The MSHCP plan area encompasses a total of 169,160 hectares (418,000 

acres) (all of Clark County and, for the Nevada Department of Transportation, portions of Nye, 

Lincoln, Mineral, and Esmeralda counties, Nevada) (RECON 2000). The underlying purpose of 

the MSHCP is to achieve a balance between the long-term conservation of listed species and 

natural resources that are an important part of the natural heritage of Clark County and the 

economic development of Clark County (USFWS 2000a). As additional mitigation under the 

MSHCP, Clark County purchased a 34,800-hectare (86,000-acre), long-term conservation 

easement (50 years) from Boulder City. 

28
 
 

 

 

 

 

 

Under the Clark County MSHCP, site-specific conservation management strategies were 

required for each of the DWMAs within the county; these include Coyote Springs, Gold Butte, 

Mormon Mesa, and Piute-Eldorado (Clark County 2007a,b,c,d, respectively). The purpose of 

each conservation management strategy is to guide species and habitat management using a 

coordinated, adaptively managed approach. Each strategy identifies management actions, 

protective measures, restoration efforts, public outreach and education, inventory and monitoring 

actions, applied research actions, and impact mitigation measures that will direct conservation of 

tortoises and their habitats. 

Habitat conservation plans are also being developed for other parts of southern Nevada. 

An HCP for the Coyote Springs Valley in Lincoln County includes allowing development of 

8,680 hectares (21,454 acres) over 40 years while setting aside a 5,570-hectare (13,767-acre) 

reserve for the desert tortoise and other sensitive species (ENTRIX et al. 2008). In addition, 

mitigation fees paid by the applicant for the loss of desert tortoise habitat would be used to fund 

management of the reserve and desert tortoise research. The Southeastern Lincoln County HCP 

is in the final planning stages. The plan area totals 720,400 hectares (1,780,140 acres), of which 

311,365 hectares (769,400 acres) is desert tortoise habitat. Approximately 9,090 hectares (20,000 

acres) of the tortoise habitat within the plan area will be developed over a 30-year time frame. 

The focus of this plan is to provide a mechanism to allow orderly growth and development north 

of Mesquite and urban expansion in the Alamo area in Lincoln County (J. Brown, USFWS, pers. 

comm. 2007). The loss of desert tortoise habitat will be mitigated through funding of restoration 

efforts within the Beaver Dam Slope and Mormon Mesa critical habitat units and various 

research and monitoring activities (J. Krueger, USFWS, pers. comm. 2009). In Nye County, 

efforts continue to work with landowners and local governments to develop HCPs for projects 

that may adversely affect desert tortoises in the Pahrump Valley. 

The Coachella Valley MSHCP in Riverside County, California, would establish 

conservation areas and a reserve system for species and natural communities covered under the 

plan, including the desert tortoise. These lands constitute approximately 301,855 hectares 

(745,900 acres) within the 485,620-hectare (1,200,000-acre) plan area boundary. About 206,790 

hectares (511,000 acres) of desert tortoise habitat lies within the areas identified for conservation 

under the Coachella Valley MSHCP, with about 65,150 hectares (161,000 acres) not yet secured 

for these purposes. The conserved lands include the 9,090-hectare (20,000-acre) Coachella 

Valley Preserve that was established in 1986 for Coachella Valley fringe-toed lizard (Uma 

inornata). Over 26,300 hectares (65,000 acres) (12 percent of all habitat and 28 percent of nonFederal land within the plan area) are subject to disturbance under the plan. This constitutes 

about 4,450 hectares (11,000 acres) of what is considered “core” habitat for various species as 

described in the Coachella Valley MSHCP. The plan was completed in 2007 (Coachella Valley 

Association of Governments 2007), and the associated record of decision and biological opinion 

were issued in October 2008 (USFWS 2008). 

The California Desert Conservation Area Plan Amendment for the Coachella Valley 

specifically commits the Bureau of Land Management to conserving at least 99 percent of 

vegetation community types on the lands it administers within the MSHCP reserve system. In the 

portion of the MSHCP area where the Northern and Eastern Colorado Desert Coordinated 

Management Plan applies to federal land, new surface disturbance is cumulatively limited to 1 

29
 
 

 

percent of the federal portion of each critical habitat unit, which is consistent with the other large 

regional plans (Coachella Valley Association of Governments 2007; BLM 2002c). 

Within the region covered by the West Mojave Plan (BLM et al. 2005), a MSHCP is 

being drafted for development on approximately 1,214,000 hectares (3,000,000 acres) of private 

lands. This plan may cover as many as 15 species, including the desert tortoise. The MSHCP is 

still in the planning stages, and the specific goals and objectives have yet to be determined. 

Desert tortoise population monitoring has occurred in association with the Washington 

County HCP and Clark County MSHCP. Sufficient time has not passed to allow for large-scale 

increases of tortoise populations because the reproductive rate of the desert tortoise is slow (see 

Population Trends and Distribution). Continued management and focused monitoring, similar to 

the recovery strategy outlined below, are required to determine whether the HCPs are meeting 

their objectives. 

5. Other Activities 

Over 404,685 hectares (1,000,000 acres) of Mojave Desert vegetation burned in wildfires 

in 2005 and 2006, fueled largely by invasive, non-native grasses. About half of the areas burned 

supports desert tortoise habitat, and if this trend continues, native plant communities and much of 

the diversity of the Mojave Desert ecosystem may eventually be lost. Because of this recent 

devastating fire activity in the Mojave Desert, research scientists, land managers, and agency 

biologists in Arizona, Nevada, and Utah have come together to develop an initiative designed to 

protect intact, functional habitats and restore key areas that have burned. This initiative is a 

collaborative effort among Federal, State, and local jurisdictions and will focus on fire 

management and habitat protection and restoration. 

During the summer of 2005, wildfires burned approximately 36,180 hectares (89,400 

acres) within the Pakoon Basin of the Grand Canyon Parashant National Monument; about 

14,570 hectares (36,000 acres) are located within the Gold Butte-Pakoon critical habitat unit for 

the desert tortoise. As a result, the Arizona Strip District of the Bureau of Land Management 

initiated soil stabilization and revegetation efforts of desert tortoise habitats using a variety of 

treatments, including aerial seed application, mechanical seed incorporation, and grazing 

exclusion (fencing). Rehabilitation objectives and success criteria were developed and control 

efforts for invasive species initiated (USFWS 2006c). The Bureau of Land Management and the 

U.S. Geological Survey in Nevada have also implemented emergency rehabilitation projects 

after wildfires (DeFalco et al. 2007). Restoration efforts in response to wildfires and other land 

disturbances have been long practiced in the Mojave Desert. Because natural plant succession is 

variable over time subsequent to disturbance, land managers and researchers attempt to facilitate 

revegetation of disturbed sites and typically observe mixed results (Ostler et al. 2002; Warren 

and Ostler 2002; Ostler and Hansen 2003; Abella et al. 2007; DeFalco et al. 2007). Site 

treatment, soil amendments, timing of the projects, and the environmental conditions all work to 

influence effectiveness of these efforts. 

To facilitate fire suppression activities, the Fish and Wildlife Service’s California-Nevada 

Operations (now, Pacific Southwest Region) manager issued a memo to the Desert Tortoise 

30
 
 

 

 

 

Management Oversight Group in May 2006 recommending that when feasible, implementing 

suppression techniques that minimize impacts to the habitat is desirable; however, reduction of 

total acreage lost to fire, especially in critical habitat, through the use of mobile attack with 

engines, fireline construction with bulldozers, aerial fire retardant, or other necessary techniques 

should be prioritized. Subsequently, the Mojave Desert Initiative developed more specific 

priorities and guidance for incident commanders. We are actively working with our partners to 

identify the most appropriate locations for firefighting personnel and ways to improve 

communication during incidents. 

We are currently undertaking efforts to reduce human subsidies of food, water, and nest 

sites to the common raven in the California desert. Activities designed to reduce raven predation 

on desert tortoises include reducing trash availability at landfills, removing illegal dumps, 

fencing along highways to reduce road-kills, and removing or modifying nesting and roost sites. 

The program also provides immediate protection to hatchling and juvenile desert tortoises by 

identifying and removing ravens that have preyed or attempted to prey on desert tortoises. The 

environmental assessment we recently released provides a full description of the proposed 

activities (USFWS et al. 2008). 

Bureau of Land Management’s West Mojave Plan includes a series of recommendations 

to reduce raven predation on the desert tortoise including, but not limited to, controlling solid 

and organic wastes and standing water at and outside of sanitary landfills; encouraging livestock 

operators to reduce availability of food sources for ravens; limiting availability of nesting and 

perch substrates, especially in the urban interface; selectively removing problem ravens 

especially within the Desert Tortoise Natural Area, critical habitat units, and head-starting sites; 

conducting additional research on raven life history, behavior, and efficacy of control methods; 

and implementing adaptive management and public education programs (BLM et al. 2005). In 

addition, most of the counties and local jurisdictions, such as San Bernardino and Kern counties, 

have taken considerable steps to improve their operations to minimize windblown litter and bird 

vectors. 

The California Desert Managers Group oversees a program to develop and implement an 

information and education campaign about the desert tortoise to build public support for, and 

involvement in, its recovery. The Clark County (Nevada) Desert Conservation Program also 

includes an education component that targets communities in southern Nevada and extends into 

portions of Arizona. The outreach efforts attempt to inform the public about desert tortoise 

conservation issues through brochures, surveys and feedback, and educational materials for 

schools. 

I. BIOLOGICAL CONSTRAINTS AND NEEDS 

The biological constraints that were identified in the 1994 Recovery Plan (i.e., life history 

and reproductive characteristics and maintenance of genetic and ecological variability) remain 

important considerations in current and future recovery planning and implementation. Desert 

tortoises possess a combination of life history and reproductive characteristics that affect the 

ability of populations to survive external threats. For instance, this long-lived species requires 13 

to 20 years to reach sexual maturity and has low reproductive rates during a long period of 

31
 
 

 

 

 

reproductive potential (Turner et al. 1984; Germano 1994). Also, similar to other turtles, desert 

tortoises experience relatively high mortality early in life. These factors make recovery of the 

desert tortoise more difficult, and one or two good years of reproductive success do not signal 

a trend toward recovery any more than several poor ones signal inevitable extirpation (USFWS 

1994a). Delayed but prolonged reproduction is advantageous where availability of resources is 

unpredictable and juvenile survival rates are highly variable, but even moderate downward 

fluctuations in adult survival rates can result in rapid population declines (Congdon et al. 1993; 

Doak et al. 1994; Wisdom et al. 2000). Thus, high survivorship of adult desert tortoises is 

critical to the species’ persistence, and the slow growth rate of populations can leave them 

susceptible to extirpation events in areas where adult survivorship has been reduced (USFWS 

1994a). 

Another factor integral to desert tortoise recovery is maintaining the genetic variability 

of the species and sufficient ecological heterogeneity within and among populations (Murphy 

et al. 2007; Hagerty and Tracy 2010). This variation is necessary to allow tortoises to adapt to 

changes in the environment over time (USFWS 1994a). Finally, because desert tortoises 

occupy large home ranges, the long-term persistence of extensive, unfragmented habitats is 

essential for the survival of the species (USFWS 1994a). The loss or degradation of these 

habitats to urbanization, habitat conversion from frequent wildfire, or other landscapemodifying activities place the desert tortoise at increased risk of extirpation because the 

tortoise depends on the cover of shrubs and annuals for forage provided by contiguous native 

vegetation communities. 

32
 
 

 

II. RECOVERY PROGRAM
 

A. RECOVERY STRATEGY
 

Recovery of the desert tortoise has been and will continue to be complex and challenging. 

Tortoise populations face a wide range of threats. Desert tortoises require over a decade to reach 

sexual maturity, have reproduction that varies through time, and juveniles have variable but 

low survival rates. Therefore, tortoise populations will be naturally slow to increase in 

response to strategies designed to ameliorate anthropogenic impacts. These life history 

characteristics, combined with reduced populations and extended time periods for recovery of 

desert ecosystems, also make it difficult to assess relative impacts of individual threats. 

The 1994 Recovery Plan described a strategy for recovering the desert tortoise, which 

included the identification of six recovery units, recommendations for a system of Desert 

Wildlife Management Areas (DWMAs) within the recovery units, and development and 

implementation of specific recovery actions focused within the DWMAs. Maintaining high 

survivorship of adult desert tortoises was identified as the key factor in recovery, and because 

the list of threats to the species remains mostly unchanged, the requisite management or 

recovery actions also remain appropriate. We recognize that the most significant challenge in 

the implementation of the 1994 Recovery Plan was not the number or types of actions 

implemented, but rather the coordination, description, documentation, and evaluation of 

implementation of the actions (Tracy et al., 2004). As a result, the revised strategy described 

herein builds upon the foundation laid by the 1994 Recovery Plan by emphasizing partnerships 

to direct and maintain focus on implementing recovery actions and a system to track 

implementation and effectiveness of recovery actions. Strategic elements within a multi-faceted 

approach designed to improve the 1994 Recovery Plan are: 

1.	 Develop, support, and build partnerships to facilitate recovery; 

2.	 Protect existing populations and habitat, instituting habitat restoration where necessary; 

3.	 Augment depleted populations in a strategic manner; 

4.	 Monitor progress toward recovery; 

5.	 Conduct applied research and modeling in support of recovery efforts within a strategic 

framework; and 

6.	 Implement a formal adaptive management program through which information gained 

while implementing the above strategic elements is used to revise and improve the 

recovery plan and recommend management actions on a regular basis. 

Each strategic element is described more fully below, but the recovery program does not provide 

a “cookbook” of prescriptions that will ensure recovery of the desert tortoise; therefore, the 

actions proposed do not constitute an exhaustive list. Instead, this program establishes a process 

by which recovery can be achieved. 

33
 
 

 

 

1. Strategic Element 1: Develop, Support, and Build Partnerships to Facilitate Recovery 

Implementing a recovery plan for a species with a wide distribution and facing such 

complex challenges requires many cooperators and diverse partnerships. As noted above, we 

believe the most significant challenge in the implementation of the 1994 Recovery Plan was not 

necessarily the number or types of actions implemented, but rather the coordination, description, 

documentation, and evaluation of implementation of the actions. The revised recovery plan 

emphasizes partnering across jurisdictional boundaries through standing Recovery 

Implementation Teams to maintain focus on implementing and tracking recovery actions. 

Therefore, this element relies on the successful establishment of regional, long-term Recovery 

Implementation Teams comprised of land managers, stakeholders, and scientists that will work 

together to develop recovery action plans, prioritize recovery actions on the ground, secure 

necessary resources, and compile results into a range-wide database and decision support system 

that can be applied at the local level (Element 6). Activities of implementation teams at the local 

level will be coordinated with landscape and regional-level alternative-energy coordination 

efforts. The Recovery Implementation Teams will also facilitate education and outreach 

activities to build support for, understanding of, and compliance with the recovery program. 

Organization of Recovery Implementation Teams generally will be based on recovery units, but 

it may vary depending on logistical practicalities among the representatives. Our Desert Tortoise 

Recovery Office will serve as the focal point for coordinating Recovery Implementation Teams 

in cooperation with the Desert Tortoise Management Oversight Group. 

2. Strategic Element 2: Protect Existing Populations and Habitat 

Since 1994, desert tortoise habitat has continued to be lost or degraded (e.g., by 

urbanization, fire, invasive plants; see Appendix A), keeping tortoise populations in an insecure 

state, including those that may not be currently in decline. As a result, protecting existing 

populations and habitat is extremely important. The recommended actions in the 1994 Recovery 

Plan formed a logical basis for recovery (GAO 2002), and little information since 1994 

contradicts these recommendations (Boarman and Kristan 2006). In fact, due to slow growth 

rates of individuals and populations, insufficient time has elapsed over which detectable 

increases in desert tortoise populations could be expected. In any case, applying uniform, highly 

restrictive regulations across the entire Mojave population is not feasible, even if we knew the 

precise mechanisms affecting population declines at each site. Therefore, aggressive 

management as generally recommended in the 1994 Recovery Plan needs to be applied within 

existing tortoise conservation areas (Box 2) or 

other important areas identified by Recovery 

Implementation Teams (e.g., important genetic 

linkages identified by Hagerty et al. 2010) to 

ensure that populations remain distributed 

throughout the species’ range (Element 1). 

Tortoise conservation areas capture the 

diversity of the Mojave population of the desert 

tortoise within each recovery unit, conserving 

the genetic breadth of the species, providing a 

Box 2. Tortoise conservation areas, 

collectively depicted in Figure 2, include desert 

tortoise habitat within critical habitat, Desert 

Wildlife Management Areas, Areas of Critical 

Environmental Concern, Grand CanyonParashant National Monument, Desert National 

Wildlife Refuge, National Park Service lands, 

Red Cliffs Desert Reserve, and other 

conservation areas or easements managed for 

desert tortoises. 

34
 
 

 

 

 

 

 

margin of safety for the species to withstand catastrophic events, and providing potential 

opportunities for continued evolution and adaptive change (Mace and Purvis 2008). Especially 

given uncertainties related to the effects of climate change on desert tortoise populations and 

distribution, we consider tortoise conservation areas to be the minimum baseline within which to 

focus our recovery efforts. Much of the land contained within existing tortoise conservation areas 

is managed under multiple-use directives. It should also be recognized that activities occurring 

on lands beyond the boundaries of existing tortoise conservation areas can affect tortoise 

populations, important linkages between tortoise conservation areas, and the effectiveness of 

conservation actions occurring within the conservation area boundaries. Agencies should work 

within the context of their respective land use plans to determine how to effectively implement 

recovery actions contained within this plan. 

Recovery Implementation Teams should use the decision support system (Element 6) to 

guide management both inside and outside tortoise conservation areas, according to different 

opportunities or constraints within different areas and jurisdictions. While recovery efforts may 

be prioritized within existing desert tortoise conservation areas, populations, habitats, and actions 

outside of these areas may also contribute to (or hamper) recovery of the species, and their 

importance is in no way diminished (other local, State, or Federal regulations may apply to 

actions potentially impacting tortoises and habitat outside tortoise conservation areas). For 

example, Department of Defense lands are subject to more dramatic changes in management or 

use than other Federal lands depending on the changing national security situation. However, the 

value of military lands to conservation has long been recognized (Stein et al. 2008). Similarly, 

wilderness designation on public lands entails restrictions on the types of activities that may be 

conducted there, precluding or otherwise limiting several forms of active management activities. 

Military lands, wilderness areas, and other land designations with conservation objectives 

include a great deal of desert tortoise habitat outside of and contiguous with tortoise conservation 

areas (see Figure 3), making them valuable components of the recovery landscape. In addition to 

habitat management recommendations, specific recommendations for managing desert tortoise 

populations relative to disease have been recommended by the Science Advisory Committee 

(Hudson et al. 2009) and are incorporated herein. 

3. Strategic Element 3: Augment Depleted Populations through a Strategic Program 

Due to appreciable declines of tortoise populations across the range, in conjunction with 

multi-faceted interacting threats, we see the need to introduce population augmentation as a tool 

for conservation of the desert tortoise. While tortoises seem to respond well to translocation 

itself, unaddressed threats which remain on the landscape and affect all tortoises, regardless of 

origin, may make the goal of population growth challenging to realize. Augmentation will be 

approached experimentally, in terms of both the continued development and evaluation of 

techniques and through the use of augmentation to help assess specific threats and recovery 

actions (Tracy et al. 2004; Armstrong and Seddon 2007). Population augmentation in 

conjunction with threats management and restoration activities (Element 2), as well as research 

(Element 5) designed to investigate the effectiveness of these actions is a means to gain insights 

into causes of declines and to increase the rate at which depleted populations could be revived. It 

is important to realize that if the causes of tortoise population declines are not addressed, simply 

increasing population numbers in the wild through augmentation will not result in recovery. 

35
 
 

 

 

 

 

 

 

Augmentation will not be a long-term strategy for conservation of the desert tortoise, but rather 

an intermediate strategy aimed at increasing populations more rapidly than possible through 

natural processes. 

An augmentation strategy will be developed by the Desert Tortoise Recovery Office, 

with advice and input from the Science Advisory Committee, topical experts, and representatives 

from pertinent regulatory and land management agencies. The strategy will include specific 

guidance on head-starting and translocation, which are fundamental aspects of the augmentation 

program, and on the need to consider a multitude of factors that include genetics and disease. 

Locally depleted or extirpated populations, particularly within desert tortoise conservation areas, 

will be identified. Translocation and head-starting (described below) will be used to augment (or 

re-establish) these populations in conjunction with elevated threat management and/or habitat 

restoration (Element 2) or directed research on the factors affecting success of the augmentation 

strategy (Element 5). 

Head-starting is the raising of young in captivity to allow them to reach sizes at which 

they are less vulnerable to certain threats, such as predation by ravens, before translocation to the 

wild. Head-starting has proven helpful in the conservation of other tortoise species, most notably 

in the Galapagos Islands where predators had greatly reduced juvenile survival in already 

extremely depressed populations (Caporaso 1991). On the other hand, head-starting and release 

of young desert tortoises may be relatively inefficient in meeting population growth goals 

compared to addressing other life stages. Nevertheless, this tool may be valuable in research 

programs designed to evaluate effectiveness of management actions or to assess the presence of 

threats by providing statistically suitable numbers of study animals for analysis (Tracy et al. 

2004; Reed et al. 2009). Currently, experiments in head-starting desert tortoises are taking place 

at several locations in California. Research at the National Training Center’s Fort Irwin Study 

Sites (FISS 1 and FISS 2), Edwards Air Force Base, and the Marine Corps Air Ground Combat 

Center at Twentynine Palms has laid a foundation on which to build (see Morafka et al. 1997; 

Dickson et al. 2006; Henen et al. 2007; Nagy 2008), and facilities at these sites will likely be 

important in a collaborative head-starting effort. Head-starting facilities are lacking in Arizona, 

Nevada, and Utah, but proposals are being developed to use the Desert Tortoise Conservation 

Center in Las Vegas as the site for new facilities servicing surrounding recovery units. The 

Desert Tortoise Recovery Office will coordinate development of guidelines and protocols for the 

head-starting of desert tortoises range-wide in accordance with our controlled propagation policy 

(USFWS 2000b). 

Augmentation also involves translocation of tortoises to pre-selected sites. The efficacy 

of translocation itself has been questioned over the years. Early studies did not provide sufficient 

evidence to support or refute translocation as a conservation strategy (see Berry 1974; Cook et 

al. 1978; Cook 1983). More recent studies have shown initial success in translocation to be high 

(Field et al. 2000; Nussear 2004; Field et al. 2007). Predators, especially during drought, have 

been shown to negatively impact tortoise populations across their range. Despite data to the 

contrary (Nussear 2004; Field et al. 2007; Esque et al. 2010), many critics have been quick to 

deem translocation an unsuitable conservation tool for desert tortoises because of the impacts 

predators may have. Because desert tortoises do appear to be suitable candidates for 

translocation, instances where predators have impacted translocated tortoises do not indicate that 

36
 
 

 

 

translocation should be abandoned but rather emphasize the need to address threats which 

impact all tortoises regardless of origin. As noted above, the Desert Tortoise Recovery Office, 

with advice from the Science Advisory Committee, topical experts, and representatives from 

pertinent regulatory and land management agencies, will develop translocation guidelines and 

protocols to be implemented range-wide, taking into account guidelines for addressing disease 

issues in translocation developed by the Science Advisory Committee (Hudson et al. 2009). 

4. Strategic Element 4: Monitor Progress toward Recovery 

Monitoring is a fundamental requirement for adaptive management (Element 6). It is one 

process by which information is updated and the success of recovery actions can be evaluated. 

This information can be used adaptively, to refine management during the course of recovery, to 

evaluate progress toward achieving recovery criteria, and to help evaluate whether delisting the 

species may be appropriate. While the 1994 Recovery Plan focused exclusively on monitoring 

desert tortoise populations, a multi-dimensional monitoring program is necessary to assess the 

status of tortoise populations, habitat, and threats (Tracy et al. 2004). Monitoring activities 

described in this plan are therefore tied directly to individual recovery criteria related to the 

status of populations, habitat, and threats. Recovery progress will be measured by monitoring 

trends in tortoise distribution, abundance, and population growth. The quantity and quality of 

habitat and the distribution of threats across the landscape also will require monitoring over time. 

The protracted life history and longevity of the desert tortoise, as well as the long time 

frame necessary for habitat restoration in the desert, require long-term monitoring to measure 

success. However, evaluations at 5-year intervals will identify potential trends, will feed into 5­

year status reviews, and will provide an opportunity to adjust management based on any 

observed trends. Effectiveness monitoring of specific management actions is also needed 

(Boarman and Kristan 2006) and is discussed below as applied research (Element 5). It is also 

important that monitoring be conducted as an integrated effort, coordinated through the Desert 

Tortoise Recovery Office, to ensure that efficiency of the recovery program and review of its 

progress are maximized. Consistent agency reporting through the decision support system 

(Elements 1 and 6) will help identify correlations between management efforts or threat 

reduction and tortoise populations, which can signify successful management. 

5. Strategic Element 5: Conduct Applied Research and Modeling in Support of Recovery 

Efforts within a Strategic Framework 

In this plan we update the research recommendations from the 1994 Recovery Plan with 

new priorities. Although scientists have studied desert tortoises for over three decades, many 

important questions remain unanswered. In particular, we have a relatively poor understanding of 

how some human activities interact with ecological factors to affect tortoise populations and 

what threat-abatement measures might counteract those effects. As mentioned above, the desert 

tortoise’s life history makes it difficult to tease apart relative impacts of individual threats 

(although some impacts, such as widespread habitat loss, are fairly straightforward in that, if 

unchecked, they eliminate populations completely). As a result, studying most individual 

threats/management actions in isolation from other possible threats/actions is impractical. 

However, such topics should be studied experimentally whenever possible. Given the difficulties 

37
 
 

 

 

 

surrounding applied ecological research on the desert tortoise, ecological models should be codeveloped with management actions to make and test predictions about tortoise population 

responses to threats or management actions. These models then can be modified as new 

information becomes available (Element 6). Finally, similar to the coordination required of the 

monitoring program (Element 4), research should be coordinated through the Desert Tortoise 

Recovery Office (with advice from the Science Advisory Committee and input from the 

Recovery Implementation Teams) to ensure that principles of strategic habitat conservation are 

used. 

6. Strategic Element 6: Implement a Formal Adaptive Management Program 

Integrating the results of recovery actions into a formal adaptive management program is 

critical to recovering the desert tortoise and serves as the foundation of an effective recovery 

plan if successfully implemented. Even though the 1994 Recovery Plan called for regular 

updates based on new information, a formal process for accomplishing this task was not 

established. Using research and monitoring to revise management efforts on an ad hoc basis is 

inefficient and has contributed to slow progress in the recovery of desert tortoise since 1994. The 

Department of Interior technical guide on adaptive management provides an operating definition 

adopted from the National Research Council: 

Adaptive management [is a decision process that] promotes flexible decision making that 

can be adjusted in the face of uncertainties as outcomes from management actions and 

other events become better understood. Careful monitoring of these outcomes both 

advances scientific understanding and helps adjust policies or operations as part of an 

iterative learning process. Adaptive management also recognizes the importance of 

natural variability in contributing to ecological resilience and productivity. It is not a 

‘trial and error’ process, but rather emphasizes learning while doing. Adaptive 

management does not represent an end in itself, but rather a means to more effective 

decisions and enhanced benefits. Its true measure is in how well it helps meet 

environmental, social, and economic goals, increases scientific knowledge, and reduces 

tensions among stakeholders (Williams et al. 2007). 

Adaptive management is a structured approach (implementation-monitoring-evaluationadjustment) that emphasizes accountability and explicitness in decision making (Williams et al. 

2007). The decision analysis process requires clear objectives (e.g., related to desert tortoise 

populations or habitat), a set of potential actions, and some expectation of the consequences of 

each possible action relative to the objectives, described through conceptual models (Lyons et al. 

2008). Implementing a formal structured decision-making/adaptive management program, 

integrated among agencies as much as possible, will enable us to continually update and improve 

models and the accuracy of predictions regarding the effects of management actions. 

Expectations of adaptive management should recognize, however, that the life history of desert 

tortoises and the complex interactions among tortoise populations, habitat, and threats will 

typically result in extended learning cycles over which improvements in understanding and 

management will occur. Therefore, we should not expect rapid cycles of implementationmonitoring-evaluation-adjustment. In many cases, intermediate or indirect benchmarks will be 

needed to measure progress. 

38
 
 

 

 

 

Given the complexities of desert tortoise recovery described above, fully active adaptive 

management that vigorously pursues learning through management under structured 

experimental designs (Williams et al. 2007) will not always be possible. In these cases, passive 

adaptive management can be used to focus monitoring on resource status and other system 

attributes (Schwarz 1998; Williams et al. 2007). An assessment of the monitoring results can 

then be applied to on-the-ground management actions as we continue to learn and better 

understand the recovery needs of the species. In either case, the use of structured decision 

making and a decision support system will facilitate the adaptive management process (Ralls and 

Starfield 1995; Rauscher 1999; Williams et al. 2007). A decision support system is an interactive 

system that computes the output of a set of models (e.g., effects of a threat on a tortoise 

population) based on underlying databases (e.g., the spatial extent of the threat, tortoise 

population, and management actions). In fact, a decision support system will provide a vehicle 

for implementing adaptive management (Starfield and Bleloch 1991). The recovery decision 

support system recommended in this plan will incorporate a range-wide, geospatial database of 

current management activities, threats, and tortoise populations, providing managers a better 

framework for recognizing and implementing successful recovery actions. Through the use of 

conceptual models and research and monitoring results (Element 5), the decision support system 

will provide an explicit, well-documented process for making decisions. 

Importantly, adaptive management requires an ongoing commitment of executive 

leadership, including management involvement and funding throughout the life of the recovery 

effort (Williams et al. 2007). It will also require effective communication among the various 

groups. Therefore, the Desert Tortoise Recovery Office will serve as the focal point for 

coordinating among agencies and researchers, through Recovery Implementation Teams 

(Element 1), to maintain and improve the decision support system. Finally, the Desert Tortoise 

Recovery Office will continue to coordinate with the Science Advisory Committee, which serves 

in an advisory role to the Fish and Wildife Service, to the interagency Desert Tortoise 

Management Oversight Group, and to the Recovery Implementation Teams to ensure that 

recovery action plans, recovery action effectiveness, research and monitoring, and recovery plan 

revision meet rigorous scientific standards. 

7. Synthesis and Implementation 

The different strategic elements of the Desert Tortoise Recovery Program fit within an 

adaptive framework (Figure 4). For example, the Land Management and Population 

Augmentation strategic elements fit within the design and implementation phases of adaptive 

management while the strategic elements of Monitoring and Research naturally fit within the 

monitoring phase of adaptive management. Partnerships are paramount throughout the adaptive 

management cycle, while the Decision Support System itself utilizes an adaptive management 

process. Regional Recovery Implementation Teams will include a member of the Desert Tortoise 

Recovery Office to provide guidance and coordination to land/wildlife managers and 

stakeholders on the teams, which will be responsible for developing step-down recovery action 

plans and implementing those actions on the ground. The Recovery Implementation Teams may 

leverage existing management partnerships such as the California Desert Managers Group or the 

Southern Nevada Agency Partnership. The Management Oversight Group will review the 

39
 
 

 

recovery-action plans, and the Recovery Implementation Teams will report to the Management 

Oversight Group on an annual basis to review progress. The Desert Tortoise Recovery Office 

will provide linkages between the Management Oversight Group, Recovery Implementation 

Teams, and Science Advisory Committee. 

Figure 4. Diagram of the adaptive management process (from Williams et al. 2007). 

Implementation of recovery actions within each strategic element will result in more 

visible progress toward recovery of the desert tortoise. Likewise, mitigation of activities harmful 

to desert tortoises should draw on the suite of opportunities provided by these elements, with the 

flexibility to apply an action most appropriate to the situation. Communication between Fish and 

Wildlife field offices, the Desert Tortoise Recovery Office, Recovery Implementation Teams, 

and other agency staff through section 7 and 10 activities will ensure that these activities are 

consistent with the Recovery Implementation Teams’ recovery-action plans and this recovery 

program. 

40
 
 

 

 

 

 

 

 

B. RECOVERY UNITS 

1. Background and Assessment of Recovery Units 

The 1994 Recovery Plan identified six Box 3. Recovery units for the desert tortoise 

recovery units (Box 3): Upper Virgin River, are special units that are geographically 

Northeastern Mojave, Eastern Mojave, Eastern identifiable and are essential to the recovery 

Colorado, Northern Colorado, and Western of the entire listed population, i.e., recovery 

Mojave (Fig units are individually necessary to conserve ure 5). When the recovery units were the genetic, behavioral, morphological, and initially delineated, genetic, morphological, ecological diversity necessary for long-term ecological, and behavioral differences were sustainability of the entire listed population. identified at a species-wide scale, and finer Recovery criteria (described below) must be differentiation with the Mojave population was evaluated for each individual recovery unit acknowledged (e.g., Woodbury and Hardy 1948; for the entire listed population of the desert Burge 1977; Jennings 1985; Turner et al. 1986; tortoise to be considered for delisting. 

Weinstein and Berry 1987; Lamb et al. 1989; 

Glenn et al. 1990; Germano 1993; Lamb and Recovery units collectively cover the entire 

Lydehard 1994; USFWS 1994a). Since 1994, we range of the species. Critical habitat and 

have gained greater insight into patterns of both other management designations included 

within “tortoise conservation areas” are focal ecological and genetic variation within the 

Mojave desert tortoise population. Our approach areas for recovery within each recovery unit. 

As a result, evaluation of recovery criteria is to examine the 1994 recovery unit boundaries for each recovery unit and implementation of in light of new information with the goal of most recovery actions will be focused within defining recovery units which balance both tortoise conservation areas as defined in Box 

distinctiveness and variability within the Mojave 2 and Figure 2. desert tortoise. Conserving meaningful 

distinctiveness through the recognition of appropriate recovery units within the species ensures 

that local adaptation as well as critical genetic diversity are maintained. Conversely, splitting a 

species into inappropriate subunits for conservation can result in artificial fragmentation and 

further loss of variability, increase extinction risk, and compromise future resiliency (Mace and 

Purvis 2008). Thus, appropriately defining conservation units which balance both distinctiveness 

and variability within the species is important for recovery. 

(a) Ecological variation. The Mojave Desert is a transitional vegetation type wedged 

between the Great Basin and Sonoran deserts (Rowlands et al. 1982; Turner 1982; MacMahon 

1992:47). Previously described subdivisions have broad, indistinct boundaries due to gradational 

transitions among subregions and with surrounding areas (Webb et al. 2009b). The Mojave 

Desert straddles the Great Basin Section of the Basin and Range Province to the north and the 

Sonoran Desert Section to the south. These two physiographic (i.e., related to the physical 

geography of the landscape) sections meet just south of Las Vegas, Nevada, and the UtahArizona border. However, the biological boundaries between Great Basin and Sonoran desert 

affinities are farther north, near Beatty, Nevada, and St. George, Utah, respectively (MacMahon 

1992:47). The lack of coincidence of the physiographic and biological subdivisions of the 

Mojave Desert demonstrates the Mojave Desert’s transitional position. 

41
 
 

 

 

 

Figure 5. Recovery units as delineated in the 1994 Recovery Plan. Recovery units encompass the entire 

range of the listed species, so the only “hard” peripheral edge is along the Colorado River; the northern, 

western, and southern boundaries are defined by the actual distributional limits of the desert tortoise. 

The Colorado Desert (a subdivision of the Sonoran Desert) is both in the southeasternmost part of California and in the Mojave population of the desert tortoise’s range; it is 

recognized as a distinct biome with a different climate than the Mojave Desert (Brown 1982). 

However, the separation of the Mojave Desert along its boundary with Sonoran (Colorado) 

desert scrub is commonly blurred because distinct coincidental breaks in indicator species’ 

ranges are lacking (Turner 1982). In addition, climate variables vary linearly across the range of 

the desert tortoise (e.g., winter:summer rainfall; Figure 6; Table 3). The central Mojave is 

topographically and climatically transitional between the southwestern and eastern Mojave 

desert. The south-central Mojave is a transitional region to the Colorado/Sonoran Desert, and the 

southern half of this region is similar climatically and floristically to the eastern Mojave. Many 

42
 
 

 

 

 

 

 

 

Figure 6. Ratio of rainfall in winter compared to summer in the Mojave Desert. Graph reprinted from 

Tracy et al. (2004). 

of the differences in vegetation can be explained by differences in climate (Rowlands 1995). 

Given the broad or incongruent transitions between identified subdivisions of the Mojave and 

Sonoran deserts, and continuous tortoise habitat and distribution within these transitions, we 

minimize the use of these areas in identifying recovery units where other supporting data are 

absent. 

Modeling desert tortoise habitat relates occurrence information to spatial data on plant 

communities, soils, topography, and geology. A recent habitat model uses desert tortoise 

occurrence data from sources spanning more than 80 years, especially including data from the 

2001 to 2005 range-wide monitoring surveys (USFWS 2006) and 16 environmental variables 

such as precipitation, geology, vegetation, and slope (Figure 1) (Nussear et al. 2009). This model 

elucidates areas of continuous habitat, as well as imporant topographic barriers, both of which 

we use in defining recovery units. 

(b) Genetic variation. The U.S. Fish and Wildlife Service (USFWS 1994a) and Tracy et 

al. (2004) acknowledged that additional genetic analysis would be valuable to delineate recovery 

units. Two population genetic analyses have been recently completed; the authors of each 

suggest different recovery unit delineations (Murphy et al. 2007; Hagerty and Tracy 2010). As 

we considered how to delineate recovery units in this plan, we were cognizant that modern 

molecular genetic tools increasingly make it possible to find genetic differences between 

population subunits, whether or not those differences are biologically significant (Hedrick 1999). 

Such differences potentially confound the goal of conserving the evolutionary potential of a 

species; they can over-emphasize differences between population subunits and lead to separately 

conserving any subunit that shows evidence of genetic differentiation. Management based on 

dividing a species into more subunits than is appropriate can result in loss of variability within 

the species that is vital for recovery (i.e., artificially segregating population segments needed to 

maintain the inherent variation within a larger whole; Mace and Purvis 2008). 

43
 
 

 

 

 

 

 

All recent genetic studies of the desert tortoise have suggested that its population 

structure is characterized by isolation-by-distance (Britten et al. 1997; Edwards et al. 2004a; 

Murphy et al. 2007; Hagerty and Tracy 2010). That is, populations at the farthest extremes of the 

distribution are the most differentiated, but a gradient of genetic differentiation occurs between 

those populations, across the range of the species. This genetic gradient is similar to the 

ecological gradient across the Mojave and Colorado deserts. 

Recent genetic work also suggests that, historically, levels of gene flow among 

subpopulations were likely high, corresponding to high levels of connectivity among habitat 

types (Murphy et al. 2007; Hagerty 2008; Hagerty and Tracy 2010; Hagerty et al. 2010). The 

capability for long-distance dispersal (Berry 1986; Edwards et al. 2004b), combined with 

longevity and opportunities to reproduce annually throughout adulthood, indicates high potential 

for gene exchange outside of local areas. Free genetic exchange throughout the distribution will 

be constrained, however, by the large range of the species given the relatively much smaller 

home range size and dispersal ability of individuals (see Allendorf and Luikart 2007:209). 

Topographic features (e.g., mountain ranges) and other potential barriers (e.g., impassable 

habitat types, extreme climate conditions) can structure regional populations and lead to variable 

exchange of migrants among populations, allowing populations to differentiate over time by 

means of genetic drift and natural selection. 

Based on the relatively continuous distribution of habitat occupied by the Mojave 

population of the desert tortoise, especially relative to the more fragmented habitat occupied by 

the Sonoran population (Figure 1; see also Germano et al. 1994), genetic differentiation within 

the Mojave population is generally consistent with isolation by distance in a continuousdistribution model of gene flow. The continuous-distribution model of gene flow describes a 

situation in which populations of a particular neighborhood size could be identified anywhere 

(such as the sample sites of Murphy et al. 2007), and individuals inside those neighborhoods 

would represent a panmictic (randomly mating) group (Allendorf and Luikart 2007:209-211). To 

describe genetic relationships within species, particularly boundaries between divergent units, 

methods require analysis of many individuals sampled across relatively evenly spaced locations 

to avoid wrongly inferring genetic discontinuities between disjunct sampling locations (Pritchard 

et al. 2000; Allendorf and Luikart 2007:400; see also criticism of sampling from discrete study 

plots established for other purposes in Berry et al. [2002]). An assessment of gene flow among 

subunits of the Mojave population revealed broad patterns of migration interrupted by major 

topographic barriers (Hagerty et al. 2010). The apparent isolation-by-distance and pattern of 

gene flow among desert tortoise populations leads us to use genetic information to validate or 

reinforce other ecological or topographic boundaries, rather than as the primary means of 

identifying recovery units. 

2. Revised Recovery Units 

Given the generally continuous variation in genetic structure and biomes across the 

Mojave desert tortoise’s range, our approach in delineating revised recovery units stresses 

identification of geographic discontinuities or barriers that coincide with any observed variation 

among tortoise populations. Several potential barriers are evident from topographic maps, the 

U.S. Geological Survey habitat model (Figure 1), and landscape genetic analyses (Hagerty et al. 

44
 
 

 

 

 

 

 

 

 

 

 

 

 

2010). We used differences in genetic, ecological, and physiological characteristics to help 

highlight boundaries or other differences between units. In doing this, we considered 

demographic, ecological, and behavioral considerations to be of greater importance than genetic 

issues alone, as have been suggested by researchers providing recommendations on the 

formulation of conservation plans for threatened or endangered species (Avise 2004:486-487; 

Mace and Purvis 2008). 

With the aid of modern GIS tools we are able to map boundaries of each recovery unit 

(Figure 7) much more precisely than in 1994, although as indicated above, transitions between 

recovery units are not always as precise on the ground as depicted by lines on a map. We have 

reduced the number of recovery units from six to five and have changed some boundaries of the 

1994 recovery units, as described and justified below. Note that we drew the peripheral 

boundaries depicted in Figure 7, other than the Colorado River, with the intention of simply 

encapsulating the entirety of the desert tortoise’s current range, not to precisely circumscribe 

current desert tortoise habitat or populations (Box 3). 

Descriptions of vegetation communities and complexes as well as related desert tortoise 

ecology are as generally described by Rowlands et al. (1982) and USFWS (1994a) except where 

otherwise noted. Finally, we note that variation in genetics, behavior, morphology, ecology, or 

other evidence within recovery units emphasizes the need, when evaluating management actions 

(particularly head-starting and translocation), to consider whether environmental conditions or 

habitat-type differences have been different for many generations. If so, this could lead to 

adaptations that are important for the long-term persistence of the species even in the face of 

high gene flow (Allendorf and Luikart 2007:415; Murphy et al. 2007). The recovery criteria 

(described in the next section) emphasize conserving tortoise populations and habitat within each 

recovery unit (Box 3), thus conserving the diversity present within each recovery unit. 

Even though the 1994 Recovery Plan described the initial recovery units as “distinct 

population segments” (DPSs), recovery units should not be confused with DPSs. Designation of 

DPSs can only be done through a formal rule-making process; they cannot be designated in 

recovery plans. Policy enacted following publication of the 1994 Recovery Plan states that 

vertebrate populations that are “discrete” and “significant” and formally designated as DPSs can 

be considered for listing or delisting (USFWS 1996). While the listed Mojave population does 

meet the DPS criteria, individual subunits do not qualify as DPSs under the 1996 policy 

(USFWS 2010). As described above, (historically) occupied habitat and genetic differentiation 

across the Mojave DPS are relatively continuously distributed, and variation in other 

characteristics are likely related to the transitional nature of, or environmental gradations 

between, subdivisions of the Mojave and Colorado deserts. These factors disqualify subunits of 

the Mojave DPS according to the discreteness criterion of the policy. As a result, under current 

policy, status changes (i.e., uplisting or delisting) may only be applied to the entire Mojave DPS 

based on evaluation of the recovery criteria and analysis of the five listing factors. 

(a) Upper Virgin River Recovery Unit. This recovery unit is equivalent to the original 

Upper Virgin River Recovery Unit in the 1994 Recovery Plan (USFWS 1994a) and encompasses 

all desert tortoise habitat in Washington County, Utah, east of the Beaver Dam Mountains 

(Figure 8). 

45
 
 

 

 

 

 

 

Figure 7. Revised recovery units for the Mojave population of the desert tortoise. Recovery units 

encompass the entire range of the listed species, so the only “hard” peripheral edge is along the Colorado 

River; the northern, western, and southern boundaries are defined by the actual distributional limits of the 

desert tortoise. 

Unique habitat characteristics and tortoise behavior in this region justify separating the 

most northern extreme of the tortoise’s range, east of the Beaver Dam Mountains, into a separate 

recovery unit (Figure 8). The tortoise population in the area of St. George, Utah, is at the extreme 

northeastern edge of the species’ range and experiences long, cold winters (about 100 freezing 

days), as well as mild summers during which the tortoises are continually active (Table 3). Here 

the animals live in a complex topography consisting of canyons, mesas, sand dunes, and 

sandstone outcrops where the vegetation is a transitional mixture of sagebrush (Artemisia spp.) 

scrub, creosote bush scrub, blackbrush scrub, and a psammophytic (sandy-soil) community. 

Desert tortoises often use sandstone and lava caves instead of burrows, travel to sand dunes for 

egg laying, and use still other habitats for foraging. 

46
 
 

 

 

 

 

Figure 8. Upper Virgin River Recovery Unit. Modeled tortoise habitat depicted directly south of the Red 

Cliffs Reserve and extending into Arizona has either been lost to urbanization or is not known to have 

ever been occupied (Bury et al. 1994). DWMA = Desert Wildlife Management Area; ACEC = Areas of 

Critical Environmental Concern. 

Recent DNA microsatellite1 evidence (Hagerty and Tracy 2010) suggests that there is 

little genetic differentiation between the Upper Virgin River and the neighboring recovery unit, 

which supports findings from allozyme (protein) and mitochondrial DNA (mtDNA ) markers 

(Lamb et al. 1989; Britten et al. 1997). Although assignment tests correctly placed 95 percent of 

individuals in the Upper Virgin River Recovery Unit (Murphy et al. 2007), samples from nearby 

populations west of the Beaver Dam Mountains were not included in the study. 

1 A variety of genetic tools are available to assess genetic variation or genetic structure in organisms. These tools are 

often referred to as “genetic markers.” Allozymes are proteins which are used as genetic markers because DNA 

contains information that is used by cells to build protein. Molecular techniques, such as microsatellites and 

mtDNA, allow biologists to examine variation in DNA directly, rather than looking at the product derived from 

DNA (i.e., protein). It is important to be aware of which genetic marker has been used because different markers 

have different characteristics, and these characteristics influence how genetic data are best and most reliably 

interpreted (described in detail in Parker et al. 1988 and Avise 2004). 

47
 
 

 

 

 

 

 

 

 

The recovery unit includes the Upper Virgin River critical habitat unit and Washington 

County’s Red Cliffs Desert Reserve. Modeled tortoise habitat depicted directly south of the Red 

Cliffs Reserve and extending into Arizona has either been lost to urbanization or is not known to 

have ever been occupied (Bury et al. 1994). 

(b) Northeastern Mojave Recovery Unit. The Northeastern Mojave Recovery Unit is 

similar to the original Northeastern Mojave Recovery Unit (USFWS 1994a), extending into 

extreme southwestern Utah and northwestern Arizona, but excluding portions south of Las 

Vegas (Figure 9). The east end of the unit extends south from the Beaver Dam Mountains, across 

the north end of the Virgin Mountains, down to the Colorado River. From the Colorado River at 

Las Vegas Bay, the southern boundary extends west generally along Las Vegas Wash through 

the city of Las Vegas to the Spring Mountains. From here, the western boundary extends north 

up the Sheep Mountains. 

Recent DNA microsatellite data indicate that this unit is genetically similar to the Upper 

Virgin River Recovery Unit, but the Northeastern Mojave Recovery Unit does contain distinct 

microsatellite differences compared to the remainder of the range (Hagerty and Tracy 2010). The 

Sheep Mountains down to the Spring Mountains act as a near barrier for the western portion of 

this unit. Some variation may occur to the south and west from the Mormon Mesa, but genetic 

breaks appear to be ambiguous relative to at least semi-permeable topographic barriers to gene 

flow, such as the Muddy Mountains. An allozyme cluster at one locus from populations in the 

Mormon Mesa critical habitat unit overlaps another cluster identified from populations in Piute 

Valley in the Eastern Mojave Recovery Unit (Britten et al. 1997). A distinct shell phenotype also 

occurs in the Beaver Dam Slope region (USFWS 1994a; Britten et al. 1997), but these tortoises 

are not genetically isolated from adjacent populations within the recovery unit (Bury et al. 1994). 

Desert tortoises in this recovery unit are generally found in creosote bush scrub 

communities of flats, valley bottoms, alluvial fans, and bajadas, but they occasionally use other 

habitats such as rocky slopes and blackbrush scrub. Desert tortoises are often active in late 

summer and early fall, in addition to spring, reflecting the fact that this region receives up to 

about 40 percent of its annual rainfall in summer (Table 3) and supports two distinct annual 

floras on which tortoises can feed. Average daily winter temperatures usually fluctuate above 

freezing, and summer temperatures are typically a few degrees cooler than in the western Mojave 

and Colorado deserts. Two or more desert tortoises often den together in caliche caves in bajadas 

and washes or caves in sandstone rock outcrops, and they typically eat summer and winter 

annuals, cacti, and perennial grasses. 

This recovery unit includes the Beaver Dam Slope, Gold Butte-Pakoon, and Mormon 

Mesa critical habitat units (Figure 9). It also includes Lake Mead National Recreation Area south 

to Las Vegas Bay, Grand Canyon-Parashant National Monument on the Arizona Strip, and the 

eastern edge of Desert National Wildlife Range. 

48
 
 

 

 

 

Figure 9. Northeastern Mojave Recovery Unit. DWMA = Desert Wildlife Management Area; ACEC = 

Areas of Critical Environmental Concern.

 (c) Eastern Mojave Recovery Unit. The Eastern Mojave Recovery Unit is similar to 

the original Eastern Mojave Recovery Unit (USFWS 1994a), spanning the Nevada-California 

border, including Oasis Valley, Amargosa Desert, Pahrump Valley, and extending south into 

Shadow Valley, but now including habitat north of the Spring Mountains east to the Sheep 

Mountains as well as Las Vegas and Eldorado valleys north to the city of Las Vegas (Figure 10). 

The Eastern Mojave Recovery Unit borders the Northeastern Mojave Recovery Unit to the east, 

extending down the Sheep Mountains to the Spring Mountains, east to Las Vegas Bay on Lake 

Mead, then down the Colorado River. From the Colorado River at approximately Cottonwood 

Cove, the southern boundary extends west through Searchlight, down the New York and 

Providence mountains to the Granite Mountains. From there the western boundary extends north 

through the Bristol Mountains, Soda Lake, and Silurian and Death valleys. The Spring 

Mountains, which provided much of the separation between the former Northeastern Mojave and 

Eastern Mojave recovery units, narrowly channel gene flow through habitat corridors to the north 

49
 
and south, connecting this recovery unit to the Northeastern Mojave Recovery Unit (Figure 10; 

Hagerty 2008; Hagerty et al. 2010). 

A majority of this unit had not been sampled previously; however, recent microsatellite 

data reflect unique nuclear allele frequencies, indicating that this area is relatively isolated from 

other recovery units (Hagerty and Tracy 2010). Allele frequencies from tortoises at Amargosa 

Desert and Pahrump Valley sites also form a homogeneous cluster different from other Nevada 

sites (Britten et al. 1997). The Sheep Mountains appear to form a barrier to tortoise movement 

between the eastern side of the recovery unit and the Northeastern Mojave Recovery Unit. The 

New York and Providence mountains isolate Ivanpah/Shadow valleys from Eldorado/Fenner 

valleys in the Colorado Desert Recovery Unit to the east. Saline Valley and Death Valley 

extending south into Silurian Valley and Soda Dry Lake act as a barrier between this recovery 

unit and the Western Mojave Recovery Unit. Although gene flow likely occurred intermittently 

Figure 10. Eastern Mojave Recovery Unit. DWMA = Desert Wildlife Management Area; ACEC = Areas 

of Critical Environmental Concern; DTCC = Desert Tortoise Conservation Center. 

50
 
 

 

 

 

 

 

 

 

during favorable conditions across this western edge of the recovery unit, this area contains a 

portion of the Baker Sink, a low-elevation, extremely hot and arid strip that extends from Death 

Valley to Bristol Dry Lake. This area is generally inhospitable for desert tortoises. 

Desert tortoises in this recovery unit are generally found in creosote bush scrub 

communities of flats, valley bottoms, alluvial fans, and bajadas, but they occasionally use other 

habitats such as rocky slopes and blackbrush scrub. As in the northeastern Mojave Desert, desert 

tortoises are often active in this recovery unit in late summer and early fall, in addition to spring, 

reflecting the fact that this region receives up to about 40 percent of its annual rainfall in summer 

(Table 3) and supports two distinct annual floras on which tortoises can feed. They typically eat 

summer and winter annuals, cacti, perennial grasses, and herbaceous perennials. Average daily 

winter temperatures usually fluctuate above freezing, except in the higher elevations. Summer 

temperatures are typically a few degrees cooler, except in the lowest elevations of Death Valley, 

than the recovery units to the south and west (Table 3). 

The recovery unit includes the east side of Death Valley National Park, much of Mojave 

National Preserve, and Lake Mead National Recreation Area between Las Vegas Bay and 

Cottonwood Cove, as well as the Nevada Test Site and the western end of Desert National 

Wildlife Range. It also includes the Ivanpah Valley critical habitat unit and the Eldorado Valley 

portion of the Piute-Eldorado critical habitat unit (Figure 10). A lack of desert tortoise habitat 

dedicated to conservation to the west of the Spring Mountains and in Las Vegas Valley 

highlights the need for careful management in these areas to maintain connectivity among 

populations and the genetic variation within this recovery unit. Corridors north and south of the 

Spring Mountains warrant particular management attention to prevent genetic isolation of 

populations on either side of this mountain range. 

(d) Colorado Desert Recovery Unit. This recovery unit combines the 1994 (USFWS 

1994a) Eastern Colorado and Northern Colorado recovery units, as well as a portion of the 

Eastern Mojave Recovery Unit in Piute and Fenner valleys. It is primarily found in California, 

though it extends into Piute Valley, Nevada, in the northern corner (Figure 11). Patchy habitat 

southeast of the Cadiz Valley appears to provide some linkage and gene flow, at least 

historically, between the former Northern and Eastern Colorado recovery units (Figure 11; 

Nussear et al. 2009; Hagerty et al. 2010). This linkage, combined with minimal genetic 

differentiation and a gradient of environmental variation between units (see below), eliminates 

the biological justification for maintaining these as separate recovery units. Piute and Fenner 

valleys span the northern border of the northern Colorado Desert and southern edge of the 

eastern Mojave Desert. The recovery unit shares its north and west boundaries with the Eastern 

Mojave Recovery Unit: west from Cottonwood Cove Road, through Searchlight, down the New 

York and Providence mountains, to the Granite Mountains. From the Granite Mountains, the 

boundary extends through the Old Dad and Bristol mountains, southeast through Bristol Lake 

and Cadiz Valley, to the southern end of the Calumet Mountains. From there, the boundary drops 

down to and extends west along California State Highway 62 all the way to the San Bernardino 

Mountains, including the Morongo Basin. The southern boundary circumscribes the tortoise’s 

range east to the Colorado River. 

51
 
 

 

 

Figure 11. Colorado Desert Recovery Unit. DWMA = Desert Wildlife Management Area; ACEC = Areas 

of Critical Environmental Concern. 

The prominent Providence and New York mountain ranges, which transect Mojave 

National Preserve, largely isolate this recovery unit from the Eastern Mojave Recovery Unit to 

the west (Figure 11). Searchlight Pass is the northern boundary, which separates Eldorado and 

Piute valleys. The central portion of this recovery unit is separated from the Western Mojave 

Recovery Unit by the Baker Sink, a low-elevation, extremely hot and arid strip that extends from 

Death Valley to Bristol Dry Lake and Cadiz Valley. To the south, the transition between the 

Colorado and Mojave deserts is more subtle. However, urban development along California State 

Highway 62 now largely separates the two recovery units; use of this highway as the recovery 

unit boundary is justified based on the broad transition between the two deserts (Turner 1982) 

and the lack of a natural break in desert tortoise habitat. While the Baker Sink almost divides this 

recovery unit in half, as generally reflected in the 1994 Northern and Eastern Colorado recovery 

units (Figure 5), the Colorado Desert is a distinct biome that encompasses a continuum of 

climatic and floristic characteristics (Turner 1982) and only subtle differences were originally 

52
 
 

 

 

 

noted in these recovery unit descriptions (USFWS 1994a). Furthermore, substantial historic gene 

flow is now recognized within the entire Colorado Desert biome (Murphy et al. 2007; Hagerty et 

al. 2010; Hagerty and Tracy 2010). Tortoises from the northern and eastern Colorado deserts 

lumped within the same basal genetic clusters in two different analytic models (Hagerty 2008). 

What little genetic differentiation that has been observed between the former Northern and 

Eastern Colorado recovery units is likely due to an absence of sampling from (at least historical) 

populations in the central part of the combined unit, south of Highway 62 and east of Highway 

177 (cf. Allendorf and Luikart 2007:400; Figures 7 and 11). 

Desert tortoises in this recovery unit share mtDNA haplotypes (sets of closely linked 

genetic markers on a single chromosome that tend to be inherited together; a chromosome is a 

long strand of DNA on which genes are found) with the Western Mojave Recovery Unit (Lamb 

et al. 1989; Murphy et al. 2007) and possess the California shell type (USFWS 1994a). They are 

differentiated from desert tortoises in the Northeastern Mojave and Western Mojave recovery 

units at several allozyme loci (Rainboth et al. 1989; Britten et al. 1997). Microsatellite data also 

support the boundary between the Colorado Desert and Northeastern Mojave and Eastern 

Mojave recovery units (Murphy et al. 2007), but less so with the Western Mojave Recovery Unit 

(Hagerty 2008; see also the continuous-distribution model discussion above). Inclusion of the 

Fenner and Piute valleys in this recovery unit is justified by the contiguous habitat, the failure to 

reliably assign sampled tortoises to the correct site between Fenner and Chemehuevi valleys 

(Murphy et al. 2007), and the inclusion of individuals from these valleys as part of the Colorado 

Desert subunit in more extensive genetic analyses (Hagerty and Tracy 2010). 

In the Colorado Desert Recovery Unit, desert tortoises are found in the valleys, on 

bajadas, desert pavements, rocky slopes, and in the broad, well-developed washes (especially to 

the south). Vegetation is characterized by relatively species-rich succulent scrub, creosote bush 

scrub, and blue paloverde (Parkinsonia florida)-ironwood (Olneya tesota)-smoke tree 

(Psorothamnus spinosus) communities. Tortoises feed on both summer and winter annuals, 

because this region receives about 1/3 of its annual rainfall in summer (Table 3) and supports 

two distinct annual floras on which they can feed. The climate is somewhat warmer than in other 

recovery units, with very few freezing days per year (Table 3). Tortoises within this recovery 

unit near Goffs produce relatively smaller eggs, produce more eggs overall, lay their second 

clutches earlier, and are smaller overall than tortoises in the Desert Tortoise Research Natural 

Area in the Western Mojave Recovery Unit (Wallis et al. 1999). They also produce more eggs 

than similarly sized females at the Nevada Test Site in the Eastern Mojave Recovery Unit 

(Mueller et al. 1998). 

The recovery unit includes the Piute-Eldorado critical habitat unit (south of Eldorado 

Valley) and the Chemehuevi, Pinto Mountains, and Chuckwalla critical habitat units. This unit 

encompasses the eastern end of Mojave National Preserve, the southernmost limits of Lake Mead 

National Recreation Area, Joshua Tree National Park, and the Chocolate Mountains Gunnery 

Range. Unprotected habitat southeast of the Cadiz Valley may provide important connectivity 

necessary to maintain overall genetic variability among populations in this recovery unit. 

(e) Western Mojave Recovery Unit. This recovery unit is generally equivalent to the 

original Western Mojave Recovery Unit in the 1994 Recovery Plan (USFWS 1994a) and is 

53
 
 

 

 

found entirely in California (Figure 12). It includes the central, southwestern, south-central, and 

part of the northern Mojave regions described by Rowlands et al. (1982). The eastern boundary, 

which it shares with the Eastern Mojave Recovery Unit, extends down Death and Saline valleys, 

through Soda Lake and the Bristol Mountains, to the Granite Mountains. The eastern boundary 

continues down the low-lying Baker sink and Cadiz Valley, separating it from the Colorado 

Desert Recovery Unit. The boundary extends west along California State Highway 62 to the San 

Bernardino Mountains. 

Habitat in California was well connected prior to human development, allowing gene 

flow to occur over long geographic distances and multiple vegetation types (Murphy et al. 2007) 

and which is evidenced by results from a landscape-genetic analysis which illustrated diffuse 

gene flow throughout the recovery unit (Hagerty et al. 2010). The north half of this recovery unit 

borders the Eastern Mojave Recovery Unit along the Baker Sink, a low-elevation, extremely hot 

and arid strip that extends from Death Valley to Bristol Dry Lake and Cadiz Valley (Figure 12). 

To the south, the transition between the Colorado and Mojave deserts is more subtle. However, 

urban development along California State Highway 62 now largely separates the Western 

Mojave and Colorado Desert recovery units. 

Microsatellite evidence concerning the degree of differentiation between the Western 

Mojave and Colorado Desert recovery units is conflicting, although genetic differentiation is 

generally low (Murphy et al. 2007; Hagerty and Tracy 2010). Morphological characteristics and 

mtDNA from populations in the Western Mojave also overlap those in the Colorado Desert 

Recovery Unit (Lamb et al. 1989; USFWS 1994a; Murphy et al. 2007). Yet, tortoises in the west 

Mojave from the Kramer Hills region are differentiated from desert tortoises at in the 

Chemehuevi Valley in the Colorado Desert Recovery Unit at several allozyme loci (Rainboth et 

al. 1989). There is significant genetic differentiation between the Western Mojave Recovery Unit 

and the adjacent Eastern Mojave Recovery Unit (Murphy et al. 2007; Hagerty and Tracy 2010). 

There also may be some sub-structuring within the Western Mojave Recovery Unit (Murphy et 

al. 2007), which, like the differentiation between this and the Colorado Desert Recovery Unit, 

may be an artifact of discrete sampling within generally continuous habitat (Allendorf and 

Luikart 2007:400). Substructuring within the Western Mojave Recovery Unit was not found 

under more continuous sampling (Hagerty and Tracy 2010). 

A pronounced difference between the Western Mojave and other recovery units, 

including the closely allied Colorado Desert Recovery Unit, is in timing of rainfall and the 

resulting vegetation. In the Western Mojave Recovery Unit, most rainfall occurs in fall and 

winter (Table 3) and produces winter annuals, which are the primary food source of tortoises. 

The Western Mojave Recovery Unit contains a unique combination of vegetation types, 

including the Mojave saltbush (Atriplex spp.)-allscale (A. polycarpa) scrub complex, blackbrush 

scrub, cheesebush (Hymenoclea salsola) scrub, iodinebush (Allenrolfea occidentalis)-alkali scrub 

complex, desert needlegrass (Achnatherum speciosum) scrub steppe, big galleta (Pleuraphis 

rigida) scrub steppe, and the Indian ricegrass (Achnatherum hymenoides) scrub-steppe complex, 

extending slightly into the southwestern Colorado Desert (USFWS 1994a). Above-ground 

activity occurs primarily (but not exclusively) in spring, associated with winter annual 

production. Thus, tortoises are adapted to a regime of winter rains and rare summer storms. Here, 

desert tortoises occur primarily in valleys, on alluvial fans, bajadas, and rolling hills. The 

extreme differences in precipitation and food availability relative to the other recovery units 

54
 
 

 

 

correspond to different foraging and activity patterns as well as to different life history 

characteristics. Tortoises dig deep burrows (usually located under shrubs on bajadas) for winter 

hibernation and summer estivation due to generally warm summers and cold winters (Table 3). 

Tortoises in the Desert Tortoise Research Natural Area within this recovery unit produce 

relatively larger eggs, produce fewer eggs overall, lay their second clutches later, and are larger 

overall than tortoises near Goffs in the Colorado Desert Recovery Unit (Wallis et al. 1999). 

Tortoises in the western Mojave Desert have the smallest reported minimum size at first 

reproduction (less than 18 centimeters [7 inches]) compared to populations in other recovery 

units (Germano 1994). Behaviorally, western Mojave tortoises are much less active during 

summer than are tortoises in other recovery units. 

The recovery unit includes the Fremont-Kramer, Superior-Cronese, and Ord-Rodman 

critical habitat units. The recovery unit also includes the western half of Death Valley National 

Park, Marine Corps Air Ground Combat Center, Fort Irwin National Training Center, China 

Lake Naval Weapons Center, and Edwards Air Force Base. 

Figure 12. Western Mojave Recovery Unit. DWMA = Desert Wildlife Management Area; ACEC = 

Areas of Critical Environmental Concern. 

55
 
 

 

 

Table 3. Climatic summary for weather stations within desert tortoise recovery units. %J-S = percent of precipitation falling in summer; W and S = 

number of winter and summer days with 2.5 mm precipitation. Some stations are listed more than once where they occur near the boundary of 

multiple recovery units. Superscripts are initials of recovery units which particular stations border. Table modified from Table E1 in USFWS 

(1994a). 

No. Days with 2.5 

Temperature (oC) Precipitation (mm) mm Ppt 

Mean Ann Mean July No. Days 

Station Elev (m) Min Mean Jan Max Freeze Mean Ann %J-S W S 

Upper Virgin River Recovery Unit 

St. George 823 15.6 -5.3 38.4 96 209.6 29.2 16 4 

Northeastern Mojave Recovery Unit 

Littlefield 567 18.2 -1.1 40.3 74 157.5 23.8 15 3 

Las Vegas WPAPEM 

Desert NWREM 

659 

890 

18.9 

16.8 

-0.1 

-1.5 

40.1 

38.2 

46 

127 

99.1 

103.9 

40.0 

27.1 

8 

6 

3 

3 

Eastern Mojave Recovery Unit 

Cow Creek -38 25.1 4.9 46.7 3 49.5 17.4 4 0 

Greenland -51 22.4 3.1 46.6 8 41.4 18.4 4 0 

BakerWM 319 --­ 0.9 42.9 --­ 75.2 20.7 8 1 

56

Las Vegas WPAPNM 659 18.9 -0.1 40.1 46 99.1 40.0 8 3 

Boulder City 

Desert NWRNM 

770 

890 

19.4 

16.8 

3.3 

-1.5 

38.4 

38.2 

13 

127 

137.2 

103.9 

33.4 

27.1 

11 

6 

3 

3 

Beatty 

SearchlightCD 

1010 

1070 

15.3 

17.5 

-2.4 

1.7 

37.5 

36.1 

88 

34 

118.0 

208.7 

14.9 

37.3 

11 

11 

2 

5 

Mountain Pass 1442 --­ -2.0 34.8 --­ 173.0 31.2 --­ --­

Colorado Desert Recovery Unit 

Thermal -37 22.8 3.9 41.8 12 70.1 21.4 4 1 

Indio 3 22.9 3.4 41.6 15 79.8 19.7 4 0 

Blythe 81 22.2 2.0 42.2 12 100.3 32.7 5 1 

Palm Springs 128 22.3 4.4 42.2 12 138.9 11.2 9 2 

Parker Res 225 23.3 5.3 42.3 1 129.3 32.8 8 3 

Needles 278 22.5 4.7 42.3 6 111.8 33.9 7 3 

Iron Mtn 281 23.0 5.6 42.1 2 79.5 20.1 5 2 

Eagle Mtn 297 23.0 5.6 41.0 1 82.8 36.5 5 1 

Hayfield 

Twentynine PalmsWM 

Joshua TreeWM 

418 

602 

838 

21.1 

19.7 

--­

3.4 

1.6 

--­

40.5 

37.2 

--­

15 

29 

--­

95.6 

104.4 

123.7 

31.9 

36.3 

23.4 

6 

5 

--­

1 

4 

---

SearchlightNE 1070 17.5 1.7 36.1 34 208.7 37.3 11 5 
Table 3. Continued. 

57

No. Days with 2.5 

Temperature (oC) Precipitation (mm) mm Ppt 

Mean Ann Mean July No. Days 

Station Elev (m) Min Mean Jan Max Freeze Mean Ann %J-S W S 

Western Mojave Recovery Unit 

Baker 319 --­ 0.9 42.9 --­ 75.2 20.7 8 1 

Trona 517 18.9 -0.6 41.3 47 82.0 8.4 8 0 

Twentynine PalmsCD 602 19.7 1.6 37.2 29 104.4 36.3 5 4 

Barstow 653 17.7 -0.4 39.1 57 108.5 27.2 10 2 

Lancaster 717 16.1 -1.9 37.4 80 124.2 2.9 11 0 

Inyokern 744 17.6 -1.1 39.4 65 90.7 5.6 8 0 

Palmdale AP 767 15.8 -1.6 36.7 81 139.2 3.2 12 0 

Buckus Ranch 806 16.6 -1.2 37.0 67 162.9 5.5 12 1 

Palmdale 809 16.5 -2.7 36.6 60 130.8 3.7 12 0 

Joshua TreeCD 838 --­ --­ --­ --­ 123.7 23.4 --­ ---

Mojave 846 --­ -0.7 37.4 --­ 128.5 8.1 --­ ---

Victorville 871 15.3 -2.7 35.4 84 135.7 5.6 9 0 

Lucerne Valley 919 15.8 -2.4 38.9 104 108.2 18.1 10 3 

Fairmont 933 15.7 2.2 32.6 29 376.7 2.3 20 0 

Hesperia 974 --­ --­ --­ --­ 157.7 6.3 --­ ---

Randsberg 1076 17.2 1.6 36.7 33 149.6 9.9 11 1 

Valyermo 1129 13.9 -2.5 40.3 103 263.3 7.6 13 1 

Llano 1164 16.1 0.9 34.5 44 174.8 7.9 13 2 

Haiwee 1166 15.5 -1.3 37.0 73 150.6 9.6 8 2 

Wildrose RS 1250 --­ -1.6 35.1 --­ 185.2 19.8 --­ ---

Kee Ranch 1318 --­ --­ --­ --­ 167.6 9.2 7 2 
 

 

 

 

C. RECOVERY GOAL, OBJECTIVES, AND CRITERIA 

Downlisting or delisting is warranted when a listed species no longer meets the definition 

of threatened or endangered under the Endangered Species Act. We set recovery criteria to serve 

as objective, measurable guidelines to assist us in determining when a species has recovered to 

the point that the protections afforded by the Endangered Species Act are no longer necessary. 

However, the actual change in listing status is not 

solely dependent upon achieving the recovery Box 4. Definitions according to section 3 of 

criteria set forth in a recovery plan; it requires a the Endangered Species Act. 

formal rule-making process based upon an 

analysis of the same five factors conside Endangered Species – Any species that is in red in the 

danger of extinction throughout all or a listing of a species (Reasons for Listing and significant portion of its range. Continuing Threats). The recovery criteria 

presented in this recovery plan thus represent our Threatened Species – Any species that is best assessment of the conditions that would most likely to become endangered within the likely result in a determination that delisting of foreseeable future throughout all or a the desert tortoise is warranted as the outcome of significant portion of its range. 

a formal five-factor analysis in a subsequent 

regulatory rule-making. 

The recovery criteria can be viewed as the targets (rather than strict rules) by which 

progress toward achievement of recovery objectives can be measured. The revised criteria 

address a) representation (conserving the breadth of the genetic makeup of the species to 

conserve its adaptive capabilities), b) resiliency (ensuring that each population is sufficiently 

large to withstand stochastic events), and c) redundancy (ensuring a sufficient number of 

populations to provide a margin of safety for the species to withstand catastrophic events). 

Recovery criteria must be measurable and objective, but they need not all be quantitative. 

Importantly, recovery criteria should also include the management or elimination of 

threats, addressing the five statutory (de-)listing factors. However, even though a wide range of 

threats affect desert tortoises and their habitat (and some such as disease and fire have attracted 

much recent attention), very little is known about their demographic impacts on tortoise 

populations or the relative contributions each threat makes to tortoise mortality (Boarman 2002; 

Tracy et al. 2004). As described previously, the facts that desert tortoises require over a decade 

to reach maturity, they have temporally variable reproduction, and juveniles have low survival 

rates, make it difficult to tease apart relative impacts of individual threats (although some 

impacts, such as habitat loss, are fairly straightforward in that they eliminate populations 

completely). Therefore, specific and meaningful threats-based recovery criteria cannot be 

identified at this time. For example, we lack quantitative data on the specific contribution of 

raven predation, disease, or other individual threats on tortoise population declines. Specific 

criteria to reduce one or more of these threats by a specified amount may ultimately be 

unnecessary as we learn more about, and better manage, other particular threats. 

In the meantime, threats are addressed in the recovery actions outlined in the next section, 

and we assume that threat mitigation will have been successful if the current recovery criteria 

have been met (taking into consideration any head-starting or translocation efforts). While it is 

58
 
 

 

 

 

 

 

important to understand as much as possible about the direct links between threats and tortoise 

population response (i.e., cause and effect), the number of potential threats affecting desert 

tortoises and the nature of the species’ life history (long generation time) may make it 

impractical to reach this level of understanding completely. However, evaluating the extent and 

intensity of threats across the landscape over time will allow recovery efforts to be better tailored 

to specific areas in conjunction with information gained through research (see Recovery Action 

4.4). Specific recovery actions, including research, must be implemented to identify sets of 

threats that contribute to a greater number of mortality mechanisms or affect size structure or 

fecundity. Experimental (or, in some cases, observational) studies should be applied to specific 

plots or areas to better understand the relationship of threats, management actions, and tortoise 

populations (Recovery Actions 3.4, 5.4, 5.5). 

The relative strengths of postulated connections between threats and mortality must also 

be evaluated (some individual linkages may be more important than multiple linkages from other 

threats). This assessment should be based on data from research designed specifically to 

elucidate relationships between threats and mortality. As quantitative information on threats and 

tortoise mortality is obtained, more specific threats-based recovery criteria may be defined 

during future recovery plan review and revision, and effective management actions can be 

identified, prioritized, and implemented through land use plans, cooperative agreements, or other 

recovery management agreements. In fact, given the list of – and uncertainty surrounding the 

relative importance of – threats to the desert tortoise, the desert tortoise may well fit within the 

concept of a conservation-reliant species, requiring ongoing, concerted management efforts even 

after our recovery criteria have been achieved (Scott et al. 2005). 

1. Recovery Goal 

The goal of the recovery plan is recovery and delisting of the desert tortoise. 

2. Recovery Objectives and Criteria 

Recovery objectives and criteria are outlined below, followed by more detailed 

explanation and rationale. Note that the recovery criteria generally will be measured within 

tortoise conservation areas or other areas identified by Recovery Implementation Teams (see 

Recovery Action 1), and they are not independent of each other but must be evaluated 

collectively. Recovery does not depend on absolute numbers of tortoises or comparisons to prelisting estimates of tortoise populations, but rather the reversal of downward population trends 

and elimination or reduction of threats that initiated the listing. 

(a) Recovery Objective 1 (Demography). Maintain self-sustaining populations of 

desert tortoises within each recovery unit into the future. 

Recovery Criterion 1. Rates of population change (λ) for desert tortoises are 

increasing (i.e., λ > 1) over at least 25 years (a single tortoise generation), as 

measured 

a) by extensive, range-wide monitoring across tortoise conservation areas within each 

recovery unit, and 

59
 
 

 

 

 

b) by direct monitoring and estimation of vital rates (recruitment, survival) from 

demographic study areas within each recovery unit. 

(b) Recovery Objective 2 (Distribution). Maintain well-distributed populations of 

desert tortoises in each recovery unit. 

Recovery Criterion 2. Distribution of desert tortoises throughout each tortoise 

conservation area is increasing over at least 25 years (i.e., ψ [occupancy] > 0). 

(c) Recovery Objective 3 (Habitat). Ensure that habitat within each recovery unit is 

protected and managed to support long-term viability of desert tortoise populations. 

Recovery Criterion 3. The quantity of desert tortoise habitat within each desert 

tortoise conservation area is maintained with no net loss until tortoise population 

viability is ensured. When parameters relating habitat quality to tortoise populations 

are defined and a mechanism to track these parameters established, the condition of 

degraded desert tortoise habitat should also be demonstrably improving. 

3. Rationale 

(a) Recovery Objective/Criterion 1 (Demography). This objective and associated 

criteria emphasize the need to increase desert tortoise populations across tortoise conservation 

areas in each recovery unit over 25 years (a tortoise generation). Achievement of these criteria 

will indicate that all listing factors (A-E) will have successfully been addressed. 

The original listing of the desert tortoise was based on documented downward trends in a 

number of populations rather than on absolute numbers of tortoises being below a threshold level 

(USFWS 1990). In addition, while we have some historical information on desert tortoise 

densities within some localized areas, no historical (pre-listing) information exists on regional 

population levels. Therefore, evidence that the ecological processes maintaining tortoise 

populations have been sufficiently restored to warrant consideration for delisting will be based 

on observation of a positive population trend over a period of at least 25 years. Basing the 

criteria on trends has an advantage over setting specific target numbers (e.g., 40 tortoises per 

kilometer2

 [104 tortoises per mile2]), because absolute tortoise numbers may show considerable 

variation between regions as a result of ecological differences or other factors, but a positive 

population trend is a clear indication that mechanisms leading to recovery are in place and that 

recovery is occurring. For example, there is evidence that historic natural population densities 

differed between the Upper Virgin River and Colorado Desert recovery units (USFWS 2006), 

but the reason for different population densities is not known. There is no reason to think that a 

single target density should be applied to all recovery units, yet attempting to set unique targets 

for each recovery unit would not be prudent given the lack of data on both historic population 

numbers and what numbers would constitute sustainable populations in the current environment. 

However, if all areas demonstrate a positive population trend regardless of actual population 

counts, the interpretation will be that recovery is occurring. 

60
 
 

 

 

 

 

 

 

The way ecologists estimate whether a population is increasing or decreasing is by using 

a variable called lambda (λ), which indicates population change. When λ is greater than one, the 

population is considered to be increasing and when it is less than one, the population is 

decreasing. Several kinds of data (e.g., counts of individuals, recruitment and survival rates) can 

be used to derive estimates of λ. This is reflected in our use of two recovery criteria here. 

Recovery Criterion 1a is based on data that are relatively easy to gather over large areas using 

range-wide monitoring with counts of individuals (i.e., line distance sampling), while Recovery 

Criterion 1b is based on data that are more difficult to gather but that may give us a more precise 

indication of population change using vital rates such as recruitment and survival from 

demographic study areas. 

Natural variability in population size and inherent measurement error make it extremely 

difficult to detect realistic natural increases (i.e., less than 2 percent per year) in desert tortoise 

populations in as few as 25 years (USFWS 2006). For this and other reasons, the Science 

Advisory Committee recommended the recovery criteria rely on a suite of measures instead of 

relying primarily on a single quantitative estimate that is difficult to measure in a species with a 

low intrinsic growth rate and is difficult to detect. At the same time, the Science Advisory 

Committee suggested using a 90 percent confidence band (α = 0.10) to describe population 

trends. For an increasing trend, the lower 90 percent confidence limit for each estimate of λ 

should exceed 1. This precision level makes it possible to distinguish a small (less than 2 percent 

per year) trend from a non-growth trend, but is still fairly conservative. Although an arbitrary 

convention exists to use 95 percent confidence intervals (α = 0.05) for many statistical tests, 

setting α = 0.10 has the conservative effect of guarding against incorrectly concluding a decline 

in tortoise density has not occurred at the expense of a slightly increased possibility that an 

increasing or declining trend is “detected” when, in fact, the population is stable (ShraderFrechette and McCoy 1993:155-156; see also McGarvey 2007). Anderson and Burnham (1996), 

proposed α = 0.15 for this monitoring program at the time they proposed the design. The Science 

Advisory Committee also noted that combined use of independent measures of recovery 

(population trends, habitat quantity and quality, threat abatement) provides additional assurance 

that detected trends are meaningful. 

Range-wide monitoring (Criterion 1a). The number of tortoises in each recovery unit is 

related to the density of tortoises estimated by line distance sampling techniques (USFWS 2006). 

It can also be related to the extent of the habitat occupied by tortoises and how that extent 

expands or contracts over time (e.g., Royle et al. 2005; see Recovery Criterion 2). Either 

approach can relate changes in an index (density or occupancy) to changes in time to estimate the 

population growth rate λ. Either density or occupancy will focus on particular size classes, often 

neglecting the smallest size class, for instance. This approach therefore assumes that if the focal 

size class is increasing, this is because it is recruited from and contributing to the neighboring 

size classes, which must also be increasing. When evaluating an endangered species, however, 

this assumption should be validated by independent evidence that the other size classes are 

recruiting as well, hence we will also validate the recovery-unit-wide estimates through more 

intensive study of the underlying recruitment and survival rates on smaller scales within recovery 

units (Criterion 1b). 

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Vital rates (Criterion 1b). Validating that vital rates are at increasing levels will be 

important to ensure that populations are able to maintain their size or trajectory upon delisting. 

Demographic (vital) rates describe the proportion of each size class, for instance, that grows into 

the next size class and/or produces offspring in a given time period. These rates also include 

mortality rates, estimating the proportion of each size class that dies during that time interval. 

These rates allow us to describe how a population changes from one time period to the next. 

Because the total number of tortoises changes from one time period to the next, dynamic models 

should be used to provide an independent estimate of the population growth rate λ. 

However, measuring recruitment and survival across the entire range of the tortoise is 

logistically difficult and prohibitively expensive. Therefore, the concept of “demographic study 

areas” is introduced to focus sampling efforts at a scale at which statistically defensible trends of 

the desired population parameters can be measured (see Recovery Actions 4.1, 5.1). The number, 

size, and sampling frequency of demographic study areas remain to be defined, with advice from 

the Science Advisory Committee and Recovery Implementation Teams, but they should be small 

relative to the size of each recovery unit, and they should be representative of each recovery unit. 

Existing permanent study plots may be incorporated into the set of demographic study areas 

within each recovery unit, if appropriate. Measuring recruitment and survivorship rates within 

demographic study areas within each recovery unit addresses the recovery concepts of 

representation and resiliency. 

(b) Recovery Objective/Criterion 2 (Distribution). This objective and associated 

criterion emphasize increasing the distribution of desert tortoises (within tortoise conservation 

areas) over at least 25 years. As such, it applies to Listing Factor A, the present or threatened 

destruction, modification, or curtailment of the tortoise’s habitat or range. 

Recovery Criterion 1 focuses on population growth. Recovery Criterion 2 focuses on the 

distribution of tortoises across the landscape. The 1994 Recovery Plan only indirectly addressed 

this issue by recommending enough habitat be conserved to ensure viable tortoise populations, 

but it did not directly address population processes acting across the spatial scale of entire 

recovery units. The purpose of Criterion 2 is to prevent range contraction of the desert tortoise. 

To detect changes in desert tortoise distribution, we will monitor the ratio of samples at which 

tortoises are detected across tortoise conservation areas within each recovery unit. The 

probability that randomly sampled sites are occupied by the desert tortoise is referred to as 

occupancy (indicated by ψ; MacKenzie et al. 2006). Similar to λ in Recovery Criterion 1, we 

specify that the lower 90 percent confidence limit be used to evaluate the slope of ψ within each 

recovery unit (which must exceed 0). An average increase in tortoise density in a recovery unit 

reflected by growth only in highly localized areas, while tortoises in other areas are extirpated, 

would not reflect recovery. 

This recovery objective provides for representative, resilient, and redundant populations. 

Although habitat is explicitly addressed by Recovery Objective 3, implicit in Objective 2 is the 

maintenance of sufficient habitat to sustain tortoises on the landscape. That is, increasing tortoise 

distributions, even if augmented by translocation or head-starting, can only be achieved by 

managing habitat appropriately. Establishing a precise geographic baseline across all lands 

within tortoise conservation areas will help ensure that habitat loss does not result in a 

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comparison of similar relative measures of tortoise occupancy across smaller absolute areas in 

the future. 

(c) Recovery Objective/Criterion 3 (Habitat). This objective and associated criterion 

emphasize maintaining desert tortoise habitat within desert tortoise conservation areas, but are 

not meant to diminish the importance of populations and habitat outside the conservation areas. 

Therefore, they directly apply to Listing Factor A, the present or threatened destruction, 

modification, or curtailment of the tortoise’s habitat or range. 

Habitat is the suite of resources 

(food, shelter) and environmental 

conditions (abiotic variables such as 

temperature and biotic variables such as 

competitors and predators) that 

determine the presence, survival, and 

reproduction of a population (Caughley 

and Sinclair 1994). Quality of habitat 

can affect reproductive success and 

survival of individuals occupying the 

habitat (Pulliam 1996), and declining or 

extirpated populations typically require 

intensive habitat management to 

stabilize and reverse trends. Much is 

known about what constitutes desert 

tortoise habitat, and a range-wide model 

of habitat for the Mojave population of 

the desert tortoise has been recently 

completed (Nussear et al. 2009). 

Criterion 3 establishes a target 

for no net loss (Box 5) of current habitat 

within tortoise conservation areas. The 

geographic baseline over which trends in 

habitat quantity will be monitored 

includes all potential desert tortoise 

habitat (Box 5) within tortoise 

conservation areas at the time of 

publication of the final, revised recovery 

plan (see Recovery Action 4.3). This 

baseline will be “memorialized” in a 

range-wide recovery database (managed by the Desert Tortoise Recovery Office) by applying the 

U.S. Geological Survey habitat model to habitat data at the time the recovery plan is published, 

in coordination with Recovery Implementation Teams (see Recovery Action 6.1). Habitat 

degradation or loss in some areas should be balanced with habitat acquisition or restoration of 

degraded habitat in other areas, as specified in the West Mojave Plan for example (BLM et al. 

2005), thus achieving the no-net-loss standard and maintaining tortoise occupancy through 

Box 5. Terms related to monitoring habitat. 

“Habitat loss” (evaluated under Recovery Criterion 3) 

is considered here as acreage subject to the complete or 

absolute removal of elements necessary for desert 

tortoise occupation (i.e., grading or paving of the 

landscape so that no food or shelter resources are 

available) or other identified thresholds of habitat 

quality fall below that which can support desert 

tortoises. 

"No net loss" of desert tortoise habitat refers to 

balancing acreage of habitat loss on public lands within 

tortoise conservation areas with new, restored, or 

enhanced acreage of habitat, such that at least the 

minimum conditions for desert tortoise occupation are 

met. No net loss of habitat may be relaxed under 

special circumstances in which we determine greater 

recovery benefits can be achieved through other means, 

and it will be evaluated over the expected 25-year 

recovery period. 

“Habitat degradation” involves impacts to desert 

tortoise habitat, short of absolute habitat loss, that 

compromise its ability to support desert tortoises (e.g., 

invasion of fire-adapted, non-native vegetation or 

increased incidence of unauthorized off-highway 

vehicle trails). 

“Potential desert tortoise habitat” as defined here is 

based on the U.S. Geological Survey habitat model, 

regardless of current occupancy by desert tortoises. 

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maintenance of (quality) available habitat. However, the target for no net loss established by 

Recovery Criterion 3 may be relaxed on a limited, case-by-case basis, if we determine that 

greater recovery benefits can be achieved through other means than replacing every acre of lost 

habitat with another acre elsewhere. Given that tortoise conservation areas include both 

designated critical habitat and BLM’s Desert Wildlife Management Areas and Areas of Critical 

Environmental Concern, which do not always coincide, the Recovery Implementation Teams 

will refine and recommend the geographic baseline for measuring no net loss of habitat, using 

available tortoise data in coordination with and approval by the Desert Tortoise Recovery Office. 

Given the vast amount of desert tortoise habitat already under Federal management, 

Criterion 3 does not apply generally to private lands. However, private or other non-Federal 

lands under conservation management for desert tortoises are included in tortoise conservation 

areas (see Box 2, page 34) and can contribute substantially to this recovery objective. In addition, 

habitat loss and degradation elsewhere must be minimized and mitigated, while not appreciably 

reducing the likelihood of survival and recovery of the tortoise, pursuant to section 10(a)(2) of 

the Endangered Species Act. 

In order to manage desert tortoise habitat well enough to meet Objectives 1 and 2, we 

would also benefit from statistical models linking habitat data to tortoise demographic data (see 

Recovery Action 5.1). Information from this type of model would allow us to identify minimum 

habitat conditions for potential tortoise occupancy and, therefore, to analyze occupancy as a 

function of habitat characteristics. We ultimately need to define specific parameters that relate to 

the quality of desert tortoise habitat (see Recovery Action 5.1) and to develop and implement a 

system for tracking habitat quality over time. In particular, we need to identify thresholds below 

which habitat degradation is so severe that the habitat fails to provide the minimum conditions 

for potential occupancy (e.g., due to fires). Measures related to habitat quality could include 

miles of roads and trails or the number and size of habitat fragment polygons created by roads. 

Incorporating a GIS “ledger” of habitat status into the range-wide recovery database, accounting 

for restored areas on the positive side and degraded or lost areas on the negative side, will enable 

managers to quantitatively measure the amount of occupied habitat, the amount of newly 

available (restored) habitat for tortoises to disperse into, the rate that restored habitat is occupied, 

and effectiveness of the restoration (e.g., BLM 2002b: Appendix G). Through the Recovery 

Implementation Teams, management agencies should report habitat status (particularly habitat 

loss/gains) on their lands (Recovery Action 1.1). 

Land management agencies must work within the context of their respective land use 

plans, including the provisions of adaptive management such as Recovery Actions 6.2-6.3 

contained within this recovery plan, to determine measures to assure no net loss and to improve 

quality of existing desert tortoise habitat. Until better population/habitat viability models are 

developed (see Recovery Action 5.3), land managers should also strive to limit the loss of desert 

tortoise habitat outside conservation areas as much as possible, although we reiterate that the 

most aggressive recovery efforts are targeted toward tortoise conservation areas. A variety of 

means are available to improve existing desert tortoise habitat both within and outside 

conservation areas. Re-establishment of native vegetation on burned landscapes may increase 

desert tortoise populations (see Recovery Action 2.6, especially for associated research needs). 

Closure of unnecessary or illegal routes of travel can create larger unfragmented blocks of 

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habitat. Additional mitigation for habitat impacts outside conservation areas could include 

options such as habitat acquisition or restoration of degraded habitat in other areas or recovery 

units, contributions to research, or facilitating population augmentation programs within 

conservation areas, depending on current needs, priorities, and opportunities. 

Actions or projects occurring outside tortoise conservation areas, which will be reviewed 

under existing State laws and the Federal section 7 and 10 processes, should seek to minimize (1) 

negative impacts in adjacent areas, (2) creation of edge effects (impacts within an area from 

projects or activities outside that area) within the conservation areas, or (3) the severing of 

genetic linkages between tortoise conservation areas (see Hagerty et al. 2010). This approach 

recognizes the need for large natural areas to accommodate stochastic events (i.e., resiliency). 

Tortoise conservation areas should be as undisturbed as possible and include intensive 

restoration or other management (e.g., weed management), as necessary. Modeling should help 

better quantify what proportion of the habitat needs to be occupied or is available to be occupied 

for population sustainability. 

D. RECOVERY ACTIONS 

As noted previously, the recommended actions in the 1994 Recovery Plan formed a 

logical basis for recovery (GAO 2002), little information since 1994 contradicts these 

recommendations (Boarman and Kristan 2006), and insufficient time has elapsed over which 

detectable increases in desert tortoise populations or natural recovery of habitat could be 

realistically expected as a result of actions implemented to date. Therefore, many of the specific 

recommendations listed below, especially under Strategic Element 2, are adapted from the 1994 

Recovery Plan. However, the revised plan places a greater emphasis on solidifying partnerships 

across jurisdictional boundaries to maintain focus on continuing to implement the recommended 

actions and on conducting applied research, modeling, and effectiveness monitoring to evaluate 

actions in a structured adaptive management context. As previously discussed, recovery actions 

will be focused within tortoise conservation areas; however, this does not preclude 

implementation of recovery or management actions outside these boundaries. Table 4 at the end 

of this section provides a side-by-side comparison of recovery actions recommended in the 

revised plan with those in the 1994 Recovery Plan. Table 5 identifies the listing factors and 

recovery objectives addressed by each major recovery action. 

1. Develop, Support, and Build Partnerships to Facilitate Recovery 

1.1.	 Establish regional, inter-organizational Recovery Implementation Teams to 

prioritize and coordinate implementation of recovery actions. Implementation of 

this recovery plan throughout the four-state range of the desert tortoise is a daunting 

prospect. However, if approached from a coordinated, regional or local level, 

recovery becomes much more feasible. Therefore, regional Recovery Implementation 

Teams need to be established within six months of publication of the final recovery 

plan to develop step-down plans and maintain focus on implementing recovery 

actions. Recovery Implementation Teams will encourage cross-jurisdictional, 

landscape-level action that will be tracked, monitored, and evaluated. 

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The Recovery Implementation Teams will be formed pursuant to section 4(f)(2) of 

the Endangered Species Act and are exempt from the Federal Advisory Committee 

Act. The teams should have broad representation by communities and the public 

involved in the recovery effort. The Desert Tortoise Recovery Office will work with 

interested managers and stakeholders in coordination with the Desert Tortoise 

Management Oversight Group to identify prospective participants, but members 

ultimately will be appointed by the Fish and Wildlife Service Region 8 Director. Both 

technical experts and stakeholders should be represented. Representatives on the 

Recovery Implementation Teams are encouraged to coordinate among their interest 

groups. 

Organization of Recovery Implementation Teams should be based on a combination 

of recovery units and land management planning areas configured to be logistically 

practical for implementation activities from an agency jurisdictional perspective (such 

as Western Mojave Desert, Eastern Mojave Desert, Colorado Desert, ArizonaNevada-Utah, and Upper Virgin River), rather than in strict congruence with 

individual recovery units. Recovery Implementation Teams will either coordinate 

directly with or perform as workgroups of existing regional partnerships, such as the 

California Desert Manager’s Group, Southern Nevada Agency Partnership, and 

Washington County Habitat Conservation Plan’s Adaptive Management Team, as 

appropriate. Recovery Implementation Teams will report annually to existing regional 

groups and Management Oversight Group meetings, both of which are open to the 

public and will provide a forum for further public input into team recommendations. 

Specific tasks for each Recovery Implementation Team are to: 

1.	 Develop a coordinated, science-based, implementable five-year recovery action 

plan for the assigned geographical area through a process of informed consent; 

2.	 Coordinate implementation of recovery actions contained in the recovery action 

plan through the development of annual work plans; 

3.	 Provide/secure the necessary resources for implementation of annual work plans; 

4.	 Assess effectiveness of implemented recovery actions; 

5.	 Compile up-to-date information on threats and recovery action implementation 

and effectiveness into a range-wide database and local-level decision support 

system; 

6.	 Annually report findings and status to appropriate regional groups and the 

Management Oversight Group; 

7.	 Annually review recovery action plans and revise as necessary. 

Recovery Implementation Teams are the fundamental partnerships tying the adaptive 

management process together (Strategic Element 6; Figure 4). As a result, it is 

important that their regional/local efforts are productive and contribute to the rangewide effort. In order to ensure timely performance of tasks and cooperation between 

groups with disparate views, we recommend the following procedures: 

 Each Recovery Implementation Team should have a chair to facilitate each 

meeting, and the Desert Tortoise Recovery Office should help organize activities 

66
 
 

 

 

through its regional recovery coordination staff. Independent facilitation should 

be secured, if necessary. 

 Once the Recovery Implementation Team is constituted, the minimum list of 

participants to go forward with any meeting will be set. Unless decisions are 

adopted by all relevant parties, the Recovery Implementation Team is not making 

progress. 

 The Recovery Implementation Team chair will alert participants to deadlines and 

ensure that all parties are aware of the need and schedule for moving the process 

forward. 

Recovery Implementation Teams should also identify areas not included within 

existing tortoise conservation areas that may warrant focused management efforts to 

ensure recovery of the desert tortoise within their respective recovery units. 

Additional tasks of the Recovery Implementation Teams are described under 

Recovery Action 6 within the context of implementing the adaptive management 

program. 

2.	 Protect Existing Populations and Habitat 

A prototype decision support system (Strategic Element 6, Appendix C), using 

information provided by managers during recovery planning workshops, produced preliminary 

recovery action priorities relative to protecting desert tortoise populations and habitat for each 

recovery unit. While general priorities for each recovery unit are included in the descriptions of 

the remaining actions below, relative priorities for each action may change as additional 

information is integrated into the decision support system at local levels within each recovery 

unit or as new information is gained through research and monitoring. Most of the actions 

described below have been implemented to a greater or lesser extent in various parts of the desert 

tortoise’s range. Inclusion in the revised plan reflects an emphasis on maintaining these actions 

where implemented, although general priorities may be lessened for actions that have been more 

broadly implemented (e.g., managed livestock grazing) and effectiveness generally needs to be 

more specifically evaluated. Note that other State or Federal agency policies and regulations may 

impose specific measures or processes to determine appropriate compensation or mitigation both 

within and outside of tortoise conservation areas. 

At this stage (i.e., prior to development of regional step-down recovery action plans), the 

following actions serve as guidelines, especially within tortoise conservation areas as defined in 

Box 2, that management agencies should implement according to their respective land-use or 

similar plans. For example, specific measures designed to minimize or mitigate habitat loss (i.e., 

maintain the “no net loss” standard of Recovery Criterion 3) or habitat degradation should be 

implemented by each land management agency in coordination with their respective Recovery 

Implementation Teams according to the local situation (e.g., short-term or long-term impact, 

effect to high-quality or low-quality habitat) and governing authorities. Deviations from the 

following actions may be appropriate in some cases, but they should be supported by scientific 

67
 
 

 

 

 

rationale or justification as to how they can contribute to recovery. Again, quantifying the 

effectiveness of these or modified recovery actions is important, as specified under Action 5.4. 

2.1.	 Conserve intact desert tortoise habitat. Land disturbances should be precluded 

within tortoise conservation areas. Disturbances to be avoided include those caused 

by development, off-highway-vehicle use, overgrazing by domestic livestock, 

construction of roads or other linear facilities, increased fire frequency, and other 

surface disturbing activities. For example, fire prevention and management should be 

pursued throughout the Mojave and Colorado deserts to contain the grass-fire cycle. 

Minimizing the size and intensity of fires will ease subsequent restoration efforts 

(2.6), even in previously burned areas. Fire suppression would also minimize direct 

and indirect effects on individual tortoises. Identifying and mapping priority areas and 

developing a fire plan for habitat protection, fire-crew access, and the use of natural 

or created fuel breaks could help limit response time and fire spread. 

Development of alternative energy sources has also recently come to the forefront as 

a necessary and congressionally mandated use of public lands that could have largescale impacts to desert tortoise habitat. Pursuant to the Bureau of Land Management 

land use plans, solar project facilities will be sited outside Desert Wildlife 

Management Areas and Areas of Critical Environmental Concern. Current proposals 

for energy projects within these land allocations should be relocated so that impacts 

to these areas are avoided. A cumulative impacts assessment should be conducted and 

appropriate areas and mitigation measures for this type of activity should be 

identified. 

2.2.	 Minimize factors contributing to disease. Strategies for managing natural 

populations depend on the disease status of the population, deemed broadly as a) 

uninfected, b) recently infected with infection spreading, or c) infection status 

endemic. An endemic-status population is defined as one where the proportion that is 

seropositive is above zero and remains stable over time, although actually 

determining the disease status of populations is extremely challenging. Specific 

recommendations are listed below. 

 Do not release infected individuals into the wild (Hudson et al. 2009). 

 All tortoises found in the wild that may have been released from captivity without 

a health evaluation should be removed from the wild and used for breeding, 

adoption, or research programs unless they are determined to be uninfected and 

are genetically acceptable for that population (Hudson et al. 2009). 

 No action should be taken to remove infectious or seropositive individuals from 

wild populations, particularly where data indicate the disease status of that 

population is endemic. This recommendation seeks to prevent the removal of 

individuals that are resistant to infection (Hudson et al. 2009). 

In populations where less than two percent of individuals are known to be 

infected, individual tortoises exhibiting clinical signs of acute infection can be 

68
 
 

 

 

 

removed for further testing, but should be returned to the point of capture if 

diagnostic tests confirm they are uninfected. Uninfected populations that have 

recently become infected should be carefully monitored with the removal of all 

individuals exhibiting acute infections (Hudson et al 2009). 

 Site quarantines may be considered should an acute outbreak or chronic issue of 

disease be determined to put the larger population at risk. 

 Prior to any human-facilitated movement of tortoises (translocation), tortoises 

must undergo a health assessment that includes disease screening as described in 

the most recent guidance issued by the U.S. Fish and Wildlife Service. 

 Implement disease minimization measures based on the results of research 

conducted under Recovery Action 5.4 and evaluate and update these actions 

through Recovery Action 6’s adaptive management program. 

2.3.	 Establish/continue environmental education programs. Environmental education, 

a high priority in all recovery units, is a preventative action that has been shown to 

effectively change learned behavior and can be used to reduce stakeholder conflict 

before it happens (Hungerford and Volk 1990). An educated public is more likely to 

be aware of the consequences they can have on desert tortoises and to be more willing 

to take responsibility for their actions than those with less knowledge (Vaske and 

Donnelly 2007). Aggressive and widespread efforts in schools (such as the Mojave 

Max program in Clark County, Nevada), museums, hunting clubs, and in Bureau of 

Land Management and National Park Service visitor centers and interpretive sites are 

needed to inform the public about the status of the desert tortoise and its recovery 

needs. 

Interpretive kiosks or visitor centers should be used to disseminate information about 

the desert tortoise and the need for regulated access and use of habitat. The Desert 

Tortoise Conservation Center in Las Vegas provides an opportunity for development 

of a regional education and research facility for these purposes. Education programs 

should include such subjects as husbandry and adoption programs for captive 

tortoises, the importance of discouraging unauthorized breeding of desert tortoises in 

captivity, and the illegality under State laws of releasing captive tortoises into 

wildlands. Education efforts should be focused on groups that use the desert on a 

regular basis, such as rock-hounds and off-highway vehicle enthusiasts. A permit 

system for access to sensitive areas would offer one way to educate desert 

recreationists. Additional educational tools include public service announcements, 

news releases, informational videos, brochures and newsletters, websites, and 

volunteer opportunities. 

2.4.	 Increase law enforcement. People may conduct illegal activities either because they 

are unaware of the laws, they do not realize the consequence of their behavior, or they 

enjoy some personal benefit that outweighs the risk of being caught. Increased law 

enforcement presence is a relatively high priority in all recovery units (especially 

69
 
 

 

 

 

 

 

Upper Virgin River) and includes enforcing regulations pertinent to the specific 

recommendations to protect tortoises or their habitat listed below. This action also 

includes using existing officers to ensure law enforcement presence during peak 

recreational use periods, such as weekends and holidays, on a rotational basis so 

enforcement activity is not lost on casual users during standard work-week hours. 

Increasing fines and establishing agreements between offices of adjacent management 

authorities to enforce regulations across jurisdictional lines would also improve the 

effectiveness of law enforcement efforts. 

An increased law enforcement presence need not be restricted to commissioned peace 

officers, but could also include “rangers” or other personnel with a physical presence 

in the field who would make contact with public land users, communicate with law 

enforcement officers, and conduct other activities, as necessary (e.g., minor 

restoration or trash removal). Such personnel, while unable to issue citations and 

warnings, should be coordinated with the appropriate agencies to focus on particular 

issues in their respective areas. Brochures identifying and encouraging reporting of 

problem illegal activities could be developed and distributed to management agencies 

for further distribution to recreationists or others. The following is a list of illegal 

activities known to negatively affect the desert tortoise and warrant increased 

enforcement. 

 Unauthorized off-road vehicle travel. Across all recovery units, this aspect of law 

enforcement is the most important. Impacts from off-highway vehicle use include 

mortality of desert tortoises on the surface and below ground; collapsing of desert 

tortoise burrows; damage or destruction of plants used for food, water, and 

thermoregulation; damage or destruction of the mosaic of cover provided by 

vegetation; damage or destruction of soil crusts; soil erosion; proliferation of 

weeds; and increases in numbers and locations of wildfires. Unauthorized offhighway vehicle use also results in increased human access and associated 

impacts such as deliberate maiming, killing, and removal of tortoises. 

 Deliberate maiming and killing of tortoises. Formerly referred to as vandalism 

(Luke et al. 1991), specific examples include shooting, crushing, driving over, 

flipping over, and decapitating tortoises. Shooting (also called “plinking”), by far, 

is the most prevalent method (Boarman 2002). Preventing the discharge of 

firearms, except for hunting authorized by State wildlife agencies, in problem or 

other sensitive areas could help minimize this threat. 

 Unauthorized breeding and release of captive tortoises. Captive release of 

tortoises (not limited to desert tortoises) poses numerous problems to wild 

resident populations. Examples include genetic pollution, hybridization between 

populations and possibly other tortoise species, the potential for introducing or 

spreading disease (e.g., upper respiratory tract disease), and disturbance to the 

social structure of the resident population. Unauthorized breeding and release of 

pet desert tortoises particularly contributes to genetic pollution and disease 

spread. Placement of excess tortoises in adoption or translocation programs places 

70
 
 

 

 

 

 

a large burden (e.g., cost of pick-up services, health testing, placement or 

adoption efforts) on resources that would otherwise be available for more 

productive recovery efforts. New State or local regulations may be necessary to 

prohibit unauthorized breeding of desert tortoises, and (increased) fines may be 

warranted for the release of captive tortoises into the wild. New State and/or local 

regulations regarding keeping tortoises as pets may be necessary and existing 

regulations should be enforced. New regulations to reduce the risk of disease 

introduction should restrict the number of desert tortoises a household can 

possess, restrict or ban contact with other tortoises species, require health 

assessments, and specify containment conditions to minimize the chances of 

escape. Regulations to reduce the risk of genetic contamination should restrict the 

number of desert tortoises a household can possess, prohibit the movement of 

captive desert tortoises from one geographic area to another, limit breeding, and 

specify containment conditions to minimize the chances of escape. 

 Uncontrolled dogs. Domestic and feral free-roaming dogs are documented threats 

to captive and wild tortoises (Bjurlin and Bissonette 2001; see Boarman 2002). 

With the growing number and sizes of cities, towns, and settlements in the desert, 

this type of threat is increasing and will be difficult to control. Dogs singly, and in 

packs, may roam miles from home, dig up, and injure desert tortoises. This action 

entails implementing measures to control off-leash dogs (domestic dogs should at 

least be within sight and voice control), live-trapping free-ranging dogs, and 

developing free-ranging dog management plans. 

 Dumping and littering. Dumping and littering provide subsidies to predators, thus 

elevating their populations and predation pressure on tortoise populations. It can 

also introduce toxic chemicals or hazardous materials to the environment. Release 

of balloons also contributes to litter in the desert and poses a threats to tortoises 

through entanglement or if balloons are ingested (Burge 1989; Walde et al. 2007). 

2.5.	 Restrict, designate, close, and fence roads. Paved highways, unpaved and paved 

roads, trails, and tracks have significant impacts on desert tortoise populations and 

habitat. In addition to providing many opportunities for accidental mortality, they also 

provide access to remote areas for collectors, vandals, poachers, and people who do 

not follow vehicle-use regulations. Substantial numbers of desert tortoises are killed 

on paved roads. Roads also fragment habitat and facilitate invasion of non-native 

vegetation. Collectively, the actions described below are of relatively high priority in 

all recovery units. 

 Establishment of new roads should be avoided to the extent practicable within 

desert tortoise habitat within tortoise conservation areas; tortoise conservation 

areas should have a minimum goal of “no net gain” of roads. 

 Existing roads should be designated as open, closed, or limited. This action is 

especially pertinent for closed or limited designations, which can help mitigate 

impacts mentioned above. Maintenance of route designation signs may also be 

71
 
 

 

required due to vandalism. Route designation is a particularly high priority in all 

recovery units except Upper Virgin River (moderate priority). 

 Non-essential or redundant routes should be closed, especially within tortoise 

conservation areas. Emergency closures of dirt roads and routes may also be 

needed to reduce human access and disturbance in areas where human-caused 

mortality of desert tortoises is a problem. Road closures are a particularly high 

priority in all recovery units except Upper Virgin River (moderate priority). 

 Tortoise-barrier fencing should be installed, according to specifications provided 

in Appendix C, and maintained along highways in desert tortoise habitat. In 

particular, all highways and paved roads within or adjacent to tortoise 

conservation areas should be fenced with appropriate modification to avoid 

population fragmentation. Fencing projects need to be completely implemented 

and maintained to ensure effectiveness. 

“Hot-spots” of road mortality should be identified and prioritized, but fencing 

roads is a particularly high priority in the Upper Virgin River Recovery Unit. 

Other areas in California in need of fencing include parts of US-395, I-40, and 

SR-247 in the Western Mojave Recovery Unit and US-95, I-10, I-15, I-40, 

redundant roads within Mojave National Preserve and Joshua Tree National Park, 

and the Union Pacific rail line in the Eastern Mojave and Colorado Desert 

recovery units. Many roads have already been fenced in Clark County, Nevada, 

but remaining areas include US-93 from I-15 to Pahranagat, SR-75 (Valley of 

Fire Road) from I-15 to State Park Boundary, SR-168 from I-15 to US-93, CalNev-Ari (tie in fencing to US-95), and Cottonwood Cove Road. 

Recovery Unit Roads and Railways where Tortoise 

Fence is Needed 

kilometers miles 

Western Mojave Road 178 110 

Rail 72 45 

North-East Mojave Road 186 116 

Rail 142 88 

Colorado Desert Road 271 168 

Rail 154 96 

Upper Virgin River Road 17 11 

Rail 0 0 

Total Road 652 405 

Rail 368 229 

Alternatives to fencing may be investigated in areas of high-maintenance (e.g., 

subject to flash flooding) or viewshed concern. Culverts and underpasses should 

be incorporated into road-fencing projects as well as any State or Federal road or 

highway improvement/expansion to minimize the fragmenting effects of the road 

(2.11). 

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 Consideration should also be given to posting speed limits on appropriate rural 

paved and all unpaved roads at 40 kilometers per hour (25 miles per hour). This 

speed limit will reduce the likelihood of vehicles hitting tortoises on the road, 

reduce the need for road grading due to washboarding, and allow law enforcement 

to cite people for speeding or driving off-road in conservation areas. 

 While graded roads typically need not be fenced, berms should be maintained 

such that tortoises do not get trapped in the roadbed. This is a particular issue in 

the Colorado Desert Recovery Unit, as well as throughout the Mojave National 

Preserve. 

2.6.	 Restore desert tortoise habitat. Habitat restoration is a countermeasure to many of 

the impacts discussed above, such as grazing, military operations, off-highway 

vehicle use, roads and trails, construction, mining, horses and burros, invasive 

species, fire, environmental contaminants, and utility corridors. As such, this action is 

highly prioritized within the Western Mojave and Colorado Desert recovery units and 

moderately prioritized within other recovery units. The specific restoration activities 

may vary by recovery unit and management agency. 

A first step in restoration is assessing habitat status and desired conditions, then 

targeting restoration (or protection) efforts to meet those conditions. Natural recovery 

of severely degraded desert scrub is expected to occur over centuries, not decades 

(Webb et al. 2009a), so active restoration efforts will be required in such areas. A 

great deal of research has been conducted on restoration and rehabilitation of habitats 

in arid and semi-arid ecosystems with varied results (see Bainbridge 2007; Weigand 

and Rodgers 2009). Previous and ongoing studies should be used to inform 

implementation of restoration activities in desert tortoise habitats. 

In general, because of the uncertainties and costs associated with revegetation and the 

long periods required for natural recovery, the first priorities in habitat conservation 

should be to preclude land disturbance in the first place and to conserve remaining, 

intact habitats (2.1). Even so, incentive programs to restore habitat through habitat 

rehabilitation credits or mitigation banking could be used to encourage persons or 

entities to rehabilitate degraded habitat (BLM et al. 2005). Several restoration 

activities warrant specific attention below, although methods for successful 

implementation for most need to be developed or refined. 

 Eradicate or suppress invasive weeds. Methods for weed suppression or 

eradication on large scales are currently unavailable, but the use of herbicides or 

other measures may be particularly appropriate on smaller scales in tortoise 

conservation areas. 

 Revegetate degraded areas with native plants of high nutritive quality to desert 

tortoises, as well as shrubs needed for cover. Given the vast scales of recent 

wildfires, post-fire rehabilitation should be approached strategically toward areas 

determined to have a higher likelihood of successful restoration, considering fire 

73
 
 

 

 

 

 

 

 

 

 

 

 

severity, soil types, biological connectivity of native source plants, etc. Nonnative, invasive species should not be included in seed mixes used in restoration 

efforts. This action may also be appropriate for smaller-scale applications such as 

mitigating utility corridor disturbances. 

 Collection of native seed is recommended to ensure adequate seed is available to 

conduct restoration. Agencies should seek partnerships where possible to grow 

native plants for restoration. 

 Obscure closed segments of roads/routes and illegal incursions within tortoise 

conservation areas that are visible from points along nearby open routes. In areas 

where revegetating is viable, native vegetation should be planted in the roadbed of 

the closed route segments. In areas where revegetating is likely to fail or invite 

invasive species, vertical coarse debris (“vertical mulching”) should be used to 

obscure the closed routes. If obliteration is not possible, closed roads or routes 

should be physically blocked at the entrance and wherever they intersect open 

roads, routes, and non-motorized trails (see Recovery Action 2.7). 

 Remove toxicants and unexploded ordnance. Areas with elevated levels of 

elemental toxicants associated with mining, other industrial operations, 

unexploded ordnance, and unauthorized dump sites should be identified and 

remediated where possible. 

2.7.	 Install and maintain urban or other barriers. Urban development indirectly affects 

desert tortoise populations through spillover of human impacts, such as unauthorized 

off-highway vehicle use and free-roaming dogs, into the surrounding habitat. 

This action entails installing and maintaining appropriate barriers at the urbanwildland interface or adjacent to other uses incompatible with desert tortoise 

populations, particularly adjacent to tortoise conservation areas. Depending on the 

particular impacts of interest, the actual type of barrier may differ. For example, 

tortoise-proof fencing (Appendix C) may be sufficient adjacent to aqueducts or offhighway vehicle areas, but larger fences or block walls may be necessary adjacent to 

urban development to limit off-highway vehicle use and free-roaming dogs. Priority 

areas for this action include: 

 around the Red Cliffs Desert Reserve in the Upper Virgin River Recovery Unit; 

 around areas that are currently dedicated to off-highway vehicle activity and that 

are located adjacent to tortoise conservation areas, such as Johnson Valley OHV 

area; 

 around new developments (e.g., Coyote Springs Valley) and the edges of the Las 

Vegas metropolitan area in the Eastern and Northeastern Mojave recovery units; 

74
 
 

 

 

-------------------------

 around the Desert Tortoise Natural Area, Helendale, Barstow/Daggett, Yucca 

Valley, Joshua Tree, and Twentynine Palms in the Western Mojave Recovery 

Unit; and 

 around the town of Goffs in the Colorado Desert Recovery Unit. 

2.8.	 Sign and fence boundaries of sensitive or impacted areas. This action (relatively 

high priority in the Upper Virgin River Recovery Unit and moderate priority 

elsewhere) entails marking boundaries of particularly sensitive or heavily impacted 

areas with signs and fencing to regulate authorized use and to discourage 

unauthorized use. This can include physically blocking or marking boundaries of 

protected areas, mitigation lands, translocation areas, research sites, off-highway 

vehicle routes, roads, military lands, and parks, particularly when an area is 

vulnerable to vehicular or livestock intrusion. Signs or kiosks may also be used for 

educational purposes and to raise awareness. 

2.9.	 Secure lands/habitat for conservation. This action is of moderate priority in all 

recovery units. It counters habitat loss and protects tortoises, provided secured lands 

are suitable habitat (see Action 2.1) or can serve as corridors or buffers. Given the 

vast amount of desert tortoise habitat already under Federal management or primary 

conservation use, land acquisition should be strategic, focusing on particularly 

sensitive areas that would connect functional habitat or improve management 

capability of the surrounding area. For example, some tortoise conservation areas 

have significant inholdings of private land on which development and associated 

access roads would threaten the conservation value of these areas. Land acquisitions 

should include surface and subsurface mineral rights whenever possible. 

Conservation agreements and other private-landowner incentives could also be 

developed to protect desert tortoise habitat in such areas. 

Land managers should coordinate with the Department of Defense on efforts such as 

the Readiness and Environmental Preparedness Initiative and the Army Compatibility 

Use Buffer program to acquire lands that would serve a dual purpose of preventing 

encroachment on military installations and conserving desert tortoise habitat. 

Areas of particular emphasis noted by managers for this recovery action include the 

Western Mojave Recovery Unit and inholdings within National Parks. In addition, 

consolidating private lands within the Red Cliffs Desert Reserve is important for 

habitat connectivity. 

The following actions typically ranked as mid- to lower-level priorities should be 

addressed as higher priority actions are implemented, as part of elevated management within 

tortoise conservation areas, or as other opportunities or needs arise. 

2.10.	 Restrict off-highway vehicle events within desert tortoise habitat. This action 

refers to large- or small-scale competitive races or non-competitive events involving 

75
 
 

 

 

 

 

 

 

 

 

up to thousands of motorcycles and other recreational off-highway vehicles. Prior to 

the implementation of current permitting and management practices (see for example 

BLM 1998a), competitive off-highway vehicle events led to the widening of old 

routes, creation of new routes, camping and staging by race participants and observers 

in unauthorized areas, littering, and inability of race monitors to prevent unauthorized 

activities. 

This action entails prohibiting or demonstrably minimizing the effects of such events 

within tortoise habitat; limiting the number of events per year, limiting events to the 

winter season, and limiting the number of participants per event; and ensuring all 

participants stay on designated roads. Event planning should avoid existing tortoise 

conservation areas to the extent practicable. 

2.11.	 Connect functional habitat. Connecting fragmented habitat helps to maintain gene 

flow between isolated populations. This action improves species fitness (ability to 

maintain or increase its numbers in succeeding generations) by maintaining diversity, 

allowing populations to interbreed, and providing access to larger habitats (Forman et 

al. 2003). Roads and urban areas form barriers to movement and tend to create small, 

local populations which are much more susceptible to extinction than large, 

connected populations (Wilcox and Murphy 1985). 

This action is of consistently moderate priority among recovery units. It entails 

connecting isolated blocks of desert tortoise habitat, particularly through corridors of 

natural habitat for large-scale connectivity (e.g., habitat corridor around the north end 

of the Spring Mountains, Nevada), as well as culverts for smaller-scale connectivity 

across fenced roads and railroads. 

2.12.	 Limit mining and minimize its effects. Impacts from mining can include habitat 

destruction and direct mortality from off-road exploratory travel; habitat loss to road 

and development construction, sand and gravel extraction, leachate ponds, tailings, 

and trash; introduction of toxins; fugitive dust and soil erosion; development of 

ancillary facilities to support large mining operations; temporary (short- or long-term 

oil and gas leases) use of public lands; refuse of stakes and wire from seismic testing; 

and creation of disturbance zones for invasive plant species to establish. 

Within tortoise conservation areas and where indirect effects would affect these areas, 

mining should be withdrawn (if feasible) or limited through mining plans of 

operations. Monitoring plans and mitigation/minimization measures should be 

implemented at mining sites. 

2.13.	 Limit landfills and their effects. Landfills impact tortoise populations by removing 

habitat, spreading garbage, introducing toxic chemicals, increasing road kills by 

vehicles going to and from the landfill, and facilitating proliferation of predators. 

Predator proliferation is considered the most significant of these impacts with 

landfills providing food subsidies for ravens and coyotes, leading to more young that 

move into adjacent areas in the spring to prey upon tortoises (Boarman 2002). Proper 

76
 
 

 

 

 

 

 

 

 

landfill management (including dumps and sewage ponds) can help reduce several 

threats to tortoises, but especially from ravens (Boarman and Kristan 2006). 

This action entails reducing or eliminating the use of authorized landfills or other 

waste-disposal facilities by tortoise predators, siting new facilities outside of desert 

tortoise habitat, and/or precluding new facilities within 8 kilometers (5 miles; as 

recommended by the West Mojave Plan [BLM et al. 2005]) of existing tortoise 

conservation area boundaries. 

2.14.	 Minimize excessive predation on tortoises. Desert tortoises have several natural 

predators, including coyotes, kit foxes, feral dogs, bobcats, skunks, badgers, common 

ravens, and golden eagles (Boarman 2002). The dominant predator probably varies 

temporally (through time), spatially, and with the size of the tortoise. Coyotes have 

been seen preying upon numerous adult desert tortoises within local areas, especially 

in times of drought. Predation by the common raven is generally focused on younger 

age classes of the desert tortoise. During the first 5 to 7 years of life, the tortoise shell 

is incompletely ossified and so is soft and easy to puncture and open. 

Several other recovery actions (2.4, 2.5, 2.13) address predator management by 

limiting human subsidies (e.g., food obtained at landfills and from roadkills, as per 

Boarman [2003]). In addition, predator access to concentrated anthropogenic (caused 

by humans) resources, including commercial trash bins, confined livestock feeding 

operations such as dairies and stables, sewer and evaporation ponds, and 

campgrounds, should be reduced (W.C. Webb et al. 2009). 

This action also emphasizes direct predator-control programs to reduce predation on 

tortoises where specific problem areas or offending individuals are identified. For 

example, we are implementing with several cooperating agencies a phased-approach, 

integrated predator management plan to reduce predation by the common raven in the 

California desert (USFWS et al. 2008). Control methods can include targeted removal 

of known tortoise predators by shooting or trapping (live or lethal), as well as nest 

removal, directed at specific problem areas within tortoise conservation areas or 

where predation is affecting specific recovery-related research. We consider lethal 

predator control to be a short-term, temporary solution to predation problems, and we 

do not consider general, widespread predator control to be an appropriate recovery 

action. 

2.15.	 Minimize impacts to tortoises from horses and burros. Wild horses and burros 

alter desert tortoise habitat through soil compaction and vegetation change (Boarman 

2002). Tortoises and horses and burros may also compete for the same food. The 

California Desert Managers Group has been coordinating among member agencies 

since 1998 to substantially remove horses and burros from outside herd management 

areas. Herds have been eliminated in most critical habitat, and efforts are continuing 

to reduce their numbers. Within the Las Vegas District of the Bureau of Land 

Management, all herd management areas are at appropriate management levels, and 

herds outside of herd management areas have been eliminated. 

77
 
 

 

 

 

 

 

This action entails continued exclusion of horses and burros from desert tortoise 

conservation areas by fencing and/or removal. Managing for zero population levels 

and gathering animals to maintain this goal inside desert tortoise conservation areas is 

consistent with existing land use plans and the Wild Free Roaming Horses and Burros 

Act of 1971. 

2.16.	 Minimize impacts to tortoises from livestock grazing. Grazing by livestock (cattle 

and sheep) affects desert tortoises through crushing animals or their burrows, 

destroying or altering vegetation (which may introduce weeds and change the fire 

regime), altering soil, and competing for food (Boarman 2002). There is currently no 

evidence that cattle grazing will restore habitat or prevent fire in Mojave Desert 

environments. Cattle grazing may help create and maintain habitat for natives where: 

1) the grassland ecosystem is highly productive; and 2) disturbance was previously 

caused by native grazers and browsers (e.g., Brooks 1995; Marty 2005). The Mojave 

Desert is neither highly productive, nor is it an environment which historically 

supported native cattle-sized grazers. 

The Service should work to assist grazing managers to develop experimental 

application of more flexible grazing practices, such as allowing or reducing grazing 

during specific times of the year (e.g., after ephemeral forage is gone or winter only) 

or under certain environmental conditions (e.g., following a specified minimum 

amount of winter rain), in order to investigate the compatibility of grazing with desert 

tortoise populations. Collaboration with grazing managers to identify appropriate 

experimental applications would facilitate this process. Experimental applications 

would be most appropriate outside desert tortoise conservation areas to collect data to 

determine whether specific grazing regimes can be compatible with tortoise recovery. 

Until research determines grazing compatibility with tortoise populations, this 

recovery action entails continuing to minimize the impacts to tortoises from livestock 

grazing within tortoise conservation areas. Appropriate site-specific management 

actions would vary for any given site, but some of these management actions might 

include reducing impacts by fencing, removing trespass cattle, retiring allotments 

through acquisitions from willing sellers or allotment exchanges to locations outside 

tortoise conservation areas, or prohibiting supplemental feeding. 

3. Augment Depleted Populations through a Strategic Program 

3.1.	 Develop protocols and guidelines for the population augmentation program, 

including those specific to head-starting and translocation. Specific guidelines and 

protocols will be developed by the Desert Tortoise Recovery Office, with advice and 

input from the Science Advisory Committee, topical experts, and representatives from 

pertinent regulatory and land management agencies. Guidelines will draw from 

knowledge gained through recent research into head-starting and translocation and 

from recommendations made by the Science Advisory Committee relative to 

controlling disease (Hudson et al. 2009). Within the first year after publication of the 

78
 
 

 

 

 

 

 

 

revised recovery plan, draft guidelines and protocols for the strategic population 

augmentation program will be developed. We expect the documents to be continually 

updated as new information is evaluated. 

3.2.	 Identify sites at which to implement population augmentation efforts. Populations 

to be augmented should be identified based upon knowledge of population trends, 

habitat, and threats in the area, unique opportunities to learn about augmentation 

techniques or threats through a research-based program, and feasibility. Data from 

previous population monitoring efforts, including a spatial analysis, and recent 

advances in genetics will facilitate selection of the target areas. 

3.3.	 Secure facilities and obtain tortoises for use in augmentation efforts. 

 Secure facilities for head-starting tortoises. Several groups in California have 

begun research into head-starting techniques. Currently, facilities exist at Edwards 

Air Force Base, Marine Corps Air Ground Combat Center at Twentynine Palms, 

and Mojave National Preserve. These facilities may be used, and additional 

facilities will need to be constructed. For example, the addition of facilities in the 

Las Vegas area could serve surrounding recovery units. The existing Desert 

Tortoise Conservation Center could be renovated to house such facilities in a 

secure location. See also Science Advisory Committee recommendations related 

to desert tortoise holding facilities and the control of disease (Hudson et al. 2009). 

 Obtain adult tortoises for generation of progeny. Tortoises used in the headstarting program will be of known origin and of the genotype (genetic makeup) 

that inhabits the specific areas to be augmented. Depending on several factors, 

breeding colonies may be maintained in captivity, or wild females may be 

periodically captured and released after collection of eggs. 

 Head-start progeny. Maintain progeny in captivity as specified in guidelines 

developed under 3.1. 

 Obtain adult tortoises for translocation. Some adult tortoises removed from 

construction sites or other disturbed areas may be suitable for translocation to 

target areas. Refer to guidelines developed under 3.1. 

3.4.	 Implement translocations in target areas to augment populations using a 

scientifically rigorous, research-based approach. Translocation and head-starting 

efforts should be implemented in conjunction with directed research on the factors 

affecting success of the augmentation, including methodological factors, but 

especially including factors related to management of habitat and threats. Refer to 

guidelines developed under 3.1 for information on target areas. 

4.	 Monitor Progress toward Recovery 

The ability to describe range-wide trends depends on reliable, adequate, and consistent 

funding. A key recommendation of the General Accounting Office’s audit of the desert tortoise 

79
 
 

 

 

 

 

 

 

 

 

 

 

recovery program was that the Departments of the Interior and Defense work with other agencies 

and organizations “to identify and assess options for securing continued funding for range-wide 

population monitoring” (GAO 2002). Rather than developing monitoring based on individualagency annual budgeting considerations, the Desert Tortoise Management Oversight Group 

should implement the GAO’s recommendation (for example, through five-year time frames) to 

allow effective planning, contracting, and hiring to be implemented under a long-term study 

plan. The following recovery actions parallel the recovery criteria described earlier, helping 

ensure that progress toward recovery is measured effectively. 

4.1.	 Monitor desert tortoise population growth. Trends in tortoise populations should 

be assessed both by directly enumerating the number of tortoises and by estimating 

the rate of births, deaths, and related recruitment into each age or size class so that the 

resulting trend in population growth can be determined. 

 Monitor the number of tortoises in each recovery unit. We will estimate 

population change (λ) on a recovery-unit-wide scale through measures of 

population size, density, and/or occupancy. Refinement of range-wide monitoring 

techniques should continue, as recommended by USFWS (2006a). 

 Use demographic rates in key areas of each recovery unit (i.e., demographic study 

areas) to independently estimate population growth in each recovery unit. Surveys 

of demographic study areas should document age distributions sufficiently to 

characterize age distributions that distinguish stable or increasing populations 

from decreasing ones, especially including the proportion of juveniles 

represented. Dynamic vital-rate models should be used to provide an independent 

estimate of the population growth rate λ. Some existing or prior study plots may 

be appropriate for inclusion in the set of demographic study areas to make use of 

long-term datasets. 

4.2.	 Monitor the extent of tortoise distribution in each recovery unit. Monitoring 

changes in desert tortoise distribution by estimating occupancy of tortoises entails 

investigating the most feasible scale at which occupancy would be evaluated, as well 

as the number of visits to a given site that would be needed to estimate detection 

probability if tortoises are present. Taken together and repeated over the years of the 

recovery program, occupancy estimation would provide a description of the rates at 

which tortoises are being locally extirpated from occupied habitat as well as 

recolonizing currently unoccupied habitat across the range. Occupancy estimation, if 

feasible, would also provide another estimate of population growth rate λ. In addition, 

historical study-plot and sign-count data should be compared with current patterns of 

live and dead tortoise concentrations to provide insights into recent larger scale 

declines relative to those reported from some plots (USFWS 2006). 

4.3.	 Track changes in the quantity and quality of desert tortoise habitat. A baseline 

for tracking habitat quantity across each recovery unit exists with the newly 

developed habitat model (Nussear et al. 2009). Trends in habitat quality over time 

should be integrated into the recovery database/decision support system (6.1) as 

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conditions affecting habitat quality are identified (5.1). Remote sensing and GIS data, 

validated by ground truthing as necessary, can be used to quantify the loss or 

restoration of habitat against the baseline (for instance, habitat completely lost to 

urbanization, degraded by wildfires, or authorized for use as rights-of-way or energy 

projects; the number and average size of habitat fragment polygons created by roaded 

boundaries). 

4.4.	 Quantify the presence and intensity of threats to the desert tortoise across the 

landscape. Remote sensing, GIS data, ground truthing, and other surveys should be 

used to update and refine information on threats presented in the background of this 

recovery plan and used in the initial decision support system (6.1, Appendix B), 

including disease and other threats that may be related to habitat quality discussed 

above. This information will allow recovery efforts to be better tailored to specific 

areas while being incorporated with additional information gained through research 

and monitoring. 

5.	 Conduct applied research and modeling in support of recovery efforts within a strategic 

framework 

5.1.	 Determine factors that influence the distribution of desert tortoises. 

 Validate and refine the desert tortoise habitat model (Nussear et al. 2009). The 

habitat model should be expanded to model potential effects of global climate 

change on existing desert tortoise habitat. Data collected from the range-wide 

monitoring program or other surveys, especially those outside currently 

designated critical habitat, may also be used to refine the model. 

 Determine characteristics that contribute to the relative condition (e.g., high, 

medium, or low quality) of desert tortoise habitat. Variation in desert tortoise 

habitat quality likely contributes to habitat-specific demographic rates (e.g., 

higher recruitment in habitats with nutritious forage and few ravens; see Pulliam 

1996) and occupancy. Some environmental factors, such as water available from 

rainfall, may be beyond the scope of management, but identifying specific, 

measurable characteristics of habitat that contribute to high rates of survival, 

reproduction, and recruitment is important to inform effective recovery efforts. 

Information from this recovery action is essential to meeting Recovery Criterion 3 

relative to ensuring that habitat quality increases over at least the next 25 years. 

Research in this area should identify: 

•	 factors that affect how desert tortoises function within altered landscapes or 

habitat affected by climate change; 

•	 landscape attributes, if any, that cause clumping of desert tortoises; and 

•	 minimum conditions for potential desert tortoise occupancy. 

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5.2.	 Conduct research on the restoration of desert tortoise habitat. 

 Evaluate the effectiveness of different restoration methods. While a body of 

research exists on the science of restoration and revegetation of desert ecosystems 

(Lovich and Bainbridge 1999; Ostler et al. 2002; Warren and Ostler 2002; Ostler 

and Hansen 2003; Webb 2002), managers lack a comprehensive source of 

information on methods, techniques, and results of past restoration projects in the 

Mojave Desert (Weigand and Rodgers 2009). More work is necessary to identify 

effective restoration methods in order to successfully implement Recovery Action 

2.6. 

 Identify methods to eradicate non-native, invasive plants within desert tortoise 

habitat. Invasive plants are a significant threat to desert tortoise habitat and 

populations across the species’ range. Research is needed to identify methods for 

weed suppression or eradication in order to successfully implement Recovery 

Action 2.6. 

 Assess the ecological consequences of climate change on future vegetation 

communities within the range of the desert tortoise. Integrated modeling, 

monitoring, and experimentation is needed to assess restoration opportunities 

relative to changes in vegetation communities and in the face of potential retreat 

of some invasive species (Bradley et al. 2009). 

 Correlate habitat restoration with desert tortoise population status. The response 

of tortoise populations to restoration efforts should be evaluated, especially as 

habitat-specific demography is clarified (5.3). This action may also be 

implemented in coordination with population augmentation (3.1-3.4) and 

monitoring demographic study areas (4.1). 

5.3.	 Improve models of threats, threat mitigation, and desert tortoise demographics. 

The decision support system (6.1) requires information on how threats affect desert 

tortoise populations and how management actions abate those threats. This 

information has currently been incorporated in the decision support system in a very 

rudimentary way. 

 Develop conceptual and quantitative models of threats. Models of desert tortoise 

threats are needed to clarify interactive relationships between threats and to 

identify critical synergies that contribute to population declines. In addition, the 

demographic effects of individual threats and suites of threats on desert tortoise 

populations should be determined experimentally whenever possible. 

 Develop and test models of the effectiveness of management actions. The 

corollary of modeling and experimentally investigating threats is determining the 

effectiveness of threat mitigation by specific management actions (for example, 

developing effective grazing-related mitigation practices outside of tortoise 

conservation areas to determine whether specific grazing regimes can be 

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compatible with tortoise recovery). Recovery Implementation Teams should 

identify and secure funding for applied research on the effectiveness of recovery 

actions based on local priorities. Conceptual models should be developed for all 

recovery actions, and these models should be quantified with new research and 

monitoring information, as it becomes available. 

 Model desert tortoise demography relative to habitat condition to determine the 

proportion of habitat that needs to be occupied (or is available to be occupied) for 

recovery. As habitat-specific demography is clarified, population models should 

be developed to refine estimates of habitat quantity and tortoise occupancy 

necessary to sustain populations into the future. Models should incorporate 

predicted effects of climate change on desert tortoise demography as well as on 

the current composition of tortoise habitat. Information from this recovery action 

is essential to refining Recovery Criterion 3 relative to the amount of habitat 

needed to meet the conditions for delisting. 

 Update previous population viability analyses (USFWS 1994a). New 

demographic data should be used to conduct population viability analyses with an 

emphasis on exploring the impact of environmental catastrophes and spatiotemporal variation (variation in space and time) on long-term persistence within 

tortoise conservation areas. 

5.4.	 Conduct research on desert tortoise diseases and their effects on tortoise 

populations. While the precise role of disease in desert tortoise population declines 

relative to other threats is unclear, disease has been a high-profile and controversial 

topic. Therefore, we provide specific recommendations to better understand the 

nature and relative importance of disease to desert tortoise populations. The first three 

recommendations below arise from the working hypothesis that mycoplasmosisinduced die-offs are initiated by environmental stressors. 

 Determine whether population declines through environmental stress are less 

severe when Mycoplasma is absent. 

 Determine if desert tortoises exposed to simulated drought conditions become 

more susceptible to infection and more infectious. 

 Determine whether diets high in plants of low nutritional value increase 

susceptibility to disease, as well as infectiousness. 

 Identify the virulent and less virulent strains of Mycoplasma circulating in wild 

and captive populations and monitor temporal and spatial change in prevalence in 

relation to host genetic status and environmental stressors. Identification of genes 

expressing toxin production and the circumstances when these genes are 

expressed could be a fruitful area of research. Studies examining the level of cross 

immunity between strains and variation in resistance in relation to the plane of 

nutrition and availability of water would be of great assistance. This research aims 

83
 
 

 

to examine the presence and variation in Mycoplasma strains with the aim of 

containing virulent strains. 

 Identify which individual tortoises are shedding, how they shed (i.e., transmit), 

when they shed, and for how long they shed infectious Mycoplasma particles. 

Identify whether individuals removed from drought-stressed areas or areas with 

severely deteriorated habitats continue to shed Mycoplasma and for how long. 

This research will identify in more detail seasonal forces of infection, the period 

of infectiousness, and how infectiousness varies under different circumstances. 

 Undertake trials to determine if it is possible to cure individuals with Mycoplasma 

infections, even if only feasible in captive individuals. Preliminary veterinary 

trials with mixed antibiotics and anti-inflammatory steroids have met with some 

success and could be extended. 

 Examine the behavior of infectious tortoises in comparison to uninfected tortoises 

in the wild. Obtain estimates of contact rate according to sex, age, and season. 

This research will help us understand the most critical epidemiological parameters 

associated with transmission and, with other data, allow us to produce a predictive 

model of outbreak. 

 Examine the implications of releasing sick tortoises into uninfected populations. 

Such studies should occur within enclosures at captive holding facilities. 

 Further explore natural antibodies in desert tortoises. 

 Create a comprehensive disease-tortoise population model that incorporates the 

above information. A disease-tortoise population model could be used to 

anticipate outbreaks and patterns of spread. 

 Evaluate other known or emerging diseases for effects on desert tortoise 

populations. Less is known about other diseases that have been identified in the 

desert tortoise (e.g., herpesvirus, cutaneous dyskeratosis). Continued study of 

Mycoplasma will help facilitate investigations of other diseases. In the meantime, 

surveys or pathological study of other diseases should be conducted within the 

context of other threats (e.g., 5.4). 

5.5.	 Determine the importance of corridors and physical barriers to desert tortoise 

distribution and gene flow. Determining the importance of corridors and barriers 

will allow population models to be made spatially explicit relative to current land 

management (e.g., population and habitat fragmentation due to roads, urbanization, 

and energy development) and potential distributional shifts resulting from climate 

change. 

84
 
 

 

 

 

 

 

6.	 Implement an Adaptive Management Program 

Recovery Implementation Teams (established under Strategic Element 1; Partnerships in 

Figure 4) will be the driving force, in coordination with the Desert Tortoise Recovery Office, 

behind implementation of the adaptive management program. Here, we describe the specific 

steps that the Recovery Implementation Teams and Desert Tortoise Recovery Office must apply 

in order to fully implement the program. We refer to these steps, depicted in Figure 4, with 

italicized labels in the text below. 

6.1.	 Revise and continue development of a recovery decision support system. The 

Recovery Implementation Teams begin the adaptive management process by 

Assessing the Problem. Toward that end, a spatial decision support system is being 

developed (Appendix B) to identify and prioritize recovery actions relative to 

managing desert tortoise populations and habitat. Due to the lack of data on the 

effects of individual threats on tortoise demography, the initial decision support 

system has been based largely on information collected from workgroups convened 

during the recovery planning process or other sources, simple preliminary models, 

and expert opinion. Initial application of the decision support system is not an attempt 

to represent certainties about the relationship between tortoise populations, habitat, 

threats, and management, but instead to establish a “rapid prototype” that will identify 

key assumptions and allow evaluation of the relative importance of different 

assumptions, components, or gaps in the model (Starfield 1997; Nicolson et al. 2002). 

The models contained within this rapid-prototype decision support system, including 

any new monitoring or research results, should be regularly Evaluated (at least 

biennially) by independent reviewers, including the Science Advisory Committee. 

The decision support system should be then be Adjusted to achieve goals that a) 

ensure the overall decision support system is clearly partitioned into a suite of models 

with clear purposes, b) ensure all models or components are transparent and 

comprehensible, and c) the sensitivity of model output to different parameter values 

and assumptions is adequately tested. It is especially critical to continue to update the 

underlying data in the decision support system with a range-wide, geospatial database 

of current management activities, landscape information on threats, habitat quality 

and quantity, and tortoise populations. In addition to contributing to models, 

maintaining an up-to-date database will facilitate reporting of implementation 

progress. 

Specific tasks and timelines relative to this action include: 

 Within the first year after publication of the final, revised recovery plan, the 

Recovery Implementation Teams, Desert Tortoise Recovery Office, and other 

partners, should update the underlying data in the decision support system for at 

least two recovery units, including data on threats and current recovery-action 

implementation. This stage should be completed for the remaining recovery units 

within the second year, and regular updates to all recovery units should occur on 

an ongoing basis thereafter. 

85
 
 

 

 

 

 Within the second year after publication of the revised recovery plan, the Desert 

Tortoise Recovery Office, Science Advisory Committee, and other independent 

reviewers should evaluate the underlying models in the decision supports system. 

Re-evaluation should occur at least biennially, although it is likely that different 

models will be in different stages of evaluation or revision within each biennium. 

 Refinement of the decision support system should continue to clarify and 

operationalize recovery action terminology. One of the challenges in developing 

the prototype decision support system was making the list of recovery actions 

more operational. For example, not all actions are mutually exclusive of one 

another; several are complementary and can be implemented in tandem. Several 

actions listed in the 1994 Recovery Plan overlap with one another, and it was 

clear from the recovery planning workshops that various actions meant different 

things to different people. 

6.2.	 Develop/revise recovery action plans. Recovery Implementation Teams should use 

the decision support system to tier off the recovery plan by developing five-year 

action plans and budget needs with priorities for management scaled down to local or 

jurisdictional levels (i.e., participation plans, as described in USFWS and National 

Oceanic and Atmospheric Adminstration [NOAA] 1994). Five-year action plans 

should be coordinated with the Management Oversight Group and completed within 

the first year of publication of the revised recovery plan. Initial application of the 

decision support system for prioritizing actions at the local or regional level will vary 

among recovery units according to the timeline for updating the system, as described 

above. 

 The first step in each adaptive-management iteration includes prioritizing general 

actions, followed by identification of spatially and temporally explicit actions, 

specific enough that the action plans can be reviewed, critiqued, and adopted 

without confusion in relevant planning documents of the participating land 

management agencies. For instance, if “roads” are identified as a priority threat in 

a particular Recovery Implementation Team area, the general action 

recommended might be “road closures.” The Recovery Implementation Team 

would then proceed to recommend specific roads for closure, so that the 

appropriateness of this action can be evaluated, and the action agencies have clear 

understanding of the Recovery Implementation Teams’ recommendations. 

 In conjunction with prioritizing recovery actions, the Recovery Implementation 

Teams must prioritize needs for effectiveness Monitoring or other Research. In 

order to rank monitoring priorities, a further step from the decision support 

system is required. Recovery Implementation Teams will need to describe 

conceptual models that link each threat to each of the pathways that impact 

tortoise health, survival, movement, population structure, recruitment, or 

fecundity. These models are part of Assessing the Problem and are the first step in 

describing the linkages that will be affected by management activities, so they 

also point to the type of Monitoring or Research that will capture the 

86
 
 

 

 

 

 

effectiveness of these activities in breaking the links. Population augmentation in 

conjunction with other land management, effectiveness monitoring, or research 

activities may also be recommended through the procedures described under 

Recovery Action 3. These 4 elements (Strategic Elements 2-5) will be reviewed 

by the Desert Tortoise Recovery Office and placed within the larger range-wide 

strategy. 

 Once the recovery action plans, including prioritized actions, monitoring, and 

research, have been developed by the Recovery Implementation Teams and 

Desert Tortoise Recovery Office and approved by the Management Oversight 

Group, the relevant land management agencies will use their own processes to 

Design and Implement actions. By Design, we mean that the necessary planning 

processes will be engaged to formalize each agency’s commitments to the 

adopted actions. Because all Recovery Implementation Team members should 

remain fully engaged, it is important that all represented land management 

agencies have clear tasks for each Recovery Implementation Team cycle. 

 All Recovery Implementation Teams will have access to the data and models in 

the system, via one or more of the following capabilities: 1) a desktop application 

in which land managers and stakeholders spatially define and prioritize recovery 

actions and enter implementation metrics; 2) an online web application where 

land managers and stakeholders can register, update, and edit implementation 

metrics, and review progress; and 3) an online web application where land 

managers and stakeholders can create monitoring programs, adding and editing 

effectiveness metrics, updating results, and reviewing progress. 

 The Recovery Implementation Teams and Desert Tortoise Recovery Office 

should report progress on recovery implementation to the Management Oversight 

Group on an annual basis and revise the recovery action plans accordingly. 

6.3.	 Amend land use plans, habitat management plans, and other plans as needed to 

implement recovery actions. Federal, State, County, and City land managers should 

Adjust recovery efforts based on outcomes of the processes described above by 

amending planning documents as needed. Broad land-use plans, such as Bureau of 

Land Management resource management plans, may not need revision, as they often 

include language stipulating that agencies will strive to implement recovery for 

federally listed species. Program-level or area-specific plans, such as habitat 

management plans, wilderness plans, and Area of Critical Environmental Concern 

plans, are an opportunity to work with stakeholders to build in detailed planning at 

local levels. 

6.4.	 Incorporate scientific advice for recovery through the Science Advisory 

Committee. The Desert Tortoise Recovery Office should continue to work directly 

with the Science Advisory Committee and other independent experts, meeting at least 

annually to Evaluate progress in Research and Monitoring and other recovery plan 

accomplishments. The Science Advisory Committee should make new 

87
 
recommendations, as needed, based on progress in implementing the recovery plan. A 

particular need exists for vigilance in focusing on large-scale, range-wide tortoise 

recovery, maintaining connection to Recovery Criteria in the 25-year horizon, 

through at least five-year evaluations of the range-wide monitoring program. Annual 

Science Advisory Committee meetings should include an opportunity for stakeholder 

and manager interaction, in association with Management Oversight Group meetings, 

to provide direct feedback and information exchange. 

88
 
 

 

 

 

 

 

 

 

 

 

 

Table 4. Comparison of recovery actions between the 1994 and 2011 recovery plans. Acronyms are 

defined at the end of the table. 

Recovery Action 1994 2011 Comments 

1994: DWMAs designated and are now managed as 

ACECs on BLM lands, where critical habitat 

generally coincides. 2011: Expands "tortoise 

conservation areas" to include desert tortoise habitats 

within critical habitat, DWMAs/ACECs, and other 

Establish DWMAs and implement areas managed for the desert tortoise. Recovery 

management plans D.1.a-b, d 6.2 action plans are recommended for each area. 

Specifically, establish regional Recovery 

Develop, support, and build Implementation Teams to prioritize and coordinate 

partnerships to facilitate recovery 1 implementation of recovery actions. 

Emphasis is placed on DWMAs/tortoise 

conservation areas. 2011: 2.11 also emphasizes 

Secure habitat D.1.c 2.9 connecting functional habitat. 

2011: Includes using the Desert Tortoise 

Environmental education D.2, E.2.h 2.3 Conservation Center as education/research facility. 

1994: Recovery action E.1 includes a list of activities 

recommended for prohibition throughout all 

DWMAs. 

All vehicle activity off of 

designated roads; all competitive 

and organized events on designated 

roads 

Exclude from DWMAs/tortoise conservation areas 

E.1 2.4,10 

Habitat destruction and other 

surface-disturbing activities E.1 2.1 

1994: Mining acceptable on a case-by-case basis, 

provided that cumulative impacts do not significantly 

impact desert tortoise habitats or populations, that 

any potential effects on desert tortoise populations 

are carefully mitigated during the operation, and that 

Mining 2.12 the land is restored to its pre-disturbance condition. 

Action recommended until research finds grazing 

Domestic livestock grazing E.1 2.16 regimes compatible with tortoise recovery. 

Grazing by feral ("wild") burros and 

horses E.1 2.15 

Vegetation harvest, except by 2011: Not considered to be an action that warrants 

permit E.1 focus above existing land management plans. 

Collection of biological specimens, 2011: Enforcing prohibitions on collection of desert 

except by permit E.1 2.4 tortoises is inherent to the law enforcement action. 

Dumping and littering E.1 2.4 2011: Included under law enforcement action. 

Deposition of captive or displaced 

desert tortoises or other animals, 

except under authorized 

translocation research projects E.1 2.4 2011: Included under law enforcement action. 

Uncontrolled dogs out of vehicles E.1 2.4 2011: Included under law enforcement action. 

Discharge of firearms, except for 

hunting of big game or upland game 

birds from September through 

February E.1 2.4 2011: Included under law enforcement action. 

Restrict establishment of new roads E.2.a.1 2.5 

89
 
 

 

 

 

 

 

 

 

 

Table 4. Continued. 

Recovery Action 1994 2011 Comments 

Implement closure to vehicular 

access with exception of designated 

routes E.2.a.2 2.5 

2011: Existing roads should be designated as open, 

closed, or limited. Non-essential or redundant routes 

should be closed. 

Implement emergency closures of 

dirt roads and routes as needed to 

reduce human access and 

disturbance in areas where humancaused mortality of desert tortoises 

is a problem E.2.a.3 2.5 

2011: Existing roads should be designated as open, 

closed, or limited. Non-essential or redundant routes 

should be closed. 

Fence or otherwise establish 

effective barriers to tortoises along 

heavily-traveled roads; install 

culverts that allow underpass of 

tortoises to alleviate habitat 

fragmentation E.2.a.4 2.5,2.11 

25mph speed limits on appropriate 

rural roads 2.5 1994: Not included in the 1994 plan. 

Maintain berms along dirt roads 

such that tortoises do not get 

trapped in the roadbed 2.5 1994: Not included in the 1994 plan. 

Enforce regulations E.2.b 2.4 2011: Increase law enforcement. 

Restore disturbed areas E.2.c 2.6 

2011: The revised plan expands on and provides 

additional specific recommendations from the 1994 

plan. 

Eradicate or suppress invasive 

weeds 2.6 1994: Not included in the 1994 plan. 

Revegetate degraded areas with 

native plants of high nutritive 

quality to desert tortoises, as well as 

shrubs needed for cover 2.6 1994: Not included in the 1994 plan. 

Remove toxicants and unexploded 

ordnance 2.6 1994: Not included in the 1994 plan. 

Sign and fence DWMA/protected 

area boundaries E.2.d 2.8 

2011: Also specifies signing boundaries of heavily 

impacted areas 

Install and maintain urban and other 

barriers 2.7 

1994: Not included in the 1994 plan. 2011: Several 

specific locations are described in the plan. 

Implement appropriate 

administration E.2.e 1 

2011: The actions described by the 1994 plan are 

functionally covered by Recovery Implementation 

Teams. 

Modify ongoing and planned 

activities so they are consistent with 

desert tortoise recovery E.2.f 6.2,6.3 

2011: This is covered in detail in the adaptive 

management strategic element. 

Control use of landfills and sewage 

ponds by desert tortoise predators 

(no new landfills in DWMAs; 

address unauthorized dumping) E.2.g 2.13 

Minimize factors contributing to 

disease 2.2 

1994: Not included in the 1994 plan. 2011: Several 

specific actions are described in the plan. 

Minimize excessive predation on 

desert tortoises in identified 

problem areas 2.14 1994: Not included in the 1994 plan. 

90
 
 

 

 

 

Table 4. Continued. 

Recovery Action 1994 2011 Comments 

Continue development of recovery 

decision support system 6.1 1994: Not included in the 1994 plan. 

Incorporate scientific advice for 

recovery through the Science 

Advisory Committee 6.4 1994: Not included in the 1994 plan. 

Population Augmentation 

Develop protocols and guidelines 3.1 1994: Not included in the 1994 plan. 

Identify sites at which to implement 

population augmentation 3.2 1994: Not included in the 1994 plan. 

Secure facilities and obtain tortoises 

for use in augmentation 3.3 1994: Not included in the 1994 plan. 

Implement translocations in target 

areas to augment populations using 

a scientifically rigorous, researchbased approach 3.4 1994: Not included in the 1994 plan. 

Monitoring 

Monitor population growth D.1.f 4.1 

Monitor tortoise distribution 4.2 1994: Not included in the 1994 plan. 

Monitor tortoise habitat 4.3 1994: Not included in the 1994 plan. 

Quantify threats 4.4 1994: Not included in the 1994 plan. 

Research 

Densities inside and outside 

DWMAs D.3.a 5.3 

2011: While not specific to comparisons inside and 

outside of DWMAs, the basic concepts of the 1994 

action are subsumed under research 

recommendations relative to threats, management, 

and tortoise demographics in the revised plan. 

Model desert tortoise demography D.3.b 5.3, 5.2 

2011: Includes modeling demography relative to 

habitat condition, including predicted effects of 

climate change, to determine the proportion of 

habitat that needs to be occupied for recovery, as 

well as updated population viability analyses. Also 

correlate habitat restoration with desert tortoise 

population status. 

Epidemiology of URTD and other 

diseases D.3.b.1 5.4 

2011: The revised plan expands on and provides 

additional specific recommendations from the 1994 

plan. 

Determine whether population 

declines through environmental 

stress are less severe when 

Mycoplasma is absent 5.4 

Determine if desert tortoises 

exposed to simulated drought 

conditions become more susceptible 

to infections and more infectious 5.4 

Determine whether diets high in 

plants of low nutritional value 

increase susceptibility to disease, as 

well as infectiousness 5.4 

91
 
 

 

 

 

 

 

 

 

Table 4. Continued. 

Recovery Action 1994 2011 Comments 

Identify virulent and less virulent 

strains of Mycoplasma circulating 

in wild and captive populations and 

monitor temporal and spatial 

change in prevalence in relation to 

host genetic status and 

environmental stressors 5.4 

Identify which individual tortoises 

are shedding, how they shed (i.e., 

transmit), when they shed and, for 

how long they shed infectious 

Mycoplasma particles 5.4 

Undertake trials to determine if it is 

possible to cure individuals with 

Mycoplasma infections, even if only 

feasible in captive individuals 

5.4 

Examine behavior of infectious 

tortoises in comparison to 

uninfected tortoises in the wild 5.4 

Examine implications of releasing 

sick tortoises into uninfected 

populations 5.4 

Further explore natural antibodies 

in desert tortoises 5.4 

Create a comprehensive diseasetortoise population model that 

incorporates the above information 5.4 

Evaluate other known or emerging 

diseases for effects on desert 

tortoise populations 5.4 

Sources and relative contribution of 

mortality D.3.b.2 5.3 

2011: Develop conceptual and quantitative models of 

threats. 

Recruitment & survivorship of 

young age classes D.3.b.3 5.1+ 

2011: The basic concepts of the 1994 action are 

subsumed within the research recommendation to 

determine factors that influence the distribution of 

desert tortoises, among others, in the revised plan. 

Population structure D.3.b.4 2011: Not included in the revised plan. 

Long-term research on impacts of 

grazing, road density, barriers, 

human-use levels, restoration, 

augmentation, and translocation on 

desert tortoise populations D.3.c 5.3 

2011: Develop conceptual and quantitative models of 

threats. 

Effectiveness of protective 

measures D.3.d 5.2,3 

2011: Specifically includes effectiveness of different 

habitat restoration methods. 

Spatial variability of climate and 

plant productivity, correlated with 

population parameters D.3.e 5.1 

2011: More specifically, determine characteristics 

that contribute to the relative condition of desert 

tortoise habitat. 

Nutritional and physiological 

ecology D.3.f 5.4 

2011: See nutrition/disease research recommendation 

above. 

Reproductive behavior and 

physiology D.3.g 5.1 

2011: This is integral to the demography research 

recommendation. 

92
 
 

Table 4. Continued. 

Recovery Action 1994 2011 Comments 

Validate and refine the desert 

tortoise habitat model 5.1 1994: Not included in the 1994 plan. 

Identify methods to eradicate nonnative, invasive plants within desert 

tortoise habitat 5.2 1994: Not included in the 1994 plan. 

Determine importance of corridors 

and physical barriers to desert 

tortoise distribution and gene flow 5.5 1994: Not included in the 1994 plan. 

ACEC: Area of Critical Environmental Concern 

BLM: U.S. Bureau of Land Management 

DWMA: Desert Wildlife Management Area 

URTD: upper respiratory tract disease 

93
 
 

 

 

 

 

Table 5. Reference table connecting major recovery actions to listing factors and recovery objectives. 

Recovery actions are categorized according to each strategic element of the recovery program. Subactions 

for each major recovery action are not listed (see the recovery narrative). 

Recovery Action Listing 

Factor 

Recovery 

Objective 

1. 

1.1 

Develop, support, and build partnerships to facilitate recovery 

Establish regional, inter-organizational Recovery Implementation 

Teams to prioritize and coordinate implementation of recovery actions. 

All All 

2. 

2.1 

2.2 

2.3 

2.4 

2.5 

2.6 

2.7 

2.8 

2.9 

2.10 

2.11 

2.12 

2.13 

2.14 

2.15 

2.16 

Protect existing populations and habitat 

Conserve intact desert tortoise habitat. 

Minimize factors contributing to disease. 

Establish/continue environmental education programs. 

Increase law enforcement. 

Restrict, designate, close, and fence roads. 

Restore desert tortoise habitat. 

Install and maintain urban or other barriers. 

Sign and fence boundaries of sensitive or impacted areas. 

Secure lands/habitat for conservation. 

Restrict off-highway vehicle events within desert tortoise habitat. 

Connect functional habitat. 

Limit mining and minimize its effects. 

Limit landfills and their effects. 

Minimize excessive predation on tortoises. 

Minimize impacts to tortoises from horses and burros. 

Minimize impacts to tortoises from livestock grazing. 

A,E 

C 

All 

A-D 

A-D 

A,E 

A-C 

A,B 

A 

A,B 

A 

A,C 

A,C 

C 

A 

A 

3 

1,2 

All 

All 

All 

3 

All 

3 

3 

All 

2 

All 

1,3 

1 

3 

3 

3. 

3.1 

3.2 

3.3 

3.4 

Augment depleted populations through a strategic program 

Develop protocols and guidelines for the augmentation program. 

Identify sites at which to implement population augmentation efforts. 

Secure facilities and obtain tortoises for use in augmentation efforts. 

Implement translocations in target areas to augment populations. 

All 

All 

All 

All 

1-2 

1-2 

1-2 

All 

4. 

4.1 

4.2 

4.3 

Monitor progress toward recovery 

Monitor desert tortoise population growth. 

Monitor the extent of tortoise distribution in each recovery unit. 

Track changes in the quantity and quality of desert tortoise habitat. 

All 

All 

A,D,E 

1 

2 

3 

94
 
 

 

 

 

 

 

 

 

 

Table 5. Continued. 

Recovery Action Listing 

Factor 

Recovery 

Objective 

4.4 Quantify the presence and intensity of threats to the desert tortoise 

across the landscape. 

All All 

5. 

5.1 

5.2 

5.3 

5.4 

5.5 

Conduct applied research and modeling in support of recovery efforts within a 

strategic framework 

Determine factors that influence the distribution of desert tortoises. All 2,3 

Conduct research on the restoration of desert tortoise habitat. A,E 3 

Improve models of threats, threat mitigation, and desert tortoise 

demographics. 

All 1,3 

Conduct research on desert tortoise diseases and their effects on tortoise 

populations. 

C 1,2 

Determine the importance of corridors and physical barriers to desert 

tortoise distribution and gene flow. 

All 1,2 

6. 

6.1 

6.2 

6.3 

6.4 

Implement an adaptive management program 

Revise and continue development of a recovery decision support system. All All 

Develop/revise recovery action plans. All All 

Amend land use plans, habitat management plans, and other plans as 

needed to implement recovery actions. 

All All 

Incorporate scientific advice for recovery through the Science Advisory 

Committee. 

All All 

Listing Factors: 

A.	 The present or threatened destruction, modification, or curtailment of its habitat or range 

B.	 Overutilization for commercial, recreational, scientific, or educational purposes 

C.	 Disease or predation 

D.	 The inadequacy of existing regulatory mechanisms 

E.	 Other natural or manmade factors affecting its continued existence 

Recovery Objectives: 

1.	 Maintain self-sustaining populations of desert tortoises within each recovery unit into the future. 

2.	 Maintain well-distributed populations of desert tortoises throughout each recovery unit. 

3.	 Ensure that habitat within each recovery unit is protected and managed to support long-term viability of desert 

tortoise populations. 

95
 
96
 
 

 

 

 

 

 

 

 

III. IMPLEMENTATION SCHEDULE 

The implementation schedule outlines the recovery actions discussed in the Recovery 

Program chapter and indicates action numbers, priorities, durations, estimated costs, and partners 

that may be involved in implementing the action. When accomplished, these actions should 

result in improved habitat conditions and favorable population responses that would enable the 

desert tortoise to be delisted. The costs for each actions are rough estimates, and actual budgets 

will have to be determined when each action is undertaken (TBD = to be determined). Cost 

estimates are unavailable for several actions, such as research, due to uncertainties in the scope 

and magnitude of the specific action. Recovery plans are non-regulatory documents, and as such, 

identified partners are not obligated to implement recovery actions. Cost estimates do not 

commit funding by any agency. 

Action priorities in the implementation schedule are assigned as follows: 

Priority 1: An action that must be taken to prevent extinction or to prevent the species from 

declining irreversibly in the foreseeable future. Note that no recovery actions have been assigned 

at the Priority 1 level based on the judgment that the desert tortoise is not on the verge of 

extinction or declining irreversibly at this time (reflected by its status as Threatened, rather than 

Endangered). 

Priority 2: An action that must be taken to prevent a significant decline in species population 

numbers or habitat quality or some other significant negative impact short of extinction. 

Priority 3: All other actions necessary to provide for full recovery of the species. 

We have attempted to provide an overall priority for each recovery action that applies 

across recovery units. However, threats, and therefore the importance of recovery actions that 

ameliorate those threats, vary by recovery unit. Recovery Implementation Teams need to be 

established upon publication of the final revised recovery plan (Recovery Action 1.1), and they 

should guide recovery action priorities and develop updated budget projections within each 

recovery unit through the use of an updated/improved decision support system (6.1-6.2). 

Task duration in Column 4 indicates the number of years estimated to complete the task. 

A Continuing task will continue to be conducted once implemented. Many tasks are listed as 

Ongoing; these are already being conducted and should continue. The Responsible Party 

indicates the lead agency or agencies identified for a particular task and includes the full suite of 

local, State, and Federal land and wildlife management agencies within the desert tortoise’s 

range (= Land Managers). Other stakeholders or organizations (included in “All”) may also 

contribute to particular recovery actions. However, other parties may also have significant roles 

in different tasks, and (as mentioned above) the listing of a party does not require the identified 

party to implement the action(s) or to secure funding for implementing the action(s). 

Abbreviations of the responsible parties identified in the Implementation Table are 

defined as follows: 

97
 
BLM – Bureau of Land Management 

CC MSHCP – Clark County, Nevada, Multiple Species Habitat Conservation Plan 

CS MSHCP – Coyote Springs, Nevada, Multiple Species Habitat Conservation Plan 

DOD – Department of Defense 

MNP – Mojave National Preserve 

NPS – National Park Service 

USFWS – U.S. Fish and Wildlife Service 

USGS – U.S. Geological Survey 

WC HCP – Washington County, Utah, HCP 

98
 
 

 

 

 

 

 

 

 

 

 

 

99

Implementation Schedule Costs (thousands of dollars) 

Duration Responsible 

Recovery Action Priority (years) Party FY 1 FY 2 FY 3 FY 4 FY 5 Total 

1. Develop, support, and build partnerships to facilitate recovery 

1.1 Establish regional, inter-organizational RITs to coordinate 2 Continuing USFWS (All) 500 500 500 500 500 12,500 

implementation activities of recovery actions. 

2. Protect and manage existing populations and habitat 

2.1 Conserve intact desert tortoise habitat. 2 Ongoing Land Managers Negligible additional costs above normal activities. 

2.2 Minimize factors contributing to disease. 2 Continuing All 10 10 10 10 10 250 

2.3 Establish/continue environmental education programs. 2 Ongoing All 100 100 100 100 100 2,500 

2.4 Increase law enforcement. 2 Ongoing Land Managers 1000 1000 1000 1000 1000 25,000 

2.5 Restrict, designate, close, and fence roads. 2 Ongoing BLM, NPS 1000 1000 1000 1000 1000 10,000 

2.6 Restore desert tortoise habitat. 2 Continuing Land Managers TBD TBD TBD TBD TBD TBD 

2.7 Install and maintain urban or other barriers. 

Upper Virgin River Recovery Unit 2 2 WC HCP, BLM 0 0 01 

Eastern/Northeastern Mojave recovery units 2 5 CC MSHCP 

CS MSHCP 0 0 0 0 0 01 

Western Mojave Recovery Unit 2 5 Land Managers 200 200 200 200 200 1,000 

Remainder of desert tortoise range 3 5 Land Managers 500 500 500 500 500 2,500 

2.8 Sign and fence boundaries of sensitive or impacted areas. 

Upper Virgin River Recovery Unit 2 2 WC HCP, BLM 0 0 01 

Remainder of desert tortoise range 3 Ongoing Land Managers 600 600 600 600 600 3,500 

2.9 Secure lands/habitat for conservation. 

Upper Virgin River, Colorado Desert, and Western Mojave recovery 2 Ongoing Land Managers TBD TBD TBD TBD TBD TBD 

units 

Remainder of desert tortoise range 3 Ongoing Land Managers TBD TBD TBD TBD TBD TBD 

2.10 Restrict off-highway vehicle events within desert tortoise habitat. 3 Ongoing BLM 50 50 50 50 50 1,250 

2.11 Connect functional habitat. 3 Ongoing Land Managers TBD TBD TBD TBD TBD TBD 
 

 

 

 

 

 

 

 

 

 

Implementation Schedule Continued	 Costs (thousands of dollars) 

Duration Responsible 

Recovery Action Priority (years) Party FY 1 FY 2 FY 3 FY 4 FY 5 Total 

2.12 Limit mining and minimize its effects.	 3 Ongoing BLM 100 100 100 100 100 1,000 

2.13 Limit landfills and their effects.	 3 Ongoing Counties 100 100 100 100 100 2,500 

2.14 Minimize excessive predation on tortoises.	 3 10 Land Managers 100 100 100 100 100 1,000 

2.15 Minimize impacts to tortoises from horses and burros.	 3 Ongoing BLM, NPS 500 500 500 500 500 12,500 

2.16 Minimize impacts to tortoises from livestock grazing.	 3 Ongoing BLM, MNP 100 100 100 100 100 2,500 

3.	 Augment depleted populations through a strategic program 

3.1	 Develop protocols and guidelines for the augmentation program. 2 1 USFWS 50 50 

3.2	 Identify sites at which to implement population augmentation 2 1 USFWS 50 50 

efforts. 

3.3	 Secure facilities and obtain tortoises for use in augmentation efforts. 2 10 USFWS, DOD, 500 500 500 500 500 5,000 

MNP 

10

0

3.4	 Implement translocations in target areas to augment populations 2 15 USFWS, Land TBD TBD TBD TBD 

using a scientifically rigorous, research-based approach. Managers 

4.	 Monitor progress toward recovery 

4.1	 Monitor desert tortoise population growth. 3 Ongoing USFWS (All) 1,500 1,500 1,500 1,500 1,500 37,500 

4.2	 Monitor the extent of tortoise distribution in each recovery unit. 3 Continuing USFWS (All) 1,500 1,500 1,500 1,500 1,500 37,500 

4.3	 Track changes in the quantity and quality of desert tortoise habitat. 3 Continuing USFWS (All) TBD TBD TBD TBD TBD TBD 

4.4	 Quantify the presence and intensity of threats to the desert tortoise 3 Continuing USFWS (All) TBD TBD TBD TBD TBD TBD 

across the landscape. 

5.	 Conduct applied research and modeling in support of recovery efforts within a strategic framework 

5.1	 Determine factors that influence the distribution of desert tortoises. 3 TBD USFWS, USGS TBD TBD TBD TBD TBD TBD 

(other research 

institutions) 
 

 

 

 

 

 

 

 

 

Implementation Schedule Continued	 Costs (thousands of dollars) 

Duration Responsible 

Recovery Action Priority (years) Party FY 1 FY 2 FY 3 FY 4 FY 5 Total 

5.2	 Conduct research on the restoration of desert tortoise habitat. 3 TBD All, research TBD TBD TBD TBD TBD TBD 

institutions 

5.3	 Improve models of threats, threat mitigation, and desert tortoise 3 TBD USFWS (All; TBD TBD TBD TBD TBD TBD 

demographics.	 research
 

institutions)
 

5.4	 Conduct research on desert tortoise diseases and their effects on 3 TBD USFWS TBD TBD TBD TBD TBD TBD 

tortoise populations.	 (research
 

institutions)
 

5.5	 Determine the importance of corridors and physical barriers to desert 3 3 Research TBD TBD TBD TBD 

tortoise distribution and gene flow. institutions 

6.	 Implement an adaptive management program 

6.1	 Revise and continue development of a recovery decision support 2 Ongoing USFWS (All) 50 10 5 5 5 175 

system. 

6.2	 Develop/revise recovery action plans. 2 Continuing All Costs included under Action 1.1 

6.3	 Amend land use plans, habitat management plans, and other plans as 3 Continuing Land Managers TBD TBD TBD TBD TBD TBD 

needed to implement recovery actions. 

6.4	 Incorporate scientific advice for recovery through the Science 3 Ongoing USFWS (All) 5 5 5 5 5 125 

Advisory Committee. 

10

FY Totals (These totals are minimum cost estimates that do not include TBD costs.) 8615 8475 8470 8470 8470 1

Costs for minimizing mortality and Habitat Conservation Plan activities are not included because these costs are typically required by regulatory processes, rather than as 

proactive recovery actions. 

Total cost of recovery through 2025: $159,000,000 plus additional costs that cannot be estimated at this time. 
10 
 

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Huxman, A.K. Knapp, G. Lin, W.T. Pockman, M.R. Shaw, E.E. Small, M.D. Smith, S.D. 

Smith, D.T. Tissue, and J.C. Zak. 2003. Assessing the Response of Terrestrial 

Ecosystems to Potential Changes in Precipitation. Bioscience 53:942-952. 

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Williams, B.K., R.C. Szaro, and C.D. Shapiro. 2007. Adaptive Management: The U.S. 

Department of the Interior Technical Guide. Adaptive Management Working Group, 

U.S., Department of the Interior, Washington, D.C. 

Wisdom, M.J., L.S. Mills, and D.F. Doak. 2000. Life stage simulation analysis: estimating vitalrate effects on population growth for conservation. Ecology 81:628-641. 

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Wittenberg, R., and M.J.W. Cock. 2005. Best practices for the prevention and management of 

invasive alien species. Pages 209-232 in H.A. Mooney, R.N. Mack, J.A. McNeely, L.E. 

Neville, P.J. Schei, and J.K. Waage (eds.), Invasive Alien Species: A New Synthesis. 

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Ventura, California. 

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APPENDIX A 

THREATS TO THE MOJAVE POPULATION OF THE DESERT TORTOISE
 

AND ITS HABITAT SINCE THE TIME OF LISTING
 

Below is a synopsis of the threats that formed the basis for listing the desert tortoise as a 

threatened species (USFWS 1990), were further discussed in the 1994 Recovery Plan (USFWS 

1994), and continue to affect the species. A substantive body of data has been accumulated since 

1994 for some of the threats, but others remain relatively unstudied. New information is provided 

where available, and all of the threats warrant continued attention and data collection that will 

inform management actions and recovery implementation through the use of a range-wide 

database and decision support system. 

The vast majority of threats to the desert tortoise or its habitat are associated with human 

land uses. Extensive research shows that all of these individual threats directly kill or indirectly 

affect tortoises. Research has also clarified many mechanisms by which these threats act on 

tortoises. However, despite the clear demonstration that these threats impact individual tortoises, 

there are few data available to evaluate or quantify the effects of threats on desert tortoise 

populations (Boarman 2002; Tracy et al. 2004). While current research results can lead to 

predictions about how local tortoise abundance should be affected by the presence of threats, 

quantitative estimates of the magnitude of these threats, or of their relative importance, have not 

yet been developed. Thus, a particular threat or subset of threats with discernable solutions that 

could be targeted to the exclusion of other threats has not been identified for the desert tortoise. 

The assessment of the 1994 Recovery Plan emphasized the need for a greater 

appreciation of the implications of multiple, simultaneous threats facing tortoise populations and 

a better understanding of the relative contribution of multiple threats on demographic factors 

(i.e., birth rate, survivorship, fecundity, and death rate; Tracy et al. 2004). The approach of 

focusing on individual threats may not have produced expected gains toward desert tortoise 

recovery since 1994 because multiple threats act simultaneously to suppress tortoise populations 

at any given location within the species’ range. Therefore, this revised recovery plan focuses on 

expanding our knowledge of individual threats and places emphasis on understanding their 

multiple and combined effects on tortoise populations. 

A. The Present or Threatened Destruction, Modification, or Curtailment of Its Habitat or 

Range 

1. Urbanization 

Urban development directly affects desert tortoise populations through fragmentation 

and permanent loss of habitat. Areas of the desert southwest occupied by desert tortoises have 

been subject to episodic human settlements and associated impacts since the mid to late 1800s 

(USFWS 1994). Urbanization and associated infrastructure within desert ecosystems continues 

to take place at a rapid pace (Table A-1), and currently more than 30 million people live in close 

proximity to the desert, which is popular with recreationists (Berry et al. 2006a; Hughson 2009). 

Between the years 2000 and 2005, the West experienced an 8.1 percent change in population, 

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compared to 7.3 percent in the South, 2.4 percent in the Midwest, and 2.0 percent in the 

Northeast (U.S. Census Bureau 2005). During this same time period, Nevada saw a 20.8 percent 

increase, Arizona a 15.8 percent increase, Utah a 10.6 increase, and California a 6.7 percent 

increase in population growth (U.S. Census Bureau 2005). 

Table A-1. Human population growth in the states and counties 

within the range of the Mojave population of the desert tortoise 

between 1994 (when the Recovery Plan was published) and 2006. 

State/Counties 1994 Population 

Estimate1 

2006 Population 

Estimate2 

Percent 

Change 

Arizona 4,147,561 6,166,318 48.7 

Mohave 116,320 193,035 66.03 

California 31,317,179 36,457,549 16.4 

Imperial 136,248 160,301 17.7 

Inyo 18,450 17,980 -2.5 

Kern 608,858 780,117 28.1 

Los Angeles 9,048,129 9,948,081 9.9 

Riverside 1,354,966 2,026,803 49.6 

San Bernardino 1,553,732 1,999,332 28.7 

Nevada 1,456,388 2,495,529 71.4 

Clark 938,611 1,777,539 89.4 

Esmeralda 1143 790 -30.9 

Lincoln 3849 4738 23.1 

Nye 21,648 42,693 97.2 

Utah 1,930,436 2,550,063 32.1 

Washington 65,520 126,312 92.8 1 Byerly and Deardorff 1995 

2 U.S. Census Bureau 2007b 

3 Most population increase has been outside the Arizona Strip and the range of the Mojave population of 

the desert tortoise. 

Population growth and urban development in the desert region of the Southwest continue 

to expand into previously undisturbed areas, putting intense pressures on the natural resources. 

St. George, Utah, was the fastest-growing metropolitan area in the U.S. between 2000 and 2006, 

with growth of 39.8 percent. Las Vegas, Nevada, grew 29.2 percent, making it one of the top five 

fastest-growing areas during this time period (U.S. Census Bureau 2007a). In fact, the population 

of the Las Vegas metropolitan area nearly doubled between 1995 and 2005, as more than 5,000 

newcomers continue to move to the Las Vegas area every month. The growth rate is projected to 

slow to approximately 7 percent per year in the longer term (2020 through 2025) as the economy 

matures and fewer new hotels are added (Clark County Department of Aviation 2006). 

Rapid growth is not limited to metropolitan areas. Mohave County, Arizona, grew 66 

percent between 1994 and 2006, and Nye County, Nevada, grew 97 percent during the same time 

period (Table A-1). The Beaver Dam/Littlefield community (within the Virgin River Basin) on 

the Arizona Strip supported some 1,580 persons in 2000. This area saw more than 200 percent 

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growth between 1990 and 2000. Given this rapid growth rate, the population for the basin will be 

between 3,000 and 4,000 persons in 2010 (S. Donahue, Mohave County, pers. comm. 2007). 

Related to population growth, the border with Mexico in both California and Arizona has 

experienced a high level of illegal immigration activity. Illegal immigration traffic can degrade 

habitat for desert tortoises through surface disturbance and dumping. Law enforcement efforts to 

address illegal crossings, such as construction of new roads and the use of off-road vehicles, 

have intensified environmental damage (Sancho 2008). 

Increasing human populations result in corresponding increases in impacts to desert 

tortoise habitat not only through direct habitat loss. Impacts to desert tortoise habitat also occur 

as more people recreate in or otherwise spread into the desert and as greater infrastructure is 

needed to support growing communities and increased desire for access. Lovich and Bainbridge 

(1999) identified various types of anthropogenic impacts from which desert ecosystems may take 

50 to 300 years to recover to pre-disturbance plant cover levels. However, areas that have 

experienced permanent, direct habitat loss due to intense urbanization will never be restored or 

recovered. In addition, urban environments have indirect impacts on desert tortoise populations 

and habitat at their interface with the desert (Berry and Burge 1984; Berry and Nicholson 

1984). Unconfined pets may kill or wound tortoises (see section C(3), Predation), and 

unauthorized collecting of desert tortoises may affect populations (see section B(1), Collection 

by Humans). Human populations subsidize (i.e., provide food for) increasing predator 

populations, which then apply greater pressure on desert tortoise populations near the urbanwildland interface (see section C(3), Predation). Indiscriminate use of firearms and off-highway 

vehicles, dumping of trash, and removal of vegetation or unimproved road proliferation are 

activities that occur in and beyond the urban-desert interface that may result in injury and 

mortality to tortoises and degradation of their habitats (see section E, Other Natural or Manmade 

Factors). Pollution from increasing human populations leads to nitrogen deposition within the 

desert which can lead to increased biomass of non-native grasses and associated impacts (Allen 

et al. 2009). Habitat fragmentation resulting from infrastructure associated with urbanization 

such as residential fencing, roads, and railroad tracks, can greatly inhibit desert tortoise 

movements (Edwards et al. 2004; Brooks and Lair 2005). These barriers to movement and 

population connectivity have implications to exchange of genetic material, which can lead to 

inbreeding, and may result in mortality of individuals (Boarman and Sazaki 1996) (see section 

A(2), Roads). 

2. Paved and Unpaved Roads, Routes, Trails, and Railroads. 

Vehicular roads, routes, and trails are the most common type of human disturbance 

observed in desert ecosystems, and much emphasis has been placed on understanding the 

impacts these linear features have on arid environments (Brooks and Lair 2005). Brooks and Lair 

(2005) cite vehicular routes as one of the biggest challenges to land managers in the desert 

southwest, especially as they relate to the conservation status of the desert tortoise. 

Direct and indirect impacts of roads and railroads on desert tortoise populations are well 

documented and include habitat and population fragmentation and degradation as well as mortality of 

individual tortoises (USFWS 1994, Boarman 2002). Paved and unpaved roads serve as corridors for 

urbanization and dispersal of invasive species and provide access to recreation; railroads also 

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facilitate urbanization and the spread of non-native plants. Roads and railroads also act as barriers to 

movement. Railroads are similar to roads as sources of mortality for desert tortoises, as tortoises can 

become caught between the tracks causing them to overheat and die or be crushed by trains (U.S. 

Ecology 1989). 

Direct effects to desert tortoise habitat from roads, routes, trails, and railroads also occur 

during initial stages of construction or off-highway vehicle route/trail establishment when 

vegetation and soils are lost or severely degraded. Construction of these features can result in 

physical and chemical changes to soils within unpaved roadways as well as in adjacent areas 

(Brooks and Lair 2005). In addition, roadside vegetation is often more robust and diverse 

because water that becomes concentrated along roadside berms promotes germination, which 

attracts tortoises and puts them at higher risk of mortality as road-kill (Boarman et al. 1997). 

Raised roadbeds or other types of linear human infrastructure also affect water runoff patterns 

across the landscape, decreasing soil moisture on upland areas between channels downslope of 

the linear structure and resulting in lower shrub density and biomass (Schlesinger and Jones 

1984; Brooks and Lair 2009). 

Hoff and Marlow (2002) demonstrated that there is a detectable impact on the abundance 

of desert tortoise sign adjacent to roads and highways with traffic levels from 220 to over 5,000 

vehicles per day. The extent of the detectable impact was positively correlated with the measured 

traffic level; the higher the traffic counts, the greater the distance from the road reduced tortoise 

sign was observed (Hoff and Marlow 2002). This supports LaRue (1993) and Boarman et al. 

(1997), wherein depauperate desert tortoise populations were observed along highways. 

Subsequent research shows that populations may be depressed in a zone at least as far as 0.4 

kilometers (0.25 miles) from the roadway (Boarman and Sazaki 2006). Hoff and Marlow (2002) 

also surmised that unpaved access roads with lower traffic levels may have significant effects on 

tortoises. Desert tortoise populations may also be indirectly affected by road corridors that 

fragment habitat and limit an animal’s ability to migrate and disperse (Boarman et al. 1997). 

Subsequently, populations may become isolated and at higher risk of localized extirpation from 

stochastic events or from inbreeding depression (Boarman et al. 1997; Boarman and Sazaki 

2006). Data suggest fences may reduce mortality of desert tortoises as well as other wildlife 

species (Boarman et al. 1997), and tortoises have been documented to use culverts to cross 

beneath roadways (Boarman et al. 1998), although the degree to which this use mitigates 

population-fragmenting effects has not been investigated. 

(a) Spread of Invasive Plants. Construction and maintenance of roadways facilitates 

changes in plant species composition and diversity. Non-native, invasive species and edgeassociated species often become dominant along these linear features, which serve as corridors 

for weed dispersal (Boarman and Sazaki 2006; Brooks 2009). Vegetation removal and 

manipulation and addition of soils in preparation for road construction, as well as grading of 

unpaved roads, create areas of disturbance that allow weedy species to become established and 

proliferate (Gelbard and Belnap 2003). Brooks and Berry (2006) found that the density of dirt 

roads was the best predictor of non-native plant proliferation as measured by non-native species 

richness and biomass of Erodium cicutarium. Vehicles serve as a major vector in dispersal of 

non-native species along roadways (Brooks and Lair 2005). 

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Near Canyonlands National Park in Utah, cover of the non-native grass Bromus tectorum 

(cheatgrass) was three times greater along paved roads than four-wheel-drive tracks, and richness 

(the number of species) and cover of non-native species were more than 50 percent greater and 

native species richness 30 percent lower at interior sites along paved roads than four-wheel-drive 

tracks (Gelbard and Belnap 2003). There also appears to be a correlation between the level of 

road improvement (i.e., paved, improved, unpaved) and the level of invasion by non-natives 

(Gelbard and Belnap 2003). As previous studies show (LaRue 1993; Boarman et al. 1997; Hoff 

and Marlow 2002; Boarman and Sazaki 2006), the greater the distance from the road, the more 

desert tortoise sign is observed. Similarly, the cover and richness of non-native species decreases 

as distance from the road increases (Boarman and Sazaki 2006). 

As natural areas are impacted by linear features such as roads, routes, trails, and railroads, 

previously intact, contiguous habitats become degraded and fragmented, and non-native invasive 

species play a more dominant role in ecosystem dynamics. For instance, increases in plant cover 

due to the proliferation of non-natives have altered fire regimes throughout the Mojave Desert 

region (Brooks 1999; Brooks and Esque 2002; Esque et al. 2003; Brooks et al. 2004) (see 

sections A(4)(b) and A(5) on Invasive Species and Increasing Fuel Load and Fire). 

(b) Predator Subsidies. In the desert southwest, common raven populations have 

increased over the past 25 years (greater than 1000 percent), probably in response to increased 

human populations and anthropogenic changes to the landscape, including roads, utility 

corridors, landfills, and sewage ponds (Knight and Kawashima 1993; Boarman and Berry 1995; 

Boarman et al. 1995; Knight et al. 1999; Boarman et al. 2006). See section C(3), Predation, for a 

detailed description of the effects of predator subsidies on the desert tortoise. 

3. Off-Highway Vehicles 

Off-highway vehicle activities take many forms, from organized events, small- or largescale competitive races involving up to thousands of motorcycles, to casual family activities. 

Organized events and off-highway vehicle tours are now reviewed and permitted by land 

managers. Generally, an education component and speed limitations are requirements of the 

permit. Nonetheless, unauthorized off-highway vehicle use continues to be of concern, for 

instance south of Interstate 10 in the Colorado Desert and adjacent to the Johnson Valley Open 

Area in the Western Mojave Recovery Unit, and present a variety of threats to the desert tortoise. 

Repeated off-highway vehicle trail use leads to new routes that are not included in road 

databases (Brooks and Lair 2009), a difficulty we found in trying to compile these data for the 

spatial decision support system described elsewhere in this plan. 

Impacts from off-highway vehicle use include mortality of tortoises on the surface and 

below ground, collapsing of desert tortoise burrows, damage or destruction of annual and 

perennial plants and soil crusts, soil erosion and compaction, proliferation of weeds, and 

increases in numbers and locations of wildfires (Brooks 2009; Lei 2009). Despite the many 

observations that have been documented and reported, statistical correlation between offhighway vehicle impacts and reduced desert tortoise densities continues to be lacking (Boarman 

2002). However, it is evident that off-highway vehicle activities remain an important source of 

habitat degradation and could result in reductions in desert tortoise densities (Boarman 2002). 

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Damage to or destruction of shrubs and burrows can lead to disruption of desert tortoises’ water 

balance, thermoregulation, and energy requirements, and the loss of annual plants reduces the 

availability of food (USFWS 1994). One of the most significant ecological implications of offhighway vehicle routes is the exacerbation of erosion and changes in drainage patterns (Brooks 

and Lair 2005). 

Bury and Luckenbach (2002) compared habitat, abundance, and life history features of 

desert tortoises on one unused, natural area and a nearby area used heavily by off-highway 

vehicles. The unused, natural area had 1.7 times the number of live plants, 3.9 times the plant 

cover, 3.9 times the number of desert tortoises, and 4 times the number of active tortoise burrows 

than the area used by off-highway vehicles. The two largest tortoises in the off-highway vehicle 

use area weighed less than would be expected based on what is known about season-to-season 

fluctuations. Despite the lack of pre-disturbance data for the off-highway vehicle area and the 

patchy distribution of tortoises, the areas furthest from concentrated off-highway vehicle activity 

(pit areas) still reflected the least amount of habitat impact and supported more tortoises (Bury 

and Luckenbach 2002). 

Jennings (1997) found that desert tortoises are vulnerable to negative effects from offhighway vehicles because of their habitat preferences. Tortoises in a study at the Desert Tortoise 

Natural Area spent significantly more time traveling and foraging in hills and washes than on the 

flats. Tortoises use washes for travel, excavation of burrows, and foraging, and at least 25 

percent of their forage plants were found to occur within washes. Hills and washes are also 

favored by users of motorcycles, trail bikes, all-terrain vehicles, and other four-wheel vehicles. 

Because tortoises prefer washes and hills, they are more vulnerable to direct mortality from offhighway vehicles. Additionally, off-highway vehicle use in these habitats causes degradation of 

vegetation and loss of forage species important in the desert tortoise diet (Jennings 1997). 

Surface disturbance from off-highway vehicle activity can cause erosion and large 

amounts of dust to be discharged into the air. Recent studies on surface dust impacts on gas 

exchanges in Mojave Desert shrubs showed that plants encrusted by dust have reduced 

photosynthesis and decreased water-use efficiency, which may decrease primary production 

during seasons when photosynthesis occurs (Sharifi et al. 1997). Sharifi et al. (1997) also showed 

reduction in maximum leaf conductance, transpiration, and water-use efficiency due to dust. Leaf and 

stem temperatures were also shown to be higher in plants with leaf-surface dust. These effects may 

also impact desert annuals, an important food source for tortoises. 

Off-highway vehicle activity can also disturb fragile cyanobacterial-lichen soil crusts, a 

dominant source of nitrogen in desert ecosystems (Belnap 1996). Belnap (1996) showed that 

anthropogenic surface disturbances may have serious implications for nitrogen budgets in colddesert ecosystems, and this may also hold true for the hot deserts that tortoises occupy. Soil 

crusts also appear to be an important source of water for plants, as crusts were shown to have 53 

percent greater volumetric water content than bare soils during the late fall when winter annuals 

are becoming established (DeFalco et al. 2001). DeFalco et al. (2001) found that non-native 

plant species comprised greater shoot biomass on crusted soils than native species, which 

demonstrates their ability to exploit available nutrient and water resources. Once the soil crusts 

are disturbed, non-native plants may colonize, become established, and out-compete native 

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perennial and annual plant species (D’Antonio and Vitousek 1992; DeFalco et al. 2001). 

Invasion of non-native plants can affect the quality and quantity of plant foods available to desert 

tortoises (see section A(4)(a), Invasive Plants and Nutrition) and can contribute to increased fire 

frequency (see sections A(4)(b) and A(5), Increasing Fuel Load and Fire). Brooks and Lair 

(2009) provide a comprehensive overview of the ecological effects of various types of vehicular 

routes in the Mojave Desert. 

4. Invasive Plants 

Proliferation of invasive plants is increasing in the Mojave and Sonoran deserts, largely 

as a result of human disturbance, and is recognized as a significant threat to desert tortoise 

habitat (Brooks 2009). Many species of non-native plants from Europe and Asia have become 

common to abundant in some areas, particularly where disturbance has occurred and is ongoing. 

As non-native plant species become established, native perennial and annual plant species may 

decrease, diminish, or die out (D’Antonio and Vitousek 1992). 

Land managers and field scientists identified 116 species of non-native plants in the 

Mojave and Colorado deserts, including Erodium cicutarium (redstem filaree), Bassia 

hyssopifolia (bassia), Ambrosia acanthicarpa (sand bur), Ambrosia psilostachya var. californica 

(western ragweed), Hemizonia pungens (common spikeweed), Matricaria matricarioides 

(pineapple weed), Amsinckia intermedia (fiddleneck), A. tessellata (bristly fiddleneck), 

Descurainia sophia (flixweed), Sisymbrium altissimum (tumble mustard), S. irio (London 

rocket), Salsola iberica (Russian thistle), Eremocarpus setigerus (turkey mullein), and 

Marrubium vulgare (horehound) (Tierra Madre Consultants, Inc.1991; Brooks and Esque 2002). 

Annual grasses include: Bromus rubens (red brome), B. tectorum, Hordeum glaucum (smooth 

barley), H. jubatum (foxtail barley), H. leporinum (hare barley), Schismus barbatus (split grass), 

and S. arabicus (Arab grass). Brassica tournefortii (Sahara mustard) and Hirschfeldia incana 

(Mediterranean mustard) are rapidly spreading, non-native winter annuals invading the desert 

southwest, especially in sandy soils (LaBerteaux 2006). 

Brooks and Berry (2006) found that while non-native plant species comprised only a 

small fraction of the total annual plant flora (i.e., a small fraction of the total number of plant 

species), they were the dominant component of the annual plant community biomass. For 

instance, in 1995, a high rainfall year in the Mojave Desert, non-native species comprised 6 

percent of the flora and 66 percent of the biomass; in 1999, a low rainfall year, non-natives 

comprised 27 percent of the flora and 91 percent of the biomass. Annual species dominate the 

non-native flora, with Bromus rubens, Schismus barbatus, and Erodium cicutarium comprising 

up to 99 percent of the non-native biomass. 

Increased levels of atmospheric pollution and nitrogen deposition related to increased 

human presence and combustion of fossil fuels can cause increased levels of soil nitrogen, which 

in turn may result in significant changes in plant communities (Aber et al. 1989; Allen et al. 

2009). Many of the non-native annual plant taxa in the Mojave region evolved in more fertile 

Mediterranean regions and benefit from increased levels of soil nitrogen, which gives them a 

competitive edge over native annuals. Studies at three sites within the central, southern, and 

western Mojave Desert indicated that increased levels of soil nitrogen can increase the 

131 
 

 

 

 

 

 

 

 

dominance of non-native annual plants and promote the invasion of new species in desert 

regions. Furthermore, increased dominance by non-native annuals may decrease the diversity of 

native annual plants, and increased biomass of non-native annual grasses may increase fire 

frequency (Brooks 2003). 

(a) Nutrition. Nutritional intake affects growth rates in juvenile desert tortoises (Medica 

et al. 1975) and female reproductive output (Turner et al. 1986, 1987; Henen 1992). Invasion of 

non-native plants can affect the quality and quantity of plant foods available to desert tortoises, 

and thereby affect nutritional intake. Desert tortoises are generally quite selective in their choices 

of foods (Burge 1977; Nagy and Medica 1986; Turner et al. 1987; Avery 1992; Henen 1992; 

Jennings 1992, 1993; Esque 1992, 1994), and in some areas the preferences are clearly for native 

plants over the weedy non-natives. 

As native plants are displaced by non-native invasive species in some areas of the Mojave 

Desert, non-native plants can be a necessary food source for some desert tortoises. However, 

non-native plants may not be as nutritious as native plants. Recent studies have shown that 

calcium and phosphorus availability are higher in forbs than in grasses and that desert tortoises 

lose phosphorus when feeding on grasses but gain phosphorus when eating forbs (Hazard et al. 

2010). Nagy et al. (1998) conducted feeding trails on four plant species (native and non-native 

grasses Achnatherum hymenoides [Indian ricegrass] and Schismus barbatus [split grass] and 

native and non-native forbs Malacothrix glabrata [desert dandelion] and Erodium cicutarium 

[red-stemmed filaree]) to compare the nutritional qualities for the desert tortoise. The 

digestibility of the nutrients in the two forbs were similar. The dry matter and energy digestibility 

of the two grasses were much lower than the forbs, providing little nitrogen, and tortoises lost 

more water than they gained while processing grasses. Results of these feeding trials suggest that 

the proliferation of non-native grasses such as Schismus to the exclusion of forbs (D’Antonio and 

Vitousek 1992) places desert tortoises at a nutritional disadvantage. Furthermore, if, instead of 

eating to obtain a given volume of food, tortoises consume just enough food to satisfy their 

energy needs (as commonly noted in other vertebrate groups), then the native forbs provide 

significantly more nitrogen and water than the non-native forbs (Nagy et al. 1998). 

Changes in the abundance and distribution of native plants also may affect desert 

tortoises in more subtle ways. In the Mojave Desert, many food plants are high in potassium 

(Minnich 1979), which is difficult for desert tortoises to excrete due to the lack of salt glands that 

are found in other reptilian herbivores such as chuckwallas (Sauromalus obesus) and desert 

iguanas (Dipsosaurus dorsalis) (Minnich 1970; Nagy 1972). Reptiles are also unable to produce 

concentrated urine, which further complicates the ability for desert tortoises to expel excess 

potassium (Oftedal and Allen 1996). Oftedal (2002) suggested that desert tortoises may be 

vulnerable to disease as a result of physiological stress associated with foraging on food plants 

with insufficient water and nitrogen to counteract the negative effects of dietary potassium. Only 

high quality food plants (as expressed by the Potassium Excretion Potential, or PEP, index) allow 

substantial storage of protein (nitrogen) that is used for growth and reproduction, or to sustain the 

animals during drought. Non-native, annual grasses have lower PEP indices than most native 

forbs (Oftedal 2002; Oftedal et al. 2002). Oftedal et al. (2002) found that foraging juvenile 

tortoises favored water-rich, high-PEP, native forbs. Much of the nutritional difference between 

available and selected forage was attributable to avoidance of abundant, non-native split grass 

132 
 

 

(Schismus spp.) with mature fruit, which is very low in water, protein, and PEP. Of the species 

eaten, Camissonia claviformis, a native Mojave desert primrose, accounted for nearly 50 percent 

of all bites, even though it accounted for less than 5 percent of the biomass encountered, and was 

largely responsible for the high PEP of the overall diet. Impacts to vegetation (such as livestock 

grazing, invasion of non-native plants, and soil disturbance) that reduce the abundance and 

distribution of high PEP plants may result in additional challenges for foraging desert tortoises 

(Oftedal et al. 2002). 

Tracy et al. (2006) also quantified the rates of passage of digesta (food in the stomach) in 

young desert tortoises in relation to body size and diet quality. They observed that, compared to 

adults, young, growing tortoises need higher rates of nutrient assimilation to support their higher 

metabolic rates. Juvenile desert tortoises also forage selectively by consuming plant species and 

plant parts of higher quality (Oftedal et al. 2002) and pass food through the gut more quickly 

(Tracy et al. 2006). Hence, these findings of differential passage rates suggest that it is beneficial 

for young tortoises to specialize on low-fiber diets, as this would allow for more efficient uptake 

of nutrients. In addition, habitat disturbances (e.g., invasion of annual grasses) that favor species 

with little nutritional value and preclude access to low-fiber foods may negatively impact the 

physiological and behavioral ecology of young desert tortoises. Adults, on the other hand, may 

be better adapted to tolerate low-quality foods for a longer period of time because of their lower 

metabolism, more voluminous guts compared to subadults, and consequent longer retention 

times (Tracy et al. 2006). 

(b) Increasing Fuel Load. The proliferation of non-native plant species has contributed 

to an increase in fire frequency in tortoise habitat by providing sufficient fuel to carry fires, 

especially in the inter-shrub spaces that are mostly devoid of native vegetation (Brown and 

Minnich 1986; USFWS 1994; Brooks 1998; Brooks and Esque 2002). Invasive, non-native 

annual grasses and forbs increasingly spread over the desert floor, resist decomposition, and 

provide flash fuel for fires. Brooks (1999) found that non-native annual grasses contributed most 

to the continuity and biomass of dead annual plants and to the spread of summer fires compared 

to native forbs. Red brome in particular has contributed to significant increases in fire frequency 

since the 1970s (Kemp and Brooks 1998; Brooks et al. 2003). 

Fire also appears to affect the spread of non-native plants. Brooks and Berry (2006) 

found that proliferation of non-native plants was best predicted by disturbance, specifically 

frequency and size of recent fires for biomass of Bromus rubens. Once fires occur, opportunities 

for invasion and proliferation of non natives increase because they regenerate on burned areas 

more quickly than native plants (Brown and Minnich 1986). Changes in plant communities 

caused by non-native plants and recurrent fire negatively affect the desert tortoise by altering 

habitat structure and species composition of their food plants (Brooks and Esque 2002) (see also 

section A(5), Fire). 

5. Fire 

Fire has the potential to be an important force governing habitat quality and persistence 

of desert tortoises. Tortoises can be killed or seriously injured by burning and smoke inhalation 

during fire events. The extent of the direct impacts experienced by tortoises is influenced by 

tortoise activity at the time of fire (whether inside or outside burrow), depth of burrow (to afford 

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protection), fire intensity (amount of heat generated), speed of fire (how quickly it moves 

through an area), and patchiness (extent of an area burned) (Esque et al. 2003). Early-season 

fires may be more threatening than summer fires because desert tortoises are active above ground 

and more vulnerable to direct effects of fire at that time. Fire can also compromise the quality of 

tortoise habitat by reducing the vegetation that provides shelter, cover, and nutrition (key forage 

plants) for tortoises (Brooks and Esque 2002; Esque et al. 2003). 

Natural fire regimes have been altered due to profuse invasions of non-native grasses 

throughout much of the range of the desert tortoise. The biomass of weedy species has increased 

remarkably in the desert Southwest as a result of disturbance from vehicles, grazing, agriculture, 

urbanization, and other human land uses (Brooks and Berry 1999; Brooks and Esque 2002; 

Brooks et al. 2003; Brooks and Berry 2006; Brooks and Matchett 2006). Fuel loads that consist of 

dense annual grasses rather than sparse cover of native species make it more likely for fire to become 

hot enough to damage native shrubs, which are poorly adapted to survive and/or regenerate quickly 

after fire and are poor colonizers (Tratz and Vogl 1977; Tratz 1978). Ultimately, recurrent fire can 

result in conversion of shrublands to annual grasslands, which can be devastating for desert tortoises 

that depend upon shrubs for cover (Brooks and Esque 2002). Conversion to grassland also tends to 

create a self-perpetuating grass/fire cycle as fuels continuously reestablish in burned areas 

(D’Antonio and Vitousek 1992). 

Years of high rainfall promote the growth of invasive annuals that increase the fine fuel 

loads, but high rainfall also increases food and water availability for desert tortoises. Desert 

tortoise reproduction also increases in high rainfall years. Small hatchlings are more vulnerable 

to fire than larger tortoises, and tortoises in general are more vulnerable to fire when they are 

above ground foraging. Thus, the high rainfall episodes that are important to maintaining healthy 

desert tortoise populations may also create the highest fire risk (Brooks and Esque 2002). 

Plant litter produced by non-native annual grasses decomposes more slowly than native 

annuals and accumulates during successive years, thus providing an excess of fine fuels that 

sustains and spreads fires throughout the desert ecosystem (Brooks 1999). Historical fire 

intervals of 30 to greater than 100 years have been shortened to an average of 5 years in some 

areas of the Mojave Desert, due to the invasion of non-native grasses. Additionally, fires can 

increase the frequency and cover of non-native annual grasses within 3 to 5 years of a fire event, 

thus promoting the continuity of this grass/fire cycle that shortens the fire interval (Brooks et al. 

1999; Brooks and Esque 2002; Brooks and Minnich 2006). Increased levels of surface-disturbing 

activities, rainfall, and atmospheric nitrogen and carbon dioxide may also increase the 

dominance of non-native plants and frequency of fires in the future (Brooks and Esque 2002; 

Brooks et al. 2003). 

The most striking changes in fire frequency in the Mojave Desert have been observed in 

the middle elevations dominated by Larrea tridentata (creosote bush), Yucca brevifolia (Joshua 

tree), and Coleogyne ramosissima (blackbrush), at the upper limits of desert tortoise distribution, 

where most of the fires occurred between 1980 and 2004 (Brooks and Matchett 2006). The 

combination of enough cover of native vegetation to carry a fire and the accumulation of fuels 

from non-native annual grasses following years of above average rainfall may result in 

significantly larger fires at shorter return intervals than normally expected in this zone. Lower 

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elevations are less susceptible to larger fires because of the natural lack of native plant cover, 

whereas upper elevations may experience larger fires as they generally support enough native 

fuels to carry large fires (Brooks and Matchett 2006). Brooks and Matchett (2006) advise, 

however, that additional research is necessary to confirm their results due to a limited dataset, 

and that longitude, elevation, and regional climatic conditions may cause substantial variation in 

observations. 

The year 2005 was a particularly bad fire year in the Mojave Desert. According to the 

Bureau of Land Management, U.S. Forest Service, and California Department of Forestry 

geospatial data of the extent of fires in 2005, the wildfires burned over 58,208 hectares (140,000 

acres) of critical habitat that year (Table A-2). The Bureau of Land Management’s geospatial fire 

data depict slightly different acreages than have been reported elsewhere. According to 

McLuckie et al. (2007), 3,191 hectares (7,885 acres) burned within the Red Cliffs Desert 

Preserve, which emcompasses the majority of the Critical Habitat within the Upper Virgin River 

Recovery Unit. 

Table A-2. Area (hectares) of desert tortoise critical habitat burned during 2005.* 

Critical Habitat Unit Area Burned 

(hectares) 

Percent of CHU 

area burned 

Beaver Dam Slope 21,662 26 

Chemehuevi 23 <1 

Fenner 12 <1 

Fremont-Kramer 11 <1 

Gold Butte-Pakoon 26,442 13 

Ivanpah 397 <1 

Mormon Mesa 5,241 3 

Ord-Rodman 11 <1 

Superior-Cronese 137 <1 

Upper Virgin River 4,272 19 

*Complete data sources: CA fire data from California Department of Forestry and Fire Protection's Fire and Resource Assessment 

Program: http://frap.cdf.ca.gov/data/frapgisdata/download.asp?rec=fire; NV fire data from BLM as a single 2005 file: 

http://www.blm.gov/nv/st/en/prog/more_programs/geographic_sciences/gis/geospatial_data.html; AZ fire data from Forest Service, 

part of historic files [cross referenced against BLM ADSO fire data]: http://www.fs.fed.us/r3/gis/datasets.shtml; UT fire data from 

BLM, as part of historic fires file: http://www.blm.gov/ut/st/en/prog/more/geographic_information/gis_data_and_maps.print.html. 

Studies were conducted in five burned areas within the range of the desert tortoise to 

determine immediate effects of the fire and fire suppression tactics and to monitor the recovery 

of habitats (Esque et al. 1994, 2003). Between 16 to 81 hectares (40 and 200 acres) were 

surveyed for wildlife remains on each fire via walking transects 9 to 15 meters (30 to 50 feet) 

apart. Desert tortoise mortality was documented at 0 to 7 per transect, but live tortoises were also 

observed. There were statistically significant losses of perennial cover, but some fires left 

unburned patches of vegetation that can serve as refugia for tortoises and plants. These refugia 

may be important to the long-term recovery of burned desert ecosystems. No destroyed burrows 

or desert tortoise mortalities were observed in surveys of routes used for off-road fire 

suppression activities in Utah, indicating that carefully planned and monitored fire suppression 

maneuvers can help stop the spread of damaging wildfires while reducing immediate and longterm tortoise mortality (Esque et al. 1994, 2003). 

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In general, as fire becomes more prevalent throughout the range of the desert tortoise, the 

threats to the species from mortality or injury by burning and smoke inhalation during fire events 

and impacts to desert habitats will also increase. Changes in habitat structure from shrubdominated communities to non-native annual grasslands would limit the availability of cover 

sites for tortoises as well as alter species composition of food plants. 

6. Grazing 

Impacts of grazing on arid lands are well documented (Fleischner 1994; Jones 2000). 

Recovery from these impacts is variable, but can take decades, will likely require significant 

management effort beyond excluding livestock, and will be affected by other factors such as 

drought (GAO 1991; Friedel 1991; Laycock 1991). Livestock grazing (sheep and cattle as well as 

horses and burros) is known to have direct and indirect impacts on desert tortoises and their habitats 

through trampling that results in direct mortality, either while above ground or in burrows, and 

degradation of vegetation and soils, including the spread of non-native plants or the displacement 

of native plants (Brooks 1995; Avery 1998; Boarman 2002). The magnitude of the threat on desert 

tortoise populations remains unclear, and the degree of impact depends on a number of factors 

including, but not limited to, resiliency of soil and vegetation types, type of livestock, stocking rates, 

season of use, and years of use with and without rest (USFWS 1994). Other factors can interact with 

livestock grazing and can affect the degree and extent of impacts to desert tortoises (e.g., introduction 

and spread of weeds [Brooks 2009], changes in vegetation due to grazing, fire, drought, and other 

land uses [USFWS 1994]). 

Oldemeyer (1994) suggests that the primary evidence that grazing adversely affects 

desert tortoises relates to an overlap in food habits of livestock and tortoises. Grazing is thought 

to reduce cover of shrubs and annual forbs. Studies in the eastern Mojave Desert on foraging 

behavior and food preferences of range cattle and desert tortoises showed that a dietary overlap 

(spatial and temporal) exists and that this overlap is greatest in the spring when fresh annual 

plants preferred by both desert tortoises and livestock are at their peak biomass and densities. 

Competition for these food plants is expected to be greatest when annual plants start to dry in the 

spring, before cattle and tortoises switch to other forage plants (Avery and Neibergs 1997). 

Avery and Neibergs (1997) observed direct and indirect interactions between cattle and 

tortoises. Their study indicates that grazing during winter may destroy a large percentage of 

active tortoise burrows. They noted that tortoises outside an ungrazed cattle exclosure spent more 

nights outside of burrows than tortoises within the exclusion area, because more burrows were 

destroyed in the grazed area than in the ungrazed area. Almost 200 tortoise burrows were 

recorded as trampled during a survey of the 2.6-square-kilometer (1-square-mile) East Bajada (of 

the Black Mountains), Arizona, study plot in 1997 (Woodman et al. 1998). The presence of 

cattle dung, tracks, and trails suggested that most trampled burrows were caused by livestock, 

but some may have been due to horses or burros. In a study on translocated tortoises in the 

northwest Mojave Desert, one tortoise was found alive in its hibernation burrow even though the 

burrow had been crushed by cattle. It had skin lesions and had been parasitized by fly larvae. The 

tortoise was removed from the study because it was assumed that it would have died if it had 

been left in the crushed burrow (Nussear 2004). Tortoises with home ranges located in areas of 

poorly-managed cattle grazing may experience increased risk of mortality, increased energetic 

136 
 

 

 

 

costs, and changes in activity time budgets (caused by additional time and effort required to build 

new burrows). 

Comparative studies of historically grazed and never-grazed grasslands in southeast Utah 

(Neff et al. 2005) showed that grazing can continue to impact soil biogeochemical characteristics 

three decades after grazing had been removed. Reduced soil nutrient levels in the historically 

grazed site compared to the never-grazed site were attributed to erosion of nutrient-rich fine soil 

materials due to disturbance caused by grazing practices. Soil organic matter, carbon and 

nitrogen content, and microbial biomass were also lower in the grazed site. The decline of 

organic matter content may be attributed to the destruction of biological soil crusts or long-term 

changes in vegetation cover/composition resulting from grazing. This study illustrates the 

sensitivity of arid land biogeochemical processes to land use change and the need for a better 

understanding of potential long-term impacts from grazing practices in the southwestern United 

States. Furthermore, wind erosion may contribute significantly to loss of soil nutrient content and 

should be considered in management of arid land ecosystems (Neff et al. 2005). 

Unmanaged livestock grazing, especially where plants are not adapted to large 

herbivorous mammals or where the non-native species are less palatable than the natives, can 

preferentially remove native vegitation, leaving non-native plants to grow under reduced 

competition (Wittenberg and Cock 2005:228). Studies at the Desert Tortoise Natural Area 

showed that both abundance and diversity of native plants and animals is higher inside than 

outside of the protected desert tortoise habitat (Brooks 2000). It should be noted that the Desert 

Tortoise Natural Area has received limited protection since 1973, but has been effectively 

protected from sheep grazing and off-highway vehicle use through the installation of exclusion 

fencing for the last 10 years (Brooks 2000). Similarly, grazing (and simulated grazing 

treatments) negatively impacted native plant species, while non-native species were unaffected 

and demonstrated superior competitive abilities, at Carrizo Plain National Monument, California 

(Kimball and Schiffman 2003). 

7. Agriculture 

Lands in the Mojave Desert have been used for agricultural purposes since the early 

nineteenth century when peoples of the Mohave Tribe planted crops within the floodplain of the 

Colorado River to sustain their populations (Mojave Desert.net 2007). The 1994 Recovery Plan 

stated that the most significant effect agriculture has on desert tortoises is loss of habitat. Since 

the 1950s, losses of tortoise populations have been attributed to urbanization and agriculture in 

the western Mojave Desert in the Indian Wells, Antelope, Victor, Apple, Lucerne, and Johnson 

valleys (Berry and Nicholson 1984). Once converted to agricultural fields, the habitat becomes 

unsuitable to tortoises for foraging or burrowing. Agricultural activities may also result in 

drawdown of the water table, introduction of invasive plants, production of fugitive dust, and 

possible introduction of toxic chemicals (Koehler 1977; Wilshire 1980; Berry and Nicholson 

1984). Additionally, agricultural fields can support ravens, which prey upon juvenile tortoises 

(Knowles et al. 1989; Camp et al. 1993; Knight et al. 1999). Old agricultural fields are often 

invaded by non-native, invasive species, which compete with native plants for resources and may 

reduce the abundance and diversity of the native species that provide shelter and food for desert 

tortoises (Hobbs 1989; USFWS 1994). 

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8. Energy and Mineral Development 

Exploration for and development of energy and mineral resources, as well as sand and 

gravel extraction, result in habitat fragmentation and permanent habitat loss due to haul roads, 

development of facilities necessary to support large mining operations, ancillary facilities, leachate 

ponds, and mine tailings. Additional impacts to the desert tortoise may result from soil erosion, 

establishment of invasive plant species in disturbance zones (see section C(4), Invasive Plants), and 

fugitive dust and introduction of toxins (see section C(1), Disease). Tortoises may be killed during 

exploration, construction and ongoing operations, and maintenance activities (USFWS 1994; 

Boarman 2002). 

At the time the 1994 Recovery Plan was approved, it was estimated that 41 percent of highdensity tortoise habitat throughout the species’ range was leased or partially leased for oil or gas, 

and 2 percent was directly impacted by mining operations or leased for geothermal development 

(Luke et al. 1991; USFWS 1994). The extent of impacts to desert tortoise habitat and effects to 

tortoise populations from energy and mineral development are still not well documented. 

Cumulative habitat loss from mining-related disturbances combined with increased development 

to support those operations may pose the most significant impact resulting from mining (Lovich 

and Bainbridge 1999; Boarman 2002). 

In 2005, the Federal Energy Security Policy Act established a mandate to approve 10,000 

megawatts (MW) of non-hydropower, renewable-energy generation on public lands by 2015, a 

five-fold increase from the current level of approximately 1,900 MW. In 2008, California 

Governor Schwarzenegger signed Executive Order S-14-08, which increased the target for 

California’s renewable-energy portfolio to 33 percent by 2020. Nevada has mandated a 20­

percent renewable-energy portfolio by 2015, Arizona requires 15 percent by 2015, and Utah has 

a voluntary portfolio of 20 percent by 2015. The President established broader goals of 

generating 10 percent of the nation’s electricity from renewable sources by 2012 and 25 percent 

by 2025. To achieve these goals, the Secretary of Interior issued a Secretarial Order in March 

2009 that makes the development, production, and delivery of renewable energy top priorities of 

the Department of the Interior. The U.S. Congress underscored the need for accelerated 

development of renewable-energy projects with the passage of the American Recovery and 

Reinvestment Act (ARRA), which confers economic benefits to developers of renewable-energy 

projects that begin construction before the end of 2010. 

By April 2009, the Bureau of Land Management had received approximately 160 

applications for solar energy, mostly in California and Nevada; these applications comprised 

approximately 728,000 hectares (1.8 million acres) of public land and proposed a combined 

generating capacity of approximately 97,000 MW. In order to facilitate project permitting and 

approval to meet ARRA deadlines, several projects were categorized as “fast track” and became 

the top priority of local field and regional office staffs in both Federal and State wildlife and 

resource agencies. As of November 2010, within the range of the desert tortoise, six fast-track 

solar projects in California and one in Nevada were approved on public lands, constituting 

3,037.5 MW on 9,683 hectares (23,926 acres) and 430 MW on 3,173 hectares (7,840 acres), 

respectively. Three additional solar projects on private lands in California have been approved, 

totaling 1,063 MW on 1,686 hectares (4,165 acres). Seven fast-track solar projects on public 

138 
 

 

 

 

lands are still pending, totaling 1,450 MW on 4,314 hectares (10,659 acres) in California and 900 

MW on 6,955 hectares (17,186 acres) in Nevada. Three fast-track wind projects within the range 

of the desert tortoise are also pending, totaling 536.5 MW on 11,775 hectares (29,096 acres) of 

public and private rights-of-way; one of the California projects is proposed within designated 

critical habitat. No applications have been submitted for solar or wind projects on public lands 

within the range of the Mojave population of the desert tortoise in Arizona or Utah. As of 

November 2010, 31 solar and wind-energy right-of-way applications were for example, pending 

within the Bureau of Land Management’s California Desert District, totaling 16,979 MW on 

85,210 hectares (210,558 acres). The area of approved and pending solar and wind-energy 

applications on public lands in California exceeds 100,000 hectares (247,000 acres). 

At this time, we do not have information on renewable-energy projects proposed on 

private lands within the range of the Mojave population of the desert tortoise outside California, 

but according to the California Energy Commission, more than 51 solar projects, totaling 5,475 

MW, had been proposed on private lands. Depending on the technology used, projects may 

require 2-3.6 hectares (5-9 acres) per MW; therefore, approximately 15,500 hectares (38,300 

acres) would be developed by these projects, assuming an average need of 2.8 hectares (7 acres) 

per MW. At least 10 wind projects had been proposed on private lands in southern California, 

totaling about 2,700 MW. 

Conflicts between energy development and the desert tortoise have been recognized at 

least since 1986 (Pearson 1986). A typical 250-400MW solar energy project requires about 1,200 

hectares (3,000 acres). The land is typically contoured and fenced, resulting in habitat loss and 

availability for other public land uses. While developing utility-scale solar projects on public 

lands could help achieve the national and regional energy goals, it would also require large 

reallocations of land and water resources and have significant environmental impacts. Many of 

these impacts will directly affect the desert tortoise and desert ecosystems. The BLM has 

committed to excluding these projects from designated critical habitat for the desert tortoise and 

Desert Wildlife Management Areas; however, potential long-term effects of utility-scale energy 

development fragmenting or isolating desert tortoise conservation areas and restricting gene flow 

between these areas have not been evaluated. The energy development process on Bureau of 

Land Management lands has been constantly changing, with applicants submitting multiple 

requests to modify their projects or withdrawing their applications altogether (J. Crisp, Bureau of 

Land Management, pers. comm. 2007). 

9. Landfills 

There are more than 50 authorized sanitary landfills and waste disposal facilities known 

in the California and Nevada deserts (Boarman 2002). In urban areas throughout the range of the 

tortoise, all communities produce solid waste that must be transported to appropriate facilities. 

Landfills and other waste disposal facilities potentially affect desert tortoises and their habitat 

through fragmentation and permanent loss of habitat, spread of garbage that attracts predators, 

introduction of toxic chemicals, increased road kill of tortoises on access roads, and increased 

predator populations (Boarman 2002) (see also section C(3), Disease and Predation). With the 

exception of raven predation, which is considered one of the most important consequences of 

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landfills, negative effects on tortoises associated with the presence of landfills have not been 

quantified (Boarman 2002). 

10. Military Operations 

Military operations in the Mojave Desert have taken place since as early as 1859 

(USFWS 1994; Boarman 2002). Military activities that impact desert tortoises and their habitats 

can be categorized as: (1) construction, operation, and maintenance of bases and support 

facilities (air strips, roads, etc.); (2) development of local support communities, including urban, 

industrial, and commercial facilities; (3) field maneuvers including tank traffic, air to ground 

bombing, static testing of explosives, and abandonment of unexploded ordnance, shell casings, 

and ration cans; and (4) distribution of chemicals. These activities result in degradation and 

permanent loss of desert tortoise habitat and are often coupled with other impacts associated with 

large human settlements in the desert (i.e., collection of tortoises, trash dumping, increased raven 

populations, domestic pets as predators, off-highway vehicle use, increased exposure to disease, 

and increased road-kill mortality) (USFWS 1994). 

The military bases and test ranges in the Mojave Desert include the Nevada Test and 

Training Range and Nellis Air Force Range in Nevada, and Edwards Air Force Base, 

Twentynine Palms Marine Corps Air Ground Combat Center, Barstow Marine Corps Logistics 

Bases (includes the Yermo Annex, Main Base at Nebo, and the Marine Corps Rifle Range), Fort 

Irwin National Training Center, China Lake Naval Air Weapons Station, and the Mojave B and 

Randsburg Wash Test Ranges in California. The Chocolate Mountains Aerial Gunnery Range in 

California is the primary base affecting desert tortoise habitat in the Colorado Desert (USFWS 

1994). All of these military facilities encompass desert tortoise habitat. 

All of the threats associated with military activities described above continue to affect 

desert tortoises and their habitat. For example, in a study of tortoise populations at several sites 

on the Fort Irwin National Training Center, tortoises living in historically or recently used 

military maneuver areas had significantly higher frequencies of shell disease than a site where 

military activities had not taken place (Berry et al. 2006b). The expansion of military bases and 

activities into previously unused areas occupied by desert tortoises also threatens the species. In 

2004, we issued a biological opinion to the Department of the Army for the use of additional 

training lands at the Fort Irwin National Training Center in California. This action will result in 

the loss or degradation of approximately 76,081 hectares (188,000 acres) of desert tortoise 

habitat, including approximately 30,351 hectares (75,000 acres) within the Superior-Cronese 

critical habitat unit, and the translocation of several hundred desert tortoises from harm’s way. 

To date, the Department of the Army has purchased approximately 40,104 hectares (99,100 

acres) of lands formerly owned by the Catellus Development Corporation and portions of cattle 

allotments in the western Mojave Desert to minimize impacts associated with the expanded 

training areas (R. Bransfield, U.S. Fish and Wildlife Service, pers. comm. 2007). The Bureau of 

Land Management subsequently retired these allotments and removed grazing on over 129,499 

hectares (320,000 acres). A plan has also been developed to guide the translocation of tortoises 

in the expansion area (Esque et al. 2005). 

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11. Utility Corridors 

By 1994, most critical habitat units had one or more power lines, natural gas pipelines, 

fiber optic cables, and/or communication sites within their proposed boundaries (USFWS 1994). 

Disturbances associated with these corridors are usually linear in nature, and the zone of 

disturbance can vary in width from 15.2 to 30.5 meters (50 to 100 feet) to several hundred 

meters/yards, depending on the number of transmission lines (USFWS 1994). Impacts to 

desert tortoise habitat and individuals occur both during initial construction as well as during 

long-term maintenance activities (Boarman 2002). Additionally, utility corridors are often used 

by the public for off-highway vehicle and recreational access. LaRue and Dougherty (1999) 

evaluated results of over 230 biological opinions issued by our southern California and Nevada 

offices and found that 80 percent of the tortoises reported killed in these two states were found 

along utility corridors. Most of these mortalities resulted from a few large projects during the 

construction phases, and very few tortoises have been killed during utility maintenance projects 

(R. Bransfield, U.S. Fish and Wildlife Service, pers. comm. 2007). While tortoises may be 

observed within these corridors, continual vehicular use along access roads may alter use by 

tortoises both for foraging and movement and may result in road-kills (Boarman 2002). Utility 

towers also provide nesting substrate and hunting perches to avian predators, such as ravens and 

red-tailed hawks. 

12. Vandalism and Harvest of Vegetation 

Vandalism and harvest of vegetation, particularly cacti and yuccas, were identified as 

potential threats to desert tortoises and their habitats in the 1994 Recovery Plan. Harvest of 

vegetation includes the removal of vegetation for personal or economic purposes (i.e., use in 

landscaping or sale for profit). Vandalism of vegetation is considered to be the deliberate destruction 

of vegetation (i.e., shooting, crushing). While these activities may still occur on a relatively small 

scale and may pose some threat on a localized level, there is no recent documentation that 

indicates this activity poses a significant or widespread threat to tortoise populations throughout 

their range. 

B. Overutilization for Commercial, Recreational, Scientific, or Educational Purposes 

1. Collection by Humans 

Some of the threats to the desert tortoise identified in the 1994 Recovery Plan include the 

deliberate removal of desert tortoises by humans for use as food (Berry and Nicholson 1984; 

Swingland and Klemens 1989; Schneider and Everson 1989; Ditzler 1991; BLM files 2006), and 

collection and commercial trade for pets (Berry and Burge 1984; Berry and Nicholson 1984; St. 

Amant 1984). Collection of desert tortoises for personal or commercial purposes was evidently 

significant in the past (Grant 1936; Berry and Burge 1984; Berry and Nicholson 1984; Ditzler 

1991; Berry et al. 1996; USFWS 1994). Desert tortoises are protected from collection under both 

Federal and State law in all states where it occurs; however, the legal status has not always 

served as a deterrent to this activity (Boarman 2002). For example, nine cases of illegal 

141 
 

 

 

collection were documented from the Red Cliffs Desert Reserve, Washington County, Utah, 

between May 2003 and May 2006, including four cases within 5 weeks during 2006 (A. 

McLuckie, Utah Division of Wildlife Resources, pers. comm. 2006). While illegal collection of 

desert tortoises still occurs and could possibly impact local populations, little quantitative 

evidence exists to support it as a significant threat causing declines in the Mojave populations 

(Boarman 2002). Also, information specific to this threat is limited owing to the wide 

distribution of the species coupled with the need for additional law enforcement officers and 

wardens on the ground (see section D, Inadequacy of Existing Regulatory Mechanisms). 

2. Deliberate Maiming and Killing by Humans 

Little additional information regarding maiming and killing of desert tortoises has been 

obtained since the 1994 Recovery Plan. Postmortem forensic analysis determined that 14.3 

percent of 635 carcasses collected at 11 of 27 California desert sites between 1976 and 1982 

showed evidence of gunshots (Berry 1986). Evidence of gunshot was significantly higher in 

carcasses from the west Mojave than from the east Mojave or Colorado Desert (Berry 1986), 

which may be a function of the proximity of human populations in the west Mojave region 

compared to that in the east Mojave or Colorado Desert. 

3. Research Activities 

We permit various research activities that will inform management and recovery of the 

desert tortoise but that may result in infrequent injury or mortality. Potential stress to desert 

tortoises from handling may vary depending on the time, frequency, and activity involved. 

Invasive procedures associated with obtaining physiological data can cause significant stress to 

individuals (Berry et al. 2002a). For example, female tortoises that void their bladders during 

handling may be at a reproductive disadvantage since the loss of fluid may negatively affect egg 

production, which requires higher total body water in reproductive females than nonreproductive females. In one analysis, tortoises that urinated when handled during repeated 

surveys of three sites in Arizona had lower survival than those that did not (Averill-Murray 

2002). 

Despite the inherent low-level risk associated with activities covered under recovery 

permits, incidental injury or mortality of desert tortoises is not expected. However, if injury or 

mortality should occur, the permit is suspended until the circumstances surrounding the incident 

are reviewed and appropriate procedures are in place to prevent further injury or mortality. In 

any given year, we generally issue fewer than 15 recovery permits for desert tortoise research. 

Because of the emphasis that we, through the Desert Tortoise Recovery Office, intend to place 

on recovery-related research activities pertaining to the desert tortoise, the number of permits 

issued may increase over the next few years. 

142 
C. Disease or Predation 

1. Disease 

Disease is a natural phenomenon within wild animal populations, and epidemic outbreaks 

can have catastrophic effects on small or declining populations. To date, the available evidence 

indicates that upper respiratory tract disease is probably the most important infectious disease for 

desert tortoises (Hudson et al. 2009). Less is known about other diseases that have been 

identified in the desert tortoise (e.g., herpesvirus, cutaneous dyskeratosis or shell disease, shell 

necrosis, bacterial and fungal infections, and urolithiasis or bladder stones) (Jacobson et al. 1994, 

1995; Homer et al. 1998; Berry et al. 2002b; Origgi et al. 2002). Additional research is needed to 

clarify the role of disease in desert tortoise population dynamics relative to other threats and the 

level of effort we should expend in disease control as compared to other threats. 

Upper respiratory tract disease. At least two pathogenic species of Mycoplasma known to 

cause upper respiratory tract disease in desert and gopher tortoises have been identified (M. 

agassizii and M. testudineum) (Brown et al. 1994, 1999, 2001; Brown et al. 2002). The 

pathogens are likely transmitted by contact with an infected individual or aerosols (airborne 

liquid droplets or solid particles). Once infected, tortoises may develop lesions in the nasal 

cavity, excessive nasal discharge, swollen eyelids, sunken eyes, lethargy, and possible death 

(Jacobson et al. 1991; Schumacher et al. 1997; Homer et al. 1998; Berry and Christopher 2001). 

However, these clinical signs, which may not always be evident in an infected individual, may 

also be symptomatic of other conditions, such as dehydration, or pathogens (Brown et al. 2002). 

Various tests have been developed to detect the presence of antibodies to M. agassizii or help 

determine active infection (Schumacher et al. 1993; Brown et al. 1995; Wendland et al. 2007; 

Hunter et al. 2008). Johnson et al. (2006) uncovered a positive link between tortoises with antiMycoplasma antibodies and the severity of clinical signs of upper respiratory tract disease, as 

well as with age class, with adults being more likely to test positive for presence of antibodies. 

However, in-depth study of the desert tortoise’s immune system and epidemiological study of 

disease dynamics across space and time is necessary to more thoroughly understand the factors 

involved in the spread and virulence of the disease in the wild (Boarman 2002; Sandmeier et al. 

2009). 

Because the release or escape of infected captive tortoises has been implicated as a 

potential cause of outbreaks of upper respiratory tract disease in natural populations in the 

Mojave Desert, Johnson et al. (2006) evaluated captive tortoises in Barstow, California, to 

investigate pathogen exposure. Anti-Mycoplasma antibodies (indicating exposure to the 

pathogen) were present in 82.7 percent of the tortoises tested (sample size of 179), and antiherpesvirus antibodies were observed in 26.6 percent of the animals (sample size of 109). Jones 

(2008) also found captive tortoises to be 1.8 to 5.4 times more likely to test positive for antiMycoplasma antibodies than free-ranging Sonoran desert tortoises around Tucson, Arizona. 

Further, a higher incidence of disease was found in suburban areas around Tucson, suggesting 

that habitat degradation associated with urbanization may be a stressor that contributes to disease 

outbreaks (Jones 2008). These studies, however, were completed prior to Hunter et al.’s (2008) 

work that indicates some tortoises may carry innate anti-Mycoplasma antibodies. Reasons for the 

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susceptibility of tortoises to upper respiratory tract disease remain speculative and require further 

study (Boarman 2002). 

Shell disease. The most commonly described shell disease in desert tortoises is cutaneous 

dyskeratosis, which manifests itself as lesions along scute sutures of the plastron and sometimes 

on the carapace, which then spread to the scutes themselves (Jacobson et al. 1994; Homer et al. 

1998). Shell diseases have been seen in tortoise populations in the eastern Mojave and Colorado 

deserts of California but less so in the western Mojave Desert (Jacobson et al. 1994; Christopher 

et al. 2003). Shell diseases occur in all sizes and ages of desert tortoises but are usually more 

common in adults (Jacobson et al. 1994; Homer et al. 1998). It appears that shell diseases reflect 

metabolic and physiological changes that involve more than the shell itself (Homer et al. 1998, 

2001). Little is known about the causes of shell disease; no evidence indicates a bacterial or viral 

origin, despite directed research efforts by pathologists to find one (Jacobson et al. 1994; Homer 

et al. 1998). Five-years of health profiles at three sites in the California Mojave Desert (Desert 

Tortoise Research Natural Area, Ivanpah Valley, Goffs) found that the numbers of tortoises with 

moderate to severe plastron disease and active carapace lesions increased significantly between 

1990 and 1995, especially at Goffs (Christopher et al. 2003). Shell disease was also found to be 

significantly more severe with increasing tortoise age, suggesting a chronic, cumulative problem 

(Christopher et al. 2003). Cutaneous dyskeratosis has been associated with mortality on the 

Chuckwalla Bench in California (Berry 1997). However, the extent to which shell diseases 

contribute to population declines in desert tortoises remains unclear (Jacobson et al. 1994). 

Herpesvirus. In tortoises with herpesvirus infection, clinical signs range from a mild 

conjunctivitis (inflammation of the membrane surrounding the eye) to a severe lesions and 

plaques on the tongue and hard palate (Johnson et al. 2006). Plaques (small growths) typical of 

herpesvirus were reported in tortoises in Goffs and Ivanpah (Christopher et al. 2003). 

Herpesvirus infections have also been reported in other species of turtles and tortoises, especially 

in those associated with the exotic trade (Martel et al. 2009). 

The contribution of herpesvirus to population declines in desert tortoise is unknown. 

However, herpesvirus infections have been reported in captive desert tortoises and have been 

associated with illness and mortality (Johnson et al. 2006). Clinical herpesvirus infections can be 

rapid and progressive, resulting in large die-offs in other species of vertebrate animals as well 

(Johnson et al. 2006). Therefore, at least in theory, herpesvirus could become a serious threat to 

desert tortoise populations, especially for those living near the urban-desert interface where wild 

individuals are more likely to encounter infected captive tortoises or turtles. 

Effects of one disease on susceptibility to other diseases. There is evidence that any one 

disease may predispose desert tortoises to other diseases (Christopher et al. 2003). However, it is 

not known whether this is a cause or effect. That is, it is not known whether disease in an 

individual increases susceptibility to other diseases in that individual or whether an individual’s 

baseline susceptibility to disease causes that individual to get more diseases. Nevertheless, 

positive nasal cultures for Mycoplasma agassizii had relatively high positive predictive values 

for tortoises with moderate to severe shell disease (Christopher et al. 2003). Pathologists also 

report that the location and histologic (structural) appearance of lesions seen in tortoises with 

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cutaneous dyskeratosis are suggestive of either a deficiency disease or toxicosis or both 

(Jacobson et al. 1994, Homer et al. 1998). 

2. Toxicants and Disease Susceptibility 

Some have suggested that a significant source of mortality is direct induction of 

toxicosis-related diseases (e.g., liver diseases) and in increasing susceptibility to infectious 

diseases by environmental contaminants (Homer et al. 1994, 1996; Berry 1997; Christopher et 

al. 2003). Elevated mercury and arsenic levels have been associated with diseased tortoises in the 

wild (Jacobson et al. 1991; Homer et al. 1998; Seltzer and Berry 2005; Chaffee and Berry 2006). 

Necropsy and analyses of kidney, liver, and scute tissues suggested that tortoises from California 

with a variety of diseases (upper respiratory tract infection, urolithiasis, metabolic disease, and 

shell diseases) had statistically significantly higher levels of potentially toxic elements as 

compared to healthy tortoises (Berry et al. 1997). No one single element or group of known or 

potentially toxic elements was found at elevated levels in the tissues of diseased and dying 

tortoises. It has been postulated that elemental toxicity may compromise the immune system of 

desert tortoises or otherwise detrimentally affect physiological function, rendering them more 

susceptible to disease, but further investigation is needed. 

Illegal dumping of hazardous wastes that occurs in the California deserts may expose 

tortoises to increased levels and possible consumption of toxic substances. Garbage, litter, and 

toxic spills may affect tortoises on a localized level where these activities are concentrated 

(Boarman 2002). Toxicant load in the environment may also be a factor that induces diseases 

related to toxicosis (e.g., liver disease) and influences the susceptibility of tortoises to infectious 

diseases and mortality. For example, tortoises that died of mycoplasmosis at the Desert Tortoise 

Natural Area in 1989 through 1990 had 11 times the mercury content in their livers than tortoises 

from a control area (Jacobson et al. 1991). Some necropsies showed elevated levels of arsenic in 

scutes (Seltzer and Berry 2005). 

Fugitive dust containing toxicants that affect tortoises may be released from 

anthropogenic sites such as mines, roads, construction, and other disturbances. Chaffee and 

Berry (2006) collected soil, stream sediment, and plant samples at six tortoise habitat study areas 

in the Mojave and Colorado deserts. They analyzed samples for up to 66 different elements to 

determine their distribution and abundance at a regional and local level, to identify potential 

sources of toxicants in desert tortoise habitats. Some measurements of high concentrations of 

arsenic, mercury, and lead, were attributed to mining and vehicle exhaust. High levels of soil and 

plant arsenic extended more than 14 kilometers (9 miles) from some existing mine sites, and 

mercury was detected more than 5 kilometers (3 miles) from some mine tailings. Traces of lead 

were found more than 21 kilometers (13 miles) from a paved road and likely had been 

redistributed by vehicle exhaust, wind, and rain events. Elevated levels of these elements have 

been observed in ill tortoises found in these areas; however, additional research is necessary to 

ascertain the direct effects of elemental toxicants on desert tortoise health and their susceptibility 

to disease (Chaffee and Berry 2006). 

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3. Predation 

Desert tortoises are preyed upon by several native species of mammals, reptiles, and 

birds; however, the contribution of mammalian or avian predation to overall desert tortoise 

mortality has not been quantified. Natural predation in undisturbed, healthy ecosystems is 

generally not considered a threat, but under some circumstances predation comes to the forefront 

as a management concern, especially where landscapes have been altered and intensive human 

use occurs. In addition, during times of drought when typical prey species are limited, food 

habits of predators may shift and tortoises become more frequent components of their diets 

(USFWS 1994). 

The best-documented predator of small tortoises is the common raven (Corvus corax). 

For example, Campbell (1986) found 136 carcasses of juvenile desert tortoises with evidence of 

raven predation at the base of fence posts on the perimeter of the Desert Tortoise Natural Area. 

Berry et al. (1990) reported that 30 and 45 percent, respectively, of all desert tortoise deaths at two 

study plots during a 6-year period were probably caused by raven predation; up to 75 percent of 

deaths of tortoises <103 mm (4.1 in) carapace length were attributed to raven predation at these 

plots. 

In the desert southwest, common raven populations have increased over the past 25 years 

(greater than 1000 percent), probably in response to increased human populations, associated 

food and water subsidies, and anthropogenic changes to the landscape (Boarman and Berry 1995; 

Boarman et al. 1995; Boarman et al. 2006). For instance, ravens obtain food in the form of 

organic garbage from landfills and trash containers, water from sewage ponds and municipal 

areas, and nesting substrates on billboards, utility towers, bridges, and buildings (Boarman et al. 

2006). Particularly in the west Mojave and Coachella Valley, linear features such as roads and 

utility corridors and other urban sites such as landfills and sewage ponds have been shown to 

attract common ravens, red-tailed hawks (Buteo jamaicensis), and turkey vultures (Cathartes 

aura) (Knight and Kawashima 1993; Boarman et al. 1995; Knight et al. 1999). The use of 

anthropogenic nesting substrates facilitates increased predation of juvenile tortoises, especially 

within about 0.4 kilometers (0.25 miles) of the raven nest (Boarman 2002; Kristan and Boarman 

2003). The presence of roads may encourage such opportunistic species because road-killed 

animals are a reliable food source (Camp et al. 1993; Boarman and Sazaki 2006). 

Raven numbers were shown to decrease with distance from urban sites in the west 

Mojave, placing tortoises that occur in the urban-desert interface at higher risk of predation 

(Kristan and Boarman 2003). This risk also increases with the numbers of ravens in the vicinity, 

and the distribution of breeding and non-breeding ravens is likely to influence patterns of 

predation across the landscape. Breeding ravens tend to disperse more evenly across suitable 

habitats, whereas non-breeding birds are concentrated around anthropogenic sites. This suggests 

that occupied desert tortoise habitats distant from population centers and the urban-desert 

interface experience reduced predation pressures from ravens (Kristan and Boarman 2003). 

Determining precise demographic impacts of (increased) raven predation on desert 

tortoise populations is complicated because of the difficulty of monitoring small, hard to find 

juvenile tortoises (Boarman 2002). Nevertheless, the potential impact to desert tortoise 

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populations from raven predation is a conservation concern, especially where subsidized 

predators are able to persist in large numbers despite declines in their prey base. Populations of 

long-lived animals like the desert tortoise can sustain moderate levels of annual juvenile 

mortality (e.g., 25 percent), but in the face of depressed adult survival, juvenile mortality must be 

reduced to approximately 5 percent to ensure recruitment into the breeding population (Congdon 

et al. 1993). Human-subsidized predators thus put at great disadvantage any prey species such as 

the desert tortoise that is unable to rebound from predation pressures (Kristan and Boarman 

2003). 

Desert tortoise predation by coyotes (Canis latrans) was documented by Woodbury and 

Hardy (1948) who found tortoise remains in coyote scat. Berry (1990) reported that over 50 

percent of deaths at 4 study plots in California were attributable to mammalian predators. During 

a drought, coyotes killed most of the study tortoises at the Desert Tortoise Natural Area and 

killed 21–28 percent of a study population near Ridgecrest, California, in a 12-month period 

(Berry 1974). Peterson (1994a) reported high mortality in two western Mojave desert tortoise 

populations, resulting from both disease and predation attributable to ‘natural’ effects of drought 

and functional responses of predators to a diminished prey base. Predators were also a suspected 

source of mortality near Fort Irwin, California, with over 50 percent of remains showing signs of 

mammalian predation in some cases (Berry et al. 2006b). Tortoise mortality attributed to coyote 

predation exceeded 30 percent at several sites across the Mojave Desert in spring 2008 (Esque et 

al. 2010; USFWS, unpublished data). 

Red-tailed hawks, golden eagles (Aquila chrysaetos), loggerhead shrikes (Lanius 

ludovicianus), American kestrels (Falco sparverius), burrowing owls (Athene cunicularia), and 

greater roadrunners (Geococcyx californianus) have also been implicated in tortoise predation, 

although available data are minimal (Boarman 1993). Kit foxes (Vulpes macrotis), mountain 

lions (Felis concolor), ground squirrels (Citellus spp.), and free-roaming dogs are known 

mammalian predators of desert tortoise (Boarman 2002; M. McDermott, Southern Nevada 

Environmental, Inc., pers. comm. 2006; Medica and Greger 2009; Riedle et al., 2010). 

Invertebrate predators of eggs and hatchling tortoises include native fire ants (Nagy et al. 2007). 

D. Inadequacy of Existing Regulatory Mechanisms 

1. Law Enforcement 

The final listing rule acknowledged that all four states within the range of the Mojave 

population of the desert tortoise have laws in place to protect the species. However, State 

wildlife or endangered species permitting requirements do not specifically cover habitat and 

generally do not require mitigation of impacts to suitable, potentially occupied habitat. In 

addition, a great deal of effort has been dedicated to planning by the various Federal and State 

land management agencies whose jurisdictions include desert tortoise habitat. While many of the 

existing plans include language specific to protection of the species, such as limiting off-highway 

vehicle use and competitive/organized events, grazing, vegetation harvest, and collection of 

desert tortoises, agency multiple-use mandates require a complex balancing of tortoise 

conservation and public use of Federal and State lands. Also, land management agencies 

frequently do not have sufficient funding to enforce their land use regulations (Table A-3). The 

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number of law enforcement officers or game wardens on the ground does not necessarily 

translate into protection of the species, as personnel are often spread across vast landscapes and 

have multiple resource responsibilities. As calculated from the data in Table A-3, current 

information indicates that each law enforcement officer is responsible for an average of more 

than 89,000 hectares (220,000 acres). 

Table A-3. Law enforcement (LE) resources within desert tortoise habitat by agency. 

Responsible Agency/Unit1 Number of 

LE Officers 

Number of 

Vacancies 

(if applicable) 

Number of Acres 

(approx.) 

BLM-California Desert District2 43 4 10,400,000 

Barstow Field Office 8 0 3,000,000 

El Centro Field Office 12 0 1,400,000 

Needles Field Office 6 2 3,300,000 

Palm Springs – South Coast Field Office 9 2 1,700,000 

Ridgecrest Field Office 8 0 1,800,000 

BLM-Arizona Strip Field Office3 3 1 2,000,000 

BLM-NPS Grand Canyon-Parashant National Monument4 3 BLM 

2 NPS 0 1,100,000 

BLM-Las Vegas and Ely Field Offices5 14 (Vegas) 

1 (Ely) ? 3,000,000 726,000 

BLM-St. George Field Office6 1 0 630,000 

NPS-Mojave National Preserve7 9 4 1,400,000 

NPS-Joshua Tree National Park8 10 4 790,000 

NPS-Death Valley National Park9 14 ? 3,300,000 

NPS-Lake Mead National Recreation Area10 16 ? 1,500,000 

USFWS-Desert National Wildlife Refuge Complex11 5 2 1,600,000 

US Forest Service-Spring Mountains National Recreation 

Area12 3 2 317,000 

Arizona Game and Fish Department13 2 ? 

California Department of Fish and Game14 16 3 

Nevada Department of Wildlife15 16 3 

Utah Division of Wildlife Resources16 4 0 

Clark County MSHCP-Boulder City Conservation 

Easement17 1 0 86,000 

Total 163 23 >36,249,000 1 Information provided via electronic mail or personal communication (July, August 2007) from the following: 

2 Jim Abbott, Bureau of Land Management California State Office 

3 Scott Florence, Bureau of Land Management Arizona Strip District 

4 Kathleen Harcksen, Bureau of Land Management Grand Canyon-Parashant National Monument 5 Elroy Masters, Bureau of Land Management Nevada State Office 

6

Jim Crisp, Bureau of Land Management St. George Field Office

7 Debra Hughson, Kirk Gebicke, National Park Service, Mojave National Preserve 

8 Paul DePrey, Curt Sauer, National Park Service Joshua Tree National Park 

9 David Ek, National Park Service Death Valley National Park

10 Bill Dickinson, National Park Service Lake Mead National Recreation Area 11 Cynthia Martinez, USFWS Desert National Wildlife Refuge Complex 12 David Leveille, USFS Humboldt-Toiyabe National Forest 13 Cristina Jones, Luke Thompson, Arizona Game and Fish Department 14 Rebecca Jones, Mike McBride, California Department of Fish and Game 15 Polly Conrad, Fred Henson, Nevada Department of Wildlife 16 Ann McLuckie, Utah Division of Wildlife Resources 17 Sue Wainscott, Clark County 

? Information not provided or not available. 

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2. Land Acquisitions, Exchanges, and Transfers 

Land exchanges and transfers may result in loss of desert tortoise habitat, increased 

fragmentation, and displacement of resident desert tortoises. Tortoise habitat that is exchanged 

out of Federal ownership is at greater risk of development, resulting in loss of habitat on the new 

private holdings (Sievers et al. 1988). Transactions may also be executed in the interest of 

securing additional lands targeted for conservation of the desert tortoise and other sensitive 

species or habitats (see Conservation Efforts). 

In 1988, the Bureau of Land Management exchanged 11,758 hectares (29,055 acres) of 

public land in the Coyote Springs Valley in southern Nevada to Aerojet-General Corporation for 

private wetlands in Florida for wildlife conservation under the Nevada-Florida Land Exchange 

Authorization Act. An additional 5,571 hectares (13,767 acres), which are surrounded by the 

11,758 hectares (29,055 acres), were leased to Aerojet for an initial term of 99 years with a 99­

year extension. The Coyote Springs Investment (CSI) HCP was developed to address urban 

development and tortoise conservation on CSI lands in Lincoln County. The plan permits 

development over 8,682 hectares (21,454 acres) in Lincoln County, most of which is desert 

tortoise habitat (Mormon Mesa critical habitat unit). The plan also establishes a desert tortoise 

reserve on 5,571 hectares (13,767 acres) of the CSI leased land. 

Under the Bureau of Land Management’s Western Mojave Land Tenure Adjustment 

Program, which provides a mechanism pursuant to the Federal Land Policy and Management Act 

of 1976 to acquire lands within and dispose of Federal lands outside of DWMAs, approximately 

21,044 hectares (52,000 acres) of land within desert tortoise critical habitat have been acquired 

and approximately 6,880 hectares (17,000 acres) outside of designated critical habitat have been 

transferred out of Federal management since 1990. The overall ratio of acquired to disposed 

habitat of the desert tortoise is expected to be approximately 2.3:1 at the completion of the 

Western Mojave Land Tenure Adjustment Program, for a net benefit to the amount of desert 

tortoise habitat protected on Federal lands (BLM et al. 2005). 

The Southern Nevada Public Lands Management Act of 1998, as amended (Public Law 

[PL]-105-263), provides for the “disposal of certain Federal lands in Clark County, Nevada, and 

for the acquisition of environmentally sensitive lands in the State of Nevada.” The law was 

enacted partly to address the Bureau of Land Management’s extensive and complicated land 

management responsibilities for disjunct parcels that are interspersed with or adjacent to private 

land in the Las Vegas Valley and the rapid urbanization taking place in the valley. In order to 

“promote responsible and orderly development in the Las Vegas Valley, certain of those Federal 

lands should be sold by the Federal Government based on recommendations made by local 

government and the public” (PL-105-263). This legislation provided the mechanism for 

significant changes to take place in the Las Vegas area of the Mojave Desert relative to human 

occupation in the Mojave Desert wherein over 58,600 hectares (145,000 acres) of Federal land 

are identified for disposal and urban development. 

A series of other related public laws have connections to the Southern Nevada Public 

Lands Management Act and facilitate the transfer or disposal of public lands. These laws include 

the Lincoln County Conservation, Recreation, and Development Act of 2004 (PL-108-424); the 

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Lincoln County Land Act of 2000 (PL-106-298); the Clark County Conservation of Public Land 

and Natural Resource Act of 2002 (PL-107-282); the Fiscal Year 2004 Appropriations Act 

amending the Southern Nevada Public Lands Management Act (PL -105-263); the Lake Tahoe 

Restoration Act; the Mesquite Lands Act of 1986 (PL-99-548) and 1988 and PL-104-208 (1996 

amendment to the Mesquite Lands Act of 1988); the Ivanpah Valley Airport Public Lands 

Transfer Act of 2000; and the Federal Land Transaction Facilitation Act of 2000. 

E. Other Natural or Manmade Factors Affecting its Continued Existence 

1. Climate Change 

Climate change and drought were not regarded as threats to the desert tortoise in the 1994 

Recovery Plan. Since that time it has become apparent that the combined effects of global 

climate change (i.e., increased ambient temperatures and altered precipitation patterns) and 

drought may become significant factors in the long-term persistence of the species. The Earth’s 

climate has warmed by nearly 1.5 degrees Fahrenheit over the past 100 years (Walther et al. 

2002), and anthropogenic emissions of greenhouse gases play a major role in this process 

(Weltzin et al. 2003). Warming in the Mojave Desert region began approximately in the late 

1970s, and recent average temperatures have climbed well above prior values (Redmond 2009). 

While warming, as well as changes in precipitation patterns, is not uniform with regard to time 

and space, the rate of warming during the last 30 years has generally been greater than at any 

other time during the last 1,000 years, and this variation in warming and precipitation is likely to 

contribute also to variation in ecological dynamics across ecosystems. 

There is now evidence that recent climatic changes have affected a broad range of 

organisms with diverse geographical distributions (Walther et al. 2002). Interactions between 

altered precipitation patterns and other aspects of global change are likely to affect natural and 

managed terrestrial ecosystems. For example, climate models predict that Joshua trees would 

likely no longer be able to persist within Joshua Tree National Park through the 21st century 

(Cole et al. 2005). Human responses to climate change (e.g., increased infrastructure for the 

capture and use of water) may also negatively affect desert ecosystems. While little is known 

regarding direct effects of climate change on the desert tortoise and its habitat, predictions can be 

made about how global and regional precipitation regimes may be altered and the consequences 

of these changes (Weltzin et al. 2003; Seager et al. 2007). Similar to the Joshua tree example 

above, climate models also predict a reduction of 9-49 percent in suitable habitat, along with 

increasing fragmentation, for the desert tortoise within Joshua Tree National Park (Barrows 

2009). 

The Intergovernmental Panel on Climate Change has suggested that increasingly reliable 

climate change projections are now available as the result of improved modeling capabilities and 

advanced understanding of climate systems (Christensen et al. 2007). The Intergovernmental 

Panel on Climate Change’s 2007 report discussed the results of 21 Atmosphere-Ocean General 

Circulation Models that were run to predict regional changes in temperature and precipitation in 

2080 to 2099 compared to conditions that occurred between 1980 and 1999. Generally, 

predictions for the geographic range of the desert tortoise’s listed population suggest more 

frequent and/or prolonged droughts. For example, annual mean temperature is likely to increase 

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by 3.5 to 4.0 degrees Celsius (6.3 to 7.2 degrees Fahrenheit), with the greatest increases 

occurring in summer (June-July-August mean up to 5 degrees Celsius [9 degrees Fahrenheit] 

increase) (Christensen et al. 2007). In summer, the highest temperatures will likely increase even 

more than the average temperatures. Precipitation will likely decrease by 5 to 15 percent 

annually in the region with winter precipitation decreasing in the range of 5 to 20 percent. More 

than half of the models predict that changes in summer precipitation may be more moderate 

(decrease by as much as 10 percent) with the possibility for a 5 percent increase (Christensen et 

al. 2007). This prediction for more drying in winter than in summer within the range of the 

desert tortoise’s listed population differs from predictions for much of the United States. 

However, variation in the results among models suggests that specific future precipitation 

regimes are problematic to predict confidently (Smith et al. 2009). Because germination of the 

tortoise’s food plants is highly dependent on cool-season rains, the forage base could be reduced 

due to increasing temperatures and decreasing precipitation in winter. Drought is a normal 

phenomenon in the Mojave Desert (Peterson 1994a; Hereford et al. 2006). Extended periods of 

drought, however, have the potential to affect desert tortoises and their habitats through 

physiological effects to individuals (i.e., stress) and limited forage availability. 

Recent findings demonstrate that the Mojave Desert shrub ecosystem is a significant sink 

for carbon dioxide (CO2) on an annual basis, suggesting that desert ecosystems may be vital 

contributors to counteracting global and local climate change (Wohlfahrt et al. 2008). In 

particular, expansion and growth of cryptobiotic crust organisms (lichens, mosses, and 

cyanobacteria) may account for a significant portion of the carbon accretion in the Mojave 

Desert system, but further investigation into cryptobiotic crust productivity is needed. 

Experiments in Nevada at the Free-Air CO2 Enrichment Facility to predict the possible complex 

ecological and biogeochemical changes in semidesert ecosystems caused by increasing 

atmospheric CO2 have been ongoing since 1997 (Hamerlynck et al. 2000; Smith et al. 2000; 

Huxman and Smith 2001). Because deserts are both water- and nutrient-limited systems and 

many native desert plants are slow-growing, it is still too early to say with any confidence how 

even the most intensively studied desert shrub communities of the southwestern United States 

will respond to rising CO2 (Lioubimtseva and Adams 2004). However, results from the Free-Air 

CO2 Enrichment Facility site demonstrate that the non-native grass Bromus tectorum responds to 

increases in CO2 (a component required for photosynthesis) with far greater productivity than 

that of native plants during wet years (Smith et al. 2000). As discussed in sections A(4)(b) and 

A(5), Increasing Fuel Load and Fire, colonization by non-native annual grasses is known to 

increase the frequency and intensity of fires, both of which have dramatic negative effects on 

desert water cycles and wildlife habitat (Hamerlynck et al. 2000). The overall response of nonnative grasses to increased CO2 is uncertain, though, given expected reductions in precipitation. 

Climatic regimes are believed to influence the distribution of plants and animals through 

species-specific physiological thresholds of temperature and precipitation tolerance. Warming 

temperatures and altered precipitation patterns may result in distributions shifting northward 

and/or to higher elevations, depending on resource availability (Walther et al. 2002). We may 

expect this response in the desert tortoise to reduce the viability of lands currently identified as 

“refuges” or critical habitat for the species (Barrows 2009). Seager et al. (2007) ran a series of 

climate models and simulations on the precipitation history and future of the southwestern 

United States and parts of northern Mexico that consistently showed a severe drying trend in this 

region throughout the 21st century, especially in areas where evapotranspiration exceeds 

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precipitation (such as most desert regions). Bromus tectorum is expected to retreat with climate 

change, however, from the northern portion of the desert tortoise’s range (Bradley et al. 2009). 

How the closely related invasive grass Bromus rubens responds and whether it replaces B. 

tectorum in the absence of active restoration efforts is uncertain. 

Some evidence suggests that desert tortoises may be capable of adapting to changes in the 

environment through modification of their behavior, periods of activity, and diet (Morafka and 

Berry 2002). The desert tortoise evolved millions of years before the formation of the North 

American deserts, and the species experienced both more mesic and more xeric conditions within 

the last several thousand years (Morafka and Berry 2002). Paleoclimate indicators show that 

severe, multi-year droughts, some lasting up to a decade or two, occur at least once or twice a 

century (Redmond 2009). Perhaps as the habitats they occupied changed and became more arid, 

the tortoise was able to adapt and succeed in desert climes and exploit a broad ecological range. 

The probability that the desert tortoise will be able to survive ongoing changes in vegetation and 

food sources or temperature and precipitation patterns remains to be seen, especially in light of 

continued anthropogenic alterations of the environment (Morafka and Berry 2002). Models 

demonstrate large shifts in plant distributions that over a long period of time may allow 

opportunities for migration and adaptation. Under the current scenario, however, where change 

may occur within a few decades, it cannot be predicted whether or not plants and animals would 

be able to readily migrate into new habitats (Thompson et al. 2003). 

Direct climatic effects on growth and development, spatial distribution, and species 

interactions are apparent in amphibians and reptiles, which, in common with other ectotherms, 

are heavily influenced by environmental conditions. Both seasonal temperature and humidity 

affect their reproductive physiology and population dynamics (Walther et al. 2002). In addition, 

desert tortoises have temperature-dependent sex determination (i.e., the sex of the hatchlings is 

determined by the temperatures in the nest), with 1:1 sex ratios produced at approximately 31.3 

degrees Celsius (88.3 degrees Fahrenheit), all males produced at 30.5 degrees Celsius (86.9 

degrees Fahrenheit) and below, and all females produced at 32.5 degrees Celsius (90.5 degrees 

Fahrenheit) and above (Rostal et al. 2002). Although there has been some speculation that global 

temperature increases may skew sex ratios or eliminate male offspring altogether for some turtles 

(Janzen 1994), there is also evidence that temperature-dependent sex determination systems may 

be able to evolve through maternal nesting behavior if gradual changes in climate result in 

skewed sex ratios (Janzen and Morjan 2002). Sex ratios of reptiles may be robust to moderate 

temperature increases as long as eggs experience daily fluctuating temperatures (Booth 2006). 

The varying environments in which tortoises nest provide opportunities among diverse potential 

nest sites for exposure to a variety of temperature regimes, and nest placement within the burrow 

is an important determinant of what temperature regime the nest experiences during incubation 

and the resultant hatchling sex ratios (Baxter et al. 2008). The survival of reptile species with 

temperature-dependent sex determination through cycles of warming and cooling over the last 

100,000 years suggests that changes in climate were such that species were capable of shifting 

the time of nesting, choice of nest sites, the range occupied, or even temperature at which the 

sexes were produced (Booth 2006). Rapid changes in climate may challenge the ability of the 

desert tortoise to make such shifts. 

152 
 

 

 

 

Smith et al. (2009) review various types of global change relative to expected effects in 

the Mojave Desert, such as elevated carbon dioxide and altered precipitation regimes facilitating 

invasive plant species, thereby increasing fire frequency. Effects of altered nitrogen dynamics on 

the Mojave Desert are less clear. For example, increased nitrogen deposition from dust in the 

vicinity of metropolitan areas could result in higher plant production, exacerbating the effects 

from carbon dioxide noted above (Smith et al. 2009). Alternatively, increased temperatures may 

release nitrogen gases from Mojave Desert soils, reducing fertility of those soils and the ability to 

support plant life (McCalley and Sparks 2009). While it is unclear how global and regional 

changes in climate may affect the desert tortoise, continued research and monitoring relative to 

behavioral and life history traits of the species under climate change will inform conservation 

and management decisions regarding recovery of the species in the Mojave Desert. 

(a) Drought. Data exist on some of the effects of drought on the desert tortoise. Drought 

is a normal phenomenon in the Mojave Desert; desert tortoises have been inhabitants of this 

region for over 10,000 years and have adapted to variable conditions (Nagy and Medica 1986; 

Peterson 1994a,b; 1996a; Henen 1997; Hereford et al. 2006). As noted above, extended periods 

of drought may affect desert tortoises through physiological effects to individuals (i.e., stress) 

and through limited forage availability. Energy acquisition and expenditure in desert tortoises are 

strongly constrained by the contingencies of rainfall, both indirectly through effects on 

availability and quality of food, and directly through reliance on free-standing water for drinking 

(Peterson 1996a,b; Wilson et al. 2001). 

The effect of drought on demographic parameters of tortoise populations (i.e., birth, 

death, recruitment, and growth rates) is not well understood (Avery et al. 2002; Boarman 2002). 

However, studies have attributed many adverse effects to periods of drought, including 

dehydration, malnutrition, and starvation; reduced reproductive output of females; altered 

behavior such as failure to seek shelter, reduced movement, and surface activity (O’Connor et al. 

1994; Homer et al. 1996; Duda et al. 1999; Berry et al. 2002b); and increased susceptibility to 

predation and disease (Peterson 1994a,b). 

Since 1975, a tortoise population on the Beaver Dam Slope in Arizona and Utah 

experienced high mortality; malnutrition caused by reduced nutrient availability was considered 

responsible for osteoporosis and subsequent mortality (Jacobson 1994). Increased mortality in 

the Ivanpah Valley in 1981 and 1982 was attributed to drought conditions (Turner et al. 1984), 

and abnormally high levels of mortality were recorded in the east and west Mojave Desert during 

a three-year drought period (1988 through 1990). Deaths in the Ivanpah Valley study site were 

attributed to drought-induced starvation and dehydration (Turner et al. 1984). Peterson (1994a) 

found that high mortality in two desert tortoise populations in 1988-1990 was attributable to 

drought, directly in the eastern Mojave population through starvation and dehydration, and 

indirectly in the western Mojave population through functional responses of predators to a 

diminished prey base and, possibly, increased susceptibility of tortoises to disease. 

Research conducted in the early 1980s indicated a strong correlation between clutch 

frequency (the number of clutches produced by a female in one reproductive season) and 

biomass of annual plants used by tortoises for food (Turner et al. 1986, 1987). Studies conducted 

at five sites (Joshua Tree National Park, Mojave National Preserve, Palm Springs, Piute Valley, 

153 
 

 

 

 

 

 

 

 

 

 

 

and St. George) supported the results of Turner et al. These studies indicated that in high-rainfall 

years with corresponding abundant food-plant availability, more females reproduced and 

reproducing females laid more clutches per reproductive season, compared with low-rainfall 

years (Lovich et al. 1999). Clutch size (number of eggs per clutch) was relatively constant 

regardless of conditions; however, Avery et al. (2002) noted that females at higher elevations 

with greater annual rainfall had a larger mean clutch size. 

Recent studies also indicate that even a relatively short-term drought combined with little 

or no biomass of annual plants can cause a severe reduction in adult tortoise survival. A study of 

adult tortoise survival rates at two sites in the eastern Mojave desert (near or adjacent to PiuteEldorado critical habitat unit) attributed die-offs in 1996 to a period of drought that began in the 

summer of 1995, coupled with failure of annual vegetation production in 1996 (Longshore et al. 

2003). During three years of no or minimal biomass production of annual plants (1996, 1997, 

and 1999), the survival of adult tortoises decreased. In 1996, 30 percent (15 individuals) of radiomonitored adults died following a drought that began in the summer of 1995. Although the 

researchers obtained no physiological evidence, they believed these deaths likely resulted from 

dehydration, as there was no substantial evidence of other mortality mechanisms, such as disease 

or predation (Longshore et al. 2003). 

2. Garbage, Trash, and Balloons 

Turtles and tortoises are known to eat non-food objects, such as rocks, balloons, plastic, and 

other garbage. Such objects can become lodged in the gastrointestinal tract or entangle heads and 

legs, causing injury or death (Burge 1989; USFWS 1994; Walde et al. 2007). Unauthorized 

deposition and dumping of refuse is most prevalent near towns, cities, and settlements in remote 

areas as well as at the urban-desert interface. Such garbage not only contributes to direct mortality 

and habitat degradation, trash also attracts ravens and other desert tortoise predators, as discussed in 

section C(3), Predation. Some trash, such as balloons, may also be found in more remote areas. 

Walde et al. (2007) counted the number of balloons encountered during field work approximately 40 

kilometers northeast of Barstow, California. They found that in 8 months, 178 new balloons arrived 

at the remote site, and they observed a tortoise partially ingesting a balloon. Their work suggests that 

the prevalence of at least some types of garbage in the desert may not be as localized as previously 

thought (Boarman 2002). Likewise, Averill-Murray and Averill-Murray (2002) estimated that 11,207 

balloons were distributed across the 76,800-hectare (189,776-acre) Ironwood Forest National 

Monument, Arizona, in 2001. 

3. Noise and Vibration 

The 1994 Recovery Plan cited noise and vibration as having potentially significant effects 

on the desert tortoise’s behavior, communication, and hearing apparatus (USFWS 1994). Very 

limited additional data have been obtained specific to this potential. Studies on the effects of 

flight noise from jet aircraft and sonic booms on hearing, behavior, heart rate, and oxygen 

consumption of desert tortoises concluded that hearing loss and physiological changes are not 

likely to be dangerous during occasional short-term exposures; however, those results cannot be 

extrapolated to chronic exposures over a tortoise’s lifetime. The authors advise that their results 

are “best viewed as a first-order effort to determine the effects of subsonic and supersonic 

154 
 

aircraft noise on a desert reptile.” They recommend that changes in tortoise activity with 

repeated exposure to aircraft noise should be investigated under natural conditions, including 

during food and water deprivation, torpor, or exposure to dangers such as rivals and predators 

(Bowles et al. 1999). 

4. Non-motorized Recreation and Miscellaneous Human Activities 

Non-motorized recreation includes activities such as camping, hunting, target practice, 

rock collecting, hiking, horseback riding, biking, and sight-seeing. While there are no data 

correlating these activities with impacts to the desert tortoise, it may be surmised based on 

information on visitor-use days that these activities bring with them many of the threats 

associated with increased human presence, such as loss of habitat from development of 

recreational facilities and guzzlers; handling and disturbance of tortoises; increased collection, 

road kill, and vandalism of tortoises; and increased raven populations (USFWS 1994; Boarman 

2002). Off-trail use can degrade habitat by damaging vegetation and soil crusts (Belnap 1996) 

and by compacting soils (Lei 2009). 

Very few studies have been conducted to document the effects of non-motorized 

activities to desert tortoises. One study measured the effect of surface disturbance from foot, 

bike, and vehicle tracks on the nitrogenase activity in cyanobacterial-lichen soil crusts, a 

dominant source of nitrogen for cold-desert ecosystems (Belnap 1996). Results showed that the 

levels of nitrogenase activity were reduced by 30 to 100 percent, depending on the degree of soil 

disruption and the microbiotic composition of the soils (Belnap 1996). This study demonstrated 

that anthropogenic surface disturbances may have serious implications for the nitrogen budgets 

of cold-desert ecosystems, which may be confounded by increased levels of atmospheric 

pollution and nitrogen deposition associated with increased human populations (see Brooks 

2003). However, soil crusts retain greater water content than bare soils, and non-native plants 

colonize and out-compete native species on disturbed soils (DeFalco et al. 2001). 

5. Unauthorized Release or Escape of Captive Tortoises to the Wild 

Implications of infectious disease spread by the release of captive-bred animals and 

relocation of wild animals are a major concern in conservation biology (Wolff and Seal 1993). 

Captive releases have the potential to introduce disease into wild populations of desert tortoises 

(Johnson et al. 2006; Martel et al. 2009). Tomlinson and Hardenbrook (1993) reported that the 

highest prevalence of clinical signs of upper respiratory tract disease was observed in tortoises 

removed from areas where previous releases of captive animals had occurred. Release or escape 

of captive tortoises genetically different from the resident population can also lead to disrupted 

local adaptation (Tallmon et al. 2004). 

A large captive population of desert tortoises, dating prior to listing under the Endangered 

Species Act and enactment of State regulations, magnifies these risks associated with disease and 

genetics. Unauthorized breeding of pet tortoises further exacerbates these risks and can lead to 

pressures on management agencies that must direct resources toward managing the captive 

population rather than focusing resources on recovering wild populations. 

155 
 

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Wohlfahrt, G., L.F. Fenstermaker, and J.A. Arnone III. 2008. Large annual net ecosystem CO2 

uptake of a Mojave Desert ecosystem. Global Change Biology 14:1475–1487. 

Wolff, P.L., and U.S. Seal. 1993. Implications of infectious disease for captive propagation and 

reintroduction of threatened species. Journal of Zoo and Wildlife Medicine 24:229-230. 

Woodbury, A.M., and R. Hardy. 1948. Studies of the desert tortoise, Gopherus agassizii. 

Ecological Monographs 18:146-200. 

Woodman, P., P. Frank, S. Hart, G. Goodlett, M. Walker, D. Roddy, and S. Bailey. 1998. Desert 

tortoise population surveys at four sites in the Sonoran Desert of Arizona, 1997. Report to 

Arizona Game and Fish Department, Phoenix. 

PERSONAL COMMUNICATIONS 

Abbott, Jim. 2007. Bureau of Land Management, California State Office. Sacramento, 

California. 

Bransfield, Ray. 2007. U.S. Fish and Wildlife Service, Ventura Fish and Wildlife Office. 

Ventura, California. 

Conrad, Polly. 2007. Nevada Department of Wildlife. Las Vegas, Nevada. 

Crisp, Jim. 2007. Bureau of Land Management, St. George Field Office. St. George, Utah. 

DePrey, Paul. 2007. National Park Service, Joshua Tree National Park. Twentynine Palms, 

California. 

Dickinson, Bill. 2007. National Park Service, Lake Mead National Recreation Area. Boulder 

City, Nevada. 

Donahue, S. 2007. Mohave County. Kingman, Arizona. 

Ek, David. 2007. National Park Service, Death Valley National Park. Death Valley, California. 

Florence, Scott. 2007. Bureau of Land Management, Arizona Strip District. St. George, Utah. 

Gebicke, Kirk. 2007. National Park Service, Mojave National Preserve. Barstow, California. 

173 
 

Harcksen, Kathleen. Bureau of Land Management, Grand Canyon-Parashant National 

Monument. St. George, Utah. 

Henson, Fred. 2007. Nevada Department of Wildlife. Las Vegas, Nevada. 

Hughson, Debra. 2007. National Park Service, Mojave National Preserve. Barstow, California. 

Jones, Cristina. 2007. Arizona Game and Fish Department. Phoenix, Arizona. 

Jones, Rebecca. 2007. California Department of Fish and Game. Ontario, California. 

Leveille, David. U.S. Forest Service, Humboldt-Toiyabe National Forest, Supervisor’s Office. 

Reno, Nevada. 

Martinez, Cynthia. 2007. U.S. Fish and Wildlife Service, Desert National Wildlife Refuge 

Complex. Las Vegas, Nevada. 

Masters, Elroy. 2007. Bureau of Land Management, Nevada State Office. Reno, Nevada. 

McBride, Mike. 2007. California Department of Fish and Game. Ontario, California. 

McDermott, Michelle. 2006. Southern Nevada Environmental, Inc. Las Vegas, Nevada. 

McLuckie, Ann. 2006. Utah Division of Wildlife Resources, Washington County Field Office, 

St. George, Utah. 

Sauer, Curt. 2007. National Park Service, Joshua Tree National Park, Twentynine Palms, 

California. 

Thompson, Luke. 2007. Arizona Game and Fish Department. Flagstaff, Arizona. 

Wainscott, Sue. 2007. Clark County. Las Vegas, Nevada. 

174 
APPENDIX B 

A DECISION SUPPORT SYSTEM FOR DESERT TORTOISE RECOVERY:
 

A TOOL FOR EVALUATING RECOVERY ACTION EFFECTIVENESS
 

A. INTRODUCTION 

This appendix summarizes the processing steps, data inputs, and outputs of a spatial 

decision support system developed for the Fish and Wildlife Service’s Desert Tortoise Recovery 

Office (DTRO) to aid in the implementation of the Recovery Plan for the desert tortoise. The 

current decision support system is a refinement of a prototype system developed in consultation 

with land managers with jurisdiction over desert tortoise habitat through a series of recovery 

planning workshops. These workshops were conducted during March-May 2007 at which 

managers provided information on geographic distribution of threats, management actions, and 

other information described below. Additional data collection, modeling, and input by land 

managers and scientists subsequent to the publication of the Draft Revised Recovery Plan 

contributed to the current system. 

The DTRO spatial decision support system estimates the impacts of threats to tortoise 

populations and identifies and prioritizes recovery actions that are most likely to ameliorate those 

threats. The decision support system models the inter-relationships among threats and tortoise 

population changes (i.e., which threats cause other threats, and how do these threats effect 

tortoise population numbers) and recovery action-population stress relationships (i.e., what are 

the most appropriate actions given a set of population stresses faced by the species?). The system 

relies primarily on GIS data of the spatial extent of threats (i.e., where threats occur 

geographically) to calculate how changes in threats contribute to changes in tortoise population 

numbers at any geographic extent (>1 square kilometer). 

The decision support system models the relationships between threats, population 

stresses, and demographic change factors. The relationships within the model are weighted using 

expert assessments of the strengths of:1) inter-threat links, 2) threat to population stress links, 

and 3) population stress to demographic change links using the standard lexicon for biodiversity 

conservation as in Salafsky et al. (2008). The GIS data of the spatial extent of threats are then 

geoprocessed with these weights to calculate how changes in threats contribute to changes in 

tortoise population numbers and how recovery action implementation is predicted to effect threat 

to population stress linkages. All data and underlying models will be updated and evaluated on a 

regular basis as described by recovery action 6.1. 

B. DECISION SUPPORT SYSTEM ROAD MAP 

The flow chart diagram below illustrates the overall modeling process within the decision 

support system. Each model is leveraged on the previous to produce the overall assessment of 

risk to desert tortoise populations and management priorities to mitigate that risk. It is important 

to note that what is described here is a prototype system, which we are continually improving 

(Starfield and Bleloch 1991; Starfield 1997; Murphy et al. 2008). Each model is transparent and 

can be evaluated and revised independently of the others as new information or better models 

become available. For example, several simple models describing the distribution of particular 

175 
 

 

threats are being updated based on those published by Leu et al. (2008). In addition, sensitivity 

analyses still need to be conducted to determine the relative importance of different assumptions 

(e.g., relative impacts of threats to tortoise demography or relative effectiveness of recovery 

actions on abating threats) and to identify priorities for model improvement (Freick and Hall 

2004; Malczewski 2006). 

The steps and component models currently in the system can be summarized as follows: 

•	 Spatial Threats: uses geospatial data to represent where threats occur geographically and 

with what relative intensity 

•	 Stress to Population Models 

o	 Threat-Stress Interaction Model: estimates the contribution of each threat to stress to 

the population 

o	 Relative Stress Model: estimates the contribution of each stress to demographic 

change factor 

o	 Demographic Impact Model: estimates contributions of each demographic impacts to 

overall population change 

•	 Models of the Risk to Tortoise Populations on the Ground 

o	 Single Risk/Threat Model: combines degrees of threat with stress/demographic impact 

to estimate severity of each threat to the population 

o	 Pre-action Aggregate Risk Model: estimates the aggregate measure of the risk/severity 

posed to the population by all threats 

•	 Recovery Action Models 

o	 Recovery Action Effectiveness Model: estimates the effectiveness of recovery actions 

in mitigating threat-stress links 

o	 Recovery Action Risk Reduction Model: combines the estimated risk to populations 

with recovery action effectiveness to estimate the reduction in risk/threat severity 

176 
 

 

 

 

 

o	 Post-action Aggregate Risk Model: estimates the aggregate measure of the risk/threat 

severity posed to the population by all threats after management actions are applied 

•	 Spatial Prioritization: prioritizes recovery actions by their estimated effectiveness in risk 

reduction 

C. COMPONENTS OF SUPPORT SYSTEM CALCULATIONS 

1.	 Compile and Evaluate Spatial Threats Data 

The Spatial Threats Model utilizes GIS data of the spatial extent of threats. For each 

threat, GIS layers from multiple sources illustrating where threats occur geographically are 

integrated into a single layer. Initial sources of threat data include previously published datasets 

and outputs of published models and mosaic datasets verified by local biologists and managers. 

Threats for which no data exist can be derived using the best available data and inter-threat 

relationships within the conceptual model. These data will be updated by Recovery 

Implementation Teams as new information becomes available. 

2.	 Estimate Contribution of Each Threat to Overall Demographic Impact 

Even though very little is known about the demographic impacts of individual threats on 

desert tortoise populations or the relative contributions each threat makes to population numbers 

(Boarman 2002; Tracy et al. 2004), we must still estimate the relative impact of the various 

threats to tortoise populations. This involves rating the ‘severity’ or contribution of each threat 

with regard to tortoise demography and is accomplished by combining two submodels: 1) the 

Threat-Stress Interaction Model, which estimates the contribution of each threat to population 

stresses, and 2) the Relative Stress Model, which estimates the contribution of each population 

stress to overall change in tortoise population numbers. 

2.1 Estimate the contribution of each threat to stress 

The Threat-Stress Interaction Model uses conceptual models of the interrelationships of 

threats and stresses (Figure B-1). The language used in the conceptual model is based on 

Salafsky et al. (2008). The relationship among threats, between threats and population stresses, 

and between stresses and demographic change factors were weighed using expert on-line 

assessments. Assessment responses relate to range-wide, relative contributions of: 1) threats to 

threats; 2) threats to populations stresses; and 3) population stresses to demographic change 

parameters. Using the conceptual models and assessments, an average contribution of each threat 

to overall population change can be calculated. When determining a threat’s contribution to a 

stress, both direct and indirect threat contributions are considered. Indirect contributions are links 

between one and another threat that itself has a link to a stress. 

177 
Figure B-1. An example of how the relationship between a single threat and overall population change is 

represented within the conceptual model. In this example, the relationships among one focal threat, 

Energy Development, and its indirect threats, stresses to the population, and demographic change 

parameters are depicted. The numbers on the linkages represent the relative contribution weights from 

expert on-line assessments. 

2.2 Estimate the contribution of stresses to overall change in population 

In the Relative Stress Model, each stress is assigned a weight that described its relative 

contribution to demographic change parameters, as per our conceptual models of threat-stress 

relationships. For this iteration of the system, we consider only two age classes (prereproductive, juvenile and reproductive, adult), and we consider only two demographic change 

factors (death rate and birth rate [reproductive output]). Immigration and emigration rates will be 

considered in future versions of the system. To generate these weights, the contribution of each 

stress to the demographic impact is weighted on a significance scale, which resulted in an overall 

set of relative weights for each stress to the populations. Note that these same weights could be 

replaced with quantitative data from future research to provide more reliable results. The relative 

contribution of each demographic factor to overall population change is determined by assessing 

outputs of population viability analyses (Doak et al. 1994; Wisdom et al. 2000; Reed et al. 

2009). 

178 
 

 

 

2.3 Estimate threat contribution to overall change 

Combining 2.1 and 2.1 gives the threat contribution to overall population change – the 

relative contribution, over the entire range, of that threat to overall population change across the 

range. 

3. SPATIAL RISK TO POPULATIONS 

3.1 Combine degree of threat with population change factor to estimate threat severity 

This step creates a Single Risk Model for each stress by combining the spatial 

distribution of each threat with the threat contribution to population change. This step yields a 

severity rating for each threat to desert tortoise populations within a geographic area of interest 

(e.g., recovery unit, recovery implementation team workgroup area, etc). The rating represents 

both degree of threat (intensity and frequency) and the risk to population associated with that 

threat, as calculated in the previous step. 

3.2 Estimate Aggregate Threat Severity 

This step provides a synopsis of threats across the tortoises’ range. It is a GIS processing 

step that involves summing each threat layer using the severity ratings developed in the previous 

step (3.1). The output is an aggregate rating of threat severity (risk) posed to the desert tortoise, 

reported at the spatial unit of 1 square kilometer (Figure B-2). 

Figure B-2. Example of aggregated risk or population stress severity across the range of the Mojave 

population of the desert tortoise. Warmer colors indicate greater risk to the tortoise. 

179 
 

4. ESTIMATE EFFECTS OF RECOVERY ACTIONS 

The Recovery Action Effectiveness Model relates recovery actions to the threatpopulation stress relationships they address. For example, the recovery action “install tortoise 

fencing” addresses crushing of tortoises (population stress) by motor vehicles on paved roads 

(threat). Relationships between recovery actions and threat-stress links are rated on a scale of 0-5 

(0 = no effect; 5 = 100% effectiveness at eliminating the population stress due to a particular 

threat). A more thorough quantification of these relationships will provide more reliable results 

as the model-assessment process proceeds. The Recovery Action Risk Reduction Model then 

combines the risk to the tortoise before an action with the effectiveness of that action on a given 

threat. The result of this calculation yields an estimated reduction of the risk posed by a threat as 

a result of an action or suite of actions. Individual recovery actions can then be prioritized based 

on their overall predicted risk reduction score (Figure B-3). 

Figure B-3. Example of estimated risk reduction to a desert tortoise population for a proposed subset of 

recovery actions within a particular geographic area. 

Literature Cited: Appendix B 

Boarman, W.I. 2002. Threats to desert tortoise populations: A critical review of the literature. 

U.S. Geological Survey, Western Ecological Research Center, Sacramento, California. 

Feick, R., and B. Hall. 2004. A method for examining the spatial dimension of multi-criteria 

weight sensitivity. International Journal of Geographic Information Science 18:815-840. 

Leu, M., S.E. Hanser, and S.T. Knick. 2008. The human footprint in the West: a large-scale 

analysis of anthropogenic impacts. Ecological Applications 18:1119-1139. 

180 
 

 

Malczewski J. 2006. GIS-based multicriteria decision analysis: a survey of the literature. 

International Journal of Geographical Information Science 20:249-268. 

Murphy, P., N. Li, R.C. Averill-Murray, P. Burgess, and N. Strout 2008. Smart knowledge 

capture for developing adaptive management systems. Proceedings of the 14th Americas 

Conference on Information Systems, August 14-17, 2008, Toronto, Canada. 

Nicolson, C.R., A.M. Starfield, G.P. Kofinas, and J.A. Kruse. 2002. Ten heuristics for 

interdisciplinary modeling projects. Ecosystems 5:376-384. 

Reed, J. M., N. Fefferman, and R. C. Averill-Murray. 2009. Vital rate sensitivity analysis as a 

tool for assessing management actions for the desert tortoise. Biological Conservation 

142:2710-2717. 

Salafsky, N., D. Salzer, A.J. Stattersfield, C. Hilton-Taylor, R. Neugarten, S.H. Butchart, B. 

Collen, N. Cox, L.L. Master, S. O’Connor, and D. Wilkie. A standard lexicon for 

biodiversity conservation: unified classifications of threats and actions. Conservation 

Biology 22:897-911. 

Starfield, A.M. 1997. A pragmatic approach to modeling for wildlife management. Journal of 

Wildlife Management 61:261-270. 

Starfield, A.M., and A.L. Bleloch. 1991. Building models for conservation and wildlife 

management. Interaction Book Company, Edina, Minnesota. 

Tracy, C.R., R.C. Averill-Murray, W.I. Boarman, D. Delehanty, J.S. Heaton, E.D. McCoy, 

D.J. Morafka, K.E. Nussear, B.E. Hagerty, and P.A. Medica. 2004. Desert Tortoise 

Recovery Plan Assessment. Report to the U.S. Fish and Wildlife Service, Reno, 

Nevada. 

181 
182 
 

 

 

 

APPENDIX C 

RECOMMENDED SPECIFICATIONS FOR DESERT TORTOISE EXCLUSION 

FENCING (SEPTEMBER 2005)
 

These specifications were developed to standardize fence materials and construction 

procedures to confine tortoises or exclude them from harmful situations, primarily roads and 

highways. Prior to commencing any field work, all field workers should comply with all 

stipulations and measures developed by the jurisdictional land manager and the U.S. Fish and 

Wildlife Service for conducting such activities in desert tortoise habitat, which will include, at a 

minimum, completing a desert tortoise education program. 

Fence Construction 

Materials 

Fences should be constructed with durable materials (i.e., 16 gauge or heavier) suitable to 

resist desert environments, alkaline and acidic soils, wind, and erosion. Fence material should 

consist of 1-inch horizontal by 2-inch vertical, galvanized welded wire, 36 inches in width. Other 

materials include: Hog rings, steel T-posts, and smooth or barbed livestock wire. Hog rings 

should be used to attach the fence material to existing strand fence. Steel T-posts (5 to 6-foot) are 

used for new fence construction. If fence is constructed within the range of bighorn sheep, 6-foot 

T-posts should be used (see New Fence Construction below). Standard smooth livestock wire 

fencing should be used for new fence construction, on which tortoise-proof fencing would be 

attached. 

Retrofitting Existing Livestock Fence 

Option 1 (see drawing). Fence material should be buried a minimum of 12 inches below 

the ground surface, leaving 22-24 inches above ground. A trench should be dug or a cut made 

with a blade on heavy equipment to allow 12 inches of fence to be buried below the natural level 

of the ground. The top end of the tortoise fence should be secured to the livestock wire with hog 

rings at 12 to 18-inch intervals. Distances between T-posts should not exceed 10 feet, unless the 

tortoise fence is being attached to an existing right-of-way fence that has larger interspaces 

between posts. The fence must be perpendicular to the ground surface, or slightly angled away 

from the road, towards the side encountered by tortoises. After the fence has been installed and 

secured to the top wire and T-posts, excavated soil will be replaced and compacted to minimize 

soil erosion. 

Option 2 (see drawing). In situations where burying the fence is not practical because of 

rocky or undigable substrate, the fence material should be bent at a 90Ε angle to produce a lower 

section approximately 14 inches wide which will be placed parallel to, and in direct contact with, 

the ground surface; the remaining 22-inch wide upper section should be placed vertically against 

the existing fence, perpendicular to the ground and attached to the existing fence with hog rings 

at 12 to18-inch intervals. The lower section in contact with the ground should be placed within 

the enclosure in the direction of potential tortoise encounters and level with the ground surface. 

Soil and cobble (approximately 2 to 4 inches in diameter; can use larger rocks where soil is 

183
 
 

 

shallow) should be placed on top of the lower section of fence material on the ground covering it 

with up to 4 inches of material, leaving a minimum of 18 inches of open space between the 

cobble surface and the top of the tortoise-proof fence. Care should be taken to ensure that the 

fence material parallel to the ground surface is adequately covered and is flush with the ground 

surface. 

New Fence Construction 

Options 1 or 2 should be followed except in areas that require special construction and 

engineering such as wash-out sections (see below). T-posts should be driven approximately 24 

inches below the ground surface spaced approximately 10 feet apart. Livestock wire should be 

stretched between the T-posts, 18 to 24 inches above the ground to match the top edge of the 

fence material; desert tortoise-proof fencing should be attached to this wire with hog rings placed 

at 12 to 18-inch intervals. Smooth (barb-less) livestock wire should be used except where 

grazing occurs. 

If fence is constructed within the range of bighorn sheep, two smooth-strand wires are 

required at the top of the T-post, approximately 4 inches apart, to make the wire(s) more visible 

to sheep. A 20 to 24-inch gap must exist between the top of the fence material and the lowest 

smooth-strand wire at the top of the T-post. The lower of the top two smooth-strand wires must 

be at least 43 inches above the ground surface. 

(72-inch T-posts: 24 inches below ground + 18 inches of tortoise fence above ground + 

20 to 24-inch gap to lower top wire + 4 inches to upper top wire = 66 to 70 inches). 

Inspection of Desert Tortoise Barriers 

The risk level for a desert tortoise encountering a breach in the fence is greatest in the 

spring and fall, particularly around the time of precipitation including the period during which 

precipitation occurs and at least several days afterward. All desert tortoise fences and cattle 

guards should be inspected on a regular basis sufficient to maintain an effective barrier to 

tortoise movement. Inspections should be documented in writing and include any observations of 

entrapped animals; repairs needed including bent T-posts, leaning or non-perpendicular fencing, 

cuts, breaks, and gaps; cattle guards without escape paths for tortoises or needed maintenance; 

tortoises and tortoise burrows including carcasses; and recommendations for supplies and 

equipment needed to complete repairs and maintenance. 

All fence and cattle guard inventories should be inspected at least twice per year. 

However, during the first 2 to 3 years all inspections will be conducted quarterly at a minimum, 

to identify and document breaches, and problem areas such as wash-outs, vandalism, and cattle 

guards that fill-in with soil or gravel. GPS coordinates and mileages from existing highway 

markers should be recorded in order to pinpoint problem locations and build a database of 

problem locations that may require more frequent checking. Following 2 to 3 years of initial 

inspection, subsequent inspections should focus on known problem areas which will be inspected 

more frequently than twice per year. In addition to semi-annual inspections, problem areas prone 

to wash-outs should be inspected following precipitation that produces potentially fence184
 
 

damaging water flow. A database of problem areas will be established whereby checking fences 

in such areas can be done efficiently. 

Repair and Maintenance of Desert Tortoise Barriers 

Repairs of fence wash-outs: (1) realign the fence out of the wash if possible to avoid the 

problem area, or (2) re-construct tortoise-proof fencing using techniques that will ensure that an 

effective desert tortoise barrier is established that will not require frequent repairs and 

maintenance. 

Gaps and breaks will require either: (a) repairs to the existing fence in place, with similar 

diameter and composition of original material, (b) replacement of the damaged section to the 

nearest T-post, with new fence material that original fence standards, (c) burying fence, and/or 

(d) restoring zero ground clearance by filling in gaps or holes under the fence and replacing 

cobble over fence constructed under Option 2. Tortoise-proof fencing should be constructed and 

maintained at cattle guards to ensure that a desert tortoise barrier exists at all times. 

All fence damage should be repaired in a timely manner to ensure that tortoises do not 

travel through damaged sections. Similarly, cattle guards will be cleaned out of deposited 

material underneath them in a timely manner. In addition to periodic inspections, debris that 

accumulates along the fence should be removed. All cattle guards that serve as tortoise barriers 

should be installed and maintained to ensure that any tortoise that falls underneath has a path of 

escape without crossing the intended barrier. 

185
 
DESERT TORTOISE EXCLUSION FENCE (2005) 

+!itrand wire fence, 

DETAIL A 

4-stranc! wire fence 1 inch Hog ri g 

" - . n s --, ~ /' 12-18~intervars:' 

11!.c r'r 

Gaillanizeq fence: 

.r 2-in~h 

Matenal 

RECOMMENDED DESIGN FOR 

DESERT TORTOISE EXCLUSION FENCE 

GENERAL NOTES: 

1. Ensure that fence posts and materials conform 

to the standards approved by the U.S. Fish and 

Wildlife Service. 

2. Ensure that the height above ground level is no 

less than 18 inches and no higher than 24 inches. 

4-strand 

wire fence 

Hag rings 

12-18" intervals 

S.ee Detail B 

Galvanized fene 

Material 

$.ECT10NA 

UJ 

Q) 

.c 

() 

.5 

o 

(") 

7. Backfill trenches with excavated material and 

compact the material. 

8. Attach fence material to all gates. Ensure that 

clearance at base of gate achieves zero ground 

clearance. 

Ensure that the depth of fence material below 9. Substitute smooth wire for barbed wire if additional 

ground~level-is~abouU2jnches~bulno-'essjhan~~~~-",S"",U,RRort wires are necessa!}',--. ~~~~~~~~~_ 

3. 

4. 

5. 

6 inches. (See SECTION A above) 

Install additional steel posts when span between 

existing fence posts exceed 10 feet. 

Attach fence material to existing fence or wire 

using hog rings at 12-inch intervals. 

6. Fasten fence material to posts with 3 tie wires 

10. The number anti placement of support wires may be 

modified to allow sheep and deer to pass safely. 

11. Erosion at the edge of the fence material where the 

fence crosses washes may occur and requires 

appropriate and timely monitoring and repair. 

-~~ ~~-,~---- -~-DETAI~B-------------with~a-wire~near-the-topj-bottom,anEl~center-0f-the 

fence material. 

12. Tie the fence into existing culverts and cattleguards 

when determined necessary to allow desert tortoise 

passage underneath roadw~~~ ~-~ 

18
FOR BEDROCK OR CALICHE SUBSTRATE 

1. Use this fence design (see below) only for that portion of the fence where fence material cannot be placed 

6 inches below existing ground level due to presence of bedrock, large rocks or caliche substrate. 

2. Ensure that the fence height above ground level is no less than 22 inches. 

3. Ensure that there is a zero to 2-inch ground clearance at the bend. 

4. Ensure that the bent portion of the fence is lying on the ground and pointed in the direction of desert 

tortoise habitat. 

5. Cover the portion of the fence that is flush with the ground with cobble (rocks placed on top of the fence 

material to a vertical thickness up to 4 inches). 

6. When substrate no longer is composed of bedrock or caliche, install fence using design shown above. 

4,-stra.nd Wittt fet!t::e Sse OetaU'S: 

Must achievi:! a z.ero to 

WPI,md clearance af bend. 

Galvanized fenCe 

4-strand 

wire fence 

:Rog nngs' 

12-18" intervals 

See Detail"B 

Galvanized fence 

material 

Must achieve Iii· zero to 2-inch 

ground clearance at bend . 

SECTIoN B 

18 
188 
 

 

 

 

 

APPENDIX D 

COMMENTS RECEIVED ON THE DRAFT PLAN 

A. Overview of Public Comment Period 

In August 2008, we released the Draft Revised Recovery Plan for the Mojave Population 

of the Desert Tortoise (Gopherus agassizii) (draft plan) and initiated a 90-day comment period. 

We received comments from Federal agencies, State and local governments, and members of the 

public. Among six scientists asked to provide peer review of the draft plan, we received 

comments from Drs. J. Whitfield Gibbons, Ken Nagy, H. Bradley Shaffer, and Anthony 

Starfield. 

This section provides a summary of general information including the total number of 

letters received from various affiliations. It also provides a summary of the major comments. All 

letters of comment on the draft plan are kept on file in the Nevada Fish and Wildlife Office at 

1340 Financial Boulevard, Suite 234, Reno, Nevada 89502. 

We received 49 letters and over 6000 internet-generated form letters during the comment 

period. The email form letters voiced opposition to aspects of the recovery plan with only 

general reasoning provided, which was also reflected in various of the 49 more substantive 

letters. Some letters included new information or suggestions for clarity. In these cases, the 

information has been incorporated into the final version of the recovery plan. Many comments 

resulted in revisions to the draft plan. Information and comments not incorporated into the final 

version of the recovery plan were considered, noted, and are on file with the entire package of 

agency and public comments. Major comments that were not incorporated or that require 

clarification in addition to their incorporation are addressed in the summary below. 

The following is a breakdown of the number of letters received from various affiliations: 

Federal agencies 3 

State agencies 5 

Local governments 8 

Environmental/conservation organizations 10 

Academia/professional (including 4 peer reviews) 9 

Individual citizens 13 

Recreation groups 1 

B. Summary of Comments and Our Responses 

1. General Comments 

Comment: One commenter stated that the recovery plan does not establish a useful baseline from 

which to assess recovery and that the data used to justify the listing should be used to inform 

effectiveness of recovery. 

189 
Response: Reasons for not using existing data as range-wide population baseline are 

articulated in the Population Trends and Distribution section. Existing data, including 

observed local population declines from across the range of the desert tortoise, are used 

to support assumptions of downward trends. In addition, effectiveness of actions to 

benefit desert tortoises has not been monitored adequately and remains largely unknown. 

Clarifications have been made to text. 

Comment: Several commenters stated the revised recovery plan is either unchanged from the 

1994 recovery plan, is insufficient, focuses too much or not enough on the 1994 plan, or that the 

1994 plan was founded in science and should be fully implemented before being revised. 

Response: Because the threats to desert tortoises remain largely unchanged from 1994, 

previous management and recovery actions remain appropriate. Both the GAO report 

(2002) and the assessment of the 1994 recovery plan (Tracy et al. 2004) found that plan 

and its recommendations to be fundamentally sound based on the best available science. 

Therefore, the revised recovery plan uses the 1994 plan as a foundation on which to build 

and integrate new criteria, focus on effectiveness monitoring, and develop a spatial 

decision support system. Some clarifications have been made in the Executive Summary 

and under the Recovery Strategy section. 

Comment: One commenter stated the desert tortoise should be listed as endangered. 

Response: The listing status of the desert tortoise is evaluated through a process separate 

from recovery planning. Under section 4(c)(2) of the Act, we conduct 5-year reviews to 

determine if a federally listed species should be delisted, reclassified from endangered to 

threatened status or from threatened to endangered status, or if the status of the species 

should remain the same. The most recent 5-year review for the desert tortoise found that 

the threats to the species did not warrant changing its status from threatened (USFWS 

2010). 

Comment: One commenter stated that the revision should simply update the 1994 recovery plan 

with accomplishments over the past 14 years, outstanding actions, and new actions needed to 

provide greater protection of populations and critical habitat (including suggestions for site- and 

area-specific actions). 

Response: The revised recovery plan builds upon the 1994 Recovery Plan. As such, 

accomplishments, outstanding actions and new actions needed are discussed in the 

revised plan. The revised recovery plan updates the 1994 plan with new criteria, and 

additional strategies for recovery. Recovery actions are enumerated for the recovery units 

and tortoise conservation areas; many of these actions further specify priority needs 

within individual tortoise conservation areas. Additional site-specific actions will be 

identified and implemented through the Recovery Implementation Teams, as necessary. 

Comment: One commenter suggested that a change in the recovery priority number should 

include additional discussion about the timeline for improving the situation for the species and 

the immediate need to have certain actions funded. Based on the discussion of the measures that 

have been implemented, the species should be in a better position to recover today than it was in 

190 
 

 

 

1990. The plan as written does not clearly present what changed on the ground since the original 

recovery plan was issued that resulted in this change in classification. 

Response: While a change in recovery priority number is not typically associated with a 

specific list of action items or a timeline for ameliorating threats, recovery plans are 

designed to identify and prioritize actions needed to advance recovery. Recovery plans 

also identify timelines for particular actions to the extent that they can be predicted (in 

the Implementation Schedule), and recovery plans often project a timeline to recovery 

(often in the Executive Summary). These items are all found in the revised desert tortoise 

plan. The revised plan for the desert tortoise further outlines uncertainties about various 

threats and our ability to manage them, reflected in the changed recovery priority 

number, and discusses at some length the ineffective approach to recovery to date. The 

revised plan also discusses the problems arising from the lack of a centralized recovery 

database, which would help us better track the effectiveness of measures that have been 

implemented since 1994. For example, it was not possible during the recovery planning 

process to obtain accurate data from all the various land management agency offices on 

how threats or management actions have changed since the original listing and recovery 

plan publication. Efforts continue in this area in the development of the decision support 

system and recovery database, however. We anticipate that implementation of the revised 

plan will resolve key uncertainties about threats and management and improve recovery 

potential for the desert tortoise by the next recovery plan assessment. 

2. Process 

Comment: One commenter stated that we failed to follow statutory and policy requirements in 

the development of the revised plan. 

Response: We believe that we have followed applicable laws, policies and guidance in 

this recovery planning process. The Science Advisory Committee is a recovery team and 

as such is exempt from FACA pursuant to section 4(f)(2) of the Act. The workgroups/ 

workshops were information-gathering sessions to which the public as well as invitees 

were welcome. These sessions focused on gathering individual opinion, best professional 

judgement, and information about threats to and recovery actions for the desert tortoise. 

We used the information gathered in developing both the decision support system and 

recovery actions identified in the plan. 

Comment: One commenter criticized the location of recovery planning working groups in 

Nevada, which were difficult for interested parties from California to attend. 

Response: Two recovery planning workshops were held in Redlands, California, in 

addition to two in Las Vegas, Nevada, in an effort to foster broad participation in the 

planning process. We recognize that wherever workshops are held, they will be difficult 

for some parties to attend. We made our best effort to pick locations that would be 

feasible for many potential participants. Desert Tortoise Management Oversight Group 

meetings are held in Las Vegas, which is most centrally located for managers and 

stakeholders across the range. 

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3. Introduction – Population Trends 

Comment: One commenter suggested that the revised plan ignores an abundant amount of 

existing information about the status and trends of the desert tortoise. Another suggested that 

tools to accurately measure regional or range-wide trends do not yet exist; therefore, statements 

about population trends should be made with disclaimers. 

Response: The revised plan summarizes the state of rangewide information; i.e., local 

declines have been confirmed, and these local areas are across the range, supporting the 

conclusion of broader and perhaps continuing declines. The Population Trends and 

Distribution section has been revised. In the revised section, we briefly describe previous 

efforts to quantify tortoise populations, explain the weaknesses of the older desert tortoise 

status data for assessing population trends, and describe more recent monitoring efforts 

and our ability to detect trends using them. 

Comment: One commenter suggested that it was unclear if population declines have been offset 

by increases elsewhere, as no baseline exists and no consistent range-wide surveys have been 

done. 

Response: Past surveys that detected local declines were not randomly placed nor were 

they placed specifically to observe declines or increases. The Recovery Plan states that 

local declines, noted opportunistically, do not happen to be matched by local population 

increases that might also have been noted opportunistically. 

Comment: One commenter indicated that even though the draft recovery plan states that “historic 

estimates of desert tortoise density or abundance do not exist at the range-wide or regional level 

for use as a baseline” and does not acknowledge the historic triangle-transect data going back as 

far as 1980 in Nevada, these surveys did identify estimates of tortoises across the landscape and 

are still used as historical presence/absence data in daily land management decisions. 

Response: In the late 1970s and early 1980s, the Bureau of Land Management 

implemented "corrected sign" transects to assess general and relative abundance of 

tortoises across larger management areas, particularly in the California Desert District. 

These transects were placed regularly on the landscape, and in suspected tortoise habitat, 

to map relative densities of tortoises for planning purposes (Berry and Nicholson 1984a). 

The same authors note some limitations with the technique, feeling that it generally 

underestimated by a moderate amount the true number of tortoises in most areas. Since 

the 1990s, based on difficulties and inaccuracies noted with the technique, it has not been 

considered a reliable way to estimate tortoise numbers. While it is true that these surveys 

for sign can be used in a presence/absence context, this is different from using the data 

for comparative purposes or for trend estimation. See also revised text in the Population 

Trends and Distribution section. 

4. Introduction – Reasons for Listing and Appendix A (Threats) 

Comment: One commenter stated that the recovery plan translates the agency’s own failure to 

document recovery actions, the paucity of effectiveness-monitoring data, and the obviously 

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inadequate timeframe over which impacts of threat reduction could be manifest, into the notion 

that not only is the effectiveness of recovery actions unclear but that the threats are uncertain. 

Response: The GAO report (2002) found that despite considerable efforts by land 

managers to conserve the desert tortoise, the effectiveness of their actions was not the 

focus of any research or monitoring activities; therefore, the ability to determine the 

effectiveness of a given action was limited. With the establishment of the Desert Tortoise 

Recovery Office in 2004, the Fish and Wildlife Service is better equipped to track 

implementation of recovery actions, as well as focus efforts on methods to evaluate 

effectiveness of management actions. Additional considerations are the biological 

constraints and cryptic nature of the species that confound our ability to design 

meaningful studies to evaluate effectiveness as it relates to population responses. 

Comment: Several commenters criticized discussion of synergistic threats as either inadequate or 

without merit. 

Response: Little, if any, direct research has been conducted to quantify synergisms 

between various threats. However, Tracy et al. (2004) provided a conceptual model that 

illustrates how multiple individual threats act on the same mortality mechanisms, 

justifying a renewed focus on understanding how different threats interact. The spatial 

decision support system refines this conceptual model to predict effects of multiple 

threats on tortoise populations and the effects of management actions to reduce those 

threats. 

Comment: One commenter claimed that "potential" threats are treated as "real" without 

justification and stated that the fact that few data exist to evaluate or quantify effects of 

individual threats on desert tortoise populations is a weakness of the revised plan. 

Response: The revised plan documents that all the identified threats are harmful to 

individual tortoises. Inclusion of these threats in the recovery plan is supported by the 

GAO (2002) audit of the recovery program and subsequent scientific reviews. 

Quantifying the magnitude and importance of individual threats and groups of threats on 

desert tortoise populations is a major goal of the spatial decision support system 

recommended by this plan. 

Comment: Several commenters criticized the lack of description of the extent of threats in each 

recovery unit, including specific impacts to critical habitat. 

Response: Many of the threats to the desert tortoise exist across broad portions of the 

species’ range. In several cases, more local or recovery-unit based threats are highlighted 

by location-specific recovery action recommendations. The prototype decision support 

system uses the best data that could be obtained within the planning process and provides 

a guide as to what additional data are most needed. The initial datasets provide a structure 

and way to prioritize the next round of data gathering, particularly including impacts to 

critical habitat. These data, including future updates, will be made publicly available 

through the Recovery Implementation Team (RIT) process. 

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Comment: One commenter noted that Table A-1 does not reflect growth in desert areas of Kern 

County, but rather for the greater-Bakersfield area. Another was concerned that the revised plan 

implies that all private lands will convert to urban uses, which is not supported by California 

SB375 or California AB32 which will encourage more compact land uses and potentially reduce 

threats to the desert tortoise. 

Response: The data in Table A-1 are from Byerly and Deardorff (1995) and the 2007 

U.S. Census Bureau estimates for the states and counties within the range of the Mojave 

population of the desert tortoise between 1994 and 2006. Data for both entire counties 

and entire states are included. We do not mean to imply, nor do we expect, that all private 

lands will convert to urban uses. However, increasing human populations in areas 

peripheral to the range of the desert tortoise do lead to pressures on desert tortoise habitat 

and populations through recreation and other impacts. 

Comment: One commenter felt that the revised plan presents little evidence to support the 

statements regarding off-highway vehicle (OHV) impacts, such as crushed tortoise burrows, and 

asked that the number of acres of critical habitat that have been degraded by OHVs be provided. 

Response: Despite many observations of off-highway vehicle impacts to tortoise burrows 

(Berry and Nicholson 1984b, Bury and Marlow 1973, Bury and Luckenbach 1986, Berry 

1990), no statistical correlation between off-highway vehicle impacts and crushed 

tortoise burrows has been found (Boarman 2002). The revised plan describes several 

impacts to desert tortoise habitat and individuals from OHV use. Data are not readily 

available to quantify the number of acres of critical habitat degraded by OHV use; 

however, we are currently in the process of assembling various spatial data layers, such 

as aerial photography and satellite-derived land cover data, to complete these sorts of 

analyses as part of the RITs' prioritization and evaluation of recovery actions. 

Comment: One commenter asked if the draft desert tortoise habitat model includes predictions 

under climate change scenarios. 

Response: The current version of the habitat model (Nussear et al. 2009), finalized since 

publication of the draft plan, does not include climate change scenarios. The revised plan 

includes a research recommendation to model the predicted effects of climate change on 

desert tortoise demography and habitat (Recovery Action 5.1). 

Comment: One commenter suggested that the Intergovernmental Panel on Climate Change 

(IPCC) report provides sufficient detail to predict population consequences that climate change 

will have on the desert tortoise and that these predictions should be included in the revised plan. 

Response: The models and conclusions published in the 2007 IPPC report provide 

general information on how climate may change in the desert southwest, but they do not 

model regional or local ecological responses or effects on individual species. The revised 

plan describes many of these general effects and potential consequences to desert 

tortoises, but additional research and modeling, as recommended in Recovery Action 5.1, 

is necessary to determine specific consequences and develop actions that may be 

necessary to mitigate effects of changing climate. 

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5. Introduction – Conservation Efforts 

Comment: One reviewer suggested a section called "Progress and Failures to Date" to answer 

questions about population trends, actions taken, and effectiveness of those actions since listing. 

Response: We agree that such a section would be valuable. Unfortunately, despite clear 

demonstration that threats to the desert tortoise impact individual tortoises, there are few 

data available to evaluate or quantify the effects of these threats on desert tortoise 

populations. Likewise, effectiveness of actions to benefit desert tortoises has not been 

monitored adequately and remains largely unknown, especially since historic estimates of 

desert tortoise abundance do not exist at the range-wide or regional level for use as a 

baseline. Therefore, the information for the section the reviewer recommends is not 

readily available. The prototype decision support system recommended in the revised 

plan uses the best data that could be obtained within the planning timeframe and provides 

a guide as to what data are most needed. 

Comment: One commenter stated that the role of the Clark County Multi-Species Habitat 

Conservation Plan’s (HCP) Conservation Management Strategies (CMSs) in desert tortoise 

recovery is unclear. What is the implementation schedule/strategy and what is the Fish and 

Wildlife Service's role? 

Response: The CMSs for Desert Wildlife Management Areas in Nevada were finalized in 

February 2007 and implementation has not yet begun. They were drafted to fulfill a 

requirement under the Clark County Multi-Species HCP (RECON 2000) to guide the 

prioritization, mitigation, and funding needs relative to desert tortoise in each of the 

Desert Wildlife Management Areas. The County has not yet indicated how it intends to 

implement the CMSs; however, the information gathered and recommendations 

contained in the strategies can serve as a baseline for each of the Desert Wildlife 

Management Areas and should inform the Recovery Implementation Teams in their 

efforts to implement prioritized regional recovery actions. 

Comment: One commenter asked if the lands purchased under the California Desert land 

acquisition project were within critical habitat, did the lands support desert tortoises, and was 

there any study of the desert tortoises there? 

Response: The majority of lands purchased by the Department of Defense and Wildlands 

Conservancy are within designated critical habitat. No specific desert tortoise studies 

have been conducted on these lands. 

Comment: One commenter stated the recovery plan fails to acknowledge loss of recreational 

lands due to the conservation of the desert tortoise and that this acreage should be quantified. 

Response: We added text under the Conservation Efforts section relative to the California 

Desert Conservation Area Plan. Some recreational activities (e.g., off-highway vehicle 

use) have been displaced due to conservation efforts for various resources including the 

desert tortoise, but overall, recreational opportunities still exist within the same 

geographic areas. The route designation process within the California Desert 

Conservation Area resulted in closure of some routes and restricted use of open washes; 

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however, alternative routes still exist, and unauthorized routes continue to be established. 

The Bureau of Land Management does not track the number of acres of recreation that 

has been displaced. 

6. Recovery Strategic Element 1 – Partnerships 

Comment: One reviewer asked whether or not the Recovery Implementation Teams (RITs) will 

be effective. 

Response: The primary goal of the RITs is to coordinate recovery action implementation 

to reduce threats to the desert tortoise. We will be implementing a formal process to track 

and assess effectiveness of recovery efforts. The effectiveness of the RITs should be 

demonstrated by the effectiveness of regional/local recovery efforts as tracked in the 

spatial decision support system and evidenced by range-wide monitoring. 

Comment: One commenter suggested that the recovery plan is required to be a binding document 

and that we may not delegate our authority to implement the plan to RITs. 

Response: Recovery plans are non-regulatory documents, and as such, identified partners 

are not obligated to implement recovery tasks. The revised plan recommends the 

formation of RITs to facilitate cross-jurisdictional implementation of the actions 

recommended in the plan. 

Comment: Two commenters asked for clarification of the link between the RIT process and 

existing land use plans, such as the Bureau of Land Management's resource management plans 

(RMPs) and the existing Conservation Management Strategies (CMSs) in Clark County, Nevada. 

Response: Existing RMPs within the range of the desert tortoise include language 

specific to the protection and conservation of natural resources, including desert tortoises 

and their habitat. RMPs are often supplemented by more specific guiding documents, 

such as habitat management plans or wilderness management plans. The CMSs have also 

identified actions for specific areas that are important to desert tortoise recovery. The 

regional RIT action plans are intended to be supplements which prioritize recovery 

actions within an RMP jurisdictional or CMS area for the next five years. 

Comment: One commenter claimed that the recovery plan is based on a flawed management 

structure. Since we cannot ensure participation by land management agencies, nor can we 

influence budget allocations or commitment of resources to recovery, the commenter 

recommended that we assert and enforce the obligations of the federal agencies under section 

7(a)(1) of the Endangered Species Act (ESA). 

Response: Recovery plans are guidance documents, not regulatory documents. No agency 

or entity is required by the ESA to implement the recovery strategy or specific actions in 

a recovery plan. However, the ESA envisions recovery plans as the central organizing 

tool for guiding each species’ recovery. Recovery plans should also guide Federal 

agencies in fulfilling their obligations under section 7(a)(1) of the ESA, which calls on all 

Federal agencies to “utilize their authorities in furtherance of the purposes of this Act by 

carrying out programs for the conservation of endangered species and threatened species 

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... .” In addition to outlining strictly proactive measures to achieve species’ recovery, 

recovery plans provide context and a framework for implementation of other provisions 

of the ESA with respect to a particular species, such as section 7(a)(2) consultations on 

Federal agency activities, development of Habitat Conservation Plans (HCPs) or Safe 

Harbor agreements under section 10, special rules for threatened species under section 

4(d), or the creation of experimental populations in accordance with section 10(j). 

Comment: Two commenters questioned the role of public input into the RIT process, including a 

process to appeal the recommendations of the RITs. 

Response: Members of the RITs will be appointed by our Regional Director based on 

demonstrated interest and participation in the recovery planning process. Others will be 

considered upon request. Five-year action plans developed by the RITs will be completed 

and submitted to appropriate regional groups (e.g., Desert Managers Group in California) 

and the Management Oversight Group for review within the first year of publication of 

the revised recovery plan. Meetings of both regional groups and the Management 

Oversight Group are open to the public and will provide a forum for further public input 

into the RIT recommendations. 

Comment: Several commenters asked for further clarification on the RIT structure, organization, 

composition, and function. In particular, commenters asked for the number and jurisdictional 

area of the individual RITs and emphasized the need for integration with the other standing 

groups, such as groups involved in HCP processes. 

Response: RITs will either coordinate directly with the California Desert Manager’s 

Group, the Southern Nevada Agency Partnership, and the Washington County HCP’s 

Adaptive Management Team, as appropriate. Desert tortoise experts will be encouraged 

to be part of the RITs, as either agency representatives or stakeholder representatives. 

Team members will be appointed by our Regional Director and will be representative of 

both agencies (land management, wildlife management, county government, and tribal 

resource agency) and stakeholders (natural resources use group, recreation group, 

conservation organization, and the scientific community). Additional detail has been 

added to the revised plan. 

Comment: Several commenters recommended that the development of five-year action plans and 

budget needs with priorities for management should be undertaken by the Fish and Wildlife 

Service itself and not be left to regional stakeholder groups. They worried that because the RITs 

will be composed of a broad base of managers, stakeholders, and scientists, it appears that we are 

delegating guidance and implementation of recovery to the RITs, which the commenters did not 

believe are required to make decisions based on science. One did not agree that the RITs should 

be included within the Federal Advisory Committee Act (FACA) exemption because they are not 

intended to be science-based recovery teams but rather include numerous types of stakeholders. 

Response: The RITs will serve as advisory groups to the Fish and Wildlife Service 

through the Desert Tortoise Recovery Office and Region 8. The RITs will develop fiveyear recovery action plans within the scientific framework of the spatial decision support 

system. However, a plan is just that, a plan. For results, the plan must be implemented. 

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We have neither the resources nor the authority to implement many, if not most, recovery 

actions. Communication, coordination, and collaboration with a wide variety of potential 

stakeholders are essential to the acceptance and implementation of recovery plans. 

Involving stakeholders early and throughout the process may help achieve necessary 

understanding of the species’ biology, threats and recovery needs, identify and resolve 

implementation issues and concerns at the planning stage, increase buy-in, and facilitate 

more effective implementation. 

We note that the Act, our policies, and applicable guidance do not specify that a recovery 

team must include only scientists. Instead, the section 4(f)(2) of the Act indicates that we 

“may procure the services of appropriate public and private agencies and institutions, and 

other qualified persons” to serve on recovery teams. We find that stakeholders are not 

only qualified, but also valuable additions, to recovery teams. For example, they help us 

assess the feasibility of recovery actions. Appointed recovery teams are exempt from 

FACA per section (4)(f)(2) of the Act. 

Comment: Two commenters were concerned that the revised plan further delays the recovery of 

the desert tortoise, given that it will be at least six months after the publication of the final plan 

that the RITs are established and several more months before the five-year action plans are 

completed. Commenters worried that action will be delayed by the planning process prescribed 

under the Adaptive Management element, specifically the two-year deadline for updating the 

underlying data in the decision support system. 

Response: All on-the-ground recovery recommendations, especially those under Strategic 

Element 2, apply during RIT establishment and the planning process. For future recovery 

implementation, a more strategic, well-coordinated recovery effort (as detailed in the 

revised plan) will encourage cross-jurisdictional, landscape-level action that promises to 

increase effectiveness and efficiency. Unlike past desert tortoise recovery efforts, this 

coordinated approach will be tracked, monitored, and evaluated. 

Comment: One commenter asked why the RITs aren't being formed immediately. 

Response: We will be appointing the RITs once the revised recovery plan is finalized. Per 

Section 4(f)(4) of the ESA, we must “. . . provide public notice and an opportunity for 

public review and comment. . .” and “. . . consider all information presented during the 

public comment period prior to approval of the plan.” Once all public comments have 

been considered and the plan is final, we will form the RITs. 

Comment: One commenter asked that the revised plan clarify how communication among 

stakeholders will be established and maintained. 

Response: Stakeholder representatives on the RITs will be encouraged to coordinate 

among their interest groups. In addition, five-year action plans developed by the RITs 

will be completed and submitted to appropriate regional groups (e.g., Desert Managers 

Group in California) and the Management Oversight Group for review, and the RITs will 

report to these groups annually. Both regional group and Management Oversight Group 

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meetings are open to the public and will provide a forum for further public input into the 

RIT recommendations. 

Comment: One commenter noted that the draft recovery plan provides for additional steppeddown recovery planning at the recovery unit level, but that this scale of planning may yet be too 

large for some recovery units and additional teams may need to be created at the individual 

recovery unit level. The plan should provide for this level of flexibility. 

Response: RITs will have the flexibility to focus their efforts on the most appropriate 

geographic scales in their respective regions. 

7. Strategic Element 2 – Protect Populations and Habitat 

Comment: One commenter stated that intervention (means of providing elements for survival) 

should be a tool available to the Recovery Implementation Teams (RITs), especially in light of 

drought and suboptimal forage conditions. 

Response: Actions proposed in the recovery plan do not constitute an exhaustive list, so 

additional ideas may be proposed, particularly as recovery action plans are developed by 

the RITs. We added text in the Recovery Strategy section to clarify that this is the case. 

Comment: Two commenters stated that populations, habitats, and actions outside tortoise 

conservation areas are also important to recovery, while another commenter expressed concern 

that recovery efforts might be applied outside tortoise conservation areas. 

Response: We explicitly state under Strategic Element 2 and Recovery Objective/ 

Criterion 3 that while recovery efforts are prioritized within existing desert tortoise 

conservation areas, habitats, populations, and actions outside these areas may also either 

impact or contribute to recovery of the species, are subject to the section 7 and 10 

provisions of the Endangered Species Act, and their importance is in no way diminished. 

Comment: Several commenters stated that the recovery plan does not identify any meaningful 

site-specific management actions. The recovery plan focuses on the need for coordination, 

monitoring, and research on the myriad of unanswered questions instead of focusing on 

implementing what is known. 

Response: Under the Recovery Action section, actions that should be implemented within 

tortoise conservation areas are identified. Similar actions were included in the 1994 

recovery plan, which focused implementation within Desert Wildlife Management Areas. 

Additional site-specific actions will be determined by the RITs and will be based on what 

is known about the status of recovery action implementation and current conditions 

within the respective recovery units. 

Comment: One commenter stated that the inclusion of the habitat model and discussion of RITs 

identifying important habitats outside tortoise conservation areas leads the reader to believe the 

Fish and Wildlife Service's goal is to recover the desert tortoise throughout its entire range. Maps 

of occupied habitat should be included in recovery plan, and hard-line boundaries should depict 

where recovery will be focused. 

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Response: The habitat model provides "a range-wide quantification of desert tortoise 

habitat that can help direct where management actions should be implemented as well as 

provide a basis for documenting trends in habitat impacts or loss." The recovery plan 

states that habitats and populations outside tortoise conservation areas may also be 

important for recovery; therefore, the recovery plan does not restrict RITs to focusing 

solely on these areas, especially in light of potential connectivity issues and the fact that 

all desert tortoises are protected under the Endangered Species Act. However, the current 

strategy as stated in the recovery plan focuses management/recovery action priority 

within the tortoise conservation areas. 

Comment: Several commenters stated that the recovery plan fails to specify adequate 

implementable actions, how those actions are to be implemented, and a timeline for 

implementation. 

Response: The Recovery Actions section includes a series of actions, many of which 

were initially identified in the 1994 recovery plan. On-the-ground activities and 

implementation coordination will be assessed and prioritized by the RITs through 

recovery action plans that will be evaluated every five years. 

Comment: One commenter stated that the recovery plan failed to address previously stated 

concerns about the apparent decision that data inadequacies are an excuse for inaction. 

Response: As with many listed species, a lack of substantive data is often an ongoing 

issue; however, we do not view this as an excuse for inaction. In fact, a tremendous 

amount of effort and money have been spent on desert tortoise conservation, 

management, recovery, and mitigation. We acknowledge that there are gaps in the data 

relative to direct correlations between threats and population numbers and the 

effectiveness of various actions; however, the recovery plan includes numerous on-theground recovery actions based on the best available information. The revised plan 

establishes a framework for resolving data gaps through a robust research and monitoring 

program and spatial decision support system. These elements of the recovery program 

will enable us to better assess actions and their effectiveness, ensuring funds are spent 

most effectively. 

Comment: Two commenters stated that the tortoise conservation areas appear to have none of the 

important management prescriptions set forth for Desert Wildlife Management Areas and urged 

that the recovery plan clarify that the Desert Wildlife Management Areas and their existing 

management prescriptions are essential for tortoise recovery and are incorporated into the final 

recovery plan update. 

Response: The revised plan states that recovery efforts will be focused within tortoise 

conservation areas, which include various existing conservation-oriented designations 

and related prescriptions by land-management agencies. Recovery actions include the 

Desert Wildlife Management Area-specific actions contained in the 1994 plan. Desert 

Wildlife Management Areas and Areas of Critical Environmental Concern are mentioned 

throughout the plan, especially in the Conservation Efforts section. The new Table 4 in 

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the revised plan illustrates how recovery actions in this plan compare to those in the 1994 

Recovery Plan. 

Comment: One commenter stated that there is a need for bold changes in public lands 

management to decrease known or suspected causes of adult tortoise mortality while increasing 

or preserving soil integrity. 

Response: Public land management is challenging in the face of multiple-use mandates 

and conservation requirements. The recovery plan strives to achieve balance by 

discouraging future land disturbances within tortoise conservation areas as prescribed by 

the actions described therein and monitored under Recovery Criterion 3. These actions 

should also protect soil integrity in these areas. 

Comment: One commenter stated that one tortoise conservation area in each recovery unit 

should be set aside with the most restrictive management and access possible under federal land 

management guidelines (including a possible change in the lead management agency or 

institution of new designations). Another stated that all critical habitat should be protected 

against all human uses. 

Response: Wilderness is the most restrictive land use allocation, requiring Congressional 

and Presidential approval, and still does not provide for total exclusion of human uses. 

Currently, there are no land designations that would restrict all human uses on public 

lands, and private land management is at the discretion of the landowner. Land 

designations are legislative or management decisions outside our purview, but the 

recovery plan recommends specific actions to minimize or eliminate human impacts to 

desert tortoises and their habitat. 

Critical habitat receives protection under section 7 of the Endangered Species Act 

through prohibition against Federal agencies carrying out, funding, or authorizing 

activities that are likely to result in the destruction or adverse modification of critical 

habitat. Section 7(a)(2) of the Endangered Species Act requires consultation on Federal 

actions that may affect critical habitat. The designation of critical habitat does not affect 

land ownership or establish a refuge, wilderness, reserve, preserve, or other conservation 

area. 

Comment: Several commenters suggested that disposal of public lands in or adjacent to desert 

tortoise habitat should be mitigated at 1:1, and other lands used as mitigation or compensation 

for project impacts should be managed as reserves/preserves by a conservation entity. Certain 

areas should be identified as "experimental management zones." 

Response: The recovery plan suggests that "mitigation of activities harmful to the desert 

tortoise should draw on a suite of opportunities provided by" the strategic elements 

contained in the document. Acquisition and placement of lands into conservation status 

are included among these opportunities. With the emphasis on conservation efforts within 

tortoise conservation areas, experimental management would be most appropriate in 

habitat outside the tortoise conservation areas, for example, as suggested for alternative 

grazing practices in Recovery Action 2.16. 

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Comment: One commenter stated that sufficient information exists on current threats to justify 

taking immediate, corrective action (including, for example, specific areas where off-highway 

vehicle use should be controlled) and that we have disregarded threats analyses contained in 

various California Desert Conservation Area Plan amendments. 

Response: The recovery plan includes equivalent information from literature as is in the 

West Mojave Plan amendment to the California Desert Conservation Area. Specific 

recovery actions are included in the revised plan, including those from the 1994 Recovery 

Plan, and additional priority actions/areas will be identified and funding opportunities for 

implementation sought by the RITs. The priorities will be established according to 

actions already implemented, as well as pending actions or remaining threats, under 

existing land management plans. 

Comment: One commenter stated that conservation recommendations contained in biological 

opinions should be binding requirements, or the desert tortoise will continue its demise. 

Response: Under section 7 of the Endangered Species Act implementing regulations, 50 

CFR §402.02 Definitions, conservation recommendations are suggestions of the Service 

regarding discretionary measures to minimize or avoid adverse effects of a proposed 

action on listed species or critical habitat or regarding the development of information. 

Binding requirements by the Service are pursuant to 50 CFR §402.14(i)(2) Formal 

Consultations, Incidental Take, Reasonable and Prudent Measures. Per this section of the 

regulations, the Service provides nondiscretionary measures that are necessary and 

appropriate to minimize the impact of incidental take. 

Comment: One commenter stated that compatible activities in Desert Wildlife Management 

Areas from the 1994 plan are not included. 

Response: Including a list of compatible uses in the recovery plan would imply that we 

know how each of these activities affects or does not affect desert tortoise populations. 

As stated in the recovery plan, our understanding of specific and/or synergistic threats as 

they relate to tortoise populations and mortality are evolving, and data gaps will continue 

to be filled as our research program is focused and developed. Therefore, instead of 

offering what could be interpreted as an exhaustive list of compatible activities, we 

encourage avoidance and minimization of surface disturbing activities. 

Comment: Two commenters felt that the fire discussion is inadequate. They stated that the plan 

should be promoting prevention rather than rapid response for suppression given the distances 

many first responders must travel and that fuels management should be a priority, including a 

carefully managed grazing component. Other comments suggested that a fuels management 

component where grazing is used as a reduction method should be added to the revised plan. 

Response: Fire prevention is addressed by the recommendation to conserve intact desert 

tortoise habitat (Recovery Action 2.1) and indirectly by the recommendation to eradicate 

or suppress invasive plants in the habitat restoration section (Recovery Action 2.6). It has 

been demonstrated that cattle grazing may help create and maintain habitat for native 

plants where: 1) the grassland ecosystem is highly productive; and 2) disturbance was 

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previously caused by native grazers and browsers (e.g., Brooks 1995; Marty 2005). The 

Mojave Desert is neither highly productive, nor is it an environment which historically 

supported native grazers. There is no evidence that cattle grazing will restore habitat or 

prevent fire in Mojave Desert environments. Such a proposal is therefore experimental 

and is included under Recovery Action 5.3 and directed to occur outside tortoise 

conservation areas under Recovery Action 2.16. 

Comment: One commenter stated that the Recovery Plan should include a protocol for handling 

desert tortoises in the field; who can remove shedding animals and to what disposition; and how 

to mark seropositive, non-symptomatic tortoises. The commenter also stated that we and our 

contractors will never have sufficient field workers to undertake the needed removal and that 

several quarantine facilities will be required. 

Response: Appropriate management of disease within desert tortoise populations is an 

evolving field of inquiry. Protocols based on the Science Advisory Committee's and other 

expert recommendations for managing disease, including facilities management, will be 

developed separate from the recovery plan. 

Comment: One commenter stated that there must be an actual dollar commitment reflecting 

estimated costs of implementing the disease research recommendations. 

Response: All costs shown in the implementation schedule are estimates. Some costs are 

noted as TBD (to be determined); this is the case for disease research because it is 

difficult to accurately estimate costs for research projects which have not yet been 

designed. 

Comment: One commenter stated that Section 2.2 has no discussion of Brown’s environmental 

stressor hypothesis in relation to disease and fails to call out proactive and administrative 

measures, such as quarantines and translocation moratoriums, in order to localize disease 

outbreaks. 

Response: Hypotheses related to disease and environmental stress are addressed under 

Recovery Action 5.5 (conduct research on desert tortoise diseases and their effects on 

tortoise populations) and were discussed in Appendices A and B of the draft revised 

Recovery Plan. Although the Science Advisory Committee's disease recommendations 

white paper (formerly Appendix B) is not included in the final revised Recovery Plan, an 

updated June 2009 version (Hudson et al. 2009) was used by the Desert Tortoise 

Recovery Office in writing the final revised Recovery Plan. Text was added to section 2.2 

related to site quarantines and the implementation of actions based upon results of 

research conducted under Recovery Action 5.5. 

Comment: Two commenters felt that there is no means of gauging effectiveness of the identified 

outreach efforts or what corrective action is necessary if such efforts are deemed ineffective. 

Response: Environmental education has been shown to effectively change learned 

behavior (Hungerford and Volk 1990). Monitoring the effectiveness of environmental 

education efforts will be as difficult as any monitoring for the effectiveness of specific 

actions and will depend largely on the indicator (or metric) chosen to be monitored. For 

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example, a random survey regarding the attitudes of residents towards desert tortoise 

recovery, or human impacts affecting recovery, could be assessed as a metric for the 

effectiveness of the education effort (e.g., Vaske and Donnelly 2007). 

Comment: One commenter stated that the section on Unauthorized Off-road Vehicle Travel, 

within the Law Enforcement section (Recovery Action 2.4), describes the problems off-highway 

vehicle activity poses for tortoises, yet the strategy only acknowledges that more law 

enforcement is needed and provides no strategy or set of strategies to lessen the impact of such 

activity on the species or habitat. The plan should also suggest other strategies, such as simply 

closing critical habitat and other essential habitat for the desert tortoise to all off-highway vehicle 

use. 

Response: Recovery Action 2.4 addresses unauthorized off-highway vehicle use. 

Recovery Action 2.5 addresses route designations, closures, and related actions that 

would minimize vehicle impacts to desert tortoises and habitat. In addition, Recovery 

Action 2.10 addresses organized off-highway vehicle events. 

Comment: One commenter stated that before we simply call for more law enforcement we 

should be explicit in what we are asking them to do and what the expected outcomes should be in 

terms of connection to tortoise population recovery. 

Response: Regional and site-specific law enforcement needs will be evaluated and 

prioritized by the RITs, and through this process we will be able to make more explicit 

recommendations than those listed under Recovery Action 2.4. 

Comment: One commenter asked that the revised plan make state transportation agencies aware 

of connectivity and fragmentation issues when fencing roadsides. 

Response: No study has been done to identify how many underpasses are needed, from 

either a genetic or demographic standpoint, to effectively prevent population 

fragmentation. Recovery Action 5.6 calls for the determination of the importance of 

corridors and physical barriers to desert tortoise distribution and gene flow. 

Transportation agencies will be included in coordinating recovery actions dealing with 

highway fencing and culvert installation. 

Comment: One commenter recommended that we should determine the usefulness and 

effectiveness of highway underpasses designed to ensure connectivity and suggested that perhaps 

human intervention is required to move males from one tortoise conservation area to another. 

Several recommended that road fencing (Recovery Action 2.5) be considered only for those 

locations identified in the revised plan, raised concern about the cost of fencing construction and 

maintenance, or asked that Recovery Action 2.7 be rewritten to explicitly reflect actual needs 

based on the most current information. One commenter also noted that costs of such barriers 

must be borne by the agencies, not by property owners and residents. The commenter pointed out 

that costs of connecting isolated populations should be borne by the agencies, not property 

owners and residents. 

Response: No study has been done to identify how many underpasses are needed, from 

either a genetic or demographic standpoint, to connect populations. Recovery Action 5.5 

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involves determining the importance of corridors and physical barriers to desert tortoise 

distribution and gene flow. Fencing efforts will be prioritized by the RITs, but will not be 

limited to the locations identified within Recovery Action 2.5 or 2.7. We cannot predict 

how various developments will change usage and traffic density patterns, and thus 

fencing needs, for the life of the revised recovery plan. The priorities for installation and 

maintenance of urban and other barriers are based on the most currently available 

information. The Implementation Schedule currently states that land managers and funds 

from appropriate Habitat Conservation Plans should support the installation and 

maintenance of urban and other barriers and culverts. 

Comment: One commenter noted that the recovery plan recommendation of no net gain of roads 

may relate to other infrastructure associated with projects such as wind energy development. The 

commenter suggested that the recovery plan does not recognize that the potential impacts of road 

construction on desert tortoise conservation are variable based on the nature of the road and that 

if this concept in retained in the final plan, it must recognize the inherent differences among 

various types of roads as well as the extensive road planning which has previously been 

approved for Areas of Critical Environmental Concern by us through the section 7 consultation 

process. 

Response: Proposed new roads within tortoise conservation areas should be considered 

by the RITs and will continue to be evaluated by the Fish and Wildlife Service through 

the section 7 and 10 processes. 

Comment: One commenter suggested that additional critical habitat should be designated in the 

El Paso Mountains and northern Searles Valley. 

Response: Critical habitat cannot be designated through the recovery planning process. 

However, as indicated in Recovery Action 1.1, RITs should identify areas not included 

within existing tortoise conservation areas that may warrant focused management efforts. 

Comment: Three commenters suggested that the revised plan recommend the removal of all offhighway vehicle events within tortoise habitat, including recovery units and tortoise conservation 

areas, and restrict casual off-highway vehicle use within desert tortoise habitat to existing and 

designated roads and trails. 

Response: Recommending exclusion of off-highway vehicle events or restricting casual 

use within desert tortoise habitat throughout the recovery units and tortoise conservation 

areas would essentially close the entire Mojave Desert to off-highway vehicle users. The 

revised plan recommends continued effort to identify, designate, and close off-highway 

vehicle routes within desert tortoise habitat, as well as excluding off-highway vehicle 

events specifically within tortoise conservation areas. We will continue to work through 

the RITs to identify and prioritize areas where tortoises may benefit from more restricted 

access to off-highway vehicles in order to achieve sustainability of the desert tortoise 

where other, more protective designations are lacking. 

Comment: One commenter stated that the decision support system should consider both 

competitive and non-competitive off-highway vehicle events within desert tortoise habitat. 

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Response: The decision support system will incorporate as much data as are available 

regarding the threats facing the species, including from off-highway vehicle use. Our 

ability to obtain data on non-competitive off-highway vehicle events is limited; 

competitive events generally go through a permitting and consultation process and, 

therefore, data are available. Non-competitive events fall under landscape-level resource 

management plans, which generally do not have data gathering requirements. However, 

we continue to assemble spatial data layers, such as aerial photography and satellitederived land cover data, in an attempt to quantify impacts from all off-highway vehicle 

and other land uses as part of the RIT’s prioritization and evaluation of recovery actions. 

Comment: One commenter asked where does the recommendation of restricting off-highway 

vehicle events apply - all habitats or just critical habitat? 

Response: The recovery plan states that recovery actions will be focused within tortoise 

conservation areas; however, because all desert tortoises are protected under the 

Endangered Species Act, avoidance and minimization measures may be required in areas 

outside tortoise conservation areas pursuant to any consultations with the resource 

agencies. 

Comment: One commenter indicated that there is no analysis framework provided to help 

managers determine the appropriate number of off highway vehicle events and/or participants 

per event. Similarly, there is also no prioritization of areas where this issue should be addressed. 

Offices that have limitations currently in place cannot tell if further restrictions are needed. 

Response: The revised plan states that off highway vehicle events should avoid tortoise 

conservation areas to the extent practicable. Beyond this, the RITs will identify areas or 

events in particular need of attention relative to desert tortoise recovery. 

Comment: One commenter stated that data are lacking to show that modern mining poses a 

threat to desert tortoises, and thus withdrawing mining from tortoise conservation areas and 

including mining as a threat are unsupported. 

Response: Reducing the potential for negative impacts to desert tortoises and their habitat 

are fundamental for tortoise conservation areas to be successful. As stated under 

Recovery Action 2.12, activities associated with mining can degrade habitat and result in 

direct take. Boarman and Kristan (2006) found that there was strong evidence that energy 

and mineral developments can be a threat to desert tortoises by way of habitat loss and 

direct take. Should limited mining continue to occur within tortoise conservation areas, 

we expect monitoring of the effects and appropriate minimization measures to be applied. 

Comment: One commenter requested an additional Recovery Action specifically calling for the 

relocation of sand and gravel leases outside of tortoise conservation areas and recovery units be 

added to the Implementation Schedule as a priority 1. 

Response: Recovery Action 2.12 already states that mining (including sand and gravel 

extraction) should be withdrawn from tortoise conservation areas, if feasible, or 

otherwise limited if they cannot be withdrawn. While we do not call this a priority 1 

action (because we do not expect lack of implementation of this action alone to result in 

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the extinction or irreversible decline of the species), the RITs have the ability to prioritize 

recovery actions and make recommendations about specific mining activities in their 

implementation areas. 

Comment: Several commenters stated that the recovery plan overemphasizes grazing as a threat, 

ignores all that has been done to reduce grazing, and it does not make any conclusions as to 

whether or not any positive responses in terms of recovery have been measured; the recovery 

plan needs to document the degree to which grazing remains a threat within tortoise conservation 

areas and recognize its utility as a management tool. They further state that no data have been 

presented on the effectiveness of efforts to remove grazing. 

Response: The Conservation Efforts section identifies the extensive efforts that have been 

undertaken to improve grazing management within desert tortoise habitats, especially 

within critical habitat. The recovery plan cites several reports that acknowledge the lack 

of effectiveness information on the recovery actions that have been implemented to date; 

therefore, the plan emphasizes the development and refinement of the spatial decision 

support system, which will enable us to better track implementation and effectiveness of 

recovery actions. References cited in Appendix A note, however, that recovery from 

grazing-related impacts can take decades within desert landscapes. 

Comment: Several commenters stated that no justification for relaxing the standards on grazing 

is presented, despite strong scientific evidence to the contrary; grazing should be curtailed not 

only in drought years but also in good rainfall years after drought so that the desert tortoise can 

recover and need not compete with cattle or other livestock for their preferred forage of native 

annuals. 

Response: Recovery Action 2.16 carries forth recommendations in the 1994 recovery 

plan to exclude grazing within tortoise conservation areas. The revised plan 

acknowledges that more flexible grazing practices may be implemented experimentally 

outside tortoise conservation areas to help fill data gaps relative to the magnitude and 

intensity of impacts from grazing to the desert tortoise and its habitats as well as gaps 

regarding the effectiveness of grazing as a fuels-reduction tool. 

8. Strategic Element 3 - Population Augmentation 

Comment: One reviewer recommended that population augmentation be strategic with respect to 

habitat and demographics of the target populations. A warning was included that urged 

assessment of how other aspects of the program might suffer from dilution of funding given 

uncertainties associated with population augmentation. 

Response: We agree with the comment and plan to address these concerns in the 

research-based population augmentation strategy recommended by Recovery Action 3.1. 

In addition, we anticipate that much of any translocation effort will be funded directly by 

project proponents who are disturbing habitat to the extent that resident tortoises must be 

cleared from the project area, thereby minimizing dilution of funding that would 

otherwise be directed to on-the-ground management actions. 

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Comment: One commenter stated that in conjunction with head-starting there is a need to 

understand reasons for local population declines, and that due to predation on adult tortoises 

during drought, broader application of predator control in localized areas may be necessary after 

thorough evaluation by the Recovery Implementation Teams (RITs). 

Response: We agree that there is a need to understand local population declines, which is 

why we call for augmentation to be approached experimentally in conjunction with 

threats management and restoration activities such that causes of declines can be better 

elucidated. As stated in Recovery Action 2.14, we do not view widespread predator 

control as a recovery action; however the RITs may propose specific measures in 

localized areas for further consideration. 

Comment: One commenter suggested that translocation and augmentation are proven successful, 

thus we should take a strong position to implement translocation/augmentation in areas where 

RITs determine the method viable, regardless of legal challenges. 

Response: While some studies have shown initial success in translocation to be high, we 

will not know how much population augmentation will increase population numbers for 

the long-term until we implement experimental augmentations in conjunction with threats 

management. Defining success on the population level (as opposed to defining success 

based on concern over each individual’s fate) will be important as we proceed with 

translocation and/or augmentation. 

Comment: One commenter stated that the draft recovery plan fails to cite scientific studies 

(published or otherwise) on headstarting in support of using this unproven strategy for desert 

tortoise recovery. 

Response: The statement by the commenter is incorrect. The draft Recovery Plan cites 

several studies pertaining to head-starting of desert tortoises and indicates that these 

studies lay a foundation from which to build. The plan also states that augmentation will 

be approached experimentally, in terms of the continued development and evaluation of 

techniques (including head-starting). 

Comment: Two commenters state that augmentation of desert tortoise populations should not 

replace or reduce efforts to tackle critical decisions that need to be made regarding public lands 

management and that reducing or eliminating known or suspected causes of breeding adult 

tortoise mortality should remain the primary emphasis of the recovery plan. 

Response: We agree that augmentation actions should not detract from efforts to 

implement key land management actions to reduce threats. In the plan we state that it is 

important to understand that increasing numbers through augmentation alone will not 

result in recovery. The causes of population declines must be addressed and 

augmentation is only an intermediate strategy to gain insight into causes of declines and 

to attempt to increase population numbers more rapidly than possible through natural 

processes. 

Comment: Several commenters stated that threats must be minimized or eliminated at sites prior 

to augmentation attempts or the effort will be defeated. One commenter further suggested that 

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discussion about population augmentation be expanded to include consideration of habitat 

quality and carrying capacity. 

Response: We agree that ideally all existing threats would be minimized at sites where 

population augmentation is to be implemented in order to realize the greatest increase in 

tortoise numbers. In fact, when threats are known, we state that augmentation will be 

used in conjunction with elevated threats management and/or habitat restoration. 

Unfortunately, in some cases the original causes of declines at sites are unknown and too 

few tortoises remain at those sites to investigate the causes of declines and effectiveness 

of recovery actions. For these reasons, Strategic Element 3 and particularly Recovery 

Action 3.4 call for implementing augmentations using a scientifically rigorous, researchbased approach, including considerations of habitat quality that may affect carrying 

capacity. In addition to habitat considerations, Recovery Action 3.2 (identification of 

sites for population augmentation) emphasizes knowledge about the population existing 

at the recipient site when identifying sites for augmentation. Such an approach will allow 

us not only to evaluate the factors that affect the success of augmentations, but also to 

learn more about threats that continue to act on those populations and evaluate the 

effectiveness of targeted recovery actions. 

Comment: One commenter asked if population augmentation would result in greater chance for 

spread of upper respiratory tract disease due to high densities of animals. 

Response: The population augmentation strategy will take into consideration current 

knowledge of disease in desert tortoise populations to avoid spreading upper respiratory 

tract or other diseases. 

9. Strategic Element 4 – Monitoring 

Comment: One reviewer suggested that the monitoring program should be linked to the adaptive 

management program. The reviewer expressed concern that, as currently proposed, the 

monitoring program will not have the power or specificity to be useful in an adaptive 

management or decision-support framework. 

Response: The range-wide monitoring program described in the revised plan targets 

estimation of population trends at the recovery unit scale, which will provide indirect 

evidence of the effectiveness of the overall recovery program over time (e.g., 25 years). 

The monitoring component of the adaptive management five-year action plans will 

proceed primarily through directed effectiveness monitoring and effectiveness research 

(e.g., Recovery Action 5.4). Effectiveness monitoring will require the Recovery 

Implementation Teams (RITs) to identify specific impacts that will be affected by 

management activities and to develop indicators or metrics for whether or not the 

management action is affecting the threat. Recovery Action 5.3 also specifically 

recommends that models of recovery action effectiveness be developed and tested and 

that conceptual models that explicitly define expected outcomes be developed for all 

recovery actions. 

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Comment: Two commenters suggested that the current method of monitoring trends in desert 

tortoise populations (line distance sampling) may be statistically inadequate. 

Response: Improvements to the range-wide monitoring program continue to be made, and 

we are confident that the program will be sufficient to detect trends in desert tortoise 

populations over a period of approximately 25 years. 

Comment: One commenter suggested that monitoring protocols or methodologies be consistent 

across recovery units and not be left to stakeholder-driven RITs for development. 

Response: Range-wide protocols currently exist for monitoring Recovery Criterion 1a 

and are consistent across recovery units. Specific protocols for monitoring the remaining 

recovery criteria will be developed by the Fish and Wildlife Service. We will consider 

suggestions made by the Science Advisory Committee and other outside experts as we 

develop the protocols. 

Comment: One commenter suggested that we develop a suite of indicator species that could be 

monitored to provide more timely responses to changes in management actions or threat severity. 

Response: We are unaware of any evidence that there are true indicator species for the 

desert tortoise; i.e., there is no reason to believe that side-blotched lizards, kangaroo rats, 

or other recommended species will respond to environmental conditions in the same way 

as tortoises or help us to better understand the status of the tortoise. 

Comment: One commenter suggested that monitoring should be continued as part of a 

comprehensive adaptive management strategy, but it should not be as emphasized in the 

Implementation Schedule as activities that will accomplish recovery. 

Response: Monitoring is included in the Implementation Schedule as a necessary activity 

through which progress toward recovery will be measured. 

Comment: One commenter noted that it was not obvious how occupancy estimates would 

estimate population growth rate. 

Response: Applying occupancy to abundance estimation is an active area of research 

(Royle et al. 2005; MacKenzie et al. 2006, Chapter 10). While the revised plan does not 

specifically rely on occupancy estimation to assess trends in rates of population change, 

this approach may provide an additional measure in the future. 

10. Strategic Element 5 – Research 

Comment: One commenter suggested the recovery plan should be proposing testable hypotheses 

that can provide the basis for expanding our understanding. 

Response: While the recovery plan does not identify specific hypotheses, we will work 

with the Management Oversight Group, Science Advisory Committee, and Recovery 

Implementation Teams (RITs) in establishing research priorities within the broad 

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recommendations contained herein. The spatial decision support system will also aid in 

targeting research within the recovery units. 

Comment: One commenter noted that, despite the amount of research on disease that has been 

conducted to date, little research has investigated the role disease has played in tortoise 

population declines relative to other threats and that the revised plan fails to commit 

meaningfully to disease research. 

Response: We specifically considered this topic in developing the recovery plan. Detailed 

research recommendations are included in Recovery Action 5.4 to specifically focus 

research on disease. 

Comment: One commenter criticized the lack of research on habitat quality to date and asserted 

that the lack of research quantifying specific characteristics that contribute to habitat quality 

relegates statements in the revised plan about the effect of habitat degradation on tortoises to 

mere assumptions without evidentiary support. 

Response: It is well known in the ecological literature that habitat quality can affect 

wildlife demography (see Pulliam 1996, for example), and the revised plan documents 

numerous specific direct and indirect impacts to desert tortoise habitat that can, in turn, 

impact individual tortoises. The revised plan specifically recommends research to more 

directly quantify factors affecting tortoise habitat quality relative to demographics and 

population-level effects. 

Comment: One commenter suggested that effectiveness monitoring needs to demonstrate 

recovery value prior to requiring significant investments from partners least able to bear the cost. 

Response: As noted previously, recommended recovery actions are based on justifiable 

information. Recovery Actions 5.3 and 6.2 specify that the RITs should be directly 

involved in identifying priorities for effectiveness monitoring. The development of 

conceptual models and implementation of the spatial decision support system will assist 

in ensuring that effectiveness monitoring is targeted toward projects with the highest 

estimated recovery value or greatest degree of controversy or uncertainty. Recovery 

Implementation Teams should also identify funding opportunities to implement 

effectiveness monitoring projects. 

Comment: Some commenters recommended that disease research be continued, particularly with 

respect to determining the feasibility of using diseased females in headstarting, and that diseases 

other than upper respiratory tract disease be investigated. One commenter indicated that disease 

research should be reduced in priority relative to other actions. 

Response: Clarifying the role of disease and identifying effective management actions to 

alleviate it is an important task for recovery. Recovery Action 5.4 specifically 

recommends, among other topics, that other known or emerging diseases be evaluated for 

effects on desert tortoise populations. 

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11. Strategic Element 6 – Adaptive Management 

Comment: One reviewer recommended that clearly stated hypotheses about tortoises and effects 

of recovery actions be developed. Then, modeling should be used to estimate power of 

monitoring and to simulate how best to test hypotheses. 

Response: This is a primary goal of the spatial decision support system (SDSS) and 

Recovery Implementation Teams (RITs). However, most of modeling the effects of 

recovery actions will likely not include tortoise responses, rather surrogate or indicator 

responses to actions, such as an increase in habitat or reduction in threat. 

Comment: One reviewer urged that an explicit link between the SDSS and recovery objectives 

be made. 

Response: Given the lack of quantitative information on the relationships between 

threats, management actions, and tortoise populations, it is difficult to explicitly link the 

SDSS directly to the recovery objectives. Instead, we expect the SDSS to help strengthen 

our understanding of these relationships so that more direct links between management 

actions and recovery targets can be made in the future. 

Comment: Several commenters expressed concern about the revised plan's reliance on adaptive 

management. In particular, commenters felt that specific goals and objectives are lacking, which 

will lead to non-recovery and excessive paperwork and that the adaptive management portion of 

the plan is simply a poorly-veiled effort to continue with the failed policies of the last 20 years. 

Response: The emphasis on adaptive management in the revised plan is not to create 

excessive paperwork or to continue failed policies. Rather, this emphasis recognizes that 

a successful recovery program depends on clearly identifying objectives (e.g., related to 

desert tortoise populations or habitat), a set of potential actions, and some expectation of 

the consequences of each action relative to the objectives, described through conceptual 

models. The SDSS provides a framework within which to prioritize and implement 

recovery actions and develop and evaluate the conceptual models, thereby providing 

more explicit measures of recovery progress than in the past. 

Comment: One commenter asked how the monitoring component of adaptive management will 

actually work. Concern was expressed that because of the pace of the response, if measured by 

change in tortoise numbers, feedback will not likely to be a significant component of recovery 

management over the life of this recovery plan. 

Response: The monitoring component of the adaptive management five-year plans will 

proceed at three levels: 1) effectiveness monitoring, 2) population monitoring, and 3) 

effectiveness research. Effectiveness monitoring will require the RITs to identify the 

specific impacts that will be affected by management activities to develop indicators or 

metrics for whether or not the management action is affecting the threat. For example, if 

off-road vehicle use is linked to habitat degradation, and we postulate that closing roads 

and vertical mulching in a particular tortoise conservation area will decrease travel within 

the area, we can monitor the change in travel in that area with metrics such as "miles of 

open road" or "OHV track density" or "scarring" as viewed with satellite imagery. 

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Population monitoring will continue to be undertaken at the recovery unit scale to 

determine population trends through our range-wide monitoring program. Range-wide 

monitoring can assess the overall effectiveness of the recovery effort through time. 

Effectiveness research can begin to address questions such as: what is the effect of 

closing off-road vehicle routes, closing and vertical mulching off-road vehicle routes, and 

closing, mulching, and signing routes on the quality of tortoise forage? To answer these 

questions, several experimental and control plots would be created where specific 

qualities of tortoise forage could be monitored and statistically compared between control 

and experimental plots to determine the effectiveness of various recovery actions. 

Comment: One reviewer recommended testing the SDSS with historical data. 

Response: We hope that validation of the SDSS can take place within the RITs, by 

comparing model outputs conceptually or, best of all, by comparing outputs with data 

from the field. Historical data may play a role in these sensitivity analyses. 

Comment: One commenter suggested that the Desert Tortoise Recovery Office retain the 

centralized tracking system capability of the SDSS that records implementation inputs and 

accounts for desert tortoise recovery that occurs either naturally or as the result of recovery 

actions, but cautioned that the SDSS should not rely on subjective judgments by biologists or 

managers. 

Response: The "tracking" capacity of the SDSS is an important piece of the system, and 

the Desert Tortoise Recovery Office will be intimately involved in its management. To 

know where recovery actions are taking place on the ground is important in and of itself. 

The process of modeling the effects of individual threats on tortoises and the 

effectiveness of recovery actions to ameliorate these threats will be used in addition to the 

tracking capacity to assess the significance of data gaps and uncertainties and to predict 

the effects of alternative management actions. Subjective judgments by biologists or 

managers (expert opinions) that currently populate these models are simply the best 

information that we currently have to understand the relationship between particular 

threats and tortoise declines and how particular recovery actions will affect those threats. 

As management actions are implemented, "hard data" are collected, or better models 

developed regarding how particular management actions actually affect threats on the 

ground, then this information will take the place of subjective judgments in the SDSS, 

and management plans will be revised based on our improved understanding. 

Comment: Several commenters expressed concern about the publication of a prototype SDSS 

which relies on incomplete data and subjective information in the form of survey responses; as 

such, the recovery plan fails to establish a broadly acceptable and scientifically credible base of 

information. 

Response: Common misperceptions about modeling include that models cannot be built 

with incomplete understanding, with gaps in the data, or before they have been validated 

or “proven,” among others (Starfield 1997). In addition to the response above, we note 

that the prototype SDSS uses the best data that could be obtained within the planning 

timeframe and provides a guide as to what data are most needed. The initial datasets and 

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prototype SDSS provide a baseline and a way to prioritize the next round of data 

gathering. The RITs will emphasize updating and improving the database. Sensitivity 

analyses will be conducted on the initial data to create a prioritized list of data needs, and 

the RITs will then work to deepen/edit/validate that prioritization using the SDSS and 

come up with a plan for the next round of data acquisition. 

Comment: One commenter asked that we ensure that use of the SDSS as a tool to prioritize 

actions is not a black box. 

Response: Within the first year after publication of the final, revised plan, the RITs, 

Desert Tortoise Recovery Office, and other partners will update the underlying data in the 

SDSS for at least two recovery units, including data on threats and current recovery 

action implementation. This stage should be completed for the remaining recovery units 

within the second year, and regular updates to all recovery units should occur on an 

ongoing basis thereafter. The process of updating the underlying data will provide an 

important opportunity for all components of the SDSS to be revisited by the RITs and 

other interested parties and for the framework of the system to be reviewed. 

Comment: One commenter asked for clarification as to the compatibility of scales within the 

model and how the spatial extent of data layers may impact model input and output. 

Response: Some datasets cover only part of the range. The model treats areas with no 

data for a particular threat as if the threat does not exist in that area. For all scales to be 

compatible, technically, all data should be re-sampled to the least accurate scale. As we 

move from the rapid prototype to a more detailed regional tool, the most current and 

accurate data will be obtained at as fine a resolution as possible. 

Comment: Several commenters warned that the revised plan fails to confirm funding and 

resources to support the RITs and their development of action plans and that the costs of 

implementing the RIT process in both time and money is yet another set-back to tortoise 

recovery. 

Response: Recovery plans are guidance documents that identify needed actions and 

approximate costs of those actions. Their purpose is not to identify resources to 

accomplish all actions. The RIT process will focus efforts on securing the necessary 

resources to implement recovery actions on the ground. We view the RIT process to be 

an important step forward from the 1994 Recovery Plan to maintain focus on coordinated 

implementation of the actions described in the revised plan. 

Comment: One commenter asked what benchmarks will assure that the RIT action plans actually 

promote recovery. 

Response: The structure of the adaptive management process requires agreed-upon 

objectives and provides feedback to ensure that actions are effective. Benchmarks to 

determine effectiveness will be identified in the planning process by following the 

adaptive management tenants: 1) appropriate monitoring of an action, 2) agreed upon 

criteria to determine whether an action is effective, and 3) agreed-upon actions to take as 

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a necessary step for a research action or for a management action if the effectiveness 

threshold is not reached during the agreed upon timeframe. 

Comment: Two commenters recommended that the Science Advisory Committee should be 

independent of the Desert Tortoise Recovery Office or should not receive financial benefits to 

conduct research or implement actions to accomplish recovery goals. 

Response: The primary role of the committee is advisory to the Fish and Wildlife 

Service. The committee has assigned a chair from among its membership. The chair will 

coordinate with the Desert Tortoise Recovery Office on topics for the agenda. An 

important role of the Science Advisory Committee is to advise us on specific, priority 

topics which could be addressed by a variety of individuals or groups. 

12. Recovery Units 

Comment: One reviewer expressed that additional genetic data are not likely to contribute a great 

deal more to the current recovery planning; resources might be better used for field studies to 

determine why current efforts have not produced more positive results. 

Response: Recovery Action 5.5 has been modified to de-emphasize research on 

population structure per se and to focus on determining the importance of corridors and 

barriers to desert tortoise distribution and gene flow. 

Comment: One reviewer pointed out that the sampling for genetic analyses in Murphy et al. 

(2007) is a concern, leading one to wonder whether patterns observed are function of real breaks 

in genetic structure or artifacts of disjunct sampling. One commenter also suggested that given 

the isolation-by-distance character of desert tortoise population genetic structure and the discrete 

sampling of populations across large areas of continuous habitat by Murphy et al. (2007), 

assignment tests or other clustering methods should be used with caution as evidence for 

population differentiation. Violating assumptions of discrete populations can produce misleading 

interpretations. 

Response: We agree and state in the revised plan, "To describe genetic relationships 

within species, particularly boundaries between divergent units, methods require analysis 

of many individuals sampled across relatively evenly spaced locations to avoid wrongly 

inferring genetic discontinuities between disjunct sampling locations (Pritchard et al. 

2000; Allendorf and Luikart 2007:400)." 

Comment: One commenter stated that identification of multiple recovery units amounts to an 

unlawful designation of distinct population segments (DPSs). The commenter also claimed that 

the draft plan is inconsistent in stating that recovery must be achieved in all recovery units before 

delisting can occur, but also that individual recovery units could be delisted through rule-making 

procedures. 

Response: As stated in the revised plan, recovery units are tools used to identify 

geographic units that are individually necessary to conserve the diversity necessary for 

long-term sustainability of the entire listed population. They are not equivalent to DPSs 

which have been identified in a formal rule-making process. The recent 5-year review 

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concluded that individual recovery units within the Mojave population do not qualify as 

DPSs (USFWS 2010). We have clarified the text of the revised plan accordingly. 

Comment: One commenter suggested that identifying multiple tortoise conservation areas within 

multiple recovery units is unnecessary to conserve the single listed Mojave population of the 

desert tortoise. The commenter also recommended that reliance on multiple-use Bureau of Land 

Management lands be minimized for recovery relative to National Park Service, wilderness, and 

wildlife refuge designations, especially those areas that are isolated, likely disease-free, and have 

had conflicting land uses removed or mitigated. The commenter specifically recommended Red 

Cliffs, Utah; Piute Valley, Nevada; Mojave National Preserve, California; Chemehuevi, 

California; and Tassi-Pakoon, Arizona as areas for recovery emphasis. 

Response: The recovery emphasis areas suggested by the commenter fail to preserve the 

diversity necessary for long-term sustainability of the desert tortoise across its entire 

listed range. While tortoise conservation areas include all desert tortoise habitat within 

National Park Service, National Wildlife Refuge, and other lands designated for habitat 

or tortoise conservation, achieving sustainability of the desert tortoise across its range 

requires conservation on multiple-use lands in areas where other, more protective 

designations are lacking. 

Comment: Several commenters claimed that the draft plan did not use the best scientific data in 

the delineation of recovery unit boundaries, especially with respect to not subdividing the 

Western Mojave Recovery Unit. In particular, these commenters felt that the draft plan placed 

too much reliance on an unpublished report by Hagerty and Tracy compared to the published 

paper by Murphy et al. (2007). Other commenters indicated that the recovery units make sense 

and are well supported by a combination of data. 

Response: We critically evaluated the published literature and additional data that were 

available when we identified recovery unit boundaries. Differences from 

recommendations made by Murphy et al. (2007) are described in the revised plan, 

justified by documented scientific literature, and supported by peer review. We clarified 

and added additional language to the section "Assessment of Revised Recovery Units." 

Claims that the draft plan over-emphasized the Hagerty and Tracy report are not 

supported by the fact that, of the 14 times the report was cited, 9 of those times it was 

cited with additional supporting references (including 7 times in which it was cited with 

Murphy et al. [2007]). Nevertheless, Hagerty's Ph.D. dissertation has been completed and 

papers published since publication of the draft plan, and citations of the report have been 

replaced with references to Hagerty (2008), Hagerty and Tracy (2010), and Hagerty et al. 

(2010) in the final plan. 

Comment: One commenter disagreed with the combination of the original Northern Colorado 

and Eastern Colorado recovery units on the bases that Murphy et al. (2007) correctly assigned 

>70% of their samples to each unit; major differences in climate, forage availability, and 

seasonal activity occur across the region; the original recovery units are about 40 miles apart, 

separated by numerous natural and anthropogenic barriers; and different threats exist between the 

two original units. 

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Response: High gene flow across the range of the desert tortoise is supported by the fact 

that analysis of molecular variance revealed that over 88 percent of the variation occurs 

within, not among, populations (Murphy et al. 2007; Hagerty 2008). In addition, with the 

exception of the Upper Virgin River Recovery Unit, assignment tests incorrectly placed 

11 to 45 percent of individuals (Murphy et al. 2007). Some incorrect assignments could 

be explained by human-mediated translocation, but incorrectly assigning 11 to 45 percent 

of individuals is unlikely to be explained by translocations alone, especially given the 

general failure of early translocations (Berry 1986). In contrast, greater than 90 percent of 

gopher tortoises were assigned to the correct genetic assemblage (with fewer molecular 

markers than used by Murphy et al.) from where they were sampled in Georgia and 

Florida, where relocations of tortoises have been extensive (Schwartz and Karl 2005). 

The revised plan clarifies the rationale for combining the Northern and Eastern Colorado 

recovery units, particularly on the basis of evidence of historic population connectivity 

and gene flow at the southern end of the Cadiz Valley; little genetic differentiation 

between populations sampled in the two former recovery units, as well as the likely 

influence of gaps in genetic sampling in this area (as noted by the second comment in this 

section); and the gradient of environmental variation between these units. 

Comment: Several commenters claimed that the data provided in the Hagerty and Tracy report 

cited in the draft revised recovery plan are insufficient to accurately assess its findings. 

Response: We agree with the comment. The Hagerty and Tracy report was not formatted 

for publication or drafted for peer review, but rather to provide a brief overview of the 

presentation to the Science Advisory Committee in March 2007. However, Hagerty's 

Ph.D. dissertation and related papers have been completed, and citations of the report 

have been replaced with references to Hagerty (2008), Hagerty and Tracy (2010), and 

Hagerty et al. (2010) in the final plan. We note that in most cases, this study provides 

complementary, rather than contradictory, support to other cited literature. As indicated 

in the response to previous comments, identification of recovery unit boundaries are fully 

described in the final plan, justified by documented scientific literature, and supported by 

peer review. 

Comment: One commenter noted that the sample locations depicted in Fig. 1 of Murphy et al. 

(2007) appear to be broader than depicted in Fig. 7 in the draft plan. 

Response: Murphy et al. were unable to provide a digitized map of their sampling 

locations, so we circumscribed the areas as described in Table 1 of their paper. As a 

result, the depiction was somewhat imprecise, but not so imprecise as to affect related 

inferences in the revised plan. Part of the apparent discrepancy is due to the smaller scale 

of Murphy et al., Fig. 1, relative to Fig. 7 in the draft revised plan. Note that, for clarity in 

the figures, the genetic sampling areas are not depicted in the maps in the final revised 

plan. 

Comment: One commenter noted that neither Murphy et al. (2007) nor the Hagerty and Tracy 

report considered a recent paper by Evanno et al. (2005) on assessing population genetic 

structure, which could influence the results of each study, particularly in the Western Mojave. 

217 
 

 

 

 

 

Response: We agree with the comment (but note that the more recent analysis by Hagerty 

[2008] did consider this paper). As indicated in the revised plan, and supported by Berry 

et al. (2002) and Allendorf and Luikart (2007:400), other methodological issues with the 

Murphy et al. (2007) analysis make recommendations for recovery unit delineation based 

solely on that study problematic. As noted above, we generally used the Hagerty and 

Tracy report as support for recovery unit boundaries complementary to other evidence. 

We stressed identification of geographic discontinuities or barriers that coincide with any 

observed variation among tortoise populations in delineating recovery unit boundaries. 

Comment: One commenter suggested that the Fenner and Chemehuevi valleys (in the Colorado 

Desert Recovery Unit) are fragmented by I-40; tortoise movement from one valley to the other 

can only be made functional by augmentation and installation of highway culverts with fencing. 

Response: We agree with the comment. The revised plan describes the geographic, 

ecological, and genetic bases for including these valleys within the Colorado Desert 

Recovery Unit. Recovery Action 2.5 specifically addresses fencing I-40, and Recovery 

Action 2.11 addresses connecting functional habitat with culverts. 

Comment: One commenter asked whether there is good evidence that the Providence and New 

York mountains actually form a barrier between designated recovery units. 

Response: While these ranges may be somewhat permeable and may not form absolute 

barriers, landscape-genetic analysis conducted by Hagerty (2008) reveals a substantial 

break in gene flow here. 

Comment: One commenter suggested that application of the recovery unit concept within the 

desert tortoise recovery plan increases the barriers to de-listing and recovery. The commenter 

recommended that DPSs be designated so that individual units can be delisted. Another 

commenter claimed that we failed to designate DPSs according to the 1996 Policy Regarding the 

Recognition of Distinct Vertebrate Population Segments Under the Endangered Species Act. 

Response: As noted in the revised plan, DPSs must be designated through formal rulemaking processes and cannot be done in a recovery plan. Under section 4(c)(2) of the 

Act, the Service conducts 5-year reviews to determine if a federally listed species should 

be delisted, reclassified from endangered to threatened status or from threatened to 

endangered status, or status of the species should remain the same. The recent 5-year 

review for the desert tortoise found that individual recovery units within the Mojave 

population did not qualify as DPSs under the 1996 policy (USFWS 2010). 

13. Recovery Objectives and Criteria 

Comment: One commenter requested that historical permanent study plot data be correlated to 

new range-wide monitoring data (2001-2008). 

Response: A comparison of historical plot data and recent range-wide monitoring data is 

planned. As we make progress in identifying specific demographic study areas, which 

will draw heavily from the historical plots, increased emphasis will be placed on this 

analysis. This may help place local data in the context of the range-wide pattern. 

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Comment: Several commenters criticized the recovery criteria for lacking specific numerical 

baselines against which recovery will be measured. 

Response: The recovery criteria emphasize monitoring trends over a period of at least 25 

years. For trend analysis, the baseline is represented by a parameter value at the earliest 

time represented by the regression. The population size at delisting can be estimated at 

that time because it will be the result of any increasing trend since that baseline. 

However, neither of these values - the starting population size nor the ending population 

size - was used to develop recovery criteria. Some comments expressed concern about the 

possibility that basing recovery on increasing trends beginning with reduced populations 

will result in the species being delisted at numbers well below historic levels. However, 

we will never be able to do more than speculate about how recovery population size 

compares to historical "baselines," because there are no historic data on landscape-level 

population numbers to make such a comparison. Note that there is no basis to presume 

that historic densities seen on localized plots (placed largely within higher-density areas) 

are necessary for long-term survival and recovery across entire conservation areas. On 

the other hand, if positive population growth trends are seen over the recovery period, we 

should have confidence that population densities are not limiting recovery. Interim 

evaluations during the monitoring period will provide periodic checks on the progress of 

recovery efforts. 

Comment: One commenter suggested that threat-based criteria must be added to the recovery 

goals and objectives. On this topic, another commenter stated that we should eliminate all known 

or suspected sources of mortality to desert tortoises. 

Response: As indicated in the revised plan, even though a wide range of threats affect 

desert tortoises and their habitat, very little is known about their demographic impacts on 

tortoise populations or the relative contributions each threat makes to tortoise mortality. 

For example, we lack quantitative data on the specific contribution of raven predation, 

disease, or other individual threats on tortoise population declines, data which are needed 

to identify specific and meaningful threats-based recovery criteria. As quantitative 

information on threats and tortoise mortality is obtained, more specific threats-based 

recovery criteria may be defined during future recovery plan revisions. In the meantime, 

we have addressed all substantive identified threats (i.e., sources of mortality) in the 

recovery actions outlined in the plan, and we assume that threat amelioration will have 

been successful if the current recovery criteria have been met. 

Comment: One commenter criticized the lack of triggers for adaptive management if populations 

continue to decline. 

Response: Trends in population status will regularly be evaluated through Desert Tortoise 

Recovery Office oversight of the range-wide monitoring program. This evaluation, in 

conjunction with other threat- and implementation-status information, integrated into the 

spatial decision support system will provide the basis for redirecting recovery efforts 

through adaptive management. 

219 
 

 

Comment: Several commenters object to the recovery criterion (also included in the 1994 

Recovery Plan) that the rate of population change is increasing (λ > 1), suggesting that this 

criterion fails to ensure recovery. 

Response: There are no historic data on landscape-level population numbers to make a 

comparison against a specific population size, and there is no basis to presume that 

historic densities seen on localized plots (placed largely within higher-density areas) are 

necessary for long-term survival and recovery across entire conservation areas. Further, 

recovery is not linked to “lambda greatly exceeding 1,” as indicated by one commenter. 

For tortoises, with low intrinsic reproductive rate, lambda is expected to be only slightly 

positive during population growth and may well even be negative in areas at carrying 

capacity. In otherwise suitable habitat, this would reflect a healthy population. 

Comment: Several commenters oppose the use of 90-percent confidence limits instead 95­

percent. 

Response: While 95-percent confidence intervals may be more commonly used, they are 

no less arbitrary than 90-percent intervals. A 90-percent confidence interval describing 

trends of actual data will be narrower than a 95-percent interval. A 90-percent confidence 

interval could thus lead us to decide that a population trend really is increasing more 

often than would a 95-percent confidence interval (i.e., more trends, whether apparently 

increasing or decreasing, will be indistinguishable from zero at 95-percent confidence). 

However, if the true trend in the population is actually zero or declining, the narrower 90­

percent confidence interval will prevent us from describing that trend as a positive one. 

Therefore, the recommendation in the revised plan represents a more conservative 

conservation threshold in that it more effectively guards against an inaccurate conclusion 

that a declining population is actually increasing. 

Comment: One commenter suggested that given the difficulties of sampling desert tortoises, it is 

unclear whether Recovery Objective 1 can be met on Bureau of Land Management lands. 

Response: Even though the Bureau of Land Management is the predominant management 

agency of desert tortoise habitat, Recovery Objective 1 will be assessed across tortoise 

conservation areas within each recovery unit, regardless of land management authority. 

Ability to detect trends of small magnitude across tortoise conservation areas can be 

examined with a power analysis, which was first conducted by Anderson and Burnham 

(1996) when the distance sampling approach was customized for monitoring desert 

tortoises. Although there are some unknowns remaining in our assessments, such as just 

how fast tortoise populations can increase and what sort of population fluctuations to 

expect as the populations increase, detecting a trend that exists is fairly straightforward, 

and it has been demonstrated that the existing range-wide monitoring approach can detect 

these trends with sufficient resources dedicated to the monitoring effort. Much of our 

confidence in the ability to detect any positive trend (if it occurs) is that trends send a 

stronger and more detectable signal the longer we monitor them. 

Comment: One commenter suggested that achieving a well-distributed population throughout 

each recovery unit may be difficult due to variable habitat suitability and quality. 

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Response: Recovery Objective 2 does not seek an evenly distributed population within 

each recovery unit, but a well-distributed population within suitable habitat in the tortoise 

conservation areas. 

Comment: Several commenters claimed that Recovery Objective/Criterion 2 "writes off" the full 

range of the desert tortoise by limiting its focus to tortoise conservation areas and ignoring 

habitat outside of those areas. The commenters suggested that the recovery plan should address 

the possibility that the desert tortoise's range may shift in response to climate change and must 

include recovery actions that monitor and model the effects of global warming on tortoise 

demographic parameters and population growth. 

Response: The revised plan acknowledges that projects occurring both inside and outside 

these areas are subject to existing State laws and the Federal section 7 and 10 processes 

under the Endangered Species Act and that populations, habitat, and actions outside these 

areas may affect recovery of the desert tortoise. Recovery Action 1.1 directs Recovery 

Implementation Teams (RITs) to identify areas not included within existing tortoise 

conservation areas that may warrant focused management efforts to ensure recovery. 

Furthermore, Recovery Action 5.1 calls for modeling tortoise demography relative to 

habitat condition and a changing climate which may provide information on which to 

base new recovery actions or establishment of new, or expansion of existing, 

conservation areas. 

Comment: One commenter suggested that more information is needed regarding the relationship 

of Recovery Objective 2 to species recovery, specific methods, and specific goals. 

Response: Because habitat loss has been identified as one of the threats leading to decline 

of desert tortoises, the specific intent of this objective is to demonstrate recovery as 

measured by successful, increasing occupation of potential habitat. We agree that 

measurement of available habitat will reflect a shifting geographic area over this period 

of time, so the method described in the recovery plan (occupancy estimation) empirically 

determines directly whether tortoises are occupying the same, more, or less area. 

Occupancy estimation is an established monitoring technique (MacKenzie et al. 2006) 

that is based on sampling from larger areas. The ability to use a sampling approach with a 

species that is so wide-ranging makes this approach even more attractive. 

Comment: One commenter indicated that Recovery Criterion 3 should include private lands 

because of the checkerboard nature of land ownership in some areas and the potential for 

fragmentation. 

Response: We agree that checkerboard land ownership presents particular challenges to 

landscape-level recovery efforts. However, given the vast amount of desert tortoise 

habitat already under government management, we have excluded private lands from the 

"no net loss" standard of Recovery Criterion 3. We note that private lands are still subject 

to the "take" provisions of Section 9 of the Endangered Species Act and that Recovery 

Action 2.9 is directed toward acquiring, or otherwise securing for conservation benefit, 

sensitive private lands that would connect functional habitat or improve the management 

capability of surrounding land within tortoise conservation areas. 

221 
 

 

 

 

 

Comment: Several commenters suggested that habitat restoration is unproven in repairing all 

ecological functions of undisturbed habitat and that restoration (or the minimum conditions for 

such) needs to be specifically defined, particularly with respect to the length of time that 

degraded habitat may require to become suitable for desert tortoises. 

Response: We agree that it may take many years before particular parcels of “restored” 

habitat become suitable for desert tortoise occupancy, as reflected in the text describing 

Recovery Action 2.6. With respect to Recovery Objective/Criterion 3, the quantity of 

desert tortoise habitat will be measured over time against the threshold of complete loss 

of the elements necessary for desert tortoise occupation (see Box 5). Habitat restoration 

will have to provide sufficient resources for desert tortoises to reoccupy such lands, 

whether or not the habitat quality is sufficient for optimal or maximum reproductive 

output or survival. As specific habitat parameters are identified that correlate with desert 

tortoise demographic rates, restoration goals should be defined specifically according to 

those parameters. 

Comment: Two commenters were critical of the statement in the revised plan that "the target for 

no net loss established by Recovery Criterion 3 may be relaxed on a limited, case-by-case basis, 

if we determine that greater recovery benefits can be achieved ... ." 

Response: This statement acknowledges the fact described in the introduction to the 

Recovery Goal, Objectives, and Criteria section that all recovery criteria are targets, 

rather than strict rules, by which progress toward recovery is measured. The statement 

further acknowledges that in some (limited) circumstances conservation measures may be 

identified that would provide greater recovery benefit than an acre-for-acre replacement 

of lost habitat. In these cases, we should strive to achieve the greatest recovery benefit 

while maintaining an eye toward achieving the no-net-loss of habitat standard as closely 

as possible. 

Comment: One commenter suggested that we failed to provide an updated population viability 

analysis, which should be a necessary component of the revised plan. 

Response: The revised plan relies on the conclusions of population viability analyses 

included in the 1994 Recovery Plan by emphasizing protection and enhancement of 

desert tortoise populations within tortoise conservation areas, which coincide broadly 

with the Desert Wildlife Management Areas recommended in that plan. We recognize 

that as new demographic data become available (e.g., through additional monitoring of 

demographic study areas pertinent to Recovery Criterion 1b), population viability 

analyses should be reinvestigated. More emphasis should be placed on exploring the 

impact of environmental catastrophes and long-term persistence within the tortoise 

conservation areas. Toward that end, we have recently initiated a project to conduct 

spatially-explicit population viability analyses. 

Comment: One commenter noted that habitat loss, degradation, and fragmentation were not 

quantified in the revised plan and that it was therefore unclear whether habitat impacts were a 

serious threat to the desert tortoise. 

222 
 

Response: The revised plan provides numerous examples and references regarding 

habitat-related impacts to the desert tortoise. Unfortunately, as with most other threats, 

these impacts have not been systematically quantified or centrally compiled into a 

geospatial database. As a result, the revised plan emphasizes the development of a spatial 

decision support system in which such information will be compiled, reported, and used 

to help determine the relative magnitude of different threats and the local/regional 

priorities for managing those threats. 

Comment: Several commenters noted that the no-net-loss standard in Recovery Criterion 3 and 

the 1 percent allowable disturbance under the Bureau of Land Management resource 

management plans in California do not mesh. One commenter further suggested that relying on 

the draft U.S. Geological Survey habitat model is premature and that it is unclear whether the nonet-loss objective is obtainable in light of global climate change, wildfires, and spread of 

invasive plants. Tracking this criterion will require a significant infrastructure mechanism. 

Response: We note that the proposed Resource Management Plan and final 

Environmental Impact Statement for the Arizona Strip Field Office, Vermillion Cliffs 

National Monument, and Bureau of Land Management portion of the Grand CanyonParashant National Monument (BLM and NPS 2007) prescribes no net loss in the quality 

or quantity of desert tortoise habitat within Areas of Critical Environmental Concern 

(included in the revised plan as tortoise conservation areas). However, Recovery 

Criterion 3, like all recovery criteria, are targets, rather than strict rules, by which 

progress toward recovery is measured. If, after 25 years, 99 percent of current tortoise 

habitat has been conserved (rather than a net 100 percent) and tortoise populations and 

distribution have increased within that habitat as per Recovery Criteria 1 and 2, it would 

seem appropriate to evaluate whether or not delisting is warranted based on an analysis of 

the five listing factors identified in the Endangered Species Act. The habitat model has 

been finalized since publication of the draft plan, and its use should form the baseline for 

measuring changes in habitat quantity. We agree that this criterion requires a significant 

commitment to monitoring and that research into the effects of global climate change, 

invasive plants, and wildfires (as recommended in the revised plan) is essential to 

understand and mitigate effects to desert tortoise habitat. 

Comment: One commenter suggested that the no-net-loss concept is impractical and that the 

recovery plan should contain language that provides for a reasonable amount of mitigated land 

uses within tortoise conservation areas that recognizes valid existing and appropriate uses. 

Response: Given the current status of the desert tortoise, we do not believe that continued 

habitat loss within tortoise conservation areas is consistent with desert tortoise recovery, 

unless those losses are offset by habitat gains elsewhere or by other actions reasonably 

certain to enhance recovery more than habitat replacement would. 

Comment: One commenter stated that the revised plan fails to identify the baseline areas where 

“no-net-loss” shall be measured, but instead relies on this to be determined by the RITs without 

guidance as to what constitutes disturbed lands. 

223 
 

 

 

 

 

Response: As described in the revised plan, no net loss under Recovery Criterion 3 will 

be measured across all potential desert tortoise habitat (based on the final U.S. Geological 

Survey habitat model) within tortoise conservation areas at the time of publication of the 

final plan. The RITs will use this information to clarify the baseline specifically in areas 

where critical habitat does not align with designated Desert Wildlife Management Areas 

or Areas of Critical Environmental Concern. Habitat subtracted from the baseline as of 

the publication date of the final plan, habitat loss as defined in Box 5, includes lands that 

have had complete removal of the elements necessary for desert tortoise occupation. 

Comment: Two commenters questioned how mitigation acquisitions within conservation areas 

would be added to the baseline for calculating no net loss, particularly whether private lands 

were excluded from the initial baseline but could be added if acquired for conservation, thereby 

increasing the balance of conserved habitat on paper but not on the ground. One indicated that 

lands acquired as mitigation for existing projects cannot be used as grounds for allowing new 

development elsewhere. 

Response: The goal of Recovery Criterion 3 is to focus efforts on maintaining at least the 

amount of desert tortoise habitat that currently exists under Federal or conservation 

management within the tortoise conservation areas into the future. While the revised plan 

recommends protecting desert tortoise habitat from land disturbance (Recovery Action 

2.1), such projects will still occur on Federal and non-Federal lands, both inside and 

outside tortoise conservation areas. These projects must comply with sections 7 and 10 of 

the Endangered Species Act, and habitat acquisition is one tool that can be used to offset 

related impacts. Habitat acreage lost to such projects will be subtracted against the 

"ledger" of conserved habitat, and new acreage placed into conservation will be added. 

14. Implementation Schedule 

Comment: One commenter suggested that, due to the high anticipated cost of the recovery 

program, we should identify one to three actions that can be taken that will yield the biggest 

payoff at the most reasonable cost and that are likely to be funded. This approach, targeted 

toward a reduced number of recovery focal areas, would avoid the current "shotgun" approach of 

implementing only a few actions in many areas. 

Response: As noted in previous comment responses, we believe that all of the tortoise 

conservation areas and recommended recovery actions (which have been broadly 

prioritized) are necessary for recovery of the desert tortoise. We agree with the comment 

and with the conclusions of Tracy et al. (2004) that the approach of implementing a few 

actions in a lot of places is inefficient and not likely to lead to recovery. Therefore, to the 

extent that full and immediate implementation is constrained by available resources, the 

revised plan emphasizes the use of a spatial decision support system by the Recovery 

Implementation Teams to identify which actions offer the biggest return on investment 

for each Team's respective areas, implement those actions, update the decision support 

system, and re-evaluate new priorities on a regular basis. 

Comment: One commenter suggested that the statement that many tasks are already ongoing and 

should therefore continue conflicts with the premise of adaptive management and that it’s time to 

224 
 

 

 

 

 

 

stop those management actions that are not contributing to recovery and forge a new path 

forward with efficient monitoring practices in place to detect future negative or positive results in 

the tortoise populations or their habitat condition and functionality. 

Response: We agree with the sentiment of the comment. Unfortunately, as indicated in 

the plan, data on the effectiveness of most recovery actions do not exist. Therefore, the 

revised plan recommends the use of a spatial decision support system to conduct such 

analyses and change the direction of the recovery program when it is indicated, as 

recommended by the commenter. 

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Berry, K.H. 1986. Desert tortoise (Gopherus agassizii) relocation: Implications of social 

behavior and movements. Herpetologica 42:113-125. 

Berry, K.H. 1990. The status of the desert tortoise in California in 1989. U.S. Bureau of Land 

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Berry, K.H., and L.L. Nicholson. 1984a. The distribution and density of desert tortoise populations in 

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U.S. Fish & Wildlife Service 

Pacific Southewest Region 

Division of Listing, Recovery and 

Environmental Contaminants 

2800 Cottage Way, Suite W-2606 

Sacramento, CA 95825 

http://www.fws.gov/ 

May 2011 

Cover illustration used by permission 

of artist Dennis Caldwell.