Diagram of bighorn sheep (Ovis canadensis) contributed by Ken Carison for listing ofendangered status

of Peninsular bighorn sheep. Copyright granted by Mr. Carison.
Recovery Plan

for

Bighorn Sheep in the Peninsular Ranges,

California

U.S. Fish and Wildlife Service

Region 1

Manager, C ia/Nevada Operations Office

Region , U.S. Fish and Wildlife Service

Approved:

Date:
The Recovery Plan for Bighorn Sheep in the Peninsular Ranges, California, was

developed in cooperation with:

Bureau ofLand Management

U.S. Forest Service

Agua Caliente Band ofCahuilla Indians

California Department of Fish and Game

California Department ofParks and Recreation

Date: ~

Date: IQ41.7./L2Q.

Tnbal Chairman, Agua Caliente Band ofCahuilla Indians

Date: /Pz— 00 Ii.Director. Ca fornia Department Fish and Game _

Date: __________

Director, California Dep yent of Parks andRecrcation
Primary Author

The primary author ofthis recovery plan is:

Esther Rubin

University ofCalifornia, Davis

Davis, California

The plan was written with the assistance ofthe Peninsular Bighom Sheep

Recovery Team (see Acknowledgments).

i
Disclaimer

Recovery plans delineate reasonable actions required to recover andlor protect

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

sometimes preparing them with the assistance ofrecovery teams, contractors,

State and other Federal agencies, Tribes, and other affected and interested parties.

Recovery teams serve as independent advisors to the Fish and Wildlife Service.

Objectives ofthe plan will be attained and any necessary funds made available,

subject to budgetary and other constraints affecting the parties involved.

Recovery plans do not obligate cooperating or other parties to undertake specific

tasks and may not represent the views nor the official positions or approval ofany

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

They represent our official position only after they have been signed by the

Director, Regional Director, or Operations Manager as approved. Approved

recovery plans are subject to modification as dictated by new findings, changes in

species status, and the completion ofrecovery tasks.

Literature citation should read as follows:

U.S. Fish and Wildlife Service. 2000. Recovery plan for bighorn sheep in the

Peninsular Ranges, California. U.S. Fish and Wildlife Service, Portland,

OR. xv+251 pp.

Additional copies may be purchased from:

Fish and Wildlife Reference Service

5430 Grosvenor Lane, Suite 110

Bethesda, Maryland 208 14-2158

(301)492-6403 or 1-800-582-3421

FAX: 301-564-4059

E-mail: fwrs~mail.fws.gov

http://fa.r9.fws.gov/r9fwrsi

The fee for the plan varies depending on the number ofpages ofthe plan.

ii
Acknowledgments

This recovery plan was primarily prepared by Esther Rubin, with important

contributions from Dr. Vein Bleich, Dr. Walter Boyce, Jim DeForge, Dr. Ben

Gonzales, Mark Jorgensen, Stacey Osterrnann, Pete Sorensen, Steve Torres, and

Dr. John Wehausen. The plan benefitted greatly from numerous discussions with

Don Armentrout, Kevin Brennan, Ken Corey, Tom Davis, Diane Freeman, Paul

Jorgensen, JeffManning, Lilia Martinez, Scott McCarthy, Nancy Nicoli, Dr.

Jenny Rechel, Dr. Oliver Ryder, and Gavin Wright. The plan was revised and

approved by the Recovery Team and cooperating agencies. Special thanks is

extended to Randy Botta for providing telemetry data, and Jim Scrivner, Victoria

Smith, Tom Zmudka, and L. Louise Jee for their Geographical Information

System support.

An administrative draft ofthe recoveryplan was submitted fortechnical review,

comments were received from Dr. Phil Hedrick, Dr. Dale Toweill, Dr. David

Jessup, Dr. Paul Krausman, and Dr. Rob Roy Ramey II. These reviewers also

were provided copies ofthe public review draft for comment. Two ofthe these

technical reviewers also submitted comments on the public review draft.

Technical comments deemed not appropriate to incorporate into the public

review draft and final recovery plans are addressed as substantive issues in

Appendix G. The Fish and Wildlife Service and Recovery Team appreciate the

thoughtful review and comments by these colleagues. Preparation ofthe final

recovery plan by the Recovery Team, and incorporation of comments from

technical reviewers in the public review and final recovery plans, was conducted

in conformance with the peer review process under applicable Fish and Wildlife

Service policy.

iii
Mission ofthe U.S. Fish and Wildlife Service in Recovery Planning

Section 4(f) ofthe Endangered Species Act of 1973, as amended (the Act), directs

the Secretary ofthe Interior to develop and implement recovery plans for species

ofanimals and plants listed as endangered and threatened unless such recovery

plans will not promote the conservation ofthe species. The Fish and Wildlife

Service has been delegated the responsibility of administering the Act. Recovery

is the process by which the decline ofendangered orthreatened species is arrested

or reversed, and threats to survival are neutralized, ensuring long-term survival in

nature. The goal ofrecovery is the maintenance ofsecure, self-sustaining wild

populations ofspecies with the minimum necessary investment ofresources. A

recovery plan delineates,justifies, and schedules the management and research

actions necessary to support recovery oflisted species. Recovery plans do not, of

themselves, commit staffing or funds, but are used in setting regional and national

funding priorities and providing direction to local, regional, and State planning

efforts. Means within the Act to achieve recovery goals include the responsibility

ofall Federal agencies to seek to conserve listed species; and the Secretary’s

ability to designate critical habitat, to enterinto cooperative agreements with

States, to provide financial assistance to the respective State agencies, to acquire

land, and to develop habitat conservation plans with non-Federal applicants.
Peninsular Bighorn Sheep Recovery Team

Don Armentrout, Bureau ofLand Management, Susanville, California

Dr. Vein Bleich, California Department of Fish and Game, Bishop, California

Dr. Walter Boyce, University ofCalifornia, Davis, California

Tom Davis, Agua Caliente Band ofCahuilla Indians, Palm Springs, California

James DeForge, Bighorn Institute, Palm Desert, California

Diane Freeman, U.S. Forest Service, Idyllwild, California

Mark Jorgensen, California State Parks, Colorado Desert District, Borrego

Springs, California

Stacey Ostermann, Bighorn Institute, Palm Desert, California

Esther Rubin, University ofCalifornia, Davis, California

Dr. Oliver A. Ryder, Zoological Society of San Diego, San Diego, California

Pete Sorensen, U.S. Fish and Wildlife Service, Carlsbad, California

Steve Torres, California Department ofFish and Game, Sacramento, California

Dr. John Wehausen, University ofCalifornia, White Mountain Research Station,

Bishop, California

v
EXECUTIVE SUMMARY

Current Species Status: The population ofbighorn sheep in the United States~

Peninsular Ranges was listed as an endangered species on March 18, 1998. The

current population is approximately 334 animals, distributed in 8 known ewe

groups (subpopulations) in Riverside, Imperial, and San Diego Counties from the

San Jacinto Mountains south to the Mexican border.

Habitat Requirements and Limiting Factors: The Peninsular bighorn sheep is

restricted to the east facing, lower elevation slopes [typically below 1,400 meters

(4,600 feet)] ofthe Peninsular Ranges along the northwestern edge ofthe Sonoran

Desert. Bighorn sheep are wide-ranging animals that require a variety ofhabitat

characteristics related to topography, visibility, water availability, and forage

quality and quantity. Steep topography is required for lambing and rearing habitat

and for escaping from predators. Open terrain with good visibility is critical

because bighorn primarily rely on their sense ofsight to detect predators. In their

hot, arid habitat, water availability in some form is critical, especially during the

summer. A wide range offorage resources and vegetation associations is needed

to meet annual and drought related variations in forage quality and availability.

Limiting factors apparently vary with each ewe group and are not well understood

in all cases. The range offactors appear to include predation, urban related

sources ofmortality, low rates oflamb recruitment, disease, habitat loss, and

human related disturbance.

Recovery Objective: The objective ofthis recovery plan is to secure and manage

habitat in order to alleviate threats so that population levels will increase to the

point that this species may be reclassified to threatened status, and ultimately

delisted.

Recovery Priority: 3C, per criteria published by Federal Register Notice (48 FR

43098; September21, 1983).

Downlisting Criteria: Peninsular bighom sheep may be considered for

downlisting to threatened status as an interim management goal, when all ofthe

following objective, measurable criteria are met:

vi
Downlisting Criterion 1: As determined by a scientifically credible monitoring

plan, at least 25 ewes must be present in each ofthe following 9 regions ofthe

Peninsular Ranges during each of6 consecutive years (equivalent to

approximately 1 bighorn sheep generation), without continued population

augmentation:

1) San Jacinto Mountains

2) Santa Rosa Mountains--North of Highway 74

3) Santa Rosa Mountains-- South of Highway 74 through Martinez

Canyon

4) Santa Rosa Mountains-- South of Martinez Canyon

5) Coyote Canyon

6) North San Ysidro Mountains (Henderson Canyon to County Road S-22)

7) South San Ysidro Mountains (County Road S-22 to State Highway 78)

8) Vallecito Mountains

9) Carrizo Canyon/Tierra Blanca Mountains/Coyote Mountains Area

Down/isting Criterion 2: Regulatory mechanisms and land management

commitments have been established that provide for long-term protection of

Peninsular bighorn sheep and all essential habitat as described in section II.D. 1 of

this recovery plan. Given the major threat offragmentation to species with

metapopulation structures, connectivity among all portions ofhabitat must be

established and assured through land management commitments, such that

bighorn sheep are able to move freely throughout all habitat. In preparation for

delisting, protection by means other than the Endangered Species Act must be

assured. Such protection should include alternative mechanisms for regulation by

Federal, State, and local governments, and land management commitments that

would provide the protection needed for continued population stability.

Delisting Criteria: Peninsular bighorn sheep may be considered recovered to a

status no longer requiring protection under the Endangered Species Act and

thereafter removed from the List of Endangered and Threatened Wildlife (50 CFR

Part 17) when all ofthe following criteria are met:

Delisting Criterion 1: As determined by a scientifically credible monitoring plan,

at least 25 ewes must be present in each ofthe 9 regions ofthe Peninsular Ranges

vii
listed under Downlisting Criterion #1 above, during each of 12 consecutive years

(approximately 2 bighorn sheep generations) including the 6 years under

Downlisting Criterion #1, without continued population augmentation.

Delisting Criterion 2: The range-wide population must average 750 individuals

(adults and yearlings) with an overall stable or increasing population trend over

the same period of 12 consecutive years (approximately 2 generations) asin

delisting criterion 1.

Delisting Criterion 3: Regulatory mechanisms and land management

commitments have been established that provide for long-term protection of

Peninsular bighorn sheep and all essential habitat as described in section lID. I of

this recovery plan. Furthermore, connectivity among all portions ofhabitat must

be established, and assured through land management commitments, such that

bighorn sheep are able to move freely throughout the Peninsular Ranges.

Delisting would result in loss ofprotection under the Endangered Species Act;

therefore continued protection by other means must be assured. This protection

should include alternative regulatory mechanisms, land management

commitments, or conservation programs that would provide the long-term

protection needed for continued population viability.

Actions Needed: In the short-term, improving adult survivorship appears to hold

the most benefit to population increase. Over the long-term, the primary actions

needed to attain recovery involve conservation ofthe habitat base upon which

Peninsular bighorn sheep depend, and effective management ofbighorn sheep and

conserved lands. Prevention offurther fragmentation, primarily by minimizing

adverse effects of human disturbance, will be critical to the persistence ofewe

groups bordering the Coachella Valley. Adequate space along the urban interface

to absorb anthropogenic effects, and prudent management ofhuman activities

within ewe group home ranges, will also be necessary.

Recovery Costs: Total cost ofrecovery tasks in the Implementation Schedule is

estimated at $73,253,000. In addition, costs ofcertain specific recovery tasks will

be determined as information is obtained and/or final actions are undertaken.

These items are designated as “to be determined” in the Implementation Schedule.

viii
Date of Recovery: Several to many decades likely will be required before a

delisting target date can be accurately estimated. Fecundity (reproductive

potential) and rate of population increase is low compared to some ungulates of

similar size, such as deer. Periodically depressed recruitment rates and high adult

mortality rates also lengthen the time to achieve the population objectives

described in this recovery plan. Ifthe population increases sufficiently and all

recovery criteria are met, the species could be considered for delisting by

approximately 2025. However, this time frame is uncertain and could be

substantially extended if population status and protective measures fail to meet

criteria.

ix
Table of Contents

I. INTRODUCTION . 1

A. BRIEF OVERVIEW 1

1. LISTING OF BIGHORN SHEEP IN THE PENINSULAR

RANGES 1

2. ORIGIN 2

3. MORPHOLOGY AND TAXONOMY 3

4. GENETICS 4

B. ECOLOGY 6

1. HABITAT REQUTREMENTS 6

2. BEHAVIOR 10

3. REPRODUCTION 15

4. SURVIVORSHIP 20

5. CAUSES OF MORTALITY 22

6. COMPETITION 25

7. DISEASE AND PARASITISM 28

C. ABUNDANCE AND DISTRIBUTION 30

1. HISTORIC ABUNDANCE AND DISTRIBUTION 30

2. RECENT ABUNDANCE AND DISTRIBUTION 32

3. POPULATION TRENDS 35

D. REASONS FOR LISTING 38

1. THE PRESENT OR THREATENED DESTRUCTION,

MODIFICATION, OR CURTAILMENT OF THEIR

HABITAT OR RANGE 38

2. OVERUTILIZATION FOR COMMERCIAL,

RECREATIONAL, SCIENTIFIC, OR EDUCATIONAL

PURPOSES 40

3. DISEASE AND PREDATION 40

4. THE INADEQUACY OF EXISTING REGULATORY

MECHANISMS 41

5. OTHER NATURAL OR MANMADE FACTORS

AFFECTING THEIR CONTINUED EXISTENCE ... .42

x
E. PAST AND CURRENT MANAGEMENT! CONSERVATION

ACTIVITIES 46

I. FEDERAL AGENCIES 46

2. STATE AGENCIES 49

3. LOCAL ORGANIZATIONS AND AGENCIES 52

4. iNDIAN TRIBES 56

II. RECOVERY 57

A. CONSERVATION PRINCIPLES USED IN THIS RECOVERY

PLAN 57

1. POPULATION CONSIDERATIONS 57

2. GENETIC CONSIDERATIONS 58

3. ECOSYSTEM PROTECTION 60

4. THE USE OF POPULATION MODELS TO HELP GUIDE

RECOVERY ACTIONS 61

B. OBJECTIVES AND CRITERIA 62

1. RECOVERY OBJECTIVE 62

2. DOWNLISTING CRITERIA 62

3. DELISTING CRITERIA 65

C. RECOVERY STRATEGY 67

D. NARRATIVE OUTLINE FOR RECOVERY ACTIONS

ADDRESSING THREATS 69

1. PROMOTE POPULATION INCREASE AND PROTECT

HABITAT 69

1 .1 Protect, acquire, enhance, and restore habitat 69

1.2 Reduce or eliminate direct and indirect human impacts

80

1.3 Reduce mortality rates 91

1.4 Develop a long-term strategy and maintain the current

capability for captive breeding, reintroduction, and

augmentation programs 94

2. INITIATE OR CONTINUE RESEARCH PROGRAMS

NECESSARY TO MONITOR AND GUIDE RECOVERY

EFFORTS 95

2.1 Monitor population status 96

2.2 Develop population models 98

xi
2.3 Research the relationships between bighom sheep,

mountain lions, mule deer, and habitat 99

2.4 Investigate the relationships between bighorn sheep

and coyotes and bobcats 100

2.5 Investigate the efficacy oftemporary suppression of

natural predation 100

2.6 Research habitat use/selection and dispersal behavior

100

2.7 Evaluate the effect ofhuman activities on bighorn

sheep 101

2.8 Research disease and preventive measures 102

2.9 Research genetics ofbighom sheep in the Peninsular

Ranges 103

3. DEVELOP AND IIMPLEMENT EDUCATION AND PUBLIC

AWARENESS PROGRAMS 104

3.1 Distribute information related to recovery efforts

105

3.2 Continue, update, and coordinate existing education

programs 105

3.3 Develop additional educational programs 106

3.4 Distribute a protocol to select law enforcement, public

health, and safety officials for the humane treatment

ofinjured bighorn sheep 107

E. SITE SPECIFIC RECOVERY TASKS 107

III. IMPLEMENTATION SCHEDULE Ill

IV. LITERATURE CITED 117

V. APPENDICES 148

APPENDIX A. AN OVERVIEW OF THE PENINSULAR RANGES

148

APPENDIX B. DELINEATION OF ESSENTIAL HABITAT FOR

BIGHORN SHEEP IN THE PENINSULAR RANGES 153

xii
APPENDIX C. GUIDELINES FOR DEVELOPING A LONG-TERM

STRATEGY FOR REINTRODUCTION, AUGMENTATION,

AND CAPTIVE BREEDING OF BIGHORN SHEEP IN THE

PENINSULAR RANGES 168

APPENDIX D. GUIDELINES FOR SAFELY CAPTURING,

HANDLING, AND MONITORING BIGHORN SHEEP 195

APPENDIX E. PROTOCOLS FOR MONITORING POPULATION

ABUNDANCE 205

APPENDIX F. RECOMMENDED CONSERVATION GUIDELINES

216

APPENDIX G. RESPONSE TO COMMENTS 221

LIST OF TABLES

Table 1. Lamb survival per ewe group in the Peninsular Ranges from

1993to1996 17

Table 2. Peninsular bighorn ewe population estimates and recruitment (lamb

survival until December) for captive-reared and wild-reared ewes in

the northern Santa Rosa Mountains 18

Table 3. Annual survival estimates for yearling and adult bighorn sheep in the

northern Santa Rosa Mountains ewe group for calendar years 1985 to

1998 (excluding captive-reared animals) 21

Table 4. Annual survival of adult bighorn sheep between Highway 74 and the

United States - Mexico border, 1992 to 1998 22

Table 5. Abundance estimates ofbighorn sheep in the Peninsular Ranges north

of the United States - Mexico border during 1994, 1996, and 1998 . 34

xiii
Table 6. Ewe abundance estimates per ewe group generated from helicopter

surveys during 1994, 1996, and 1998 35

Table 7. Ewe population estimates for the San Jacinto Mountains from 1993 to

1999 37

Table 8. Fall population estimates of adult bighorn sheep in the northern Santa

Rosa Mountains from 1985 to 1998 37

Table 9. Past and present conservation activities in Anza-Borrego Desert State

Park 54

Table 10. Trails and areas with potential conflicts that should be addressed in the

interagency trails management plan 88

Table 11. Recovery criteria regions 108

Table 12. Site specific tasks recommended for each recovery region 109

LIST OF FIGURES

Figure 1. Distribution ofseven mitochondrial DNA haplotypes among bighorn

sheep ewe home-range groups in the Peninsular Ranges, southern

California S

Figure 2. Peninsular bighorn sheep essential habitat and physical features ... 11

Figure 3. Distribution of bighorn ewe groups in the Peninsular Ranges,

California, 1992 to 1995 33

Figure 4. Peninsular bighorn sheep essential habitat and land

ownership/management 50

Figure 5. Peninsular bighorn sheep essential habitat with recovery regions . .. 63

xiv
Figure 6. Peninsular bighorn sheep essential habitat and sheep observations . 71

Figure 7. Palm Springs - Cathedral City interface with Peninsular bighorn sheep

essential habitat 72

Figure 8. Rancho Mirage - Palm Desert interface with Peninsular bighorn sheep

essential habitat 73

Figure 9. Indian Wells- La Quinta interface with Peninsular bighorn sheep

essential habitat 74

xv
I. INTRODUCTION

The purpose ofthis recovery plan is to (1) establish interim and long-term goals

and objectives, (2) describe site-specific management actions to achieve these

goals, and (3) establish a schedule and estimate the costs required to reclassify as

threatened and ultimately delist the distinct population segment ofbighorn sheep

(Ovis canadensis) in the Peninsular Ranges of California, a northerly extension of

the mountainous formations of the Baja California Peninsula. This recovery plan

provides guidelines and recommendations to be used in developing and assessing

conservation and management activities to achieve recovery.

A. BRIEF OVERVIEW

1. LISTING OF BIGHORN SHEEP IN THE PENINSULAR RANGES

The California Fish and Game Commission listed bighorn sheep inhabiting the

Peninsular Ranges as “rare” in 1971. In 1984, the designation was changed to

“threatened” by the California Department of Fish and Game to conform with

terminology of the amended California Endangered Species Act. We (the Fish

and Wildlife Service) listed the distinct vertebrate population segment of bighorn

sheep occupying the Peninsular Ranges of southern California (see Appendix A)

as endangered on March 18, 1998 (63 FR 13134). For a population to be listed

under the Endangered Species Act as a distinct vertebrate population segment,

three elements are considered (61 FR 4722, February 7, 1996): (1) the

discreteness of the population segment in relation to the remainder of the species

to which it belongs; (2) the significance of the population segment to the species

to which it belongs, and (3) the population segment’s conservation status in

relation to the Endangered Species Act’s standards for listing (i.e., is the

population segment, when treated as ifit were a species, endangered or

threatened?). The Peninsular Ranges population will hereafter be referred to in

this recovery plan asthe Peninsular bighorn sheep and will alternatively be

referred to as a species, following the definition of”species” in section 3(15) of

the Endangered Species Act.

1
Species Distribution

The population of bighorn sheep addressed in this recovery plan extends along the

Peninsular Mountain Ranges from the San Jacinto Mountains ofsouthern

California south to the United States - Mexico international border. Though the

range extends south to Volcan Tres Virgenes near Santa Rosalia, Baja California,

Mexico, only the distinct vertebrate population segment within the United States

is listed as endangered and addressed in this recovery plan.

The decision to list the Peninsular bighorn sheep as federally endangered was

made because of declining population numbers and continuing habitat loss,

degradation, and fragmentation throughout a significant portion of the Peninsular

bighorn sheep’s range. In addition, periods of depressed recruitment, likely

associated with disease, and high predation, coinciding with low population

numbers, endanger the continued existence ofthese animals in southern

California. Perrecovery planning criteria published in the FederalRegister (48

FR 43098, September 21, 1983), the Peninsular bighorn sheep has a recovery

priority of 3C, indicating that it is a subspecies facing a high degree of threat but

has a high potential for recovery if appropriately managed. The “C” indicates that

recovery is in conflict with construction or other forms of economic activity.

2. ORIGIN

Wild sheep became established in North America after crossing the Bering land

bridge from Eurasia during the late Pleistocene (Geist 1971), which began about

1,000,000 years ago and ended 10,000 years ago at the time ofthe last Ice Ages

and the beginning of the Holocene. The range ofbighorn sheep has since spread

to include desert habitats as far south as northern Mexico (Manville 1980). In

North America, two species of wild sheep currently are recognized: the thinhorn

sheep (Ovis dalli) and the bighorn sheep (Ovis canadensis). Bighorn sheep,

originally described by Shaw in 1804 (Wilson and Reeder 1993), were once

divided into seven recognized subspecies based on differences in skull

measurements (Cowan 1940, Buechner 1960, Shackleton 1985). These

subspecies included Audubon bighorn sheep (Ovis canadensis auduboni),

2
Peninsular bighorn sheep (Ovis canadensis creinnobates), Nelson bighorn sheep

(Ovis canadensis nelsoni), Mexican bighorn sheep (Ox’is canadensis inexicana),

Weems bighorn sheep (Ovis canadensis weemsi), California bighorn sheep (Ovis

canadensis californiana), and Rocky Mountain bighorn sheep (Ovis canadensis

canadensis). Audubon bighorn sheep are now extinct. As described below, this

taxonomy has since been revised.

3. MORPHOLOGY AND TAXONOMY

The term “desert bighorn” is used to describe bighorn sheep that inhabit dry and

relatively barren desert environments, and typically includes bighorn sheep

subspecies that have, to date, been classified as nelsoni, mexicana, cremnobates,

and weemsi (Manville 1 980).~ The validity ofthese subspecies delineations has

been questioned and reassessed on the basis ofadditional morphological and

genetic analyses (Wehausen and Ramey 1993; Ramey 1993, 1995; GutierrezEspeleta et al. 1998; refer to section I.A.4). Bighorn sheep in the Peninsular

Ranges were once considered a separate subspecies and were one of the four

desert subspecies recognized by Cowan (1940) based on cranial measurements.

Cowan’s (1940) Peninsularsubspecies (Ovis canadensis cremnobates) did not

include the northern end of the Peninsular Ranges in California and extended east

across the Imperial Valley north ofthe Mexican border. Wehausen and Ramey

(1993) noted that various authors have arbitrarily changed the geographic

boundaries of this subspecies over time based on no additional data or analyses.

Ramey (1993) reanalyzed Cowan’s (1940) original data using modern statistical

methods and found little support for his subspecies of bighorn sheep. In that

reanalysis, the apparent distinction of the Peninsular subspecies was found to be

an artifact of unequal age distributions among samples. Wehausen and Ramey

(1993) conducted a new cranial morphometric analysis using a new and much

larger sample and found no statistical support for a Peninsular subspecies. Ramey

(1993, 1995) also investigated this question using restriction site polymorphism

data for mitochondrial DNA and similarly found no statistical support for

description of a subspecies in the Peninsular Ranges. Based on these

morphometric and genetic results, Wehausen and Ramey (1993) placed Peninsular

3
bighorn within the Nelson subspecies (Ovis canadensis nelsoni), which is the

current taxonomy.

4. GENETICS

By analyzing micro-satellite and major histocompatibility complex loci, Boyce et

al. (1997) found high levels ofgenetic diversity within and between populations

of desert bighorn sheep, including sheep subpopulations within the Peninsular

Ranges. Similarly, Gutierrez-Espeleta et al. (1998) found significant amounts of

variation at microsatellite loci among all bighorn sheep populations studied.

However, Ramey (1995) found very little mitochondrial DNA variation between

groups of desert bighorn. The results of Ramey (1995), Boyce et al. (1997), and

Gutierrez-Espeleta et al. (1998) differ because various molecular markers and

analytical techniques were employed. Different molecular markers (e.g.,

mitochondrial DNA, microsatellites, allozymes) are subject to various rates of

mutation and are likely affected by different evolutionary processes, thereby

providing different levels of insight into the genetic variability ofa species. One

similarity that has been found in all genetic studies of desert bighorn to date is that

genetic distance increases with geographic distance. For example, Boyce et al.

(1997) and Bleich et al. (1996) found support for partitioning ofgenetic variation

among metapopulations (e.g., the Mojave and Peninsular metapopulations), with

high levels of gene flow within metapopulations, including the Peninsular Ranges,

and low levels between metapopulations.

Within the Peninsular Ranges, at least eight subpopulations, or ewe groups,

currently exist (Rubin et al. 1998, refer to section I.C.l). Based on sampling of

about one-third of the animals in the metapopulation, Boyce et al. (1999) found

that seven haplotypes were distributed in a non-random fashion among these ewe

groups and that a significant amount ofmitochondrial DNA variation was

partitioned among ewe groups, indicating a high level ofgenetic structure among

these subpopulations (Figure 1). The observed structure among ewe groups likely

was primarily influenced by differences in founding ewes and their limited

movements through the range (W. Boyce, University of California, Davis, pers.

comm.). Boyce et al. (1999) concluded that the movement of ewes (and therefore

4
Figure 1. Distribution of seven mitochondrial DNA haplotypes among bighorn sheep ewe

home-range groups in the Peninsular Ranges, California (SJ, San Jacinto Mountains, n=6; D, Deep

Canyon, n=18; M, Martinez Canyon, n6; SSR, South Santa Rosa Mountains, n=3; COY, Coyote

Canyon, n=13; NSY, North San Ysidro Mountains, n=18; SSY, South San Ysidro Mountains, n~7; V,

Vallecito Mountains, n=14; CAR, Carrizo Canyon, n19). Note that the ewe groups are distributed

approximately along a north-south gradient. A ewe group composed primarily of captive-bred

animals, located between the Deep Canyon and San Jacinto Mountains groups, was not included in

the analysis. (Reprinted with permission from Boyce et al. 1999).

5
the flow of mitochondrial DNA) between ewe groups is limited but has occurred

at low levels in the past. This result is in contrast to the greater level of nuclear

gene flow (indicated by the analyses of micro-satellite and major

histocompatibility complex loci markers discussed above), which is mediated by

the movement of rams among ewe groups (refer to section I.B.2).

B. ECOLOGY

1. HABITAT REQUIREMENTS

Bighorn sheep have important habitat requirements that relate to topography,

visibility, water availability, and forage quality and quantity. During their

evolution, bighorn sheep developed predator evasion behaviors that depend

critically on the use of escape terrain, which is generally defined as steep, rugged

terrain (Hansen 1 980c, Cunningham 1989). Escape terrain is important because

bighorn sheep typically do not outrun their predators but, rather, use their

climbing abilities to escape their enemies (Geist 1971, McQuivey 1978). When

ewes are ready to give birth they will typically seek out the most precipitous

terrain, where their lambs will presumablybe safest (Geist 1971). The presence

ofsuch steep terrain for predator evasion and lambing is, therefore, a crucial

component ofsheep habitat (see Appendix B). Variation in slope and aspect also

help bighorn sheep to survive in a harsh environment. During hot weather,

bighorn seek shade under boulders and cliffs, or may move to north facing slopes

(Merritt 1974, Andrew 1994). During inclement weatherthey may again seek

protected caves or overhangs, or move to sunny, south facing slopes (Andrew

1994), or slopes that are protected from strong winds.

In addition to mountainous terrain, other types ofhabitat are crucial to the

viability of bighom sheep populations. M. Jorgensen (California State Parks,

pers. comm.) has observed bighorn at various times ofthe year on numerous

alluvial fans and in washes, such as (1) the Borrego Palm Canyon alluvial fan,

used for forage during cooler months and for water from Mayto November; (2)

Palm Wash tinajas in the southern Santa Rosa Mountains, a water source in late

summer/fall before winter rains; (3) Harper Flat in Anza-Borrego Desert State

6
Park; and (4) Chino Canyon, most recently in 1982, when seven ewes and lambs

were observed. Areas offlat terrain, such as valley floors, serve as important

linkages between neighboring mountainous regions, thereby allowing sheep

temporary access to resources (e.g., forage, water, or lambing habitat) in

neighboring areas, and allowing gene flow to occur between subpopulations

(Krausman and Leopold 1986, Schwartz et al. 1986, Bleich et al. 1990a, Bleich et

al. 1996).

In the Sierra Nevada and Moj ave Desert, the timing offorage green-up in winter

is strongly influenced by elevation and mediated through temperature (J.

Wehausen, White Mountain Research Station, pers. comm.; Wehausen 1980,

1983). Low rolling terrain and washes seasonally provide an important source of

high quality forage, with a greater diversity ofbrowse species than in steeper

terrain (Leslie and Douglas 1979). Washes also provide a source of high quality

browse for longer in the summer than do other areas (Andrew 1994). Leslie and

Douglas (1979) noted that these areas became increasingly important to bighorn

sheep not only in summer but during any period oflimited forage availability.

Bates and Workman (1983) observed bighorn sheep feeding in flat terrain in

Canyonlands National Park, and reported that plant production was higher in

flatter terrain than in steeper areas. Similarly, Bleich et al. (1997) reported that

during periods ofsexual segregation, rams exploited rolling hills and flat terrain

for their superior forage. After localized summer rainfall events, washes and

alluvial fans provide the diverse, high quality forage that is especially important to

lactating ewes (Turner 1976, Bureau ofLand Management 1996). Hansen and

Deming (1980) describe the importance ofsucculent spring foods at lower

elevations to lactating ewes.

In the Peninsular Ranges, bighorn sheep use a wide variety ofplant species as

theirfood source. Turner (1973) recorded the use of at least 43 species, with

browse being the food category most frequently consumed (Turner 1976, Scott

1986). Cunningham and Ohmart (1986) determined that the bighorn sheep diet in

Carrizo Canyon (at the south end ofthe U.S. Peninsular Ranges) consisted of 57

percent shrubs, 32 percent forbs, 8 percent cacti, and 2 percent grasses. Scott

(1986) and Turner (1976) reported similar diet compositions at the north end of

7
the range. Plant species eaten by bighorn sheep in the PeninsularRanges were

also reported by Jorgensen and Turner (1973) and Weaver et al. (1968). Diet

composition varied among seasons (Cunningham and Ohrnart 1986, Scott 1986),

presumably because ofvariability in forage availability, selection ofspecific plant

species during different times ofthe year (Scott 1986), and seasonal movements

ofbighorn sheep. In Arizona, bighorn sheep also used a wide variety offorage

species throughout the year to cope with the changing desert environment (Miller

and Gaud 1989).

In ruminants, such as bighorn sheep, fetal growth is relatively slow during the

early stages ofgestation, with the majority offetal growth occurring during the

final two months ofgestation (Robbins 1993). Following lambing, ewes are faced

with the costs oflactation, which are typically two to three times higher than the

energetic costs ofgestation and may range from four to seven times the basal

metabolic rate (Robbins 1993). Consequently, the time period surrounding

lambing and nursing is very demanding in terms of the energy and protein

required by bighorn ewes. Failure to acquire sufficient nutrients during the last

two months ofgestation and during nursing can adversely affect the survival of

newborn ungulates (Thorne et al. 1976, Julander et al. 1961, Holl et al. 1979).

Furthermore, females in poor condition may fail to provide adequate maternal care

following parturition (Langenau and Lerg 1976, Festa-Bianchet and Jorgenson

1996). Crude protein and digestible energy values of early green-up species, such

as annual grasses and forbs, are usually much higher than those of dormant

forages during the critical late gestation, lambing, and rearing seasons. With their

high nutrient content, even minor volumes ofthese forages within the overall diet

composition may contribute important nutritional value at critical life stages

(Wagner 2000). However, during the reproductive season, due to the varied

topography ofbighorn sheep habitat, these forages typically are concentrated on

specific sites, such as alluvial fans and washes, where more productive soils

support greater herbaceous growth than steeper, rockiersoils. Berbach (1987)

found that when ewes were confined to a pen and prevented from using all

vegetation associations during late gestation and early lactation, they and their

lambs died ofmalnutrition.

8
In hot, arid deserts, water is considered to be an important resource for bighorn

sheep (Jones et at. 1957, Blong and Pollard 1968, Leslie and Douglas 1979,

Turner and Weaver 1980, Elenowitz 1984, Cunningham and Ohmart 1986). A

number ofstudies have shown that desert bighorn sheep will concentrate around

water sources in the summer, with most animals found within a 3- to 5-kilometer

(2- to 3-mile) radius of water (Jones et at. 1957, Leslie and Douglas 1979,

Cunningham and Ohmart 1986). Lactating ewes and lambs often are more

dependent on water and may thus be found closer to water (Blong and Pollard

1968, Leslie and Douglas 1979, Bleich et at. 1997). However, these patterns have

not been observed in all habitats (summarized by Andrew 1994). Water sources

are most valuable to bighorn sheep ifthey occur in proximity to adequate escape

terrain with good visibility. Therefore, the juxtaposition ofopen escape terrain to

water sources will influence drinking patterns (Cunningham 1989, Andrew 1994).

During periods ofhigh rainfall, sheep distribution is less coincident with

permanent watersources (Leslie and Douglas 1979). The importance ofwater to

bighorn sheep has been questioned (Krausman and Leopold 1986, Broyles 1995),

and some small populations apparently exist withoutstanding water (Krausman et

at. 1985, Krausman and Leopold 1986, and additional examples summarized in

Broyles 1995). Furthermore, it has been theorized that the addition of water to

bighorn sheep habitat would be detrimental ifit attracted competing species to

areas oflimited forage resources (Smith and Krausman 1988) or expanded the

range of mountain lions (Shaw 1993). However, in most populations bighorn

sheep will drink regularly when water is available and concentrate near water

during summer months, and it is likely that lack of water is a limiting factor for

some populations. In the Peninsular Ranges, bighorn sheep have been observed to

use areas without known perennial water during some months, including the

lambing season (E. Rubin, University ofCalifornia, Davis, pers. comm.).

The predator evasion behavior ofbighorn sheep depends on the ability to visually

detect danger at a distance. Visibility has long been recognized as an important

characteristic of bighorn sheep habitat (Hansen 198Gb). Researchers have found

that bighorn sheep will avoid habitat in which dense vegetation reduces visibility

(Risenhoover and Bailey 1985, Etchberger et at. 1989). This appears to be the

9
case in the Peninsular Ranges, where bighorn sheep usually remain below the

elevation of chaparral and other dense vegetation associations.

In the Peninsular Ranges, bighorn sheep habitat occurs along the east-facing

desert slopes, typically below approximately 1,400-meter (4,600-foot) elevations

(Jorgensen and Turner 1975). In these mountains, bighorn sheep avoid higher

elevations, likely because ofdecreased visibility (and therefore increased

predation risk) associated with the denser vegetation found at higher elevations.

The elevational patterns of vegetation associations in the Peninsular Ranges, in

combination with this predator avoidance behavior, have resulted in habitat use

that is more restricted to lower elevations than in most other bighorn sheep

populations. Results from helicopter surveys and a 5-year study ofradio-collared

bighorn in the San Jacinto Mountains found that bighorn sheep in these

mountains, where elevations exceed 3,000 meters (9,842 feet), were largely

restricted to a narrow band ofhabitat between 213 and 1,037 meters (700 to 3,400

feet) in elevation (DeForge et at. 1997). In the northern Coachella Valley, this

lower elevation limit generally coincides with the developed urban interface. At

the lowest elevations of their range, bighorn sheep movement onto the valley floor

(Coachella Valley, Imperial Valley) is restricted by a tendency to avoid venturing

far from escape terrain and by anthropogenic factors that now preclude

intermountain movements such as have been recorded elsewhere in the desert.

The available habitat of Peninsular bighorn sheep can, therefore, be visualized as

a long, narrow band that runs north-south along the lower elevations ofthe

Peninsular Ranges (Figure 2). This pattern of predominantly low elevation habitat

use is unique among desert bighorn sheep populations.

2. BEHAVIOR

The social structure of bighorn sheep is matrilineal (based on female

associations). Gregarious and philopatric (faithful to natal home range) behaviors

confer adaptive advantage to prey species because home range familiarity and

group alertness decrease the risk ofpredation (Boyce et at. 1999). The ranging

patterns and habits ofewes are learned by their offspring (Geist 1971). By

following older animals, young bighorn sheep gather knowledge about escape

10

terrain, water sources, and lambing habitat (Geist 1971). Ewes that share the

same portion of a range, therefore, are likely to be more closely related to each

other than they are to other ewes (Festa-Bianchet 1991, Boyce et at. 1999), and

the term “home range group” has been used to describe such groups (Geist 1971).

These groups are referred to as “ewe groups” in this recovery plan. Rams do not

show the same level ofphilopatry and tend to range more widely, often moving

among ewe groups. As young rams reach 2 to 4 years ofage, they follow older

rams away from their natal group during the fall breeding period, or rut, and often

return after this period (Geist 1971, Festa-Bianchet 1991). Rams may follow the

same travel routes year after year (Geist 1971, Wehausen 1980, DeForge et at.

1997). The sexes tend to loosely segregate during much of the year, coming

together primarily during the rut (Geist 1971, Bleich et at. 1997), which typically

peaks from August through October in the Peninsular Ranges (Rubin et at. 2000).

During the rut, rams join the ewe groups and compete to breed with receptive

ewes. The largest rams presumably are the most successful breeders, but smaller

rams have been reported to breed as well (Hogg 1984). During the period of

sexual segregation, ewes and their lambs are typically found in steeper, more

secure habitat, while rams inhabit less steep or rugged terrain (Geist 1971, Bleich

etat. 1997).

Bighorn sheep are primarily diurnal (Krausman et at. 1985) but may be active at

any time ofday or night (Miller et at. 1984). Their daily activity pattern includes

feeding and resting periods that are not synchronous either within or between

groups. Forage quality influences activity patterns. When forages are low in

digestibility, sheep must spend more time ruminating and digesting forage.

Particle size must be reduced sufficiently to pass from the rumen and reticulum to

the omasum (Van Soest 1982, Robbins 1993). As forages green-up and

digestibility increases, passage rates increase and ruminants can feed more

frequently (Risenhoover 1986). Sheep typically increase the number offeeding

bouts rather than the length of individual bouts. Consequently, sheep establish a

cycle of feeding and ruminating that reflects forage quality and optimizes nutrient

intake (Wagner 1999, 2000).

12
Bighorn sheep rely on vigilance to detect predators. Therefore, they benefit from

gregariousness and group alertness (Geist 1971, Berger 1978). Within a ewe

home range group, ewes appear to associate with other ewes based on their

availability ratherthan on their matrilineal relationships (Festa-Bianchet 1991,

Boyce et at. 1999). Within home range groups, these subgroups are dynamic--

they may split, reform, or change membership on a daily or hourly basis as

animals move through their home ranges.

Burt (1943) defined home range as ‘...that area traversed by the individual in its

normal activities offood gathering, mating, and caring for young”. Size ofthe

home range depends on the juxtaposition ofrequired resources (water, forage,

escape or lambing habitat) and, therefore, varies geographically. Home range size

also is affected by forage quantity and quality, season, sex, and age ofthe animal

(Leslie 1977, McQuivey 1978). In most populations, ram home ranges have been

found to be larger than those of ewes (Simmons 1980, DeForge et at. 1997).

DeForge et at. (1997) reported average home range sizes (95 percent utilization

distribution) of 25.5 square kilometers (9.8 square miles) and 20.1 square

kilometers (7.8 square miles) for rams and ewes, respectively, in the San Jacinto

Mountains, using the fixed-kernel method (Seaman and Powell 1996).

Although most desert bighorn sheep do not seasonally migrate along elevational

gradients like many populations in higher latitude mountain ranges, they do

exhibit seasonal differences in habitat use patterns. In many populations, animals

will have a smaller home range in summer (McQuivey 1978, Leslie and Douglas

1979, Elenowitz 1983), presumably due to their limited movement away from

permanent watersources. During the cooler or wetter months ofthe year, bighorn

sheep often exhibit an expanded range as animals move farther from water

sources (Simmons 1980). In addition, seasonal changes in habitat use are

influenced by lambing and rutting behavior (Geist 1971, Bleich et at. 1997).

Desert sheep also seek the earliest winter green-up ofannuals and the first

flowering ofbrittlebush (Enceliafarinosa), which are elevation dependent

(J. Wehausen, pers. comm.).

13
The gregarious and philopatric behavior of ewes limits their dispersal and

exploratory abilities relative to those oframs (Geist 1967, 1971). Geist (1971)

theorized, however, that a young ewe might switch to a new ewe group if she

encountered neighboring sheep and followed them away from her natal ewe

group. In the Peninsular Ranges, movement ofradio-collared ewes between ewe

groups is rare. During a 3-year study, the most extensive movement documented

was by one ewe that moved over 30 kilometers (18.6 miles) and temporarily

joined a second ewe group (Rubin et at. 1998). No emigration ofewes has been

observed even though radio-collared animals have been regularly monitored in the

northern Santa Rosa Mountains since 1981 (Ostermann et at. in press) and

throughout the range since 1993 (li. Rubin, pers. comm.; DeForge et at. 1997).

Genetic analyses of ewe dispersal suggest that a low rate has occurred in the

Peninsular Ranges in the evolutionary past (Boyce et at. 1999). Genetic and

observational data suggest, however, that ram movements among ewe groups are

common (Boyce et at. 1997; DeForge et at. 1997; Rubin et at. 1998; Bighorn

Institute 1998, 1999).

An important consideration in the conservation ofPeninsular bighorn sheep is

their behavioral response to humans and human activity. Bighorn have been

considered a wilderness animal because they do not thrive in contact with human

development (Leopold 1933). Their response to human activity is highly variable

and depends on many factors, including but not limited to: the type of activity,

the animal’s previous experience with humans, size or composition ofthe bighorn

sheep group, location of bighorn sheep relative to elevation ofthe activity,

distance to escape terrain, and distance to the activity (Weaver 1973; McQuivey

1978; Hicks and Elder 1979; MacArthur et at. 1979, 1982; Wehausen 1980;

Hamilton et at. 1982; Whitacker and Knight 1998; Papouchis et at. 1999).

Responses can range from cautious curiosity to immediate flight or abandonment

ofhabitat, as well as disruption ofnormal social patterns and resource use.

Though the effect of human activity in bighorn habitat is not always obvious,

human presence or activity in many cases has been found to detrimentally alter

normal behavioral and habitat use patterns(refer to section I.D.5). For example,

bighorn began using urban sources offood and water in the northern Santa Rosa

Mountains when development began encroaching on sheep habitat in the 1950’s

14
(Tevis 1959). Though commonly thought to be the result of releasing captive

raised bighorn sheep, habituation of wild sheep to urban habitats occurred several

decades before the first release ofany captive-reared stock in 1985 (DeForge and

Scott 1982; Ostermann et at. in press; V. Bleich, California Department ofFish

and Game, pers. comm.).

3. REPRODUCTION

In the Peninsular Ranges, ewes estimated to be between 2 and 16 years of age

have been documented to produce lambs (Rubin et at. 2000, Ostermann et at. in

press). Yearling ewes in captivity also have produced lambs (Bighorn Institute

1999). Some rams are believed to be capable of successful breeding as early as 6

months of age (Turner and Hansen 1980), though the breeding opportunities of

young rams are limited by the social pressure oflarger rams (Hogg 1984). The

breeding period, or rut, occurs in the late summer and fall months. As parturition

approaches, ewes seek isolated sites with shelter and unobstructed views (Turner

and Hansen 1980), and seclude themselves from other females while finding sites

to bear their lambs (Etchberger and Krausman 1999). In the Little Harquahala

Mountains, the physical and biological characteristics of lambing sites did not

differ from sites used at other times ofthe year (ibid). Lambs are born after a

gestation of approximately 6 months-- 171 to 185 days(Turner and Hansen 1980,

Shackleton et at. 1984, Hass 1995). During a 4-year (1993 to 1996) study

conducted in the Peninsular Ranges south ofthe San Jacinto Mountains, the

lambing season extended from February through August; however, 87 percent of

the lambs were born from February to April, and 55 percent of the lambs were

born in March (Rubin et at. 2000). DeForge et at. (1997) and Cunningham (1982)

reported a similar onset ofthe lambing season in the San Jacinto Mountains and in

Carrizo Canyon, respectively. In the San Jacinto and northern Santa Rosa

Mountains ewe groups, the lambing season begins in January during some years

(Bighorn Institute 1997). Lambs usually are weaned by 6 months ofage (Hansen

and Deming 1980, Wehausen 1980).

From 1993 to 1996, the reproductive patterns of five ewe groups (Carrizo Canyon,

south San Ysidro Mountains, north San Ysidro Mountains, Santa Rosa Mountains

15
[Deep Canyon], and northern Santa Rosa Mountains) were monitored (refer to

section I.C. I for description of ewe groups) and annual lamb production averaged

77 percent (0.77 lambs born per “ewe-year”) for the 4-year period (E. Rubin, pers.

comm.). Using a fecal-based enzyme immunoassay, Borjesson et at. (1996)

determined that in the fall of 1992, at least 85 percent ofsampled adult ewes were

pregnant. Both ofthese observations suggest that conception rates are not

currently limiting population growth in the Peninsular Ranges.

Lamb survival (to 6 months of age) was variable among groups and across years.

A good year of lamb survival in one group was not necessarily a good year in

another group (Rubin et at. 2000, Table 1). Of the four groups studied, the

northern Santa Rosa Mountains group typically had the lowest lamb survival,

while the neighboring Deep Canyon group, located less than 8 kilometers (5

miles) away, had the highest lamb survival. Researchers working in the northern

portion of the Santa Rosa Mountains have expressed concern over the low lamb

recruitment average observed in this area since approximately 1977 (DeForge et

at. 1982, DeForge and Scott 1982, Turner and Payson 1982). Although lamb to

ewe ratios observed in the Santa Rosa Mountains have fluctuated across years

(Wehausen et at. 1987, DeForge et at. 1995), fall lamb to ewe ratios were

consistently low in the northern Santa Rosa Mountains during 1983 to 1994

(DeForge et at. 1995). During 1985 to 1998, recruitment in the northern Santa

Rosa Mountains averaged 13 lambs per 100 ewes (Ostermann et at. in press,

Table 2). Periods oflow lamb to ewe ratios, as well as clinical signs of

pneumonia among lambs, have occasionally been observed in Anza-Borrego

Desert State Park (Jorgensen and Turner 1973, Jorgensen and Turner 1975, Hicks

1978), but years ofhigh lamb to ewe ratios (Cunningham 1982, M. Jorgensen,

pers. comm.) and high lamb recruitment to 6 months of age (Rubin et at. 2000)

have been observed in these areas as well. In the San Jacinto Mountains, low fall

lamb to ewe ratios were documented from 1977 to 1983. However, this group

exhibited variable recruitment thereafter, with relatively high (greater than or

equal to 0.50) fall lamb to ewe ratios from 1994 to 1996 (DeForge et at. 1997).

Wehausen (1992) suggested that periods oflow recruitment may not warrant

alarm because long-lived animals such as bighorn sheep can exist in viable

16
Table 1. Lamb survival per ewe group in the Peninsular Ranges during 1993 to

1996 (Rubin et al. 2000, based on observations of radiocollared ewes).

Ewe

Group

Proportion (1.0~l0O percent) of lambs living to 6 months of age

1993 1994 1995 1996 1993 to 1996

(# lambs)

Carrizo

Canyon

0.67 0.78 0.50 0.50 0.68 (31)

San Ysidro

Mountainsnorth and

southa

0.75 0.25 0.57 0.71 0.57 (42)

Deep

Canyon

NA 0.80 0.67 0.75 0.74 (23)

N. Santa

Rosa Mts.

NA 0.43 0.10 0.40 0.26 (23)

adata from the north and south San Ysidro groups were combined because ofsmall

sample sizes in the south San Ysidro Mountains when years were considered separately.

populations if periods oflow offspring recruitment are interrupted by periodic

pulses of high offspring recruitment. Most ewe groups in the Peninsular Ranges

appear to have exhibited such pulses of high recruitment but declining population

trends (see section I.C.3) suggest that they have not been sufficient to balance

adult mortality over longer time periods. Chronically low lamb to ewe ratios

observed in the northern Santa Rosa Mountains ewe group (DeForge et at. 1995,

Ostermann et at. in press) are a particular concern. Signs ofillness have been

observed among lambs in this ewe group (DeForge et at. 1982, DeForge and Scott

1982, DeForge and Ostermann 1998a), and it is possible that low lamb survival is

associated with disease or disease processes complicated by environmental

conditions, such as habitat modification (refer to sections I.B.7 and I.D). This

ewe group has been augmented by captive animals since 1985 (see sections L.C. I

and I.E.3), with similar average recruitment rates (to approximately 1 year ofage)

observed among wild-reared and captive-reared ewes (Ostermann el at. in press,

Table 2). A 5-year study ofradiocollared lambs has been initiated in this

population to determine cause-specific mortality (DeForge and Ostermann

I998b).

17
Table 2. Peninsular bighorn ewe population estimates and recruitment (lamb

survival until December) for captive-reared and wild-reared ewes in the northern

Santa Rosa Mountains (Ostermann et a!. in review~.

Year wild- captive- Total

1985 22 0 22

1986 25 0 25

1987 25 5 30

1988 24 9 33

1989 21 11 32

1990 12 12 24

1991 11 10 21

1992 11 13 24

1993 7 10 17

1994 3 8 11

1995 3 7 10

1996 3 7 10

1997 2 7 9

1998 4 6 10

Mean NA NA NA

Lambs recruited

n (lambs/lOO ewes)

3 (12) NA 3 (12)

0(0) 0(0) 0(0)

2(8) 0(0) 2(6)

0(0) 1(9) 1(3)

0(0) 0(0) 0(0)

0 (0) 1 (10) 1 (5)

1 (9) 1 (8) 2 (8)

1 (14) 0 (0) 1 (6)

1 (33) 2 (25) 3(27)

0(0) 0(0) 0(0)

0 (0) 2 (29) 2 (20)

1 (50) 0 (0) 1 (11)

2 (50) 5 (83) 7 (70)

1 (13.9) 1(13.7) 2(13.3)

Wild-reared Captiv Total

4 (18) NA 4 (18)

No. of ewes greater than or equal

to 2 years ofage

Several studies have documented a positive relationship between winter

precipitation and lamb recruitment in the following year (Douglas and Leslie

1986, Wehausen et at. 1987). However, the relationship between precipitation

and lamb recruitment is not a simple one. Wehausen et at. (1987) found that

periods oflow lamb survival, believed to be a result of a disease epizootic,

coincided with periods ofincreased rainfall. These authors hypothesized that

increased standing water caused populations of Cuticoides midges, a vector of

bluetongue and epizootic hemorrhagic disease viruses (Hoff and Trainer 1981), to

increase. Another hypothesis involving the presence oflivestock as an outside

disease reservoir also was presented (Wehausen et at. 1987). The relationships

between climate, lamb recruitment, and population trends likely differ among

different bighorn sheep populations, and are not fully understood (Rubin et at.

2000).

18
In ruminants, reproductive success is related to the mothers body weight, access to

resources, quality ofhome range, and age (Etchberger and Krausman 1999).

Survival ofoffspring also depends on birth weight and date. Festa-Bianchet and

Jorgenson (1996) found that female sheep reduce the care oflambs when

resources are scarce to favor their own nutritional requirements over their lambs’

development. Excessive disturbance also can disrupt nutritional condition by

affecting optimum feeding-ruminating cycles (Wagner 2000). Ewes that fail to

acquire a minimum level ofenergy reserves (i.e., body weight) may not conceive

(Wehausen 1984) or will produce smaller offspring with a poorer chance of

survival (Price and White 1985).

Ewes in the captive herd at the Bighorn Institute had high lamb production (mean

83.6 percent) and recruitment (mean 71.0 percent) during 1985 to 1998.

Production and recruitment ofindividual ewes in captivity ranged from 0 to 108

percent; twins were produced twice. Between 1985 and 1998, 71 lambs (30

males, 41 females) were born to ewes 2 years ofage or older, resulting in a sex

ratio at birth of0.73:1. Eleven of 71 lambs (15.5 percent) born in captivity and 6

of39 lambs (15.4 percent) captured from the wild died in captivity. Lamb

mortalities were attributed to disease (n=1 1), trauma or peritonitis (n=3), and

undetermined causes (n=3) (Ostermann et at. in press). Lamb survival in the

captive herd during 1999 was the lowest recorded for this population, with only

two ofseven lambs surviving to yearling age. Results from necropsies performed

at the California VeterinaryDiagnostic Laboratory indicated acute bacterial

pneumonia (Pasteuretta spp.) as the cause ofdeath in all five lambs. Previous

studies have implicated severe stress as a factor in pasteurellosis in domestic

ruminants (Frank and Smith 1983, Gilmour and Gilmour 1989), and in bighorn

pneumonia epizootics (Feuerstein et at. 1980, Spraker et at. 1984, Festa-Bianchet

1988). During the 1999 lambing season, captive bighorn were observed fleeing

from the feeding area in response to construction noise from nearby development

projects on multiple occasions. Additionally, helicopters were documented flying

over or adjacent to the enclosures and causing alarm responses (e.g., running

uphill) among captive bighorn on over 20 occasions between January and July

1999 (Bighorn Institute 1999). Stress resulting from human disturbance may have

played a role in predisposing captive lambs to disease.

19
4. SURVIVORSHIIP

In the San Jacinto Mountains, DeForge et at. (1997) monitored the survival of

adult (2 or more years ofage) radiocollared bighorn sheep during 1993 to 1996

and estimated annual adult survival to be 0.75 (1 equals 100 percent). During

1997 and 1998, annual survival in this ewe group was 0.67 and 0.86, respectively

(Bighorn Institute 1997, 1998).

In the northern Santa Rosa Mountains ewe group, adult survivorship was

monitored during a 14-year period (1985 to 1998), and was found to range

between 0.50 and 1.00 annually (Table 3; Ostermann et at. in press). Regression

analysis did not reveal an increasing or decreasing trend in survivorship during the

14 years. In this ewe group, which has been augmented with captive animals

since 1985 (refer to sections I.C.1 and I.E.3), annual survival ofcaptive reared

animals (n equals 73, mean 0.80) was not statistically different from that of wildreared animals (n equals 43, mean 0.81; Ostermann et at. in press).

During November 1992 to May 1998, survivorship of 113 adult radio-collared

bighorn sheep (97 ewes and 16 rams) was monitored between Highway 74 (in the

Santa Rosa Mountains) and the U.S.-Mexico border. During this period, overall

annual adult survival was 0.79 (Table 4), with no significant difference among

three age classes ofadults (Hayes et at. 2000). Survivorship varied across years

(range: 0.72 to 0.91, Hayes et at. 2000), but regression analysis did not reveal a

decreasing or increasing trend in survivorship across years. Annual survivorship

ofindividual ewe groups ranged from 0.70 to 0.87, and a year of high

survivorship in one group was not necessarily a year of high survivorship in other

groups (E. Rubin, pers. comm.).

Survival ofadult bighorn sheep has been considered to be high until 10 years of

age (Hansen 198Gb), or until shortly before the age ofecological longevity

(Cowan and Geist 1971). However, observed values of annual adult survivorship

in the Peninsular bighorn sheep appear low relative to other reported desert

populations: 0.91 or greater in southeastern California (Andrew 1994), 0.86 or

greater in northwest Arizona (when highway mortalities were excluded,

Cunningham and deVos 1992), 0.82 in New Mexico (Logan et at. 1996), and

20
Table 3. Annual survival estimatesa for yearling and adult bighorn sheep in the

northern Santa Rosa Mountains ewe group for calendar years 1985 to 1998

(excluding captive-reared animals; Ostermann et at. in press).

Year Animal Months Survival

(1.0 = 100

percent)

95 percent

Confidence

Interval

1985 305 0.70 0.54-0.86

1986 282 0.88 0.76-1.00

1987 264 0.91 0.80-1.00

1988 234 0.90 0.77-1.00

1989 203 0.78 0.59-1.00

1990 145 0.79 0.57-1.00

1991 105 0.80 0.55-1.00

1992 86 0.88 0.65-1.00

1993 73 0.86 0.60-1.00

1994 45 0.50 0.10-0.90

1995 61 0.83 0.54-1.00

1996 52 0.80 0.45-1.00

1997 42 0.75 0.33-1.00

1998 42 1.00 1.00-1.00

aSu~ival calcujated usingthe Kaplan-Meiermethod modified for a staggered entry design

(Pollock et al. 1989).

0.85 or greater for four offive populations studied in the Mojave desert

(Wehausen 1992). The one exception in the Mojave desert was a small

population in the Granite Mountains, which was documented to have low adult

annual survival (0.72) resulting from predation by mountain lions (Wehausen

1992).

Survival ofBighorn Institute captive raised yearling and adult bighorn (n equals

73, 1985-1998) 12 months after release was 0.61. First year survival for females

(0.64) was higher (p less than 0.005) than for males (0.55). First year survival for

bighorn released as adults (0.75, n equals 12) was higher (p less than 0.01) than

forbighorn released as yearlings (n 61, mean 0.57). After the first year in the

wild, survival for captive-reared sheep improved substantially. Average annual

survival for captive-reared bighorn excluding the first year after release (0.88) was

significantly higher than survival during the first year after release (p less than

21
Table 4. Annual survival of adult bighorn sheep (greater than or equal to 2 years of

age)a, between Highway 74 (in the Santa Rosa Mountains) and the U.S.-Mexico

border, 1992 to 1998 (Hayes et al. 2000).

Year Animal

Months

Annual Survival

(1.0 = 100 percent)

95 percent Confidence

Interval

244 0.91 0.79-1.00

1993-1994 758 0.79 0.70-0.89

1994-1995 808 0.79 0.70-0.88

1995-1996 605 0.72 0.62-0.85

1996-1997 368 0.82 0.70-0.96

1997-1998 384 0.83 0.70-0.96

Total 3167 0.79 0.75-0.84

a Calculated using the program MICROMORT (Heisey and Fuller 1985).

bJune 1 offirst year through May 31 ofsecond year(except 1992, which started in November).

0.01) and survival for wild-reared bighorn during the same time period (p equals

0.05). Mountain lion predation was the primary cause of death for released

bighorn, followed by urbanization (Ostermann et at. in press).

Between 1985 and 1998, survival for yearling and adult bighorn in the captive

population at the Bighorn Institute ranged from 0.89 to 1.0 and averaged 0.98.

The only adult bighorn mortality during this time period was the euthanasia ofa

terminally ill 14-year-old ewe. Three yearlings died in captivity, two from disease

and one during transport for release (Ostermann et at. in press). In 1999, two

adults and a yearling died in captivity: a 15-year-old ram was euthanized after

collapsing from a broken humerus; a 14-year-old ram died from complications

with old age and bronchopneumonia; and a yearling ram died from an extensive

cervical abscess (Bighorn Institute 1999).

5. CAUSES OF MORTALITY

Cause specific mortality in the San Jacinto Mountains was studied from 1992 to

1998. During this period, five mortalities were attributed to mountain lion (Puma

concotor) predation, two were attributed to bobcat or mountain lion predation, and

three died ofunknown causes (DeForge et at. 1997; Bighorn Institute 1997,

1998).

22
In the northern Santa Rosa Mountains, artificially irrigated vegetation attracts

bighorn sheep and creates a hazard. Though commonly thought to be the product

ofreleasing captive-reared animals into the wild, behavioral habituation to urban

sources offood and water began when urbanization started encroaching into

bighorn habitat in the 1950’s, several decades before population augmentation

began in 1985 (Tevis 1959, DeForge and Scott 1982, Ostermann et at. in press, V.

Bleich, pers. comm.). A study of cause-specific mortality conducted from 1991 to

1996 revealed that predation accounted for 28 percent of32 adult bighorn sheep

mortalities (25 percent due to lion predation and 3 percent due to either lion or

bobcat predation) and 34 percent were directly caused by urbanization (DeForge

and Ostermann 1998b). The remainder ofmortalities were due to disease (3

percent) and undetermined causes (34 percent). Ofthe 11 adult mortalities

attributed to urbanization, 5 were due to automobile collisions, 5 were caused by

exotic plant poisoning, and 1 bighorn ram was strangled in a wire fence. An

additional four bighorn sheep were struck but not killed by vehicles. Toxic plants

causing mortality included oleander (Neriurn oleander) and laurel cherry (Prunus

sp.) (Bighorn Institute 1995, 1996). In 1970, a toxic, ornamental nightshade plant

may have caused the death of a young ram in Palm Springs (Weaver and Mensch

1970). Due to an absence of comprehensive studies ofthe toxicity ofnon-native

plants to bighorn sheep, it is unclear how many additional ornamental plant

species represent a risk to bighorn sheep in the Peninsular Ranges. Exposure to

chemicals, such as fertilizers, herbicides, and insecticides used in developed areas,

is also a concern (Turner 1978); however, little is known about the level of

exposure or effects on bighorn sheep. Preliminary results from an ongoing study

ofradiocollared lambs indicate that urbanization is also affecting lamb survival in

this ewe group. Ofthe nine lamb mortalities recorded in 1998 and 1999, five

were attributed to coyote or bobcat predation, one to mountain lion predation, and

three to the direct and indirect effects of urbanization (automobile collision and

drowning in a swimming pool). Dogs also have been observed to chase bighorn

ewes and their lambs near residential areas (E. Rubin, pers. comm.). Eight ofthe

nine deaths occurred within 300 meters (980 feet) ofthe urban interface (Bighorn

Institute 1999).

23
Though mule deer (Odocoiteus hemionus) are the primary prey of mountain lions

in North America (Anderson 1983), and the range ofbighorn sheep in the

Peninsular Ranges largely avoids overlap with mule deer, lion predation threatens

individual ewe groups in the Peninsular Ranges (Hayes et at. 2000) and has the

potential to affect population recovery. From November 1992 to May 1998,

Hayes et at. (2000) found the primary cause ofdeath ofradio-collared adult

bighorn sheep between Highway 74 (in the Santa Rosa Mountains) and the U.S.-

Mexico border was predation by mountain lions. Lion predation accounted for at

least 69 percent ofthe 61 adult mortalities and occurred in each ofthe ewe groups

in this portion ofthe range (Hayes et at. 2000). Annually, lion predation

accounted for 50 to 100 percent ofthe bighorn sheep mortality, and did not

exhibit a decreasing or increasing trend during 1993 to 1997. Lion predation

appeared to show a seasonal pattern, with the majority ofincidents occurring

during the cooler and wetter months of the year. A bighorn sheep’s risk of

predation did not appear to be related to its age. In this study, the remainder of

mortalities were classified as: 16 percent--causes other than predation and 15

percent--undetermined cause.

It is unknown, however, how current levels oflion predation observed throughout

the Peninsular Ranges compare to historic levels. Lions orsign oflion have been

observed in the habitat of Peninsular bighorn sheep since the 1950’s (Jones et at.

1957, Jorgensen and Turner 1973, Gross 1987, Sanchez 1988, Bighorn Institute

1990). However, the literature indicates a lack of agreement on recent mountain

lion population trends in California (Smallwood 1994, Smallwood and Fitzhugh

1995, Torres et al. 1996, Wehausen 1996). Past incidents oflion predation were

documented by Jorgensen and Turner (1975), Gross (1987), and Bighorn Institute

(1998, 1999). Reported incidents of lion predation were not common in the past

and predation was not considered to be a serious risk to bighorn sheep (Weaver

and Mensch 1970, Jorgensen and Turner 1975, Cunningham 1982), but it is

important to note that the increase in the number of radio-collared bighorn sheep

since 1993 has greatly increased the detection ofsuch mortalities. Because ofthe

rough desert terrain and the manner in which lions handle their prey (burying or

caching under dirt or brush), carcasses oflion-killed bighorn sheep are difficult to

find without the aid oftelemetry. However, dead bighorn sheep without radio24
collars have been found opportunistically during early and recent field work, and•

it has been suggested that the proportion ofthese that were killed by lions may

have increased. It is possible that other causes of mortality, for example past

episodes of diseases, have altered the proportion of mortalities attributed to lion

predation.

Past field observations and records in areas far from the Coachella Valley urban

interface documented mortalities resulting from predation (oflambs) by coyotes

(Canis tatrans)(Weaver and Mensch 1970, Jorgensen and Turner 1975, DeForge

and Scott 1982), train collisions (Jorgensen and Turner 1973), automobile

collisions (Turner 1976, Hicks 1978), poaching (Jones et at. 1957, Jorgensen and

Turner 1973, Cunningham 1982), and accidental falls (Turner 1976). Golden

eagles (Aquita chrvsaetos) and bobcats (Lynx rufus) are also potential predators.

6. COMPETITION

In the Peninsular Ranges, bighorn sheep potentially compete for resources with

other native ungulates (mule deer), domestic livestock (cattle), feral animals

(horses), and humans. Bighorn sheep and deerhabitat overlap primarily at the

upper elevations of bighorn habitat, with possible geographic and seasonal

differences in the degree ofoverlap. Jones (1980) summarized reports of possible

competition for food and water between deer and bighorn sheep in other mountain

ranges. Jones et at. (1957) and Weaver et at. (1968)speculated that competition

between the two species may occur but likely was limited in the Peninsular

Ranges. The habitat use patterns ofdeer in the Peninsular Ranges have not been

studied; therefore, levels ofcompetition are not known. Recent observations

suggest that non-native honey bees (Apis meltifera) could affect bighorn sheep use

ofcertain water sources (W. Boyce, pers. comm.).

Numerous reports and observations indicate that cattle grazing can be detrimental

to bighorn sheep populations, either through direct competition for forage or

water, or through vegetation changes in response to cattle grazing (reviewed by

McQuivey 1978 and Jones 1980) and potential disease transmission (e.g.,

DeForge et at. 1982, Clark et at. 1985, Jessup 1981, Jessup 1985, Clark et at.

25
1993, refer to section I.B.7 and I.D), although see Singer et at.(1997).

Historically, large numbers ofcattle were grazed in the Peninsular Ranges (Reed

1986; Appendix A). Numbers were greatly reduced when Anza-Borrego Desert

State Park was established in 1933 and grazing leases on park lands were

terminated in 1970, although cattle have continued to trespass on Park lands from

adjacent allotments. Cunningham and Ohmart (1986) found that dietary overlap

between cattle and Peninsular bighorn sheep in Carrizo Canyon was low (less than

or equal to 18.2 percent) but noted that during their study, the two species used

different vegetation associations. These authors cautioned that competition might

increase if: 1) cattle were introduced to bighorn sheep habitat (with the impact

being most serious at water sources), or 2) drought reduced the availability of

annual plants. In 1989, cattle were observed at a water source used by bighorn

sheep in Carrizo Canyon (Clark et at. 1993), indicating that cattle were using

bighorn sheep habitat in the study site ofCunningham and Ohrnart (1986). Cattle

were also found in bighorn sheep habitat in Coyote Canyon, Rockhouse Canyon,

Hellhole Canyon, and Bow Willow Canyon (M. Jorgensen, pers. comm.). During

1987 to 1989, Anza-Borrego Desert State Park personnel removed 117 cattle from

park land (M. Jorgensen, pers. comm.); however, cattle (both feral orstraying

cattle, and those currently grazed legally on grazing allotments) are still found in

or near bighorn sheep habitat in the Peninsular Ranges, and represent a potential

risk to bighorn sheep.

Domestic sheep present problems similar to cattle with regard to competition;

however, their presence represents an even greater threat due to an increased risk

oftransmitting fatal diseases to bighorn (refer to section I.B.7 and I.D). Domestic

goats also are potentially serious competitors because oftheir ability to maneuver

in rough country and their propensity to overgraze forage. Jones et at. (1957)

found approximately 30 goats in Martinez Canyon in the Santa Rosa Mountains in

1957 and observed that they had heavily used part ofthis canyon. R. Weaver

(California Department ofFish and Game retired, pers. comm.) also observed

goats in this area and at the southern edge ofthe U.S. Peninsular Ranges (south of

Highway 8) in the late 1960’s. Goats persisted in Martinez and Sumac Canyons

(Santa Rosa Mountains) until the early 1980’s (Bighorn Institute 1983, 1984a,

1984b, 1985a, 1985b; V. Bleich, pers. comm.; D. Jessup in tilt. 1999). There are

26
currently no known domestic sheep or goats in the range ofthe Peninsular bighorn

sheep, though transient ram movements, such as along the Sunrise Highway (51

in San Diego County) could encounter sheep or goats in peripheral areas;

reintroduction ofthese species would create a serious risk to Peninsular bighom

sheep.

Many researchers have documented high levels ofcompetition, both for water and

forage, between burros (Equus asinus) and bighorn sheep (e.g., Weaver 1959,

1972, 1973; Mensch 1970; Seegmiller and Ohrnart 1981; Andrew et at. 1997;

Jones 1980). Jones et al. (1957) reported the presence of burros in Martinez

Canyon and speculated that their use of water sources could interfere with bighorn

sheep use. Burros also inhabited Rockhouse Canyon (north) from approximately

the 1930’s to the early 1970’s (M. Jorgensen, pers. comm.). No burros are

currently known to inhabit the Peninsular Ranges, but they could pose a risk for

bighorn sheep if introduced. Feral horses (Equus cabattus) currently inhabit

Coyote Canyon in Anza-Borrego Desert State Park (Auza-Borrego Desert State

Park, unpublished data) and Palm Canyon (San Jacinto Mountains). Competition

between feral horses and bighorn sheep has not been extensively studied, but

increasing horse populations were reported to coincide with decreasing bighorn

sheep populations in the Silver Peak Range in Nevada (McQuivey 1978).

Similarly, during the 3-day waterhole counts at Anza-Borrego Desert State Park in

1999 and 2000, the continuous presence of 16 and 21 wild horses, respectively,

around a traditionally used waterhole coincided with an absence of bighorn

coming to water over both census periods (M. Jorgensen, pers. comm.).

M. Jorgensen has observed that during periods of poorrange forage conditions,

horses congregate around water sources more than usual, causing damage similar

to that ofburros by consuming the best available forage and fouling surface

waters.

Competition with domestic livestock, especially domestic sheep (Brigandi 1995),

has affected bighorn sheep in the past (refer to Appendix A). Cattle were present

in the Peninsular Ranges as early as 1775 (Bolton 1930) and were grazed in large

numbers throughout the range (Turner 1976, Reed 1986, Cunningham and Ohmart

1986). Currently, competition with livestock is low in the Peninsular Ranges

27
because ofpast and current efforts to limit livestock numbers. However,

competition may still occur in localized situations. For example, bighorn use of

Hellhole Canyon has increased measurably since the removal of over two dozen

cattle from the canyon and 117 cattle throughout the park in 1987 (M. Jorgensen,

pers. comm.). In Canebrake Canyon, current Bureau of Land Management

grazing permits allowing cattle to use water sources located below bighorn sheep

lambing areas may be affecting the Carrizo Canyon ewe group. This ewe group

also may be affected by cattle that stray out of a grazing allotment in McCain

Valley. In addition, the potential risk ofdisease transmission exists as long as

livestock occur in bighorn sheep habitat.

7. DISEASE AND PARASITISM

It has been hypothesized that disease has played an important role in population

dynamics of bighorn sheep in the Peninsular Ranges (DeForge et at. 1982,

DeForge and Scott 1982, Turner and Payson 1982, Wehausen et at. 1987).

Numerous pathogens have been isolated or detected by serologic assay from

bighorn sheep in these ranges. These pathogens include bluetongue virus,

contagious ecthyma virus, parainfluenza-3 virus, bovine respiratory syncytial

virus, Anaptasma, Chtamvdia, Leptospira, Pasz’euretta, Psoroptes, and

Dermacentor (DeForge et at., 1982; Clark et at. 1985, 1993; Mazet et at. 1992;

Elliott et at. 1994; Boyce 1995; Crosbie et at., 1997, DeForge et at. 1997).

DeForge et at. (1982) found multiple pathogens (contagious ecthyma virus, blue

tongue, Pasteuretta, and parainfluenza virus) and low lamb recruitment in

association with overall population declines. Between 1982 and 1998, 39 lambs

showing signs ofillness (lethargy, droopy ears, nasal discharge, and lung

consolidation) were collected from the Santa Rosa (northern and southern),

Jacumba, and In-Ko-Pah Mountains for disease research and rehabilitation at the

Bighorn Institute (Ostermann et at. in press). Additionally, DeForge et at. (1995)

documented a population decline throughout the Santa Rosa Mountains during

1983 to 1994, resulting from inadequate recruitment. Although a cause and effect

relationship between disease and population decline has not been clearly

established in the Peninsular Ranges, results from several studies provide support

28
for this hypothesis (DeForge et at. 1982, Clark et at. 1985, Wehausen et at. 1987,

Clark et at. 1993, Elliot et at. 1994, DeForge et at. 1995). The presence offeral

goats in portions ofthe Santa Rosa Mountains until the late 1970’s to early 1980’s

may have contributed to exposure ofwild bighorn to disease during this period of

population decline (D. Jessup, in th~t. 1999).

Analysis ofspatial variation in pathogen exposure among bighorn sheep sampled

between 1978 to 1990 showed that Peninsular bighorn sheep populations and

other populations in southern California have higher levels ofpathogen exposure

than other populations ofbighorn sheep in the State (Elliott et al. 1994).

However, serological tests have revealed the presence of antibodies to several

infectious disease agents in both healthy and clinically-ill animals (Clark et at.

1993, Elliott et at. 1994; Boyce 1995, DeForge et at. 1997), and essentially all of

the viruses, bacteria, and parasites that have been reported from Peninsular

bighorn sheep appear to be widespread among desert bighorn sheep in the western

U. S. (Jessup et at. 1990). All evidence indicates that the influence of disease in

the Peninsular Ranges has subsided in more recent years. For example, recent

sampling and examination ofbighorn sheep throughout the range indicate that

most animals were clinically normal (Boyce 1995; DeForge et at. 1997; Bighorn

Institute 1997, 1998, 1999). Several caveats should be kept in mind when

interpreting serologic test results ofwild animals (Gardner et at. 1996). An

animal testing positive for a specific pathogen: 1) may or may not be showing

clinical signs ofthe infection and may never have been adversely affected by the

infection, 2) may no longer harbor the pathogen, 3) may or may not be resistant to

subsequent re-infection, or 4) may have been exposed to a related pathogen that

induced the formation of cross-reactive antibodies. On the other hand, an animal

testing negative: 1) may never have been exposed to the pathogen, 2) may be

recently infected by the pathogen under scrutiny but not yet producing antibodies,

or 3) may have been exposed to the pathogen and developed an antibody titer that

has subsequently abated. Detection ofpathogens does not, in itself, imply a causal

relationship between disease and population declines. Additional research is

necessary to better understand this relationship. Furthermore, it appears that risk

ofdisease and parasites might differ among ewe groups based on their exposure

29
and their habitat use patterns, so future research should address these questions at

the level ofthe ewe group and the level ofthe population.

The reduced influence ofdisease on Peninsular bighorn sheep (asthey

simultaneously continue to decline) suggests that other factors, such as predation,

habitat loss/modification, and human related disturbance currently limit the

population. Nonetheless, disease and/or parasites may still threaten bighorn sheep

in the northern Santa Rosa Mountains. Bighorn sheep in this group have

exhibited low lamb recruitment (refer to section I.B.3), and clinical signs of

illness have been observed among adults and lambs (DeForge and Scott 1982;

Bighorn Institute 1997; DeForge and Ostermann 1998a; E. Rubin, pers. comm.).

In addition, during 1991 to 1998, internal parasites (trichostrongyles) were

detected in this ewe group (DeForge and Ostermann 1998b; E. Rubin and W.

Boyce, pers. comm.), while similar sampling failed to detect these parasites in

bighorn sheep from the remainder ofthe range (DeForge ei’ at. 1997; Bighorn

Institute 1998; E. Rubin and W. Boyce, pers. comm.). Habitat modification and

altered habitat use patterns may increase the risk ofdisease and parasites in this

group by increasing parasite survival or transmission rates in irrigated landscapes

(Bighorn Institute 1997, DeForge and Ostermann 1998b). It has been suggested,

for instance, that the density ofRocky Mountain bighorn sheep is important in the

transmission oflungworms (Protostrongytus) in mesic areas where the snail

intermediate hosts are sufficiently common (Uhazy and Holmes 1973). The

different ewe groups in the Peninsular Ranges apparently have different pathogen

exposure profiles and risks.

C. ABUNDANCE AND DISTRIBUTION

1. HISTORIC ABUNDANCE AND DISTRIBUTION

Bighorn sheep have been documented in the Peninsular Ranges since early

explorers such as Auza observed them in the 1700’s (Bolton 1930); however,

rangewide population estimates were not made until the I 970’s. Published

estimates were as high as 971 in 1972 (Weaver 1972), and 1,171 in 1974 (Weaver

1975), while more recent estimates were 570 in 1988 (Weaver 1989), 400 in 1992

(U.S. Fish and Wildlife Service 1992), and between 327 to 524 in 1993 (Torres et

at. 1994). Accuracy ofthe estimates in the early 1970’s (pre-helicopter surveys),

30
especially in the San Jacinto Mountains, has been questioned by several

authorities (Wehausen 1999; V. Bleich, pers. comm.) (see section I.C.3 below for

more details).

An examination of past records and current data suggests that the distribution of

bighorn sheep has been altered during the past 25 years. No new ewe groups have

been documented to form, but ewe groups along the Mexican border and in the

northern San Jacinto Mountains (north ofChino Canyon) have disappeared since

the 1980’s. Loss ofthe border population was poorly documented but the

construction ofInterstate 8 in the mid-1960’s, railroad activity, livestock grazing,

poaching, and fire suppression appear to be likely contributing causes (Rubin et

at. 1998). DeForge et at. (1997) suggested that disturbance and habitat

fragmentation were the principal causes ofchanges in distribution in the northern

San Jacinto Mountains. In the northern Santa Rosa Mountains, the number and

distribution ofewes is substantially reduced from the 1980’s, with formerly

important use areas, such as Carrizo and Dead Indian Canyons, currently

supporting few animals (J. D. Goodman, University ofRedlands, unpublished

data 1963; DeForge and Scott 1982; DeForge et at. 1995; Bighorn Institute 1998,

1999). The Fish Creek Mountains and areas to the west ofthe Vallecito

Mountains (the Sawtooth Range, Oriflamme Mountains, and the lower elevations

ofthe Laguna Mountains) are believed to have supported “transient” use by sheep

in the past (Weaver et at. 1968, Weaver 1972).

The distribution of ewes has become more fragmented in the recent past, although

evidence is not available to suggest that ram use has been curtailed. At the

southern distributional limits ofthe U.S. population, the construction ofInterstate

8 preceded the later disappearance ofbighorn sheep along the Mexican border,

though rams still continue to be found occasionally (Jessup, in titt. 2000). At the

extreme northern end oftheir range, ewe group occupation ceased in the northern

San Jacinto Mountains about 20 years after construction ofthe Palm Springs

Aerial Tramway in Chino Canyon, though rams still cross Chino Canyon and

make use ofmuch ofthe area formerly occupied by the ewe group. Rubin et at.

(1998) suggested that in portions ofthe range, roads or increased traffic have

contributed to fragmentation by restricting ewe movement, as evidenced by the

distributional limits of four ewe groups currently coinciding with roadways. In

the 1970’s, ewes were observed to cross Highway 74 in the Santa Rosa Mountains

31
(V. Bleich, pers. comm.; D. Jessup, in titt. 1999) and sheep were struck by cars

“where ancestral bighorn trails are bisected by the highway” (Turner 1976).

Though a radio-collared ewe crossed Highway 74 in 1982 (DeForge and Scott

1982), no radio-collared ewes were observed to cross this road from 1993 to the

present. California Department ofTransportation records indicate that traffic on

this road has approximately tripled since 1970. Since 1991, at least five rams

have been struck by cars while crossing Highway 74; two were killed (Bighorn

Institute 1991, 1999). In addition, a significant reduction in bighorn use in

portions ofthe Santa Rosa Mountains has been observed since the construction of

the Dunn Road (DeForge in litt. 1997).

2. RECENT ABUNDANCE AND DISTRIBUTION

Recent abundance estimates ofPeninsular bighorn sheep north ofthe U.S.-Mexico

border were 347, 276, and 334 animals (excluding lambs) in 1994, 1996, and

1998, respectively (Table 5). Currently, at least eight subpopulations (ewe

groups) exist in the range (Rubin et at. 1998) (Figure 3, Table 6). It is possible

that the Santa Rosa Mountains southeast ofHighway 74 and the Vallecito

Mountains are each inhabited by more than one ewe group, but additional data are

required to confirm this. During 1994 to 1998, the largest ewe groups in the

Peninsular Ranges typically consisted ofless than 30 ewes, while some groups

had less than 15 ewes (DeForge et at. 1997; Rubin et at. 1998, 1999; Ostermann

et at. in press) (Table 6). The San Jacinto ewe group currently consists ofsix

known ewes (Bighorn Institute 1999). Although permanent emigration of ewes

between groups has not been observed, a limited number oftemporary moves

between some groups were documented in recent years (Bighorn Institute 1998,

1999; Rubin et at. 1998), and genetic evidence indicates ewe movement in the

past (Boyce et at. 1997). Ram movements between ewe groups are more frequent

(DeForge et at. 1997, Rubin et at. 1998, refer to section I.B.2). These

observational data are supported by genetic analyses (Boyce et at. 1997, Boyce et

at. 1999, refer to section I.A.3). The existence of distinct ewe groups that are

connected by limited movement of bighorn sheep suggests that Peninsular bighorn

sheep comprise a metapopulation (Levins 1970, Torres et at. 1994, Bleich et at.

1996, Boyce et at. 1997). Bighorn sheep exhibit a patchy distribution as a result

of natural breaks in mountainous habitat (Schwartz et at. 1986; Bleich et at.

1 990a, 1996), and genetic analyses support the hypothesis that discrete ewe

32
Figure 3. Distribution of bighorn ewes in the Peninsular Ranges, California, 1992-1995. Stippled and

shaded areas indicate regions used by home-range groups of ewes identified in this study. 1-Carrizo

Canyon, 2a-south Vallecito Mountains, 2b-north Vallecito Mountains, 3-south San Ysidro Mountains,

4-north San Ysidro Mountains, 5-Coyote Canyon, 6a-Santa Rosa Mountains east of Highway 74

(south), 6b-Santa Rosa Mountains east of Highway 74 (Martinez Canyon), 6c-Santa Rosa Mountains

east of Highway 74 (Deep Canyon), 7-Santa Rosa Mountains west of Highway 74, 8-San Jacinto.

Mountains (U indicates general location of this group, DeForge et aI. 1997). Wide hatch marks

indicate possible connectivity between ewe groups in the Vallecito Mountains and in the Santa Rosa

Mountains. (Reprinted with permission from Rubin et al. 1998).

33

0 10 20 Kilometers Jacumua

Mtns

United StateS~Mexico border
groups existed in the past (Boyce et at. 1999). However, it appears that some

separations between groups are of anthropogenic origin and movement of ewes

has been reduced by human activity (DeForge et at. 1997, Rubin ei at. 1998, refer

to section L.C.2).

Two captive populations ofPeninsular bighorn sheep currently exist. The Living

Desert Museum, an educational and zoo facility in Palm Desert, California,

maintains a small group (seven adult females and two adult males) at its facility.

These animals are used primarily for educational purposes (Terrie Correll, The

Living Desert, pers. comm.). The Bighorn Institute, also in Palm Desert,

maintains a small captive herd of approximately 30 animals. This private,

nonprofit organization, established in 1982 under the authorization ofthe

California Department of Fish and Game with a Memorandum ofUnderstanding,

Table 5. Abundance estimates (and 95 percent confidence intervals) of bighorn

sheep in the Peninsular Ranges north ofthe U.S.-Mexico border during 1994, 1996,

and 1998. Estimates exclude lambs (DeForge et al. 1995; Bighorn Institute 1996,

1998).

Region 1994 1996 1998 Source(s)

Anza-Borrego

Desert State Park

(including all

habitat outside of

Santa Rosa and San

Jacinto Mountains)

214.0

(149.8 to

278.6)

163.0

(131.8 to 194.2)

180.7

(149.5 to

211.9)

Rubin et at.

1998, 1999

Santa Rosa

Mountains

115.5

(91.5 to 139.5)

93.8

(71.8 to 115.8)

129.0

(91.1 to 166.9)

DeForge et at.

1995, Bighorn

Institute 1996,

1998

San Jacinto

Mountainsa

17 (NA) 19 (NA) 24 (NA) DeForge et at.

1997, Bighorn

Institute 1998

Total 347

(253 to 458)

276

(210 to 439)

334

(262 to 434)

aMinimum number known to be alive, based on absolute counts (intensive field studies of radiocollared animals in combination with annual helicopter surveys). Confidence intervals

unavailable.

34
conducts research and maintains a breeding herd at its facility (refer to section

J.E.3). Since 1985, 77 animals from this herd have been released into the wild.

Ewe groups in the San Jacinto and northern Santa Rosa Mountains have been

augmented with captive-reared sheep (n equals 3 in 1997 and 74 during 1985-

1998, respectively) (Ostermann et at. in press).

3. POPULATION TRENDS

Although based on different techniques, a comparison of early (pre-1977) and

current population estimates suggests a great decline in Peninsular bighorn sheep

numbers. Early estimates were based on waterhole counts or foot surveys,

whereas helicoptersurveys were used to generate population estimates starting in

Table 6. Ewe abundance estimates (and 95 percent confidence intervals) per ewe

group generated from helicopter surveys during 1994, 1996, and 1998 (Rubin etal.

1998, 1999; DeForge et al. 1997; DeForge et al. 1995; Bighorn Institute 1996, 1998).

Current ewe group

delineation

Year

1994

Year

1996

Year

1998

I. Carrizo Canyon 39.0

(20.9-57.2)

23.5

(17.7-29.3)

19.0

(19.0-19.0)

2. Vallecito Mountains 17.7

(6.7-28.6)

19.0

(19.0-19.0)

30.2

(24.3-36.1)

3. South SanYsidro

Mountains

15.3

(9.9-20.6)

12.3

(6.9-17.8)

23.0

(8.3-37.7)

4. North San Ysidro

Mountains

32.0

(9.5-54.5)

22.1

(16.2-28.1)

15.3

(6.2-24.5)

5. Coyote Canyon 21.8

(15.4-28.2)

23.0

(5.5-40.5)

22.8

(17.5-28.0)

6. Santa Rosa

Mountains

east of Hwy. 74

66.2

(42.4-90.0)

83.0

(27.3-138.7)

48.3

(31.6-65.0)

7. SantaRosaMts.

west ofHwy. 74

15.9

(13.5-18.3)

14

(14.0-14.0)

11.6

(9.7-13.5)

8. San Jacinto

Mountainsa

(

(na)

(

(na)

(

(na)

~Minimumnumber known to be alive, based on absolute population counts (intensive field studies

ofradiocollared animals in combination with annual helicopter surveys). Confidence intervals are

unavailable.

35
1977. Annual helicopter surveys conducted in the Santa Rosa Mountains since

1977 indicate a regional population decline (DeForge et at. 1995, Wehausen et at.

1987), with a 69 percent decline observed between 1984 and 1994 (DeForge et at.

1995). Rubin et at. (1998) examined trends in abundance outside ofthe Santa

Rosa Mountains with the use of a 26-year dataset of annual waterhole count

observations in Auza-Borrego Desert State Park. These data indicated that

declines had occurred in some, but not all, ewe groups. This result suggests that

abundance trends are independent among ewe groups, and is in agreement with

field data that show independent differences in lamb recruitment and adult

survival among ewe groups (Rubin et at. 2000., Hayes et at. 2000, refer to

sections I.B.3 and I.B.4). Climatic patterns are highly correlated across the

Peninsular Ranges, suggesting that other local factors specific to ewe groups play

important roles in determining long-term abundance trends (Rubin et at. 1998).

Independent population trends also were observed among ewe groups in the

Mojave Desert (Wehausen 1992).

DeForge et at. (1997) found that bighorn sheep in the San Jacinto Mountains

declined between 1984 and 1987. Since that time the subpopulation inhabiting

these mountains has been stable but precariously small (Table 7). In the Santa

Rosa Mountains, mark-recapture estimates generated from helicopter survey data

indicated that bighorn sheep numbers appeared to remain stable at low numbers

from 1990 to 1995, following a large population decline (DeForge et at. 1995). In

the northern part ofthese mountains, the current number of animals is

approximately 50 percent ofthe number present during the 1980’s (Table 8).

Helicopter surveys south ofthe Santa Rosa Mountains, encompassing all

Peninsular bighorn sheep habitat outside ofthe Santa Rosa and San Jacinto

Mountains, indicated a 28 percent decline in ewe numbers in a recent 2-year

period (from an estimate of 141 females in 1994 to 102 females in 1996; Rubin et

at. 1998), and a statistically non-significant increase (from approximately 102 to

112 females) from 1996 to 1998 (Rubin et at. 1999).

Though cause and effect relationships for these population declines among ewe

groups have not been documented, likely contributing factors are: high predation

rates; disease; and cumulative effects of habitat loss, modification, fragmentation

and human-related disturbance.

36
a

Table 7. Ewe population estimates for the San Jacinto Mountains from 1993 to

1999 (DeForge et al. 1997; Bighorn Institute 1997, 1998, 1999).

Year Number of ewes

(yearlings and adults)

1993 10

1994 7

1995 8

1996 7

1997 9

1998 8

1999 6

a

Table 8. Fall population estimates of adult (1 year or older) bighorn sheep in the

northern Santa Rosa Mountains from 1985 to 1998 (Ostermann etal. in press).

Fall population Number of captiveestimate of reared bighorn in

yearling and adult the population

Year bighorn (ewes)

1985 40(22) 1

1986 46(25) 5

1987 52(30) 16

1988 52(33) 19

1989 50(32) 20

1990 41(24) 26

1991 30(21) 17

1992 35 (24) 20

1993 27(17) 16

1994 23(11) 16

1995 24(10) 16

1996 21(10) 16

1997 22(11) 16

1998 22(10) 15

a minimum number known to be alive, based on absolute population count.

37
D. REASONS FOR LISTING

The following discussion is organized according to the listing criteria under

section 4(a)(1) ofthe Endangered Species Act.

I. THE PRESENT OR THREATENED DESTRUCTION, MODIIFICATION,

OR CURTAILMENT OF THEIR HABITAT OR RANGE

Habitat loss is a leading cause ofcurrentspecies extinctions and endangerment

(Burgman et at. 1993). It represents a particularly serious threat to Peninsular

bighorn sheep because they live in a narrow band oflower elevation habitat that

represents some ofthe most desirable real estate in the California desert and is

being developed at a rapid pace. At least 7,490 hectares (18,500 acres or about 30

square miles) ofsuitable habitat has been lost to urbanization and agriculture

within the range ofthe three ewe groups that occur along the urban interface

between Palm Springs and La Quinta (see the maps referenced in Appendix B).

Within the narrow band ofhabitat, bighorn sheep need to be able to move daily,

seasonally, and annually to make use ofsparse and sometimes sporadically

available resources found within their home ranges. As humans encroach into this

habitat, these resources are eliminated or reduced in value, and the survival of ewe

groups is threatened. Bighorn sheep are also sensitive to habitat loss or

modification because they are poor dispersers (Geist 1967, 1971), largely learning

their ranging patterns from older animals rather than on their own (refer to section

I.B.2). When habitat is lost or modified, the affected group is likely to remain

within their familiarsurroundings but with reduced likelihood of population

persistence, due to reduced quantity and/or quality ofresources. Habitat

fragmentation is amajor threat to bighorn sheep (Schwartz et at. 1986, Bleich et

at. 1996) and Peninsular bighorn sheep are particularly vulnerable because ofthe

narrow elevational band ofsuitable habitat, behavior (use oflow elevation habitat

and ewe home range fidelity), and population structure. Fragmentation poses a

particularly severe threat to species with a metapopulation structure because

overall survival depends on interaction among subpopulations. Encroaching

urban development and anthropogenic disturbances have the dual effect of

restricting animals to a smaller area and severing connections between ewe

groups. Movements by rams through downtown Palm Springs (Tevis 1959,

Desert Sun, 9/12/1995, DeForge et at. 1997) may provide insight into past bighorn

38
movement patterns. Former long-distance movements across the valley floor to

the north and east ofthe Coachella Valley, though never documented, likely

occurred as they currently still do between other mountain ranges in the desert

southwest (Bleich et at. 1996; J. Wehausen, pers. comm.). The potential for such

movements now has been eliminated by high density urban development, major

freeways, fences, agriculture, and canals. The movement oframs and occasional

ewes between ewe groups maintains genetic diversity and augments populations

ofindividual ewe groups (Soul~ 1980, Krausman and Leopold 1986, Schwartz et

at. 1986, Burgman et at. 1993, refer to section II.A.2). The occasional movement

of ewes can result in a “rescue effect” (Brown and Kodric-Brown 1977) by

increasing the number ofewes in a declining ewe group. Temporary moves by

females between neighboring ewe groups could also provide new habitat

knowledge that facilitates future range expansion (Geist 1971). Increased

fragmentation reduces such possibilities.

Beyond physical barriers to movement, fragmentation also can result from less

obvious forms ofhabitat modification. As described above in section I.C.2,

increased traffic on roads apparently make bighorn sheep, especially ewes,

hesitant to cross these roads (Rubin et at. 1998). Animals that do cross suffer an

additional risk ofmortality (Turner 1976, McQuivey 1978, Cunningham and

deVos 1992, DeForge and Ostermann 1 998b, Bighorn Institute 1999), with the

result that a group whose range is bisected by the road can have reduced viability

in the long term (Cunningham and deVos 1992). Human disturbance along roads

and trails can cause sheep to avoid those areas (Papouchis et at. 1999), potentially

affecting bighorn sheep movement and habitat use (refer to section I.B.2), thereby

“fragmenting” bighorn sheep distribution although the habitat appears to be intact.

Development and human populations along the eastern slope ofthe Peninsular

Ranges continue to grow at a rapid pace at the lower and upper elevational

boundaries of Peninsular bighorn sheep habitat. The Coachella Valley

Association ofGovernments anticipates that by the year 2010, the human

population there will increase from 227,000 to over 497,000, not including

165,000 to 200,000 seasonal residents. Bighorn population declines typically have

been most pronounced in ewe groups adjoining the urban interface in Coachella

Valley. The decline in local bighorn populations in the San Jacinto and northern

Santa Rosa Mountains parallels the demise ofsheep populations near

39
Albuquerque and Tucson (Krausman et at. in prep.), other majormetropolitan

areas that have encroached into sheep habitat in the desert southwest. Other

cumulative factors caused by human activities within bighorn sheep habitat are

discussed in detail below (refer to section I.D.5).

2. OVERUTILIZATION FOR COMMERCIAL, RECREATIONAL,

SCIENTIFIC, OR EDUCATIONAL PURPOSES

There is no regulated hunting season for Peninsular bighorn sheep in the United

States, and poaching is rarely documented. Precautionsshould continue to be

taken, however, to prevent poaching. The Bighorn Institute and Living Desert

Museum each maintain a captive population of Peninsular bighorn sheep for

scientific and educational purposes. This use is thought to have no negative

impact on free-ranging bighorn sheep. Researchers are required to obtain State

and Federal permits before handling Peninsular bighorn sheep. Although current

research techniques are not believed to have a negative impact on bighorn sheep,

how research is carried out must always be a consideration (Bleich et at. 1994, see

Appendix D).

3. DISEASE AND PREDATION

The westward spread ofEuropeans and their domestic livestock across North

America was thought to play a significant role in reducing the distribution and

abundance ofbighorn sheep due to the introduction ofnew infectious diseases

(Spraker 1977, Onderka and Wishart 1984). In particular, domestic sheep have

been repeatedly implicated in Pasteuretta pneumonia die-offs ofbighorn sheep.

In the Peninsular Ranges, a number ofpathogens have been isolated or detected

by serological assay from bighorn sheep (refer to section I.B.7). In the Santa Rosa

Mountains, many years ofhigh lamb mortality from an apparent disease epizootic

contributed to a population decline from inadequate recruitment (DeForge and

Scott 1982, Wehausen et at. 1987, DeForge et at. 1995). Although diseases do

not currently appear to be limiting population growth throughout the range, they

pose a potential threat that could occur at any time, especially if disease episodes

can be precipitated by chronic levels of disturbance (Geist 1971, Hamilton et at.

1982, Spraker et at. 1984, King and Workman 1986, Festa-Bianchet 1988, Desert

Bighorn Council 1992).

40
Mountain lion predation is an apparent limiting factor forsome ewe groups in the

Peninsular Ranges; 69 percent of61 mortalities ofradiocollared sheep from 1992

to 1998 between Highway 74 in the Santa Rosa Mountains and Mexican border

are attributed to mountain lions (Hayes et at. 2000). The relatively low

survivorship ofadults (section I.B.4) and associated population declines have

recently affected the recovery of most ewe groups.

4. THE INADEQUACY OF EXISTING REGULATORY MECHANISMS

In 1971, the Peninsular bighorn sheep was listed under California State law as a

rare species. The designation was changed to “threatened” in 1984 to standardize

terminology ofthe amended California Endangered Species Act. The Peninsular

bighorn sheep also is listed by the State as a “fully protected species” under the

Fish and Game Code (Section 4700). The California Environmental Quality Act,

which allows public comment and generally requires mitigation for significant

environmental effects, including adverse impacts to State and federally listed

species, has not resulted in conservation benefits sufficient to maintain stable

populations.

The Bureau ofLand Management and California Department of Fish and Game

jointly developed the Santa Rosa Mountains Habitat Management Plan in 1980

and McCain Valley Habitat Management Plan in 1984 to address the needs, as

identified at that time, ofbighorn sheep in these areas. The Department ofFish

and Game also established the Carrizo Canyon and Magnesia Spring Ecological

Reserves to protect important watering sites. The effectiveness ofthese

management areas in the Santa Rosa Mountains has been limited because of

heavy human use, lack of management presence, and limited funding. The lack of

funds also has prevented acquisition of all private lands within the protected areas,

resulting in continued fragmentation by development. The existence of private

inholdings within the boundaries of Anza-Borrego Desert State Park is also a

potential threat to Peninsular bighorn sheep because these lands include prime

bighorn sheep habitat, but a lack offunding and/or unwilling sellers have

prevented public acquisition to date.

In California, it is Bureau of Land Management policy to conserve State-listed

plants and animals and to use its authorities in furtherance ofthe purposes ofthe

41
State ofCalifornia’s rare and endangered species laws. The Bureau ofLand

Management and California Department of Fish and Game have developed

conference procedures to promote cooperation in the application ofthis policy,

although they are inconsistently implemented. Neither State listing nor the

proposed Federal listing of bighorn sheep prompted land management agencies to

effectively address adverse effects associated with land exchanges, recreational

and commercial uses, and livestock grazing programs. Although domestic sheep

on Federal lands in the Peninsular Ranges are not a current threat, adverse effects

from cattle grazing (including resource competition, degradation of water sources,

and disease transmission) require resolution.

A number of development projects with potentially significant adverse effects on

bighorn sheep recently have been approved because project proposals and local

General Plans formost of the cities in the Coachella Valley inadequately address

threatsto the long-term conservation of Peninsular bighorn sheep. Though some

habitat protection is derived from the presence of the State and federally listed

least Bell’s vireo ( Vireo bettii pusittus) and southwestern willow flycatcher

(Empidonax traitiji extimus), benefits are limited due to the specialized habitats

(riparian woodland) used by these birds. Section 404 ofthe Clean Water Act

provides protection through the U. S. Army Corps of Engineers’ regulation ofthe

discharge ofdredged and fill material into certain waters and wetlands ofthe

United States, but Corps’ jurisdiction can be avoided under various situations.

5. OTHER NATURAL OR MANMADE FACTORS AFFECTING THEIR

CONTINUED EXISTENCE

Drought: Prolonged drought is a natural factor that can have negative impacts on

desert bighorn sheep populations, either by limiting watersources or by affecting

forage quality (Rosenzweig 1968, Hansen 1980a, Monson 1980, Douglas and

Leslie 1986, Wehausen et at. 1987, refer to section I.B.1). During drought years,

the concentration ofbighorn sheep near remaining water sources may increase

competition for forage as well as water, thereby limiting population growth

through density dependent regulation (Caughley 1977, Gotelli 1995). In addition,

increased density potentially renders animals more susceptible to diseases or

parasites (Anderson and May 1979, May and Anderson 1979).

42
Human Disturbance: Human development affects sheep through habitat loss,

fragmentation, or other modification (refer to section I.D. 1 .1), but these impacts

also extend into bighorn sheep habitat beyond the urban edge. Though a growing

human population and increased activity adjacent to and within bighorn sheep

habitat have potential to adversely affect bighorn sheep, accurate mapping oftrail

locations and quantitative monitoring of recreational trail use have not been

conducted. In addition, incremental proliferation oftrails has gone largely

unaddressed.

Numerous researchers have expressed concern over the impact of human activity

on Peninsular bighorn sheep (e.g., Jorgensen and Turner 1973, Hicks 1978, Olech

1979, Cunningham 1982, DeForge and Scott 1982, Gross 1987, Sanchez et at.

1988), as well as on sheep in other areas (Graham 1980, Gionfriddo and

Krausman 1986, Smith and Krausman 1988). Leopold (1933) considered bighorn

sheep a wilderness animal because they fail to thrive in contact with urban

development. A variety ofhuman activities such as hiking, mountain biking, hang

gliding, horseback riding, camping, hunting, livestock grazing, dog walking, and

use of aircraft and off-road-vehicles have the potential to disrupt normal bighorn

sheep social behaviors and use of essential resources, or cause bighorn sheep to

abandon traditional habitat (McQuivey 1978, MacArthur et at. 1979, Olech 1979,

Wehausen 1979, Leslie and Douglas 1980, Graham 1980, MacArthur et at. 1982,

Bates and Workman 1983, Wehausen 1983, Miller and Smith 1985, Krausman

and Leopold 1986, Krausman et at. 1989, Goodson 1999, Papouchis et at. 1999).

Attempts to ascribe relative importance, distinguish among, or generalize the

effects of different human activities on sheep behavior are not supportable, given

the range ofpotential reactions reported in the literature and the different variables

impinging on given situations.

Although cases have been cited in which bighorn sheep populations did not

appear to be affected by human activity (e.g., Hicks and Elder 1979, Hamilton et

at. 1982), numerous researchers, including these authors, have documented altered

bighorn sheep behavior in response to anthropogenic disturbance. Even when

bighorn sheep appear to be tolerant of a particular activity, continued and frequent

use can cause them to avoid an area, eventually interfering with use ofresources,

such as water, mineral licks, lambing or feeding areas, or use oftraditional

movement routes (Jorgensen and Turner 1973, McQuivey 1978, Graham 1980,

43
Leslie and Douglas 1980, DeForge and Scott 1982, Hamilton et’ at. 1982,

Krausman and Leopold 1986, Rubin ei’ at. 1998). In addition, disturbance can

result in physiological responses such as elevated heart rate (MacArthur et at.

1979, 1982), even when no behavioral response is discernable. It was repeatedly

cautioned that human disturbance threatened the viability ofa bighorn sheep

population in the Santa Catalina Mountains, outside of Tucson, Arizona

(Etchberger et at. 1989, Krausman et at. 1989, Krausman 1993, Krausman et at.

1995). In these mountains, Etchberger ei’ at. (1989) found that habitat abandoned

by bighorn sheep had greater human disturbance than occupied habitat. Today,

this population is extinct, or nearly so, and human activities apparently

contributed to its demise (Schoenecker 1997; Krausman et at. in prep.;

P. Krausman, pers. comm.).

A high level ofhuman activity occurs in the habitat ofPeninsular bighorn sheep.

For example, during a recent 10-hour period in spring, 49 hikers, 2 mountain

bikers, and 13 dogs (9 unleashed) were counted in Carrizo Canyon in the northern

Santa Rosa Mountains (Bureau of Land Management, unpublished data). This

trail bisects a lambing area that has received reduced levels ofsheep use in recent

years. A ewe and her lamb were observed to wait for over S hoursto come to

water because ofcontinuous off-road vehicle traffic (Jorgensen and Turner 1973).

Jorgensen (1974) reported that bighorn sheep use ofimportant waterholes was 50

percent lower on days with off-road vehicle traffic. In Carrizo Canyon, Hicks

(1978) observed a group ofbighorn sheep flee from a spring area when a Navy

helicopter passed overhead, Olech (1979) noted that bighorn sheep did not use

waterholes when motorcycles were heard nearby, and Cunningham (1982)

speculated that the use ofsprings by humans (recreationists and persons entering

California across the U. S.-Mexico border) reduced use ofthis resource by

bighorn sheep. Sanchez ei’ at. (1988) recommended that future management

efforts should attempt to reduce human impacts on bighorn sheep in Carrizo

Canyon. As the human population ofthe southern California desert grows, such

human activity in bighorn sheep habitat will increase.

Bighorn sheep responses to human activity are difficult to predict (Miller and

Smith 1985) and depend on type of activity, season ofthe activity, elevation ofthe

activity relative to resources (Hicks 1978, Graham 1980), and distance ofthe

activity from resources critical to bighorn sheep (Miller and Smith 1985), among

44
other variables. For instance, ewes with lambs typically are more sensitive to

disturbance (Light and Weaver 1973, Wehausen 1980), as are animals that are

approached from higher elevations (Hicks 1977, Graham 1980). Papouchis et at.

(1999) found bighorn sheep to be more sensitive to disturbance during spring and

fall, corresponding with the lambing and rutting seasons. Etchberger and

Krausman (1999) observed the abandonment of lambing habitat while

construction activities were ongoing.

Livestock Grazing and Water Diversion: Human actions also indirectly affect

use ofresources by bighorn sheep. Domestic livestock and feral animals can

reduce the availability and quality ofresources (water and forage) required by

bighorn sheep (refer to section I.B.6), and can function as potential vectors for

diseases such as bluetongue virus. In portions ofthe range, water has been

pumped from aquifers and diverted away from springs for use by ranches and

private residences, reducing and eliminating the water sources upon which

bighorn sheep depend (Tevis 1961; Blong 1967; Turner 1976; M. Jorgensen, pers.

comm.).

Non-native Plants: In the Peninsular Ranges, the presence of tamarisk (Tamarix

sp.), also known assaltcedar, represents a serious threat to bighorn sheep. This

exotic plant was introduced as an ornamental and windbreak but is now a major

weed problem (Lovich et at. 1994). It consumes large amounts of water and has

rapid reproductive and dispersal rates (Sanchez 1975, Lovich et at. 1994),

enabling it to outcompete native plant species in canyon bottoms and washes. It

has the following negative effects on bighorn sheep: 1) it reduces or eliminates

standing water that bighorn sheep depend on, 2) it outcompetes plant species that

bighorn sheep feed on, and 3) it occurs in thick, often impenetrable stands that

block access ofbighorn sheep to water sources and provide cover for predators.

Tamarisk has also been recognized as a threat to other bighorn sheep populations

(Sanchez 1975) and native ecosystems in general (Lovich et at. 1994). Effective

eradication methods are possible (Barrows 1994) and eradication programs

currently are underway by the Agua Caliente Band ofCahuilla Indians, Bureau of

Land Management, and Auza-Borrego Desert State Park.

Fire Suppression: As described in section I.B.2 of this recovery plan, bighorn

sheep rely on vigilance and visibility to detect and avoid predators. Long-term

45
fire suppression results in taller and more dense stands ofvegetation, thereby

reducing openness and visibility and in turn making bighorn sheep more

susceptible to predation (Sierra Nevada Bighorn Sheep Interagency Advisory

Group 1997). In this same manner, fire suppression can influence the distribution

and habitat use patterns ofbighorn sheep by causing avoidance of areas with low

visibility (Risenhoover and Bailey 1985, Wakelyn 1987, Etchberger et at. 1989,

Etchberger et at. 1990, Krausman 1993, Krausman et at. 1996). In addition, Graf

(1980) suggested that fire suppression reduces forage conditions in some bighorn

sheep ranges. In the Peninsular Ranges, changes in vegetation succession are

evident in some portions ofbighorn sheep range, primarily in higher elevation

chaparral and pinyon-juniper habitats, and have apparently influenced bighorn

sheep use ofcertain canyons and springs (M. Jorgensen, pers. comm.). Although

temperature and rainfall likely influence the pattern ofvegetation associations

along the eastern slopes of the Peninsular Ranges more than fire frequency does, a

number of researchers have pointed out that fire is an important tool in the

management of bighorn sheep habitat (Graf 1980, Smith and Krausman 1988,

Krausman et at. 1996, Sierra Nevada Bighorn Sheep Interagency Advisory Group

1997).

E. PAST AND CURRENT MANAGEMENT! CONSERVATION

ACTIVITIES

1. FEDERAL AGENCIES

1.1 United States Fish and Witdt~fe Service. We listed the Peninsular bighorn

sheep as a Category 2 candidate from September 18, 1985 (50 FR 37958) until

May 8, 1992, when it was proposed for Federal listing as an endangered species

(57 FR 19837). Between the date ofthe proposed rule and final listing on March

18, 1998 (63 FR 13134), certain Federal activities were reviewed under the

section 7 interagency regulations (50 CFR Part 402) and conference procedures

for proposed species. Since Federal listing, the mandatory requirements of

sections 7, 9, and 10 ofthe Endangered Species Act have been in effect, in

addition to the allocation ofrecovery funding to the State under sections 4 and 6

ofthe Act. On July 5, 2000, we proposed to designate critical habitat throughout

the Peninsular Ranges in California (65 FR 41405). This recovery plan is

prepared pursuant to section 4(f) ofthe Endangered Species Act, which requires

46
usto give priority to the preparation and implementation ofrecoveryplans to

those species that are most likely to benefit from such recovery plans, particularly

those that are, or may be, in conflict with construction or other development

projects or other forms of economic activity.

1.2 Bureau ofLandManagement. Approximately 26 percent of bighom sheep

habitat in the Peninsular Ranges is on public lands administered by the Bureau of

Land Management (Figure 4). This management was custodial in the Peninsular

Ranges until implementation ofthe California Desert Conservation Area Plan

began in 1980. Implementation ofthis plan included preparation ofthe Santa

Rosa Mountains Habitat Management Plan (1980), McCain Valley Wildlife

Habitat Management Plan (1984), and In-Ko-Pah Area ofCritical Environmental

Concern Management Plan (1988), which identified actions to be taken for the

benefit of bighorn sheep in the Peninsular Ranges. From 1988 to the present,

using Land and Water Conservation Fund dollars appropriated by Congress and

taking advantage ofland gifts ftom private individuals, the Bureau ofLand

Management acquired about 4,520 hectares (11,165 acres) ofbighorn sheep

habitat in the Peninsular Ranges, primarily in the Santa Rosa Mountains National

Scenic Area. It should be noted that without the help ofthe Santa Rosa

Mountains Conservancy, a group ofprivate citizens concerned with conservation

ofthe Santa Rosa Mountains, the Land and Water Conservation Funds ‘might not

have been made available forthese purchases. Other conservation activities

included:

• Installation ofgap fencing to eliminate cattle grazing from steep terrain

and from water sources in canyons;

• Reduction in grazing pressure on allotments;

• Closure of most routes oftravel east ofMcCain Valley Road, except to

private inholdings, to ranchers, and to Carrizo and Sacatone Overlooks;

• Designation of wilderness study areas and subsequent management for

non-impairment ofwilderness values;

• Designation ofJacumba, Carrizo Gorge, Coyote Mountains, Sawtooth

Mountains, Fish Creek Mountains, and Santa Rosa Wilderness Areas by

Congress, with attendant elimination ofvehicular access;

• Tamarisk control efforts around water sources;

• Establishment ofthe Santa Rosa Mountains National Scenic Area Visitors

Center to provide public education;

47
• Financial assistance to the Bighorn Institute during its formative years, as

well as land transfer and lease under the Recreation and Public Purposes

Act;

• Temporary closure to dogs on most lands in the Santa Rosa Mountains

National Scenic Area; and

• Closure ofroads into Dead Indian Canyon and Carrizo Canyon.

On October 25, 2000, legislation was signed to create the Santa Rosa and San

Jacinto Mountains National Monument. The monument covers 110,000 hectares

(272,000 acres), including lands administered by the Bureau of Land

Management, U.S. Forest Service, California Department of Fish and Game,

California Department of Parks and Recreation, Agua Caliente Band of Cahuilla

Indians, Coachella Valley Conservancy, and private owners. The designation will

prohibit mining and off-road vehicle use on federal lands, support coordinated

land management by federal agencies, and increase the area’s funding priority.

1.3 US. Forest Service. The San Bernardino National Forest is responsible for

management of bighorn sheep habitat on some public lands. Approximately 3

percent ofbighorn sheep habitat in the Peninsular Ranges is on U.S. Forest

Service land (Figure 4). Since 1978, the Forest Service has acquired 3,107

hectares (7,680 acres) ofland in or within 1.6 kilometers (1 mile) of Peninsular

bighorn sheep range. Current management ofthe San Bernardino National Forest

is guided by the Forest Land and Resource Management Plan (Forest Plan)

established in 1989. Forest Plan standards and guidelines pertaining to Peninsular

bighorn sheep include the following: “coordinate with Bureau of Land

Management to manage the Santa Rosa bighorn sheep population in accordance

with the (Santa Rosa Mountains Wildlife) habitat management plan”; “establish

seasonal closures as necessary to protect important habitat”; “manage domestic

sheep and goat grazing to prevent disease transfer to bighorn sheep [a minimum

3.2-kilometer (2-mile) buffer is recommended]”; and “avoid introducing barriers

to movement of bighorn sheep.” Recent proposed changes in management

relative to Peninsular bighorn sheep are discussed in a programmatic Biological

Assessment completed by the San Bernardino National Forest (January 27, 1999).

This assessment evaluated all ongoing activities occurring in Peninsular bighorn

sheep habitat within the San Bernardino National Forest. Specific actions that

will be implemented include: 1) cattle will be removed from portions of

allotments that overlap bighorn sheep habitat (Wellman allotment), 2) fences

48
within and adjacent to bighorn sheep habitat will comply with specifications listed

in section II.D. 1 .2 ofthis recovery plan, 3) a barrier will be constructed along the

gated closure on Palm Canyon Drive (also known as Dunn Road) to reduce

unauthorized vehicular use, and 4) guidelines for management of hiking, biking,

and equestrian trails (e.g., seasonal closures) will follow recommendations

outlined in section II.D. 1.2 ofthis recovery plan.

Additional actions recommended in the San Bernardino National Forest

Biological Assessment include: 1) the Forest Service should not authorize forage

use by domestic livestock where they currently do not graze in bighorn sheep

habitat, 2) other existing grazing allotments on the San Jacinto Ranger District

should not be converted from cattle to domestic sheep or goat use, and 3) the

minimum buffer distance between domestic sheep grazing and bighorn sheep

habitat should be increased from 3.2 kilometers (2 miles) (the current Forest Plan

standard) to 14.5 kilometers (9 miles) throughout the Forest.

2. STATE AGENCIES

2.1 Catfornia Department of Fish and Game. To designate areas important to

bighorn sheep conservation in the Santa Rosa Mountains, the Department of Fish

and Game established a State Game Refuge pursuant to Fish and Game Code

section 10837. State lands administered by the Department ofFish and Game

total about 3 percent of bighorn habitat in the Peninsular Ranges (Figure 4). To

further identify and implement management needs, the Department ofFish and

Game coordinated with the Bureau ofLand Management in the completion ofthe

Santa Rosa Mountains Wildlife Habitat Management Plan (Bureau ofLand

Management 1980). Currently, the Department of Fish and Game’s management

activities for bighorn sheep are at the highest level in the State’s history. Funds

provided through the sale of Environmental License Plates and through the

auction ofspecial fund-raising permits have enabled the Department of Fish and

Game to support a number ofimportant research efforts concentrating primarily

on population characteristics and the disease status ofbighorn sheep. The

Department of Fish and Game cooperates with several universities, agencies, and

non-profit organizationsin support ofbighorn sheep research and conservation in

California. Conservation goals for bighorn sheep, as published in the Statewide

Plan for Bighorn Sheep (California Department of Fish and Game 1983), are as

follows:

49

1. Maintain, improve, and expand bighorn sheep habitat where possible or

feasible.

2. Reestablish bighorn sheep populations on historic ranges where

feasible.

3. Increase bighorn sheep populations so that all races become numerous

enough to no longer require classification asrare or fully protected.

4. Provide for aesthetic, educational, and recreational uses of bighorn

sheep.

The California Department of Fish and Game’s Bighorn Sheep Management

Program maintains an inventory of the distribution of bighorn sheep in California.

This assessment of bighorn sheep populations has been conducted as part of a

long-term management plan for mountain sheep in California. The populations of

bighorn sheep in California are grouped into metapopulations, or ‘systems’ of

populations, that best represent logical regions to manage for the long-term

viability of the species. This regional approach recognizes the importance of

inter-mountain areas that allow movement and exchange of individuals between

populations, the re-colonization of vacant habitats, and the interagency

coordination of land management. The program’s definition of regional

populations considers not only vegetative and geographic boundaries, but also

man-made barriers that define distributions and have resulted in the fragmentation

of habitat. Given the need to understand the status and dynamics of regional

populations ofbighorn sheep, this type ofinventory should provide an index for

documenting regional population changes over time, and help evaluate the success

or failure of management actions at a meaningful level. Further, this approach

may help identify the “missing pieces ofthe puzzle” for optimizing future

reintroduction and management efforts to ensure population viability.

Although a metapopulation approach is an important biological principle for longterm survival of bighorn sheep populations, it is equally important as a

management concept that prioritizes regional coordination for bighorn sheep

population and habitat management. For example, data regarding extinction and

recolonization are limited, and the biological justification for considering some

regions as true metapopulations is therefore incomplete. Nevertheless, given the

need for regional management of bighorn sheep populations, metapopulations

have been defined based on the best understanding ofthe regions. Several

51
investigations have postulated the importance of population size and genetic

diversity to the long-term viability ofbighorn sheep populations.

California State law (Assembly Bill 560), which was enacted under an emergency

provision in September 1999, allows control ofmountain lions to protect

threatened, endangered, fully protected, and candidate sheep species. In these

cases, selective removal of lions is an alternative short-term emergency measure

to facilitate recovery of vulnerable sheep populations, such as in the Peninsular

Ranges (refer to section II.D. 1.3).

2.2 Catfornia Department ofParks andRecreation. Two State parks are within

the range ofthe Peninsular bighorn sheep: Auza-Borrego Desert State Park and

Mount San Jacinto State Wilderness. Anza-Borrego Desert State Park comprises

243,000 hectares (600,000 acres) along the backbone ofthe Peninsular Ranges,

encompassing approximately 47 percent of this species’ existing habitat within the

United States (Figure 4). The park also supports a majority of the rangewide

sheep population (Rubin et at. 1998). Therefore, recovery of the species hinges

greatly on the successful management ofbighorn sheep habitat in this State park.

Anza-Borrego Desert State Park has been actively involved in the conservation of

bighorn sheep for 30 years (Table 9).

2.3 Coachetta Vattey Mountains C~onservancy. The Conservancy was established

by California State legislation in 1990 to “acquire and hold, in perpetual open

space, mountainous lands surrounding the Coachella Valley and to provide for the

public’s enjoyment of and the enhancement of their recreational and educational

expenences on those lands in a manner consistent with the protection of the lands

and the resource values specified in Section 33500 [PublicResources Code]”.

The Conservancy has acquired either fee title or a conservation easement on 973

hectares (2,405 acres) in the San Jacinto and Santa Rosa Mountains, and has

assisted other entities with additional acquisitions. The Conservancy is preparing

the Coachella Valley Multiple Species Habitat Conservation Plan under contract

to the Coachella Valley Association of Governments (refer to section I.E.3.2).

3. LOCAL ORGANIZATIONS AND AGENCIES

3.1 Bighorn Institute. The Bighorn Institute is a nonprofit, tax-exempt

organization that was formed in 1982 to investigate the causes of bighorn sheep

52
declines, particularly Peninsular bighorn sheep. The Institute is located in

Riverside County, California, adjacent to the City of Palm Desert. Its facilities,

which include an office, laboratory, staff residence, and pens for a captive

breeding herd ofPeninsular bighorn sheep, are located on 120 hectares (297 acres)

of land at the base of the Santa Rosa Mountains.

The Institute began monitoring radio-collared bighorn sheep in the northern Santa

Rosa Mountains and the San Jacinto Mountains in 1982 and 1992, respectively.

Long-term studies of the population characteristics, distribution, reproductive

success, nutrition, movements, and general ecology of these bighorn sheep are

ongoing. In the spring of 1998, the Institute initiated a multi-year study of causespecific mortality of radio-collared lambs in the northern Santa Rosa Mountains.

The Bighorn Institute has conducted annual helicopter surveys of bighorn sheep in

the Santa Rosa Mountains since 1982 and in the San Jacinto Mountains since

1987, and has also surveyed bighorn sheep throughout the Peninsular Ranges in

Mexico. Since 1982, 39 sick lambs have been captured from the U.S. Peninsular

Ranges for disease research and rehabilitation at the Institute. In 1985, the

Institute began a Captive Breeding and Population Augmentation Program.

Although this program began as a by-product of disease research on causes of low

lamb survival (DeForge et at. 1982, DeForge and Scott 1982), in 1995 it was

redirected as a formal captive breeding program with the primary goals of

producing stock for augmenting and re-establishing wild populations, and

conducting a research program in the Santa Rosa and San Jacinto Mountains.

Captive bighorn are maintained in 12-hectare and 3-hectare enclosures

encompassing rugged hilltops. Rams and ewes are selectively combined for the

breeding season and the parentage of all captive-born animals is recorded.

Captive animals are not available for public viewing and a standardized feeding

and observation routine is used to limit exposure to humans (Ostermann et at. in

press).

Before release, all bighorn are health-tested, eartagged, and fitted with mortalitysensing radiocollars. Within the northern Santa Rosa Mountains, bighorn have

been released in Bradley Canyon (n equals 60), east Magnesia Canyon (n equals

6), and west Magnesia Canyon (n equals 8). Of the 74 captive-reared bighorn

released into the northern Santa Rosa Mountains, 49 (22 males, 27 females) were

captive-born and 25 (12 males, 13 females) were wild-born lambs brought into

captivity for research and rehabilitation at I to 5 months of age (Ostermann et at.

53
Table 9. Past and present conservation activities in Anza-Borrego Desert State

Park.

Year Description of activities

1968 Field studies were conducted in Anza-Borrego as part of a statewide

status report on bighorn sheep (Weaver 1972, 1975, 1989; Weaver et at.

1968; Weaver and Mensch 1970).

circa 1970 Construction ofBlue Spring guzzler in Vallecito Mountains with the

Society for the Conservation ofBighorn Sheep.

1971 The annual Anza-Borrego Bighorn Sheep Count began with about 25

volunteers. A waterhole count has been conducted every summer since

this time and now involves about 75 volunteers counting 24 watering

sites. Over 2,000 volunteers have donated over 60,000 hours to date.

1972-1975 Jorgensen and Turner (1973, 1975) conducted 4 summers of bighorn

sheep research and documented over 100 water sources used by bighorn

sheep. Russi (1978) continued this work in 1976.

1973-

present

Tamarisk removed from riparian areas within bighorn sheep habitat to

enhance water availability and native plant community regeneration.

Currently, a Riparian Restoration Team works full time to remove

tamarisk and other exotic plants. Approximately 208 kilometers (120

miles) of canyons and stream courses have been treated by the team to

date.

1975 A seasonal closure ofbighorn sheep watering areas in Coyote Canyon

during June 15 to September 15 was implemented. This closure was

expanded in 1996 from June 1 to October 1.

1982 A bighorn sheep guzzler was constructed in collaboration with

California Department ofFish and Game at Limestone Spring in the

Santa Rosa Mountains.

1982 163,085 hectares (403,000 acres) ofAnza-Borrego Desert State Park

were designated as State Wilderness Areas, setting aside a large area of

1983-

present

Park staff assisted in annual helicopter surveys of the entire Santa Rosa

and San Jacinto Mountain ranges (DeForge e at. 1995, 1997).

1983-1992 Park staff assisted the Bighorn Institute with disease research.

1987 Feral cattle (117) were removed from bighorn sheep habitat by

helicopter at a cost of $70,000, culminating 16 years of effort to remove

domestic cattle from park lands.

1987 Six bighorn sheep guzzlers were constructed in the Vallecito Mountains

to provide water where natural springs and streams had been usurped by

human activity. Over 200 volunteers and $30,000 were used and

expended respectively, in the project.

54
Table 9. Continued

1987-1988 Gap fencing [22.5 kilometers (14 miles)] was constructed in the upper

elevations ofthe park to keep stray cattle from entering from

neighboring lands. A special Senate appropriation ($200,000) was

obtained for this project.

1992-

present

Cooperated on Peninsular Ranges Bighorn Sheep Population Health

Study with University ofCalifornia (Davis) and the Zoological Society

of San Diego.

1994-1998 Helicopter surveys were conducted in Anza-Borrego Desert State Park,

in collaboration with the University ofCalifornia - Davis and California

Dept._of Fish_and_Game_(Rubin_et_al._1998,1999).

A 15-minute movie “The Bighorn of Anza-Borrego” was produced.

This movie is seen by thousands of park visitors each season in the

Anza-Borrego Visitor Center.

1995-1996

1996 The Coyote Canyon Public Use Plan was implemented, calling for the

closure of Middle Willows and Upper Willows to motor vehicular

traffic. This trail segment is 5 kilometers (3.1-miles) long.

in press). In 1997, three captive-reared ewes were released into Tahquitz Canyon

in the San Jacinto Mountains. Two of these females were captive-born, and the

third was a wild-born ewe captured as a lamb from the northern Santa Rosa

Mountains (Ostermann and DeForge 1996, Bighorn Institute 1997).

3.2 Coachetta Vaitey Mutu~te Species Habitat Conservation Plan. This ongoing

planning effort is sponsored by the Coachella Valley Association of Governments,

with the cooperation of the Fish and Wildlife Service and California Department

of Fish and Game, and has been in preparation since 1996. Within the areas at

issue in this plan, the Association’s membership includes the County of Riverside

and all nine cities in the Coachella Valley, as well as the Agua Caliente Band of

Cahuilla Indians. Though the plan is not yet complete, it currently proposes to

address the conservation needs of bighorn sheep. Lands in the San Jacinto and

Santa Rosa Mountains set aside in the past and future by the cities and Riverside

County as open space will provide important contributions to bighorn sheep

recovery and completion of the habitat conservation plan ifthose lands are

managed appropriately. If the plan is adopted, participating Federal, State, and

local governments will cooperate in implementing an agreed upon conservation

strategy for bighorn sheep and other species over a large area of the San Jacinto

and Santa Rosa Mountains in Riverside County.

55
4. INDIAN TRIBES

4.1. Agua Catiente Band ofCahuitta Indians. The Agua Caliente Band of

Cahuilla Indians (Tribe) is a federally recognized Indian Tribe whose reservation

was established in 1876 by Executive Order. The Agua Caliente Indian

Reservation encompasses 13,000 hectares (32,000 acres) ofland in the western

Coachella Valley and is encompassed within a checkerboard ownership pattern

that supports a significant amount of bighorn sheep habitat.

The Tribe has a long and rich history ofland stewardship, particularly in the

foothills ofthe San Jacinto and Santa Rosa Mountain ranges. For decades, the

Tribe has managed the area known as the Indian Canyons for cultural resource

protection and use by the public as a Tribal park. Protection ofthe natural

resources ofthe reservation and Indian Canyons has been the foremost priority of

the Tribe and has been acknowledged by the Secretary ofthe Interior.

Currently, the Tribe is preparing a comprehensive Resource Management Plan for

the reservation that will protect cultural, wetland, land use, and wildlife resources.

The Tribe actively participates and holds seats on the Coachella Valley

Association ofGovernments, Coachella Valley Mountains Conservancy, and

Planning Advisory Group ofthe Coachella Valley Multiple Species Habitat

Conservation Plan.

The Tribe’s Planning and Environmental Department presently consists of 10

professionals and technicians who, at the direction ofthe Tribal Council, oversee

all land management issues. The Tribal Resource Management Plan will address

the management and protection ofendangered species, including bighorn sheep.

To the extent feasible, the Tribe intends to cooperate with interested and affected

agencies who share in the implementation ofthis recovery plan.

4.2. Torres-Martinez Desert Cahuitta Indians. This federally recognized tribe

supports approximately six sections (1,554 hectares or 3,840 acres) of bighorn

habitat in the extreme southern Santa Rosa Mountains.

4.3. Morongo Band ofMission Indians. This federally recognized tribe supports

one irregularly shaped section (about 280 hectares or 700 acres) ofbighorn habitat

at the extreme north end ofthe San Jacinto Mountains.

56
II. RECOVERY

A. CONSERVATION PRINCIPLES USED IN THIS RECOVERY PLAN

The following sections discuss general conservation principles in the context of

our current knowledge regarding Peninsular bighorn sheep, and outline the

relationship ofthese principles to the recovery criteria for this species.

Conservation theory recognizes that population and genetic issues need to be

addressed in species conservation (Lande 1988), although population threats pose

a greater short-term risk to Peninsular bighorn sheep. The conservation of

Peninsular bighorn sheep requires an understanding ofhabitat use, population

dynamics, behavior, and spatial population structure, as well. Ecosystem

protection provides an additional important tool in species conservation. The use

of models in conservation decision-making for the recovery of bighorn sheep in

the Peninsular Ranges also is discussed below.

I. POPULATION CONSIDERATIONS

Population parameters are important to the viability ofall populations; however,

they are an especially important consideration in the conservation ofsmall

populations (Gilpin and Soul~ 1986). Variation in population parameters (birth,

death, immigration, and emigration rates, as well as population age and sex

structure) can cause fluctuations in population size that make small populations

especially vulnerable to extinction. Lande (1988) noted that a shortcoming of

some past recovery plans has been an inadequate emphasis on factors related to

population characteristics, and cautioned that for many wild populations, risks

related to population parameters are of more immediate importance than genetic

concerns.

The small number of Peninsular bighorn sheep (334 adults estimated in 1998)

mandates that population dynamics be of concern in their conservation.

Furthermore, Peninsular bighorn sheep occur in discrete ewe groups that have

ecological significance relative to the genetic and distributional structure ofthe

population (Rubin et at. 1998, Boyce et at. 1999), and therefore represent an

important management and conservation unit (Bleich et at. 1996). The

persistence ofsuch subgroups are important to the viability ofthe entire

57
population (Soul~ 1987). Some ofthese groups include less than 20 ewes, making

them highly vulnerable to chance variation in birth and death events. The high

male to female sex ratio in the San Jacinto Mountains (DeForge et at. 1997)

provides an example.

Because ewe groups are connected by movements oframs and rarer dispersal by

ewes, Peninsular bighorn sheep are considered to comprise a metapopulation

(Torres et at. 1994, Bleich et at. 1996, Boyce et at. 1997). Metapopulations

typically are assumed to exist in a state of balance between population extinctions

and colonizations (Hanski and Gilpin 1991). However, in the case ofPeninsular

bighorn sheep, the use of a metapopulation approach should not diminish the

importance of individual ewe group viability for the following reasons. Bighorn

sheep are relatively slow colonizers (Geist 1967, 1971; Bleich et at. 1996) and

therefore metapopulation extinction-colonization processes would have to

function over a very long time period. Recent abandonment of habitat and a lack

of known colonizations suggest that Peninsular bighorn sheep comprise a

nonequilibrium metapopulation” (i.e., extinctions are occurring at a faster rate

than colonizations) (Harrison 1994, Hanski and Simberloff 1997). Hanski and

Gilpin (1991) cautioned that such systems must be managed carefully because

they may not necessarily function as a metapopulation. Therefore, extirpations of

existing ewe groups should be avoided, while colonization ofhabitat should be

promoted.

In the Peninsular Ranges, a variety offactors have reduced bighorn sheep numbers

to levels where random variations in population characteristics and environmental

factors have become serious threats. Therefore, this recovery effort should strive

to increase the overall population ofbighorn sheep by addressing and, where

possible, reversing processesthat caused the past population decline. This effort

will entail implementing actions that increase the size ofindividual ewe groups by

reducing mortality rates, increasing recruitment, and allowing inter-group

movements to occur.

2. GENETIC CONSIDERATIONS

Maintaining genetic variation is an important conservation goal because loss of

genetic variability can result in inbreeding depression (a loss offitness) and the

inability of populations to respond to long-term environmental changes (Gilpin

58
and Sould 1986, Ralls ei’ at. 1988, Lande 1988, Meffe and Carroll 1994,

FitzSimmons et at. 1995). By reducing the fitness ofindividuals, loss ofgenetic

variation also can reduce the growth rates and resilience of populations (Lacy

1997). Loss of genetic variation is a special concern when dealing with small

populations because heterozygosity is lost (through the processes offounder

effects, population bottlenecks, genetic drift, and the effects ofinbreeding) more

quickly in small populations than in large ones (Meffe and Carroll 1994). In the

Peninsular Ranges, movement ofmales apparently has maintained gene flow

between ewe groups, resulting in a relatively high level of genetic diversity

(Boyce et at. 1997). However, increased habitat fragmentation could reduce the

connectivity among groups. Ifewe groups become isolated, they will face an

increased risk of losing genetic variability in addition to vulnerability to natural

random fluctuations in the population.

Even if gene flow is maintained among ewe groups in the Peninsular Ranges, the

overall population size (approximately 334 adults) is small enough to cause

concern. The effective population size (N) (Crow and Kimura 1970), which

e

determines the rate at which heterozygosity is lost, is even smaller than the census

size. Au effective population size of 500 individuals has been suggested asthe

minimum recommended for maintenance of genetic variation for future

evolutionary change (Franklin 1980, Lande and Barrowclough 1987, Franklin and

Frankham 1998), while Lande (1995) suggested that this numbershould be even

higher. The current censussize ofPeninsular bighorn sheep falls far below even

the lower recommendation. Because reduced population levels may place

Peninsular bighorn sheep at risk, important goals ofthis recovery effort are to

increase the abundance ofPeninsular bighorn sheep and maintain as much genetic

variation as possible. This recovery plan recommends maintenance of

connectivity with populations in Baja California and it may be deemed

appropriate in the future to recreate connectivity or induce gene migration with the

Mojave Desert metapopulation.

Although the observed genetic variation among ewe groups in the Peninsular

Ranges is not known to confer adaptive advantage to local environments, genetic

theoryholds that existing genetic variation should be maintained “in as near a

natural geographic distribution as possible, so that evolutionary and ecological

processes may be allowed to continue” (Meffe and Carroll 1994). In Peninsular

bighorn sheep, as in many taxa, genetic variation is partitioned among and within

59
subunits or ewe groups (Meffe and Carroll 1994, Boyce et at. 1999, refer to

section I.A.3). Although there is no evidence to suggest that bighorn sheep in the

Peninsular Ranges lack genetic diversity, a conservative approach to genetic

conservation suggests that recovery tasks should recognize and attempt to

preserve existing genetic structure whenever possible. This approach will require

preservation of multiple ewe groups, maintenance of movement opportunities

between groups (Schwartz et at. 1986), and judicious protocols forpopulation

augmentation, reintroduction, and captive breeding programs (Ryman and Laikre

1991, Elliott and Boyce 1992, see Appendix C). Because the major problems

facing bighom sheep in the Peninsular Ranges relate to population dynamics and

viability, genetic theory should not over-ride management objectives to maintain

and expand the number and size ofewe groups throughout the Peninsular Ranges.

This objective can be accomplished by selecting augmentation and reintroduction

stock from the closest available populations (Wehausen 1991, Ramey 1993,

Wehausen and Ramey 1993, Gutierrez-Espeleta et at. 1998).

3. ECOSYSTEM PROTECTION

Loss ofhabitat is recognized as the leading cause ofspecies endangerment and the

leading threat to global biodiversity (Groombridge 1992, Noss and Murphy 1995).

It is also considered the most significant threat to the viability ofbighorn sheep

populations (Bleich et at. 1996). The potentially negative impacts that habitat loss

and degradation have on bighorn sheep are presented in section I.D. Although

habitat loss may not directly cause mortality in bighorn sheep, loss ofimportant

resources (e.g., water, forage, escape terrain, lambing areas, movement linkages)

ultimately reduces carrying capacity, which can affect survival and recruitment

rates. In some cases, the cause ofdeath may be documented as disease,

malnutrition, or predation, etc., when in fact habitat loss was the underlying cause

that resulted in death. In addition, altered land uses that support larger human

populations introduce increased levels of anthropogenic disturbance in adjoining

habitat. The decline or extirpation ofbighorn populations near other metropolitan

areas such as Tucson near the Santa Catalina Mountains and Albuquerque near the

Sandia Mountains (Krausman et at. in prep.), provide case history examples of

apparent vulnerability of bighorn to urban influences. This recovery plan will

attempt to avoid repeating these scenarios, and accordingly adopts the approach of

conserving the larger ecosystem upon which bighorn sheep in the Peninsular

Ranges depend, as afforded under section 2(b) ofthe Endangered Species Act.

60
Such an ecosystem approach also will benefit numerous other common and

uncommon species.

4. THE USE OF POPULATION MODELS TO HELP GUIDE RECOVERY

ACTIONS

Models have become an important tool to scientists attempting to understand

complex processes because intuition is often not reliable (National Research

Council 1995). Conservation biologists frequently use models to gain a better

understanding ofthe many interacting factors (environmental, population, and

genetic) that place a species or population at risk. The comprehensive modeling

of these factors was christened “population vulnerability analysis” by Gilpin and

Sou1~ (1986). Typically, the goal of a population vulnerability or “viability”

analysis is to evaluate the risk of extinction, either in terms of estimated time to

extinction or the probability of extinction in a given time interval (Boyce 1992).

As such, a population viability analysis is similar, in concept, to risk analyses used

to understand issues ofpublic health and safety (Ginzburg et at. 1982).

Population viability analyses, like other forms of risk analysis, contain a degree of

uncertainty because they attempt to determine the likelihood offuture events

based on past and present patterns (of population dynamics, environmental

conditions, etc.). All models are inherently dependent onunderlying assumptions

(Starfield and Bleloch 1991) and on the quality ofdata entered into the model.

Therefore, the results of a population viability analysis must be interpreted with

caution (Caughley 1994, Beissinger and Westphal 1998). Inclusive population

viability analyses may not be appropriate when data are limited (Beissinger and

Westphal 1998). This limitation does not mean that the use ofmodels should be

discouraged (Ak~akaya and Burgman 1995, Starfield 1997, Beissinger and

Westphal 1998).

Au additional role ofmodeling in conservation biology is as a decision making

tool (Starfield and Bleloch 1991, Walsh 1995, Starfield 1997). Models can be

used to compare the relative effects (rather than the absolute outcome) of

alternative management strategies or environmental scenarios (Starfield and

Bleloch 1991, National Research Council 1995, Walsh 1995, Starfield 1997,

Beissinger and Westphal 1998) and can help guide management strategies or

61
focusfuture research efforts. Smaller, focused models have great potential in

guiding conservation decisions (Starfield and Bleloch 1991, Starfield 1997).

Use of modeling can help to elucidate several issues related to the recovery of

Peninsular bighorn sheep (refer to section ll.D.2.2). Models should be designed to

ask specific questions (Starfield 1997) that increase our understanding ofthe

ecological processes in the Peninsular Ranges, and should be coupled with field

studies ofthe bighorn sheep (Beissinger and Westphal 1998). It may be useful to

simulate shorter time periods, as well asthe 100 to 200 year intervals typically

used in population viability analyses, so that model predictions (as well as model

assumptions) can be evaluated with the use offield study results (Beissinger and

Westphal 1998). This type ofapproach will allow conservation biologists to learn

from the models and field studies, and will allow conservation efforts to be

adaptive (Minta and Kareiva 1994).

B. OBJECTIVES AND CRITERIA

1. RECOVERY OBJECTIVE

The ultimate objective ofthis recovery plan is to protect and maintain sufficient

individuals and habitat of bighorn sheep in the Peninsular Ranges to eventually

delist this species. The recovery of Peninsular bighorn sheep will involve a twostage process, beginning with an interim goal of downlisting ofthe species from

endangered to threatened status, followed by long-term recovery and removal of

threatened status. As new information becomes available, the downlisting and

delisting criteria may warrant modification through future revisions to the

recovery plan.

2. DOWNLISTING CRITERIA

As an interim management goal, Peninsular bighorn sheep may be considered for

downlisting (reclassification to threatened status) when all ofthe following

objective, measurable criteria are met:

Downtisting Criterion 1: As determined by a scientifically credible

monitoring plan, at least 25 adult ewes are present in each ofthe following

9 geographic regions (Figure 5) during each of6 consecutive years

62

(equivalent to approximately one bighom sheep generation), without

continued population augmentation:

1. San Jacinto Mountains

2. Santa Rosa Mountains--North ofHighway 74

3. Santa Rosa Mountains--South ofHighway 74 through Martinez

Canyon

4. Santa Rosa Mountains--South ofMartinez Canyon

5. Coyote Canyon

6. North San Ysidro Mountains (Henderson Canyon to County

Road S-22)

7. South San Ysidro Mountains (County Road S-22 to State

Highway 78)

8. Vallecito Mountains

9. Carrizo Canyon/Tierra Blanca Mountains/Coyote Mountains

Area

Justification: The nine regions were selected on the basis ofmaintaining:

(1) historical distribution, (2) home range herd memory, and (3)

connectivity among ewe groups to facilitate re-colonization in the event of

localized extirpations. Recovery Team members with knowledge of

current and historical conditionsjudged that each area was capable of

supporting at least 25 ewes with associated subadults and rams. Within

each ofthe nine regions, fluctuation in the number ofewe groups,

including re-colonization offormer habitats, is expected under the

metapopulation model. As such, ewe groups may merge, split, and

redistribute themselves over time. Although the 9 areas support respective

carrying capacities well in excess of 25 adult ewes, a downlisting objective

based on maximum attainable population size was not selected because

static population levels at full range capacity cannot be maintained in

naturally variable environments, even assuming intensive management

capability. The minimum group size of 25 adult females was selected by

Recovery Team consensus because it:

1. would reduce risk ofextirpation from random naturally

occurring events to an acceptable level;

64
2. should be achievable with prudent, population and land

management practices;

3. is consistent with management objectives for bighorn sheep in

other metapopulations;

4. should maintain ewe group knowledge of a large home range

that will minimize the extent of geographic gaps between ewe

groups, thereby facilitating interchange of genes and populations

within the metapopulation;

5. falls well within known or estimated historical population

levels; and

6. should provide, in all but the most catastrophic scenarios,

sufficient time for management intervention to prevent extirpation.

Downtisting Criterion 2: Regulatory mechanisms and land management

commitments have been established that provide for long-term protection

of Peninsular bighorn sheep and all essential habitat as described in

section II.D.l ofthis plan.

Justification: Given the major threat offragmentation to species with

metapopulation structures, connectivity among all portions of habitat must

be established and assured through land management commitments, such

that bighorn sheep are able to move freely throughout all habitat. In

preparation for delisting, protection by means other than the Endangered

Species Act must be assured. Such protection should include alternative

regulatory mechanisms by Federal, State, and local governments, and land

management commitments that would provide the protection needed for

continued population stability.

3. DELISTING CRITERIA

As a long-term management goal ofthe Peninsular bighorn sheep, three delisting

criteria are proposed;

Detisting Criterion I: As determined by a scientifically credible

monitoring plan, at least 25 ewes must be present in each ofthe 9 regions

(Figure 5) listed under Downlisting Criterion #1 above, during each of 12

consecutive years (approximately 2 bighorn sheep generations), including

65
the 6 years under Downlisting Criterion HI, without continued population

augmentation.

Detisting Criterion 2: The rangewide population must average 750

individuals (adults and yearlings) with a stable orincreasing population

trend over 12 consecutive years (same time period as Delisting Criterion

#1 above).

Justification: Recovery Team members with knowledge ofhistoric and

current population levels evaluated the condition ofexisting habitat and

determined a carrying capacity ofapproximately 1,000 bighorn sheep in

the Peninsular Ranges, which approaches historical population estimates.

The required 12-year average population estimate of 750 animals is based

on the assumption that achieving the objectives in Downlisting Criterion

#1 ofat least 25 females in each ofthe 9 geographic areas likely will result

in some areas supporting substantially more than 25 ewes and other sheep.

This scenario likely will result in an overall metapopulation size that

fluctuates between 600 and 1,000 sheep, averaging about 750 sheep with a

normal sex ratio, or approximately 75 percent ofestimated carrying

capacity. An average population level would allow for natural population

fluctuations in a random environment and is believed to be reasonably

attainable assuming implementation ofthe management measures

prescribed in this recovery plan.

Detisting Criterion 3: Regulatory mechanisms and land management

commitments have been established that provide for long-term protection

ofPeninsular bighorn sheep and all essential habitat as described in

section II.D. I ofthis recoveryplan. Protection considered long-term can

be provided through appropriate institutional practices, such as State Park

General Plans, an amended California Desert Conservation Act Plan, an

amended Forest Plan, a completed Coachella Valley Multispecies Habitat

Conservation Plan, and natural resource management plans on Tribal

lands. In addition, connectivity among all portions of habitat must be

established and assured through land management commitments such that

bighorn sheep are able to move freely throughout the Peninsular Ranges.

Delisting would result in loss ofprotection under the Endangered Species

Act; therefore continued protection by other means must be assured.

66
Justification: This protection should include alternative regulatory

mechanisms, land management commitments, or conservation programs

that would provide the long-term protection needed for continued

population viability.

Recovery of Peninsular bighorn sheep likely will take several decades or longer

due to a low reproductive rate (e.g., only one offspring per female per year and

reproduction starting usually at 2 years of age). The above criteria will be revised

as necessary through a recovery plan amendment or revision if new information

becomes available, or ifthese criteria no longer pass scientific muster or otherwise

meet the conservation needs ofthis species based on the best available

information.

C. RECOVERY STRATEGY

This recovery plan describes a strategy to recover and delist bighorn sheep in the

Peninsular Ranges. The strategy consists oftaking necessary actionsto: (1)

improve population variables (reproduction, recruitment, survivorship), and (2)

secure and effectively manage habitat, including linkages between ewe group

home ranges. The recovery actions to implement this strategy are organized in the

narrative outline below. This recovery strategy is a synthesis ofknowledge

accumulated on bighorn sheep in desert environments and elsewhere in North

America. Four biological principles ofbighorn biology are evident from past

research and have been incorporated into management guidelines by various

agencies (e.g., McQuivey 1978, Wilson et at. 1980, Smith and Krausman 1988,

Bureau of Land Management 1996, New Mexico Department of Game and Fish

1995):

1. Bighorn sheep are wide-ranging animals that are spatially dependent on

large tracts ofhabitat that provide a diversity ofresources needed to offset

seasonal, annual, and longer term cycles ofenvironmental variability and

scarcity;

2. Metapopulation structure requires habitat contiguity between/among

constituent demes (ewe groups) to allow for long-term shifts in

distribution and genetic interchange;

67
3. Bighorn sheep appear to lack natural or acquired resistance to some

diseases and remain highly vulnerable to diseases introduced by domestic

sheep; and

4. Behavioral responses to human-related activities can be variable among

individuals and populations, which can adversely affect habitat use

patterns and population persistence.

In the short term, acquisition and conservation ofthe relatively narrow band of

habitat that still remains is crucial to attaining the population recovery and

delisting objectives ofthis recovery plan. Given the: (1) inability ofbighorn

sheep to use higher elevation habitats because of excessive shrub and tree cover,

(2) incompatible land uses that have encroached into habitat along the lower

elevational slopes ofthe Peninsular Ranges, and (3) pervasive influence ofhuman

activities throughout bighorn habitat, the future ofbighorn sheep in the

Peninsular Ranges will depend on rapid and adequate protection oflower

elevational areas that provide critical resources, such as foraging, watering,

lambing, and rearing habitats. Short-term management actions to increase

population recruitment and adult survivorship are also necessary to effect

population increase.

Past studies on bighorn sheep in desert and mountain environments have amassed

a wealth ofapplicable knowledge that guides the management prescriptions ofthis

recovery plan. Much ofthis work applies to bighorn sheep in general and,

therefore, need not be reexamined through further research in the Peninsular

Ranges. The monitoring and research tasks recommended in this recovery plan

are intended to address the longer-term, more complex environmental

relationships that have posedmanagement difficulties in the past. These tasks

will require substantial investment by numerous partners ifthey are to be

successfully accomplished. However, only through such a cooperative effort will

it be likely that the knowledge requirements for effective management be met.

The success ofthis recovery plan will also depend on strong education and public

awareness programs. A number ofrecovery actions outlined in this plan will

directly affect the general public. Therefore, the general public needs information

and outreach on proposed actions being taken, especially in localized areas of

action. Programs that include comprehensive and accurate facts about the ecology

68
ofPeninsularbighorn sheep and the threatsthat face them, will be crucial to

obtaining public support for conservation measures.

D. NARRATIVE OUTLINE FOR RECOVERY ACTIONS ADDRESSING

THREATS

Recovery actions are first described in general below, and then are identified as

site-specific tasks, with reference to their appropriate recovery regions, in section

ll.E. The following tasks consist ofinterim and long-term management goals and

activities that range from single event actions orstudies to continuous efforts

extending acrossthe entire recovery implementation time line. The task

descriptions and the implementation schedule (Part III ofthis recovery plan) help

frame the duration ofthe respective goals/actions and responsible entities for

taking the lead or assisting others in implementation responsibilities.

1. PROMOTE POPULATION NCREASE AND PROTECT HABITAT

1.1 Protect, acquire, enhance, and restore habitat. The historic range of

Peninsular bighom sheep has been adversely affected by urban

development, agriculture, mining activities, and highways that have led to

the destruction, modification, and fragmentation ofhabitat. Further

development can be expected in the future. As pointed out in section I.D

ofthis recovery plan, the viability and, therefore, the recovery of

Peninsular bighom sheep are critically dependent on availability ofhabitat.

Consequently, an important part ofthis recovery effort is the protection

and restoration ofremaining habitat essential to Peninsularbighorn sheep

conservation.

1.1.1 Protect essential habitat. Essential habitat is that habitat

believed necessary for recovery and should, therefore, be protected

from further loss or degradation (Figures 2, 4-9). It is likely that

the valley floor to the east and the north ofthe Peninsular Ranges

(e.g., Coachella Valley, Imperial Valley) historically was used by

bighorn sheep, for example during long-distance moves to and

from other mountain ranges. Exposure to the hazards ofhigh

density urban development, major freeways, fences, agriculture,

and canals, now would be considered detrimental to bighorn sheep

69
recovery. Therefore, the vast majority ofthe valley floor to the

east ofthe Peninsular Ranges is not considered essential habitat.

Consequently, “essential habitat” comprises those areas believed to

be necessary for a self-sustaining bighorn population with a high

probability for long-term survival (recovery) in the Peninsular

Ranges ofthe United States. Essential habitat, therefore, consists

ofthose physical and biological resources (space, food, water,

cover) needed for: (1) normal behavior and protection from

disturbance, and (2) individuaL/population growth and movement,

including dispersal necessary to support a future population

expansion to meet the recovery objective (delisting criteria of

approximately 750 animals).

Much ofthe historical range ofthe sheep is needed to sustain the

larger population levels necessary for recovery because:

a. Habitat may be colonized and inhabited by future ewe

groups (Bleich et at. 1996), if, for instance, population

spatial structure or environmental conditions change, orthe

population grows as a result ofrecovery actions. The longtermpersistence ofa metapopulation depends on the

number ofhabitat patches that are available for

colonization (Hanski 1989). An important phenomenon,

which is not intuitively obvious, is that destruction ofonly

a fraction ofavailable habitat can drive a metapopulation to

extinction by disrupting the balance between colonization

and extinction rates (May 1991). Even locally abundant

species can sometimes be very close to extinction ifthe

proportion ofsuitable habitat is near the extinction

threshold (Lande 1987).

b. Movement throughout the range is needed to sustain the

metapopulation (Bleich et at. 1 990a).

70




c. The factors limiting the viability ofPeninsular bighorn

sheep are not yet fully understood and, in general, bighorn

sheep habitat use and selection need to be more thoroughly

examined (McCarty and Bailey 1994). It is therefore

necessary to protect all remaining suitable habitat.

d. The habitat of Peninsular bighorn sheep is restricted to a

narrow band along the base ofthe Peninsular Ranges, from

the San Jacinto Mountains south to Mexico. In some areas,

this band is less than 6 kilometers (4 miles) wide, so

essentiallyno true “core” habitat exists. Without

protection, connectivity could be severed at any point along

this narrow band ofhabitat.

e. Habitat near the eastern edge ofthis band often coincides

with alluvial fans and canyon washes, which provide

Peninsular bighorn sheep with important resources (refer to

section I.B.1).

f. Unpredictable changes in global climate warrant retention

offuture options in habitat conservation strategies.

The delineation ofessential habitat was based on habitat features

known to be important to bighom sheep, rather than being based

solely on current use patterns, because population numbers

currently are low and use patterns are known only for a recent short

time period. In addition, data collected on radio-collared animals

(a sample ofthe entire population) represent a subset ofthe total

area used. Methods used to delineate essential habitat are outlined

in Appendix B. Compiling historical data and conducting

recommended ecological research will further understanding of

how bighorn sheep use available habitat. See Figures 2, 4-9 for

maps ofessential habitat.

1.1.2. Secure habitat. Bighorn sheep habitat that is currently in

private ownership should be secured (e.g., purchased or acquired

by exchange on a voluntary basis) by State or Federal agencies and

75
managed compatibly through individual or regional habitat

conservation plans or programs (e.g., Coachella Valley

Multispecies Habitat Conservation Plan, which will delineate these

lands in its planning area),so that proper protection, management,

and restoration measures can be implemented. Interagency

conservation plans or other potential agreements made with local

governments and private land owners should assure: (1) long-term

protection oflands under city and countyjurisdiction, and (2)

appropriate land uses adjoining bighom sheep habitat to prevent

indirect effectsfrom degrading habitat value. Limited funds for

land acquisition will require prioritizing parcels; the value ofeach

tract ofland should be evaluated according to the following

criteria, although not necessarily in the order listed below:

a. At the level ofindividual ewe groups: how important is

this land in supporting a ewe group in this area?

b. Does this land include particularly important resources

(e.g., water sources, escape terrain, habitat for lambing, or

important forage resources) forthe bighom sheep?

c. Does this land represent important habitat for movement

and dispersal necessary for connectivity among ewe groups

throughout the Peninsular Ranges?

d. Has this ewe group already experienced habitat loss?

e. Would acquisition ofthis land reduce the cumulative

negative effects ofurban growth?

f. Is the habitat imminently threatened?

A list ofprioritized parcels should be prepared and updated

annually by land management agencies (Bureau ofLand

Management, U.S. Forest Service, California Department ofFish

and Game, Auza-Borrego Desert State Park, Coachella Valley

Mountains Conservancy) to facilitate acquisition when

76
opportunities arise. Methods to facilitate public and private

cooperation should be pursued, such as: (1) development ofland

use planning guidelines (e.g. the Coachella Valley Multiple

Species Habitat Conservation Plan, conservation guidelines in

Appendix F), (2) development ofa public education and outreach

program (refer to II.D.3), and (3) development ofsupporting maps

that better identify and explain bighorn sheep ecology and

conservation requirements.

1.1.3 Maintain, manage, and restore habitat qualit’,.’ and

connectivity. As mentioned in section I.D. ofthis recovery plan,

the recovery ofPeninsular bighorn sheep is dependent on the

existence ofadequate habitat. Maintenance, management, and

restoration ofessential habitat will allow for geographic expansion

when population numbers increase. The ability ofbighorn sheep to

move freely throughout all parts ofthe range is critical to recovery

because it: (1) facilitates exchange ofgenes between ewe groups,

(2) allows habitat colonization, and (3) allows selection of

alternative habitat in response to predation pressure ortemporary

changes in habitat quality (Schwartz et al. 1986, Bleich et al. 1996)

or human-related disturbance. Shifts in habitat use occur more

readily within existing ewe group home ranges but home range

boundaries themselves also can change, albeit less frequently and

more slowly over time. Therefore, in addition to protection of

designated essential habitat, the following measures should be

taken to restore and maintain habitat quality and to assure

connectivity throughout the range:

1.1 .3.1 Remove exotic vegetation and preventfurther

invasion by exotic plants. This item refers primarily to

control oftamansk (Tamarix species) along stream courses

but also applies to other species such as fountain grass

(Pennisetum setaceum) in select regions. Additional

funding should be secured to continue and expand current

tamarisk removal programs throughout the Peninsular

Ranges. These programs should include, or be coordinated

with, efforts to eradicate tamarisk outside ofbighorn sheep

77
habitat, as this will reduce future invasion into bighorn

sheep habitat. Tamarisk eradication, such as at Thousand

Palms Oasis, can result in immediate reappearance of

surface water (Barrows 1994), which can help expand

sheep distribution.

1.1.3.2 Reduce or eliminate wild horse populationsfrom

bighorn sheep habitat. Though burros and goats are

currently absent, they also should be eliminated ifthey

become established. The reduction orremoval ofnonnative ungulates would: (1) eliminate potential sources of

competition, (2) reduce potential destruction ofwater

sources and vegetation, and (3) benefit other riparian

dependant wildlife, such as least Bell’s vireo and

southwestern willow flycatcher. The involved State and

Federal agencies, along with the Agua Caliente Band of

Cahuilla Indians, should determine whether wild horse

management in Coyote Canyon (Anza-Borrego Desert State

Park) and Palm Canyon is consistent with bighorn recovery

objectives in these areas. Any continuation of feral horse

grazing should be contingent upon the demonstrated ability

to implement an effective management and monitoring

program to ensure against: (1) the possibility of

competition with sheep for food and water, (2) trespass

onto other land ownerships, and (3) risks to public safety.

1.1.3.3 Implement afire management plan that recognizes

fire as a natural disturbance infire-adapted habitats ofthe

Peninsular Ranges ecosystem and as a process that helps

maintain bighorn sheep habitat. A wildland fire policy

should establish fire management areas for natural and

management ignited prescribed fires. Further research on

the use offire as a management tool should help guide such

a plan (Smith and Krausman 1988, Krausman et al. 1996;

78
and refer to section II.D.2.3). However, fire can represent a

serious threat to bighorn habitat quality in Sonoran scrub

plant communities, which unlike chaparral are not well

adapted to fire disturbance.

1.1.3.4 Maintain existing water sources and consider

providing additional sources on public lands ifwater is

thought to be a limitingfactor in particular areas. Water

development should be incorporated into research that

investigates the effect that the addition ofwater has on

bighorn sheep and other species (refer to section II.D.2).

1.1.3.5 Maintain and re-establish connectivity throughout

all habitat. Bamers to movement (roads, fences, increased

use of off-road vehicle areas, renewed railroad activity)

should be prevented. Potential bighorn sheep crossing

areas should be identified and bridged or tunneled to

attempt reestablishing connectivity. Typical culverts are

not adequate because bighorn sheep are not known to move

through dark tunnels. Existing roads appear to represent

barriers between four current ewe groups (Rubin et al.

1998); solutions to promote connectivity should be

attempted. Another important recovery goal is to

reestablish connectivity to habitat south ofInterstate 8 and,

ultimately, to Mexico. This task will require the

cooperation ofthe California Department of Transportation

to incorporate bighorn sheep movement opportunities into

their future construction plans. Coordination with Border

Patrol and the Mexican government will be needed to

control human disturbance and the threat ofdisease

transmission from domestic sheep and goats while

reestablishing connectivity across the international border.

79
1.2 Reduce or eliminate direct and indirect human impacts. In addition to

habitat loss, habitat modification and human activities often directly or

indirectly affect Peninsular bighorn sheep habitat use (refer to sections

I.B.5 and I..D.5). The following actions, which should all be accompanied

by strong educational and public awareness programs (refer to section

II.D.3), will reduce these impacts.

1.2.1 Reduce impactsfrom existing andfuture developments and

projects. These recommended actions pertain to any project

(residential, recreational, resort, commercial, agricultural, or

mining) that has been constructed within bighorn sheep habitat, or

any project adjacent to bighorn sheep habitat. Though habitat and

opportunities for sheep movement throughout all suitable habitat

should be maintained, habitat use along the immediate urban

interface should not be encouraged because ofrisks associated with

behavioral habituation.

1.2.1.1 Constructfences to exclude bighorn sheepfrom

urban areas where they have begun or may begin using

urban sources offood and water. Fences serve several

functions including: (1) separating bighorn sheep from

potential threats of urbanization (e.g., toxic plants,

parasites, accidents, vector-borne diseases, traffic,

herbicides, pesticides, behavioral habituation), (2)

controlling human and pet access to remaining bighorn

sheep habitat, (3) preventing bighorn sheep from becoming

habituated to and dependent upon artificial sources offood

and water, and (4) modifying habituated behaviors and

redirection into remaining native habitat. In the northern

Santa Rosa Mountains, ongoing coordination with cities

and landowners on a regional fencing strategy will be

critical to the long-term health and maintenance ofthis ewe

group. Retrofitting existing developments with fences

where sheep currently exploit urban food and water sources

80
is particularly important; cooperation by residential

landowners will be critical to the success ofexcluding the

northern Santa Rosa Mountains ewe group from urban

habitats. Along the remainder ofthe urban interface, where

sheep have not yet shown indications ofhabituation to

human habitats, future behavioral habituation also may

occur. Although fencingmay be viewed as a last resort to

other potential forms ofaversive conditioning, prudent

planning dictates that mitigation be required to offset the

likelihood offuture adverse effects (behavioral habituation

and increased mortality rates) when new projects are

approved along the urban interface. Though actual fence

construction could be contingent upon future use by sheep

and the ineffectiveness ofother potential deterrents, the

wherewithal, responsibilities, and easements for fences

should be determined and secured at the time of project

approval. Fences should be 2.4 meters (8 feet) high, or

functionally equivalent, and should not contain gaps in

which bighorn sheep can be entangled. Gaps should be 11

centimeters (4.3 inches) orless. This fence design should

only be used at the urban interface. Refer to section

II.D. 1.2.2 for guidelines for livestock fences within bighorn

sheep habitat.

1.2.1.2 Avoid non-native vegetation along unfenced habitat

interfuces where it may attract or concentrate bighorn

sheep. Along fenced sections ofthe urban interface,

ornamental and toxic plants should not extend over or

through fences where they may be accessible to browsing

bighorn sheep.

1.2.1.3 Promote the use ofnative vegetation and limit the

planting ofexotic species (including grass) in areas

accessible to bighorn sheep. A list oflocally native plants

81
should be provided to developers, landscapers, and

homeowners. On Bureau of Land Management lands,

especially livestock grazing allotments in and near bighorn

sheep habitat, utilize only native vegetation in fire

rehabilitation and range improvement projects.

1.2.1.4 Prohibit the use ofany known toxic plants where

they may be accessible to bighorn sheep orpotentially

invade bighorn sheep habitat. A list of known toxic plants

should be provided to all developers, landscapers, and

homeowners.

1.2.1.5 Discourage the use ofplants known to invade and

degrade bighorn sheep habitat (e.g., tamarisk, fountain

grass).

1.2.1.6 Prohibit intentional enticement ofbighorn sheep

ontoprivate property. This item includes, but is not

limited to, vegetation, mineral licks, or unfenced swimming

pools, ponds, or fountains upon which bighorn sheep may

become dependent for water.

1.2.1.7 In unfenced areas, monitorthe use ofpesticides,

fungicides, herbicides, andfertilizers ifsheep are using

urban landscapes. All products used should be warranted

by the manufacturer to not be harmful to wildlife when

applied at the label rate, and no applications should exceed

the label rate. Coordination with landowners and

homeowner groups is needed.

1.2.1.8 Regulate the diversion orprocurement of water,

whetherfor human use or irrigation, and whetherfrom

springs or aqu~fers, that would reduce natural water

sources used by bighorn sheep. Coordination with land

82
owners and the State Water Resources Control Board is

needed to redress potential water rights conflicts. The

Regional Water Quality Control Board’s Basin Plan should

recognize bighorn sheep as a beneficial use for perennial

and seasonal waters within essential habitat.

1.2.1.9 Prohibit the construction ofwater bodies in

developed areas adjoining sheep habitat that may promote

the breeding ofmidges (Culicoides sp.) and

monitor/control vectors in existing problematicponds.

Water features should be designed to eliminate blue-tongue

and other vector-borne diseases by providing deeper water

(over 0.9 meters [3 feet]), steeperslopes (greater than 30

degrees), and if possible, rapidly fluctuating water levels

(see Mullens 1989, Mullens and Rodriquez 1990).

Landowners and managers should coordinate with local

mosquito and vector control districts to ensure management

ofexisting water bodies that harbor vector species.

1.2.1.10 Discourage the art~ficialfeeding of coyotes

because ofthepotentialfor increasingpredator abundance

and consequentpredation on bighorn sheep.

1.2.1.11 Establish a method and secure funding to

consistently monitor and enforce all actions listed under

task 1.2.1.

1.2.2 Reduce or eliminate detrimental human activities within

bighorn sheep habitat. A variety ofhuman activities can affect

bighorn sheep (refer to section I.D). Bighorn sheep may react in

two ways (Papouchis et al. 1999): (1) avoidance ofdisturbance or

human encounters (potentially including habitat abandonment),

and (2) habituation to sources of disturbance ifthey are sufficiently

predictable. Behavioral habituation can include adjustments to

83
timing ofuse in certain areas, such as by avoiding the area until the

disturbance is gone (Hamilton et al. 1982) or fleeing the

disturbance and returning when the disturbance is absent.

Expansive urban development in and around bighorn sheep in

desert habitats has occurred in three metropolitan areas to date--

Albuquerque, Tucson, and Coachella Valley—and in all instances,

habitat abandonment and population decline has resulted

(Gionfriddo and Krausman 1986; Krausman, in litt. 1998;

Krausman et al. In prep.). Bighorn sheep have demonstrated

greater resilience to human disturbance in more remote locales

such as Alberta (MacArthur et al. 1982) and the Sierra Nevada

(Hicks and Elder 1979), though bighorn also are known to avoid

excessive human disturbance in areas well away from urban

centers (Papouchis et al. 1999).

Given the potential behavioral vulnerabilities ofbighorn sheep to

human disturbance (including dogs) and associated risks to the

persistence ofcurrently depressed populations in the Coachella

Valley, a biologically conservative management approach is

appropriate in the Peninsular Ranges. The public should be

educated regarding problems associated with human-sheep

relationships, and encouraged to continue supporting conservation

efforts (Smith and Krausman 1988). A trails management program

is currently in place on Anza-Borrego Desert State Park and

appears to be providing a level ofmanagement that is maintaining

relatively stable population levels of bighorn sheep. The success of

this program may be attributable to an intensive educational

program, along with prohibitions against dogs(on trails) and other

disruptive activities, and a strong management presence to ensure

adequate compliance. In addition, the most heavily used areas

typically are located in steep terrain that limits the number and

location oftrails to relatively few narrow canyon bottoms. Sheep

are better able to coexist with recreational use where human

84
disturbance typically occurs at elevations lower than where sheep

spend most oftheir time (Hicks 1977).

The following section primarily focuses on the northern Coachella

Valley though the principles pertain rangewide. The relative

remoteness ofthe Anza-Borrego region renders comparisons with

the heavily populated Coachella Valley difficult, but recreation

activities could be viewed differently because they are part ofa

cumulative set offactors affecting the sheep, some ofwhich (e.g.,

development-related pressures in sheep habitat) are more intense in

the Coachella Valley. Though cause and effect relationships have

not been established, the proportionally larger population declines

in the northern Santa Rosa and San Jacinto Mountains than

elsewhere may be related in part to the relatively higher levels of

human disturbance associated with the largermetropolitan area.

Other contributing factors may include the more extensive and

interconnected trail system that is not largely restricted to canyon

bottoms. Most ofthe trails head upslope and intersect other trails

at higher elevations, forming an extensive trail network throughout

ewe group home ranges, including lambing, rearing, and watering

habitat. The patchwork of differing land ownerships has

contributed to management difficulties. The types oftrail use

activities, as well as proliferation ofnew trails, also have gone

largely unregulated. The Dunn Road, constructed illegally in the

northern Santa Rosa Mountains in the I 970s, also is considered a

trail since much ofthe use is by recreational pedestrians and

bicycles and vehicular access is restricted. Travel in washes by

vehicles and on foot also should be considered trail use.

The Agua Caliente Band ofCahuilla Indians currently is preparing

a wildlife habitat management plan for the reservation, including a

trails management program, which should be coordinated with the

larger planning effort to ensure attainment ofregional objectives.

The Tribe recently banned dog use on its trails system, and will

85
coordinate its efforts with other agencies when a draft plan is

complete.

Research should focus on how different kinds and levels of

disturbance affect bighorn behavior and habitat use patterns. The

prevailing lack ofbaseline data on location, types, and extent of

trail use must be overcome as a prerequisite to studying and better

understanding these effects.

1.2.2.1 Develop and implement a trails management

program with affected landmanagement agencies,

scientWc organizations, and user groups. A trails program

in the San Jacinto and Santa Rosa Mountains necessarily

will require interagency cooperation, with specific

responsibilities and levels offunding identified. The cities

and primary land management agencies, with the Bureau of

Land Management in a leadership role, should coordinate

with user groups in developing a plan with the Fish and

Wildlife Service and the Department ofFish and Game so

that it can be effectively implemented on a regional basis.

Regular interagency meetings should be scheduled to

ensure effective coordination and implementation. The

program should consist ofthe following components:

a. Public education. Preparation of a public education and

outreach program is needed so that trail users better

appreciate and understand bighorn sheep and other

biological values associated with the Peninsular Ranges.

Also see Section II.D.3. Most members ofthe public likely

will voluntarily refrain from recreating in sensitive habitats

during critical seasons ifthey understand the effects of

human related disturbance on bighorn sheep. Nonetheless,

monitoring and enforcement will be necessary to provide

effective management.

86
b. Prohibition ofdogs in bighorn sheep habitat. Dogs

should remain in developed or designated areas

(campgrounds, picnic areas, on paved roads, etc.) under

restraint and prevented from roaming into bighorn sheep

habitat.

c. Lambing and rearing habitat. Seasonal restrictions are

needed on selected trails that bisect lambing habitat. In this

Recovery Plan, the lambing season is defined as January 1

to June 30, and lambing and rearing habitat is defined as

those areas in which ewes and lambs are observed during

this period. These definitions were chosen to provide

protection for the majority oflambs during the first 3

months oflife and to allow ewes undisturbed access to

lambing areas prior to the peak parturition months

(February through April). Trails that are currently known to

result in disturbance to lambing and rearing habitat are

listed in Table 10.

d. Watersources. Seasonal restrictions or trail relocations

may be appropriate for selected trails that lead to water

sources. Trail use should be avoided near critical summer

water sources from June 1 through September 30, and other

times, as well, if water is scarce. Trail use is prohibited by

regulation [see California Government Code, Title 14,

Section 630(b)(l l)(A) and (30)(A)] at Magnesia Springs

and Carrizo Canyon Ecological Reserves. Trailsthat are

currently known to conflict with the summer water

requirements are listed in Table 10.

e. Trail management. Trails that conflict with lambing,

rearing, and water requirements should be addressed

through management tools, such as seasonal restrictions or

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Table 10. Trails and areas with potential conflicts that should be addressed in an

interagency trails management plan.*

Trail

Conflicts with

Lambing from

January 1

through June

30

Conflicts with

Water stress

from June 1

though

September 30

Comment

N. Lykken trail X X

Skyline trail X

Museum trail (Palm

Springs)

X X Applies above picnic

table at Desert Rider’s

Park.

South Lykken trail X

Picnic table trail

(south ofTahquitz

Canyon)

X Applies above picnic

table.

Tahguitz Canyon X X

Dunn Road X X

Murray Hill trail

complex

X X

Cathedral Canyon

trail

X X

Mirage trail (Bump

and Grind)

X Applies above the flat

overlook

Art Smith, Schey,

and connecting trails

X X

Carrizo Canyon trail X X

Bear Creek Canyon

trail

X X

Boo Hofftrail X X

Guadalupe trail X X

Morrow trail X X

This list of trails should be updated annually through the interagency trails program,

based on the most current information.

relocations. Permanent closures may be necessary where

relocation is not possible and seasonal restrictions cannot

be effectively monitored or enforced. Trails should be used

as a tool to focus human activity away from areas of

concern. New trails in bighorn habitat should be avoided,

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except in select areas along the urban edge, where they

could provide two benefits—alleviate pressure on trails that

intrude deeper into sheep habitat, and provide a disturbance

barrier to discourage potential sheep attraction to urban

sources offood and water. Any new trails should minimize

adverse impacts to alluvial fans, canyon bottoms, and other

areas that may provide essential seasonal forage conditions

while still accomplishing the objective ofrouting use away

from the more sensitive areas.

f. Monitoring, enforcement, and research. A management

presence by uniformed personnel should be deployed

during peak use periods to educate the public, monitor

compliance with trails rules, and enforce rules against any

violations. Monitoring of bighom sheep habitat use

patterns should be designed to detect behavioral responses

that can adaptively feedback into revised management

measures. Experimental research to further our

understanding of human/sheep interactions also should be

conducted. See Section II.D.2.7.

1.2.2.2 Manage activities within bighorn sheep habitat that

fragment or interfere with bighorn sheep resource use

patterns or other behaviors to reduce or eliminate adverse

effects. This task includes but is not limited to road traffic,

trail use, off-trail activity, and aerial activities, such as hang

gliders and helicopters, which may have a negative effect

on bighorn sheep. For example, the U.S. Navy currently

implements a 457-meter (1,500-foot) minimum ceiling for

military flights above bighorn sheep habitat in the north end

of the Anza-Borrego Desert State Park and a 60-meter

(200-foot) minimum ceiling in the remainder ofthe park.

The 457-meter (1,500-foot) minimum ceiling should apply

to all flights over any bighorn sheep habitat.

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1.2.2.3 Manage livestock grazing to reduce competitionfor

scarce resources and to minimize the potential for disease

transmission. Existing (Canebrake, with lambing and

watering habitat) and currently inactive (Vallecito and

Oriflamme) allotments should be evaluated and modified or

closed, if necessary to achieve recovery objectives. The

McCain Valley allotment should also be assessed to ensure

compatibility with adjoining sheep habitat. If the closure of

one or more livestock grazing allotments is determined

necessary to remove the impediments to recovery described

above in Section I.B.6 concerning competition or in Section

I.B.7 concerning disease transmission, the Bureau of Land

Management should develop proposed land use plan

amendments to effect such closure(s). Until decisions are

made regarding potential allotment modifications or

closures, the current allotment boundaries should be fenced

according to Bureau of Land Management fence

specifications for cattle and bighorn sheep (Bureau of Land

Management 1989). If any allotments, or portions thereof,

that overlap with bighorn sheep habitat are subsequently

closed through land use plan amendments, the fences

around such allotments should be removed following the

cessation of livestock grazing.

1.2.2.4 Prohibit the grazing ofdomestic sheep within 14.5

kilometers (9 miles,) ofbighorn sheep habitat to prevent

disease transmission.

1.2.2.5 Require all cattle grazing allotments adjacent to

bighorn sheep habitat to befenced where cattle straying

into bighorn sheep habitat degradesforage or water

resources. Fences should comply with Bureau of Land

Management specifications for cattle fences in bighom

sheep habitat (Bureau ofLand Management 1989).

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1.2.2.6 Prohibit the use ofgoats as pack animals in

bighorn sheep habitat. Goats are known to transmit

diseases to bighorn sheep. Other pack animals, such as

llamas and camels, should be assessed for potential disease

risk and prohibited if a risk exists.

1.2.2.7 Establish a method and secure funding to

consistently monitor and enforce all actions listed under

task 1.2.2.

1.3 Reduce mortality rates. Low survivorship of adult Peninsular bighorn

sheep currently threatens population viability (refer to section I.B.4).

Measures to improve survivorship are fundamental to this recovery effort.

1.3.1 Reduce mortality due to unnatural causes. A number of

mortalities of Peninsular bighorn sheep have been caused directly

or indirectly by human activities. Some mortality factors, such as

poisoning by plants and vehicular collisions, are a byproduct of

urban developments built within or adjoining bighorn sheep

habitat, or human presence in bighorn sheep habitat (refer to

section II.D.1.2). Additional causes ofmortality should be reduced

with the following actions:

1.3.1.1 Prohibitfences in which bighorn sheep may

become entangled orstrangled, or that interrupt habitat

connectivity or block movement ofbighorn sheep within

remaining habitat. At the urban interface, fences should

not contain gapslarger than 11 centimeters (4.3 inches)

(refer to section II.D. 1.2.1 .1). All other fences should

comply with Bureau ofLand Management specifications

for fences within bighorn sheep habitat (Bureau of Land

Management 1989).

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1.3.1.2 Post all movement areas or areas of bighorn sheep

concentration near highways with bighorn sheep crossing

signs to warn motorists. Post informational warning signs

at the entrance to blind curves. Solutions need to be

identified and implemented to reduce the extent of

vehicular related mortality along problematic road

segments such as Highway 74 above Palm Desert, S-22

west ofBorrego Springs, and Highway 78 south ofBorrego

Springs. If monitoring indicates that more effective

warning systems are needed, flashing yellow lights and

intensified signage, etc., should be phased in. Coordination

with Caltrans and the counties will be required.

1.3.2 Reduce mortality due to natural causes. Predation by

mountain lions represents a threat to the viability of bighorn sheep

in the Peninsular Ranges (refer to sections I.B.4, I.B.5, and I.D).

Selective removal of lions may therefore be necessary to facilitate

recovery. The goals of reducing predation pressure are to protect

small subpopulations from extinction and to stimulate population

increases. The following guidelines for implementing predator

management were designed to facilitate recovery ofPeninsular

bighorn sheep in accordance with the recovery criteria established

in this recovery plan. The first level of predator control is

essentially an emergency action to protect small subpopulations

from extinction. This level of management was identified to help

the population meet downlisting criterion #1 (the presence of25

ewes in each ofthe 9 recovery regions), while the second level of

lion control will be conducted, if necessary, to facilitate

achievement of delisting criterion #2.

Removal of mountain lions should be selective and only target

individual lions known to be, or suspected of, preying on bighorn

sheep. Predator management should not be implemented as a

mitigation measure for habitat loss because it is a temporary

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remedy for a potential short-term problem and does not offset the

permanent impact of habitat loss. Lion removal must be

accompanied by careful monitoring to determine if predator control

achieves the desired protection ofbighorn sheep (refer to section

II.D.2.5). The effects ofpredator management should be

incorporated into ecosystem level research on the predator/prey

relationships among bighorn sheep, lions, and deer (refer to section

ll.D.2.3). The criteria for implementing predator control may need

to be changed as knowledge regarding this predator-prey

relationship and the balance between predation and population

viability are better understood (refer to section II.D.2). The

ultimate goal is to restore an ecological system that includes viable

predator/prey systems in which no predator removal is necessary.

Predator RemovalLevel I. Predator removal should be

implemented if there are fewer than 15 adult female bighorn sheep

in a given recovery region (refer to the 9 regions in section II.B)

and predation is a known mortality factor. In this circumstance,

protection of individual bighorn sheep is critical for ensuring

bighorn population survival and persistence in the recovery region.

Lion removal should be implemented solely in the recovery region

of concern, and continue until population growth is reestablished to

a trajectory expected to achieve the downlisting threshold of25

adult ewes in the region.

Predator Removal Level 2. Predator removal may also be

implemented if there are greater than 25 ewes in each of the 9

recoveryregions, to further facilitate the long-term goals of

population recovery. Lion removal should only occur if lion

predation is the primary cause of mortality and low survivorship is

determined to be limiting population recovery. Careful

monitoring, habitat evaluation, and possibly computer simulations

should be used to determine if, when, and where predator removal

should occur. Predator removal should be discontinued if available

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evidence indicates that: (1) lion predation no longer limits bighorn

sheep population growth, and (2) continued removal would no

longer result in a population expansion within the recovery region

necessary for the overall recovery ofthe metapopulation.

1 .4 Develop a long-term strategy and maintain the current capability for

captive breeding, reintroduction, and augmentation programs. A small

captive breeding herd (14 animals in 1998) exists at the Bighorn Institute

(refer to sections I.C. 1 and I.E.3) and is managed according to the

guidelines outlined in Appendix C. This herd was established in 1984 to

facilitate the study oflow lamb survival. Animals born or rehabilitated at

the facility have been released into the northern Santa Rosa Mountains (n

equals 74) orthe San Jacinto Mountains (n equals 3), typically as small

groups ofyearlings, since 1985 (Ostermann et al. in press).

The Recovery Team should develop a long-term strategy that identifies the

process and circumstances under which captive breeding, reintroductions,

and augmentations may be appropriate and carried out, including the

potential introduction of animals from adjoining metapopulations.

Reintroduction and augmentation are potential tools to (re)establish ewe

groups and restore connectivity among neighboring groups. Augmentation

ofdwindling groups may serve as a “rescue effect” (Brown and KodricBrown 1977), thereby reducing the risks associated with naturally

occurring random variations in populations. Augmentation may also play

an important role in the conservation of bighorn sheep because habitat use

patterns are learned from experienced animals. Once use of a particular

area is discontinued by females, it maybe more difficult for inexperienced

sheep to become established in this area (refer to section I.B.2). Finally,

augmentation can be of value to address genetic concerns.

Reintroduction and augmentation programs are recognized conservation

tools and have been used extensively to manage bighorn sheep populations

(Bleich et al. 1990b, Ramey 1993); however, they come with a set of

potential problems (Campbell 1980, Kleiman 1989, National Research

94
Council 1995). Reintroductions and augmentations also must be

coordinated with other recovery efforts. That is, they are meant to play

supportive roles to other measures that protect Peninsular bighorn sheep

and their habitat, they should be supported through public relations and

education programs (Kleiman 1989, National Research Council 1995), and

they should be preceded or accompanied by other conservation measures

to restore population viability (Stanley Price 1991). Finally, decisions

regarding reintroductions and augmentation need to consider the genetic,

disease, and population structure consequences of such actions.

Although there are advantages to using free-ranging animals in

augmentations and reintroductions, captive breeding also can provide

animals for releases. In addition, captive propagation can be used as a

recovery tool to: 1) conduct recovery related research, 2) maintain genetic

diversity or genetic lineages, and 3) maintain refugial populations.

The long-term strategy should specify the goals of reintroduction and

augmentation activities, and describe the steps that will be followed to

reach these goals. The strategy should be consistent with the guidelines

adopted by the Conservation Breeding Specialist and the Reintroduction

Specialist Groups of the Species Survival Commission of the International

Union for the Conservation of Nature and Natural Resources, The World

Conservation Union, and those of the American Zoo and Aquarium

Association’s Caprinae Taxon Advisory Group. Appendix C outlines

additional considerations and a protocol for captive breeding and release

of captive animals.

2. INITIATE OR CONTINUE RESEARCH PROGRAMS NECESSARY TO

MONITOR AND GUIDE RECOVERY EFFORTS.

This section focuses on research topics with management applicability needed for

recovery. The approach is to design management actions so that: (1) results can

be measured, (2) efficacy can be evaluated as testable hypotheses, and (3)

alternative or refined actions can be formulated and tested again (adaptive

95
management, as defined by Holling 1978). However, adoption of this approach

for bighorn sheep recovery likely will be more problematic than for most species.

Many results will not become apparent for many years because sheep are longlived and behavior can be slow to change and difficult to document.

2.1 Monitor population status. The status, population dynamics, and

population trends of Peninsular bighorn sheep should be monitored so that

the success ofthis recovery effort can be evaluated. Consistent long-term

monitoring will allow use of adaptive management approaches that would

increase the effectiveness of recovery efforts. Continued monitoring is

also a necessary component offuture research. Population monitoring

(abundance, distribution, recruitment) should be coordinated with other

research (e.g., survivorship, habitat selection) to maximize cost efficiency

and the data collected per animal collared, as well as to minimize handling

and marking animals.

2.1.1 Monitor abundance. All bighorn sheep habitat in the

Peninsular Ranges should be surveyed by helicopter at least every

other year to generate population estimates. Initially, this will

require that a known number of radio-collared animals are

distributed throughout the range so that mark-recapture abundance

estimations can be generated. The number of collared animals

should be sufficient to achieve an accuracy of plus or minus 25

percent with a probability of 0.05, following the methods described

in Krebs (1989) and Robson and Regier (1964), or approximately

30 percent of the estimated ewe population should be radiocollared. However, a “sightability” estimate may be generated

after additional surveys are conducted, thereby eliminating the

need to maintain this percentage of radio-collared animals. This

approach would be especially beneficial if/when population

numbers become large. Where ewe group delineations are known,

estimates of abundance should be generated for individual ewe

groups as well as for the entire range. Annual waterhole counts

should be continued in Anza-Borrego Desert State Park and

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perhaps reinitiated in the Santa Rosa and San Jacinto Mountains.

Data from waterhole counts can be used to potentially provide

important information about population characteristics (e.g., lamb

to ewe ratios and/or ram to ewe ratios) and to index abundance.

Continuation of waterhole counts concurrent with helicopter

surveys (for 5 to 10 years) may reveal a relationship between

abundance indices and population estimates. This relationship may

allow biologists to use historical waterhole count data (collected

over 28 years) to estimate historical abundance patterns. Aerial

surveys and waterhole counts should be conducted according to the

protocols in Appendix E.

2.1.2 Monitor distribution. Further data should be collected on

distribution of Peninsular bighorn sheep. Ground surveys for

bighorn sign should supplement aerial surveys and telemetry

studies to further define habitat use patterns. Questions regarding

distribution include but are not limited to: (I) how many ewe

groups are currently found in the Santa Rosa Mountains and

Vallecito Mountains, (2) if augmentation or reintroductions are

necessary, where should these occur, and (3) how do the number

and distribution of ewe groups change over time as conditions or

population numbers change?

Abundance monitoring (see task 2.2.1.1) will initially require that

radio-collared animals be distributed throughout the range. The

location ofeach animal should be obtained via visual location or

fixed wing aircraft telemetry surveys, at least biweekly. In

addition, the locations of all observed animals without collars

should be recorded during biennial helicopter surveys.

2.1.3 Monitor recruitment. Reproductive success, which includes

lamb production and recruitment, should be monitored on a yearly

basis in all ewe groups. Tracking and observing individually

marked ewes generates the most useful data because lamb survival

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to specific ages can be determined, and the reproductive success of

individual ewes can be tracked. Alternatively, the lamb to ewe

ratio ofeach ewe group could be measured at various times ofthe

year (e.g., during waterhole counts or helicopter surveys). Ground

surveys should be organized if feasible. If lamb mortality is found

to be high in specific ewe groups, the radio-collaring oflambs may

be necessary to identify causes ofmortality. Recruitment should

be compared among ewe groups, years, and management strategies.

2.1.4 Monitorsurvivorship and cause-speqfic mortality. Adult

survivorship should be monitored annually in all ewe groups. This

monitoring would require that radio-collared rams and ewes are

present in each area and telemetry signals are monitored on a

regular (at least biweekly) basis. It is important that all mortalities

be investigated promptly so that cause specific mortality rates can

be calculated. A standardized mortality site investigation protocol

should be established. Whenever possible, fresh carcasses or tissue

samples should be collected and submitted to the California

Veterinary Diagnostic Laboratory for pathological examination.

Survivorship and cause-specific mortality should be compared

among ewe groups, years, and management strategies.

2.2 Developpopulation models. Although a substantial amount of

knowledge exists regarding bighorn sheep in the Peninsular Ranges and

elsewhere, there is a need for further research regarding their ecology and

the factors that influence population viability. Incorporating existing

knowledge into models may provide insight into the ecology of Peninsular

bighorn sheep and the system to which they belong. Rather than using the

absolute results of models to make policy or management decisions,

however, the relative outcomes of alternative models should be used to

guide management decisions (Beissinger and Westphal 1998) and future

research efforts. Models uncover knowledge gaps and thereby guide

future research and generate hypotheses that would not otherwise be

addressed. The recovery of Peninsular bighom sheep will benefit from

98
answers to a number of questions. These questions include, but are not

limited to: (1) how do the number ofewe groups, size ofgroups, and level

of connectivity among groups affect persistence probabilities ofthe

metapopulation, and (2) what are the relative long-term effects of various

levels ofadult and juvenile mortality on population viability?

Although the above questions pertain primarily to viability from the

perspective ofpopulation numbers, future models could also incorporate

data to assess genetic diversity. Additional models should explore habitat

selection versus availability.

2.3 Research the relationships between bighorn sheep, mountain lions,

mule deer, and habitat. In the Peninsular Ranges, mountain lions and

mule deer are found within bighorn sheep habitat, and are important

variables affecting this ecosystem (Hayes et al. 2000). To increase our

knowledge ofthe ecology of Peninsular bighorn sheep, a better

understanding of predation, interspecies relationships, and habitat

selection is needed. Information regarding the relationships will be

valuable in making future management decisions to facilitate population

recovery, including decisions regarding habitat management, reduction of

mortality due to predation, and whether other species should be managed

to achieve recovery of Peninsular bighorn sheep. Pertinent research goals

include, but are not limited to:

a. Estimate the number ofmountain lions preying on bighorn sheep.

b. Examine movement patterns of mountain lions within and adjacent

to bighorn sheep habitat, and attempt to identify influencing

factors.

c. Examine the spatial and temporal patterns of mountain lion

predation on bighorn sheep and mule deer in relation to the

distribution of both prey species, season, climate patterns, and

habitat characteristics.

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d. Describe the habitat use patterns and distribution ofmule deer in

and near bighorn habitat.

Answering some of these questions requires long-term study (perhaps 10

or more years). Such a study would require extensive monitoring and

habitat study of all three species. Experimental approaches involving

removal of mountain lions and manipulation ofmule deer populations and

habitat should be designed to test the outcome in terms of predation rates

on bighorn sheep.

2.4 Investigate the relationships between bighorn sheep and coyotes and

bobcats. Although mountain lions appear to be the primary predator of

adult bighorn sheep, predation by coyotes or bobcats also may affect the

viability of bighorn sheep populations, primarily through predation on

lambs. Factors that put bighorn sheep at risk from these predators should

be investigated. Studies should examine what impact expanding

urbanization, the use of urban environments, and artificial water sources

may have on the relationship between these three species.

2.5 Investigate the efficacy oftemporary suppression of natural

predation. Mountain lion predation currently is the primary cause ofdeath

ofadult radio-collared bighorn sheep in most ewe groups in the Peninsular

Ranges, and threatens population viability (refer to sections I.B.4 and

I.B.5). Any measures to intervene should be designed so that the

effectiveness ofvarious techniques can be evaluated. The presence of

lions and other predators in the area ofinterest should be monitored as part

ofthe investigation. Because mortality and mountain lion predation rates

fluctuate across years (refer to sections I.B.4 and 1.B.5), it will be

important to evaluate the effectiveness of these actions over multiple

years.

2.6 Research habitat use/selection and dispersal behavior. Habitat use by

sheep has been studied by a number ofresearchers (refer to section I.B.l),

but many questions remain. In the Peninsular Ranges, as in many other

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bighorn sheep habitats, the specific factors that limit populations are not

well understood. A better understanding ofhabitat use patterns and factors

underlying habitat selection will aid our understanding ofresource

requirements and promote informed management decisions. Selected

topics for future research include: (1) water and nutritional requirements

and how these factors affect population characteristics and distribution, (2)

how and where habitat use and movement are influenced by disturbance

barriers and sources of fragmentation, (3) habitat use and how it relates to

predator evasion, (4) how habitat quality influences dispersal behavior,

and (5) how human disturbance affects habitat use patterns.

Documentation of habitat use for essential life functions,such as lambing,

rutting, summer water stress, and dispersal, is needed. A detailed

vegetation map with sources of fragmentation for the entire Peninsular

Ranges would facilitate analyses ofthese variables on habitat use patterns.

A number of questions exist regarding dispersal behavior. For example,

how often do ewes move between groups? Although preliminary data

suggest it occurs at a low rate, long-term monitoring (two or more bighorn

sheep generations) may be necessary to more accurately estimate the

frequency of such moves. Other questions include, but are not limited to:

(1) what conditions (population density, forage quality, time ofyear) are

associated with movement ofanimals between ewe groups; (2) what

habitat features are associated with movement paths; (3) how does range

expansion occur; and (4) how far (and among how many ewe groups) do

rams typically move? The frequency and duration ofmonitoring will

depend on the specific research questions. For example, long-term studies

are needed to document dispersal behavior, while frequent or nearly

continuous monitoring maybe necessary for studying habitat selection and

use patterns (Laundre et al. 1987). The use of Global Positioning System

collars may provide a valuable tool in such studies.

2.7 Evaluate the effect of human activities on bighorn sheep. Given the

history of bighorn sheep population declines and extirpations in other

areas near urban centers, information is needed on how to manage

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recreational activity in a manner that does not interfere with bighorn

habitat use. Because knowledge ofthe location and extent of human

activity is a prerequisite to conducting research and making informed

management decisions, responsible land management agencies should

place a high priority on obtaining this information. A variety ofstudy

designs may be appropriate, such as: (1) experimentally prescribing

different management techniques and measuring results, (2) measuring

physiological changes in individuals in response to different disturbance

regimens, (3) determining the effects ofhuman activities on bighorn

population characteristics (e.g., reproduction and recruitment rates), and

(4) determining the effects ofhuman activity on bighorn behavioral

patterns or activity cycles. It is critical that studies seeking to detect the

effects of human disturbance have sufficient sample sizes and statistical

power to avoid type II statistical errors (accepting a false null hypothesis).

2.8 Research disease and preventive measures. There is a need to provide

ongoing screening forpathogens and exposure to infectious diseases to

detect and mitigate emerging epizootics. Although infectious diseases do

not currently appear to play an important role in population dynamics of

bighorn sheep in most of the Peninsular Ranges, it will be important to

continue monitoring the presence and impact ofinfectious diseases in ewe

groups because outbreaks could occur at any time. Since it will be

essential to radio-collar animals to monitor ewe groups, biological samples

should be collected at the time ofcapture and tested for presence of

infectious disease. In particular, whole blood and serum should be

analyzed for the presence of specific pathogens and antibodies to those

pathogens. A standardized sampling protocol should be developed and the

laboratories used by researchers should be identified in all reports so that

testing can also be standardized. When feasible, fresh carcasses should be

taken immediately to the California Veterinary Diagnostic Laboratory in

San Bernardino for necropsy. A standardized necropsy protocol should be

developed, and necropsy reports made available to all agencies and

researchers.

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At this time, preventive measures such as vaccination or anthelmintic

treatments do not appear to be warranted in any ofthe ewe groups with the

exception ofthe northern Santa Rosa Mountains ewe group. Nematode

parasites have been documented in this group and nematode treatment may

be appropriate. Treatment schemes should be designed so that the

effectiveness of each treatment can be evaluated (control animals or

groups should be used). Infectious disease data should be re-evaluated

periodically or continuously, and recommendations regarding treatment

and preventive strategies based on research findings.

Pathogen monitoring should be extended to cattle and mule deer in the

Peninsular Ranges. Other ungulates may serve as reservoirs for cross

transmission of bluetongue to bighorn sheep.

2.9 Research genetics of bighorn sheep in the Peninsular Ranges.

Genetic issues should be considered and re-evaluated during the recovery

process, especially as new methods become available. Samples should be

used in association with those already collected to more clearly delineate

population structure, to estimate gene flow, to identify the most

appropriate source stock (free ranging and captive) for translocation, to

assess the risk ofinbreeding and outbreeding depression, to test ifthere

has been a recent population bottleneck within a subpopulation, and to

monitor loss of variation due to changes in breeding structure. Research

directed towards the estimation ofthe effective population size (N) should

e

be a priority, and genetic variability should be directly monitored (Lande

and Barrowclough 1987). In addition, analyses ofsamples collected from

bighorn sheep within and outside of the Peninsular Ranges would be

useful to better estimate the phylogeographic structure of desert bighorn

sheep and to further identify management units. DNA samples should be

collected from every animal captured in the Peninsular Ranges and from

adjacent populations, using a standardized sampling protocol. A DNA

bank has been established at the University ofCalifornia at Davis that

consists of over 700 samples from bighorn sheep in the Southwest,

including over 100 samples from the Peninsular Ranges. Given recent and

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anticipated technological advancements, collection and long-term storage

of germinal and somatic cells from captured animals should be initiated

for future use.

3. DEVELOP AND IMPLEMENT EDUCATION AND PUBLIC AWARENESS

PROGRAMS.

Conservation efforts have a higher chance ofsuccess if they are supported by the

local community. A number ofrecovery actions outlined in this recovery plan

will directly affect the general public. It is therefore imperative that strong public

education and awareness programs be implemented. The public needs to be

informed ofthe reasons why specific recovery actions are being taken. This task

will require an education program on the ecology ofPeninsular bighorn sheep,

what threats this species is currently facing, and how recovery actions will reduce

these threats. Coordination with the public and interest groups will be particularly

important for controversial issues, such as trails and predator management. This

knowledge should translate into a respect and concern forthis species, leading to

support for conservation measures.

Several programs and sources ofinformation pertaining specifically to Peninsular

bighorn sheep already exist. Interpretive displays and materials are found at the

Visitor Center in Anza-Borrego Desert State Park, the Bureau of Land

Management Visitor Center in Palm Desert, Bighorn Institute, Living Desert in

Palm Desert, and Palm Springs Desert Museum. In addition, local interest groups

have hosted guest talks by biologists studying bighorn sheep. These programs

should be continued and additional programs established, such as information

provided to the public through the tourist industry and ecotourism operators. The

effectiveness ofeducational programs would be increased if a higher degree of

coordination existed among individual programs and other recovery activities.

This coordination would not only allow each program to present the most accurate

and updated information, but would also let the general public see that the

recovery ofPeninsular bighorn sheep is a collaborative effort supported by

multiple agencies, organizations, and individuals. Specific recovery actions are:

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3.1 Distribute information related to recovery efforts. Updated and

accurate information should be available to interested individuals, groups,

or local governments. This material should be provided by the key

agencies involved in the recovery effort and should include information on

the ecology ofPeninsular bighorn sheep, current threats to population

viability, and explain recovery actions. Information dissemination should

coordinate with the Coachella Valley Multiple Species Habitat

Conservation Plan.

The need for specific recovery actions should be explained to the general

public. For example, home owners, land managers, and developers should

be provided with information that explains: (1) why restrictions on toxic

plants, fences, and pesticides are needed, and (2) why artificial feeding of

coyotes could adversely affect bighorn sheep. Recreation groups should

be provided with information that explains why certain trail closures are

necessary. Interpretive signs should be posted at all trailheads that enter

bighorn sheep habitat. Trained docents could be present at popular

trailheads during high trail usage periods and during periods oftrail

closures to provide additional information and answer questions.

3.2 Continue, update, and coordinate existing education programs.

Existing programs should be expanded and regularly updated to provide an

accurate view of our current knowledge regarding Peninsular bighorn

sheep. Dynamic displays that feature up-to-date population status and

monitoring activities, current research projects, and conservation activities

likely will be most effective. Each program should highlight not only how

its agency’s or organization’s activities contribute to the recovery of

Peninsular bighorn sheep, but how these activities complement those of

other agencies/organizations. Au annual meeting of government officials

including the Fish and Wildlife Service, the Bureau of Land Management,

California Department ofFish and Game, California Department ofParks

and Recreation, U.S. Forest Service, researchers from the University of

California at Davis, Bighorn Institute, and others, as appropriate (e.g.

educational facility representatives or public relations directors), should be

105
held to facilitate the exchange ofinformation and ideas for improving and

updating education programs.

3.3 Develop additional educationalprograms. An educational program

targeting local schools should be developed. This program might include

a teaching packet that school teachers can use to introduce their students to

Peninsular bighorn sheep and the desert ecosystem in general. Classroom

activities could be combined with visits from biologists ortours of bighorn

sheep habitat, possibly in conjunction with existing programs (e.g., at

Auza-Borrego Desert State Park and The Living Desert). Current

conservation issues, population monitoring, and research projects could be

incorporated into this type ofprogram, possibly through the use of

informative videos or web sites. Cunningham (1993) outlined the use of

such an interactive program in Arizona.

The feasibility ofadditional educational programs should be investigated.

Possible sites/organizers are the Zoological Society of San Diego, the Los

Angeles Zoo, and museums within Riverside and San Diego Counties.

Additional goals of existing and newly developed programs should be to:

a. Reach people who would not typically be exposed to traditional

programs (i.e., individuals who might not frequent visitor centers

or who do not have school-aged children). This goal might be

accomplished by promoting informative presentations at senior

citizen centers, home owner group meetings, tourist centers, or golf

clubs. In addition, local and national television programs featuring

the Peninsular bighorn sheep should be developed, and press

releases should be encouraged.

b. Stress an ecosystem approach in which habitat protection is an

integral part ofthe recovery ofPeninsular bighorn sheep.

106
c. Encourage the public to take part in conservation activities. A

prime example is 28 years of waterhole count data that have been

collected by volunteer counters in Anza-Borrego Desert State Park.

Habitat restoration, such as tamarisk removal or water

development also represent ideal volunteer projects. An

observation logbook might be established at visitor centers to allow

visitors to record bighorn sheep and otherspecies they observed.

d. Conduct public attitude assessmentsto determine the effectiveness

ofspecific programs and guide future activities.

3.4 Distribute a protocol to select law enforcement, public health, and

safety offcialsfor the humane treatment ofinjured bighorn sheep. Injured

bighorn sheep are sometimes found by motorists, pedestrians, or hikers

who then report the situation to public officials in a variety of agencies.

Personnel ofthese agencies often are not knowledgeable about medical or

humane treatment procedures for injured animals. A protocol needs to be

developed and distributed to city, county, State, and Federal agencies that

are likely to receive reports ofinjured animals that provides information

on appropriate contacts who are qualified to diagnose and treat injured

animals. Information from such cases should be collected and maintained

by one agency so that a complete data base is available for researchers and

managers.

E. SITE SPECIFIC RECOVERY TASKS.

In this section, the recovery actions described in section II.D are further identified

as site specific recovery tasks. They are matched with the nine recovery regions

listed under the recovery criteria (Table 11). Site specific tasks for each ofthese

areas are indicated in Table 12.

107
Table 11. Recovery criteria regions.

RECOVERY REGIONS

1. San Jacinto Mountains

2. SantaRosa Mountains--North of

State Highway 74

3. Santa Rosa Mountains--South of Highway 74

through Martinez Canyon

4. Santa Rosa Mountains--South of Martinez

Canyon to slopes west ofVillage Peak

5. Coyote Canyon--east and west sides

6. North San Ysidro Mountains-- Henderson

Canyon to CountyRoad S-22

7. South San Ysidro Mountains-- County Road S-22

to State Highway 78

8. Vallecito Mountains/Fish CreekMountains

9. Carrizo Canyon/Tierra Blanca

Mountains/Coyote Mountains A/south ofInterstate 8

108
Table 12. Site specific tasks recommended for each recovery region. Refer to the narrative outline (section II.D) for a

complete description of recovery actions.

Recovery Action

(abbreviated)

Recovery Region

SRN74SY-S VM/

EC

SJ

——

x x

SRS74

—

x

SRMCS

a

x

CC

—

x

SYN

———

x x x

CC/TB!

CM

—

1.1.1 Protectessentialhabitat x

1.1.2 Secure habitat x x x x x x x x x

1.1.3.1 Remove exotic vegetation X X X X X X X X X

1.1.3.2 Reduce/eliminate wild horses x x

1.1.3.3 Implement fire management plan x x x x x x x x x

1.1.3.4 Maintain/provide water sources x x x x x x

1.1.3.5 Maintain/reestablish habitat connectivity x x x x x x x x x

1.2.1.1 Constmct fences (at urban interface) x x x

1.2.1.2 Avoid non-native vegetation x x x

1.2.1.3 Promote native plants, limit exotic plants x x x

1.2.1.4 Prohibit use of toxic plants x x x

1.2.1.5 Discourage use of exotic invasive plants x x x

1.2.1.6 Prohibit enticement onto private property x x x

1.2.1.7 Monitor use of pesticide, herbicides, etc. x x x

1.2.1.8 Regulate water diversion/procurement x x x x x x x x x

1.2.1.9 Prohibit artificial water sources (Culicoides) X X X

1.2.1.10 Discourage feeding coyotes x x x

1.2.1.11 Secure funds/methods to monitor x x x x x x x x x

1.2.2.1 Develop trails management program x x x x

1.2.2.2 Prohibit activities withnegative impacts x x x x x x x x x

1.2.2.3 Minimize livestock grazing impacts x x x

1.2.2.4 Prohibit domestic sheep grazing x x x x x x x x x

1.2.2.5 Fence neighboring cattle allotments x x x

1.2.2.6 Prohibit goats as pack animals x x x x x x x x x

1.2.2.7 Secure funds/methods tomonitor x x x x x x x x x
Table 12. Continued.

Recovery Action

(abbreviated)

Recovery Region

SJ SRN74SR574SRMCSCC SYNSY-S VM/

FC

CC/TB!

CM

1.3.1.1 Regulate fence construction and design x x x x x

1.3.1.2 Postlmonitor highway crossing areas x x x x x x

1.3.2 Reduce mortality due to natural causes x x x x x x

1.4 Develop reintro/augment. strategy x x X

2.1.1 Monitorabundance x x x x x x x x x

2.1.2 Monitordistribution x x x x x x x x x

2.1.3 Monitorrecruitnient x x x x x x x x x

2.1.4 Monitor survivorship/causes of mortality x x x x x x x x x

2.2 Developpopulation models x x x x x x x x x

2.3 Research bighom/lions/deer/habitat x x x x x x

2.4 Research impact of coyotes/bobcats x x x x x x x

2.5 Research methods to decrease predation x x x x x x

2.6 Research habitat use/dispersal x x x x x x x x x

2.7 Monitor human impacts x x x x x x x x

2.8 Research disease/prevention x x x x x x x x x

2.9 Research genetics x x x x x x x x x

3.1 Distributerecoveryinforniation x x x x x x x x x

3.2 Cont./update public education programs x x x x x x x x x

3.3 Develop new public education programs x x x x x x x x x

3.4 Distribute protocol for injured sheep treatment x x x x x x x x x

SI: San Jacinto Mountains

SR-N74: Santa Rosa Mountains - north of Highway 74

SR-574: Santa Rosa Mountains - south of highway 74

SR-MCS: Santa Rosa Mountains--South of Martinez Canyon

CC: Coyote Canyon--east and west side

SY-N:

SY-S:

North San Ysidro Mountains

South San Ysidro Mountains

VM/FC: Vallecito/Fish Creek Mountains

CC/TB/CM: Carrizo Canyon/Tierra Blanca

Mountains/Coyote Mountains
III. IMPLEMENTATION SCHEDULE

The Implementation Schedule that follows outlines actions and estimated costs for

the Peninsular bighorn sheep recovery program, as set forth in this recovery plan.

It is a guide for meeting the objectives discussed in part II ofthis plan. This

schedule indicates task priority, task numbers, task descriptions, duration oftasks,

responsible agencies, and estimated costs. The agencies responsible for

committing funds are not necessarily the entities that will carry out the tasks. The

agency or agencies with lead responsibility for each task are indicated in the table.

Initiation ofthese actions is subject to the availability offunds.

The Implementation Schedule indicates speculative, future costs (preparation of

additional plans, orresearch programs, etc.) as “to be determined”. Some costs

appear as zero because indirect costs, such as those incurred by: (1) contributions

oftime and materials by agencies and other groups, and (2) administrative or

regulatory costs by public agencies, are not included in cost totals. Costs of

continuous tasks are estimated assuming a 25-year time to recovery. Though the

Implementation Schedule does not distinguish between public and private costs,

no identifiable or specific expenditures are likely to be needed by the private

sector, other than voluntary efforts contributed by nonprofit organizations and

citizen groups. Priorities (Column 1 ofthe following table) are assigned as

follows:

Priority I - An action that must be taken to prevent extinction or to prevent the

species from declining irreversibly.

Priority 2 - An action that must be taken to prevent a significant decline in

species population/habitat quality or some other significant

negative impact short of extinction.

Priority 3 - All other actions necessary to provide for full recovery ofthe

species.

111
Abbreviations used in the Implementation Schedule:

To be determined

Continuous

Coachella Valley Multiple Species Habitat Conservation Plan,

which includes participating cities, County ofRiverside, and

landowners

Palm Springs, Cathedral City, Rancho Mirage, Palm Desert, Indian

Wells, and La Quinta

San Diego, Imperial, and Riverside Counties

ACBCI

BI

BLM

CALTRANS

CDFG

CDPR

CVMVCD

CVMC

CVWD

DoD

FWS

RWQCB

RC

RCFCWCD

SDZS

UCD

USFS

*

Agua Caliente Band ofCahuilla Indians

Bighorn Institute

Bureau ofLand Management

California Department of Transportation

California Department ofFish and Game

California Department of Parks and Recreation

Coachella Valley Mosquito and Vector Control District

Coachella Valley Mountains Conservancy

Coachella Valley Water District

Department ofDefense

U.S. Fish and Wildlife Service

Regional Water Quality Control Board

Riverside County

Riverside County Flood Control and Water Conservation District

San Diego Zoological Society

University ofCalifornia - Davis

U.S. Forest Service

Lead Agency

TBD

cont.

MSHCP

Cities

Counties

AGENCIESAND ORGANIZATIONS

112
RECOVERY PLAN IMPLEMENTATION SCHEDULE FOR PENINSULAR BIGHORN SHEEP

Responsible

Agencies

Cost (SI ,000s)

jFYj F’i’

Priority

—

I

Task Task Description

Task

Duration

(Years)

—____

cont. ACBCI*, BLM*,

FWS*, CVMC*,

MSHCP*,

CDFG*, CDPR*,

CVWD*

Total

Estimated

Cost

(SI ,OOOs)

~L2il22L2LIJL

0 0 0 0 0 0

FY FY FY

I

I I

Protect essential habitat

1.1.2 Secure habitat cont. BLM*, CDFG*,

CVMC*, CDPR*,

MSHCP*

70,000 TBD TBD TBD TI3D TBD

I 1 3 1 Remove exotic vegetation and prevent

invasion by exotic plants

cont. ACBCI*, BLM*,

CDFG*, CDPR*,

CVWD*,

RCFCWCD*

250 10 10 10 10 10

1 1.1.3.2 Reduce/eliminate wild horses 5 ACBCI*, BLM*,

CDPR*

TBD TBD TBD TBD TBD TBD

I 1.1.3.4 Maintain/provide water sources 5 13LM~, CDFG*,

CDPR*

50 20 20 10 0 0

1 1.1.3.5 Maintain/re-establish habitat

connectivity

cont. BLM* , FWS*,

CDFG*, CDPR*,

Caltrans*, MSHCP*

TBD TBD TBD TBD TBD TBD

1 1.2.1.1 Construct fences to exclude bighom

sheep from urban areas

5 MSHCP*, CDFG, FWS 500 100 100 100 100 100

I 1.2.1.4 Prohibit use of toxic plants cont. MSHCP* 0 0 0 0 0 0

I 1 2 1 8 Regulate water diversion/procurement cont. RWQCB*, CVWD* 0 0 0 0 (1 0
RECOVERY PLAN IMPLEMENTATION SCHEDULE FOR PENINSULAR BIGHORN SHEEP

Responsible

Agencies

Priority

—I

Task Task Description

Task

Duration

(Years)

—cont.

Total

Estimated

Cost

($1,000’s)

MSI~1CP* 1............... 0

Cost (S 1,000’s)

IFYI FY

..2L0 ——— 020 030 I...~2LI2~ 0 —0

FY FY

02

FY

I .2 I. II Secure funding to implement measures 03

I 1.2.2.1 Develop and implement a trails

management program

cont. RLM*, CDFG, USFS,

FWS, MSHCP

TBD TBD TBD TBD TBD TI3D

I I 2 2 2 Prohibit fragmenting and interfering

activities

cont. BLM*, USFS*, FWS*,

DoD*, CDFG*, CDPR*

Counties*, Cities*

TBD TBD TBD TBD TBD TBD

I 1.2.2.3 Minimize livestock grazing impacts 5 BLM¶ USFS* 25 5 5 5 5 5

1.2.2.4 Prohibit grazing by domestic sheep 5 BLM*, USFS* 0 0 0 0 0 0

I 1.2.2.7 Secure funding to implement measures cont. BLM*, IJSFS*, FWS*, 0 0 0 0 0 0

1.3.2 Reduce mortality due to natural causes cont. CDFG*, CDPR, FWS,

BLM

TBD TBD TI3D TBD TBD TBD

I 2 11 Monitor abundance cont. CDFG*, CDPR, BLM,

FWS, BI

323 11 15 11 15 11

I 2 I 2 Monitor distribution cont. CDFG*, CDPR, I3LM,

FWS, BI

323 II 15 11 15 II

I 2.1.3 Monitor recruitment cont. CDFG*, CDPR, BLM,

FWS, RI

323 11 15 11 15 II

I 2.1.4 Monitor survivorship and cause-specific

mortality

cont. CDFG*, CDPR, BLM,

FWS, BE

125 5 5 5 5 5

2 1.1.3.3 Implement fire management plan 5 USFS*, BLM, CDFG,

CDPR

TBD TI3D TBD TBD TBD TBD

2 1.2.1.2 Avoid non-native vegetation cont. MSHCP* 0 0 0 0 0 0
I; RECOVERY PLAN IMPLEMENTATION SCHEDULE FOR PENINSULAR BIGHORN SHEEP

Priority Task

—

I 2 1 9

Task Description

Task

Duration

(Years)

—

cont.

Responsible

Agencies

Total

Estimated

Cost

(SI,000’s)

Cost (S 1,000’s)

}FYj FY

K2LL2L

——— —

0 0 0 0 0

FY[ FY IFY

Oil 02103

2

2 Prohibit (7ulicoides water sources MSHCP* 0

2 1.2.2.5 Fence cattle allotments adjoining habitat 3 BLM* TBD TBD TBD TBD 0 0

2 1.2.2.6 Prohibit goats as pack animals cont. BLM*, USFS*,

CDFG*, CDPR*

0 0 0 0 0 0

2 1.3.1.1 Regulate fence design/construction cont. BLM*, USFS*,

MSHCP*

0 0 0 0 0 0

2 1.4 Develop captive breeding,

reintroduction, augmentation strategy

cont. BI,* CDFG,* FWS* TBD TBD TBD TBD TBD TBD

2 2.2 Develop population models 3 TBD 30 10 10 10

2 2.3 Research the relationships between

bighorn, mountain lions, mule deer, and

habitat characteristics

5 FWS,* CDFG,*

CDPR*, SDZS*, UCD*

650 130 130 130 130 130

2 2.5 Investigate the efficacy of temporary

suppression ofnatural predation

5 CDFG*, FWS, CDPR 150 30 30 30 30 30

2 2.6 Research habitat use/selection and

dispersal behavior

10 TBD ISO 15 15 15 15 IS

2 2.7 Monitor the effects of human

disturbance

3 CDFG*, BLM, CDPR,

USFS, FWS

TBD TBD TBD TBD

2 2.8 Research disease and preventive

measures

3 TBD TBD TBD TBD TBD

2 2.9 Research genetics 3 TBD TBD TBD TBD TBD
RECOVERY PLAN IMPLEMENTATION SCHEDULE FOR PENINSULAR BIGHORN SHEEP

Priority Task Task Description

Task

Duration

(Years)

Responsible

Agencies

Total

Estimated

Cost

($l,OOO’s)

Cost (51,000’s)

—1~

FY FY FY FY FY

01J02j03j04J05

— ——— —

2 2 2 2 2

2

2 3.1 Distribute information on recovery

efforts

cont. FWS*, BLM, CDFG,

BI, MSHCP, CDPR,

USFS

5

50

2 3.2 Continue, update, and coordinate

existing programs

cont. FWS*, BLM, USFS,

CDFG, BI, CDPR,

MSHCP

50 2 2 2 2 2

2 3.3 Develop educational programs cont. FWS*, BLM, USFS,

CDFG, MSHCP,CDPR,

BI

50 2 2 2 2 2

3 1.2.1.3 Promote native plants cont. MSHCP* 29 5 I I I I

3 1.2.1.5 Discourage use of exotic invasive plants cont. MSHCP* 0 0 0 0 0 0

3 1.2.1.6 Prohibit enticement on private property cont. MSHCP* 25 I I I I I

3 1.2.1.7 Monitor use of pesticide, herbicides 5 MSHCP* 25 5 5 5 5 5

3 1.2.1.10 Discourage feeding coyotes cont. MSI~1CP* 0 0 0 0 0 0

3 1.3.1.2 Post/monitor highway crossing areas cont. Caltrans*, BLM,

CDPR, CDFG

25 TI3D TBD TBD TBD TBD

3 2.4 Investigate the relationships between

bighorn, coyote, and bobcat

10 TBD 100 10 10 10 10 10

3 3 4 Injured sheep treatment protocol cont. CDFG*, FWS, I3LM,

MSHCP

0 0 0 0 0 0

Total estimated cost ofrecovery: $73,253,000 +

ON
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147
V. APPENDICES

APPENDIX A. AN OVERVIEW OF THE PENINSULAR RANGES

The Peninsular Ranges are located in southern California and Mexico, in the

Colorado Desert division ofthe Sonoran Desert (Ryan 1968). On the north, the

Peninsular Ranges are bordered by the Transverse Ranges. From this point, they

extend south into Mexico, forming the backbone ofBaja California. In

California, the ranges form a prominent natural province (Sharp 1976) that is

bounded on the east by the Salton Trough. To the west, the province extends to

the Pacific Ocean, as a 130-kilometer-wide (80-mile-wide) series ofnorthwesterly

trending basins and ranges. The basins form channels below sea level and the

ranges form the islands of San Nicolas, Santa Barbara, Santa Catalina, and San

Clemente.

The highest peak in the San Jacinto Mountains is the 3,292-meter (10,800-foot)

high San Jacinto Peak. Toro Peak, at 2,655 meters (8,700 feet), is the highest

peak in the Santa Rosa Mountains (Oakeshott 1978). The Salton Sea, located to

the east ofthe Peninsular Ranges, is found in the largest land mass below sea level

in the Western Hemisphere (Ting and Jennings 1976). Historically, the Salton

Sea has alternated between a freshwater lake fed with waters from the Colorado

River, and a dying brackish pond when the waters ofthe Colorado River flowed

instead to the Gulf ofMexico. When filled, the Salton Sea lapped at the foothills

ofthe Santa Rosa Mountains. Since approximately 1907, however, the sea has

been an increasingly salty depository for agricultural wastes ofthe Coachella and

Imperial Valleys (Ting and Jennings 1976).

Bighorn sheep inhabit the eastern slopes ofthe Peninsular Ranges in habitat

characterized by steep slopes and cliffs, canyons, washes, and alluvial fans. The

remainder ofthis appendix will, therefore, provide an overview ofthe eastern

slopes ofthe Peninsular Ranges.

Within bighorn sheep habitat, annual rainfall is variable with maxima of35 to 470

millimeters (1.3 to 18.5 inches) during the past 36 years (National Oceanic and

148
Atmospheric Administration, 1962 to 1997). Rainfall exhibits a bimodal

distribution pattern with most (approximately 70 percent) occurring in the winter

months and a lesser amount in the late summer months. Winter rains are ofthe

Pacific marine type, characterized by steady long rain showers, which promote the

spring peak in plant productivity. Summer showers are ofthe Gulfmarine type,

which result in localized and sometimes fierce thunderstorms (Lindsay and

Lindsay 1991). Maximum temperature in bighorn sheep habitat often reaches 46

degrees Celsius (115 degrees Fahrenheit) in summer, while winters are mild, with

temperatures occasionally reaching freezing (National Oceanic and Atmospheric

Administration, 1962 to 1997).

On the eastern slopes ofthe Peninsular ranges, vegetation associations are

coniferous forest, primarily ponderosa pine (Pinus ponderosa), Jeffrey pine (Pinus

jeffreyi), Coulter pine (Pinus coulteri), and white fir (Abies concolor) above

approximately 1,800 meters (5,905 feet), chaparral above approximately 1,500

meters (4,920 feet), and pinyon pine (P. monophylla)-juniper (Juniperus

cal~fornica) above approximately 1,200 meters(3940 feet). Lower elevations are

dominated by agave (Agave deserti), ocotillo (Fouquieria splendens), cholla

(Opuntia spp.) and palo verde (Cercidiumfioridurn), creosote (Larrea tridentata),

palo verde-mesquite (Prosopis spp.) associations(Ryan 1968). Bighorn sheep

typically are found at elevations less than 1,400 meters (4,600 feet) (Jorgensen

and Turner 1975), usually staying at elevations below the chaparral and pinyon

pine-juniper vegetation associations. These associations can represent visual

obstruction because ofdenser and taller structures, and therefore make bighorn

sheep more susceptible to predation (refer to section I.B. I and I.B.2).

The Peninsular Ranges are inhabited by a large number ofmammalian species

(reviewed by Ryan 1968). The only native sympatric ungulate is the mule deer

(Odocoileus hernionus). Bighorn sheep and deer distributions overlap at the upper

elevations of bighorn sheep habitat, with possible geographic and seasonal

differences in the degree ofoverlap. Deer are observed more frequently at lower

elevations during the winter months. Potential native predators ofbighorn sheep

are mountain lions (Puma conco1or~, bobcats ~Lvnxrufus), coyotes (C’anis

latrans), and golden eagles (Aquila chrvsaetos). These species are found

throughout bighorn sheep habitat in the Peninsular Ranges.

149
References

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Ryan, R. M. 1968. Mammals of Deep Canyon. The Desert Museum, Palm

Springs, California.

Sharp, R. P. 1976. A field guide to southern California. Kendall/Hunt

Publishing Company, Dubuque, Iowa. L

3Olpp.

151
References

Bolton, H. E. 1930. Anza’s California expeditions. Vol. IV. Fonts complete

diary ofthe second Anza expedition. University ofCalifornia Press,

Berkeley. SS2pp.

Brigandi, P. 1995. The livestock industry on the Anza-Borrego desert. A report

for the Anza-Borrego Desert State Park. Contract No. C4532007.

Cunningham, S. C. and R. D. Obmart. 1986. Aspects ofthe ecology ofdesert

bighorn sheep in Carrizo Canyon, California. Desert Bighorn Council

Transactions 30:14-19.

Jorgensen, M. C. and R. E. Turner. 1975. Desert bighorn ofthe Anza-Borrego

Desert State Park. Desert Bighorn Council Transactions 19:51-53.

Lindsay, L. and D. Lindsay. 1991. The Anza-Borrego Desert Region. Third

Edition. Wilderness Press, Berkeley, California. l79pp.

National Oceanic and Atmospheric Administration. 1962-1997. Climatological

data: California. National Climate Data Center, Asheville, North Carolina.

Oakeshott, G. B. 1978. California’s changing landscape: a guide to the geology

ofthe state. McGraw-Hill, New York, New York. Y79pp.

Reed, L. 1986. Old Time Cattlemen and Other Pioneers ofthe Anza-Borrego

Area. Third Edition. Anza-Borrego Desert Natural History Association,

Borrego Springs, California. l4eSpp.

Ryan, R. M. 1968. Mammals of Deep Canyon. The Desert Museum, Palm

Springs, California.

Sharp, R. P. 1976. A field guide to southern California. Kendall/Hunt

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151
Ting, I. P. and B. Jennings. 1976. Deep Canyon’s past. Pages1-6 in Deep

Canyon, a desert wilderness for science. I. P. Ting and B. Jennings, eds.

University ofCalifornia, Riverside. 177pp.

Turner, J. C. 1976. Bighorns. Pages 167-173 in Deep Canyon, a desert

wilderness for science. I. P. Ting and B. Jennings, eds. Univ. of

California, Riverside. lT7pp.

152
APPENDIX B. DELINEATION OF ESSENTIAL HABITAT FOR

BIGHORN SHEEP IN THE PENINSULAR RANGES

Intended use ofthe map (Figures 2, 4-9)

A number ofhabitat models have been developed to rate bighorn sheep habitat

(e.g., Hansen 198Gb, Holl 1982, Armentrout and Brigham 1988, Cunningham

1989, Dunn 1996) and components ofbighorn sheep habitat have been examined

or discussed by numerous researchers (e.g., Hansen 1980a, McCarty and Bailey

1994). It has been suggested that some ofthese models be used to rate bighorn

habitat in the Peninsular Ranges. However, application ofthese models here is

inappropriate because they were developed in other areas and life zones where

bighorn sheep exhibit different habitat requirements. For example, the Hansen

model has been shown to be oflimited value in measuringhabitat quality in areas

outside the habitats in which it was derived (Andrew and Bleich 1999) and is no

longer used by the California Department ofFish and Game (S. Torres, California

Department ofFish and Game, pers. comm.). Cunningham (1989) suggested that

such habitat models need to be modified before being applied to novel bighorn

sheep habitat.

The purpose ofmapping bighorn sheep habitat in this recovery plan is not to rate

the relative value ofhabitat types and areas within the Peninsular Ranges, but to

identify those lands in need ofprotection, restoration, and management that are

essential to bighorn sheep recovery (refer to section I1.D.1). Rating the quality of

sheep habitat would require a more thorough understanding of habitatselection

versus habitat availability; studies that address this topic in the Peninsular Ranges

have not been conducted to date but are recommended under section II.D.2.6.

Though bighorn sheep habitat sometimes can be described by its function (e.g.,

habitat for escape or lambing), Wilson et al. (1980) and Bleich et al. (1996)

concluded that all habitat types used by bighorn sheep in desert environments are

necessary for their population viability. The Santa Rosa Mountains Wildlife

Habitat Management Plan (Bureau of Land Management 1980), a long-standing

plan developed and implemented under the Sikes Act (16 USC 670a etseq.,

Public Law 86-797) also recognized this, stating “(e)ach acre of bighorn habitat is

important in maintaining the present population”.

153
The purpose ofthis mapping effort is to delineate those areas believed to be

necessary for a self-sustaining bighorn population with a high probability for longterm survival and recovery in the Peninsular Ranges ofthe United States.

“Essential habitat”, therefore, consists ofthose areas that provide bighorn sheep

with the various physical and biological resources (e.g., space, food, water, cover)

potentially needed for: (1) individual/population growth and movement, and (2)

normal behavior with protection from disturbance. Essential habitat should be

protected from further loss or degradation (refer to section II.D. 1.1). The valley

floor to the east and the north ofthe Peninsular Ranges (e.g., Coachella Valley,

Imperial Valley) likelywas used historically by bighorn sheep during rare, longdistance moves to and from other mountain ranges. However, no such moves

have been documented. Furthermore, the chance ofsuchmoves has essentially

been eliminated by high density urban development, major freeways, fences, and

canals. Consequently, the vast majority ofthe valley floor to the east ofthe

Peninsular Ranges is not included as essential habitat and is now detrimental to

future use by sheep.

Approach used

The delineation ofessential habitat was based on physical and biological features

known to be important to bighorn sheep. These features were identified by

reviewing pertinent literature and by drawing on the collective knowledge and

experience ofthe Recovery Team and other biologists who have studied bighorn

sheep in the Peninsular Ranges. The knowledge ofsuch biologists played an

important role in the mapping exercise because Peninsular bighorn sheep occupy a

habitat that has marked climate and vegetational differences compared to habitat

ofmost other bighorn sheep populations. The Peninsular Ranges are located in

the Colorado Desert, a division ofthe Sonoran Desert, which experiences

different precipitation patterns(timing and intensity ofrainfall) than the Mojave

or other Sonoran deserts and contains a somewhat different flora (Jaeger 1957,

MacMahon 1985). These differences appear to cause Peninsular bighorn sheep to

use habitat differently than bighorn sheep in other areas. For example, dense

vegetation at higher elevations ofthe Peninsular Ranges restricts bighorn sheep to

the more open desert slopes at lower elevations. For this reason, researchers

familiar with bighorn sheep in the Peninsular Ranges have referred to these

154
mountains as the “upside-down mountain ranges” (R. Weaver, California

Department ofFish and Game retired, pers. comm.). Therefore, published

information regarding habitat use patterns ofbighorn sheep, in general, was

supplemented with knowledge regarding habitat use patterns ofPeninsular

bighorn sheep, to identify habitat features that determine the distribution of

bighorn sheep in these ranges.

Delineation ofessential habitat is not based solely on known use patterns because:

(1) population numbers currently are low and small populations use less habitat

than larger populations, such as will be needed for recovery; (2) bighorn sheep are

difficult to detect; (3) use patterns are only known for a recent short time period;

(4) telemetry data on radio-collared animals (a sampled subset ofthe entire

population) represents only the area used by marked animals, not the entire herd;

and (5) habitat loss and human disturbance likely inhibits use ofsome lower

elevation habitat. However, the delineated habitat boundaries were reviewed by

Recovery Team biologists studying bighorn sheep in the Peninsular Ranges to

verify that the mapped habitat encompassed most areas known to be used by

animals currently or in the recent (25 to 30-year) past. However, numerous

documented locations ofsheep fell outside the essential habitat boundaries (Figure

6). The resulting map also was compared against a previous modeling effort

(Bureau of Land Management 1980) as part ofthe validation and refinement

process (see below).

Choice of habitat components

Habitat requirements have been examined by numerous researchers in the past

(e.g., Cunningham 1989, McCarty and Bailey 1994). Topographic cover, water,

and forage appear to be the most consistently recognized habitat requirements,

although other components such as mineral availability, thermal cover, as well as

absence ofcompetition with other ungulates and disturbance from human

activities also have been suggested to be important (Cunningham 1989, McCarty

and Bailey 1994).

Because these habitat components and characteristics largely determine how

bighorn sheep use their habitat in the Peninsular Ranges, information available on

155
these potential model parameters were compiled for analysis. Data that are

available consisted of: (1) a fairly comprehensive inventory ofwater sources for

Anza-Borrego Desert State Park, (2) a water source survey by the Bureau of Land

Management for the northern parts ofthe range, (3) vegetation community maps,

and (4) topographic relief.

In desert environments, water is a known limiting factor for many species of

plants and wildlife. However, some populations ofbighorn sheep are known to

exist in areas withoutsources ofperennial water (summarized in Broyles 1995), as

is known to be the case in parts ofthe Peninsular Ranges for at least some parts of

the year (refer to section lB. 1). In the Peninsular Ranges, the presence of

perennial water is known to be a limiting factor only during prolonged droughts or

summers withoutsignificant thunderstorm activity. However, given the numerous

dependable watersources in the San Jacinto Mountains and other portions ofthe

range (e.g. central Santa Rosa Mountains), water likely does not limit sheep

distribution in these regions, even under drought conditions. The variable quality

and lack ofreliable water source data in some portions ofthe Peninsular Ranges,

and the fact that water availability does not limit habitat use in much ofthese

ranges, resulted in the decision to not use water sourcesto delineate bighorn sheep

habitat. Available observational records (Figure 6) indicate that sheep range at

least 16 kilometers (10 miles) from known perennial water sources. Given the

existing distribution of water, sheep are capable of using, and therefore can be

expected to use, all areas mapped as essential habitat.

Generalized plant community mapping has been completed within bighorn habitat

throughout Riverside County, and detailed mapping has been completed in AnzaBorrego Desert State Park. However, bighorn sheep are generalist foragers and

plants known to be eaten are broadly distributed across habitat types in the

Peninsular Ranges. Extreme topographic relief provides a diversity of

interdigitated habitats and plant communities across the mountainous slopes,

canyons, washes, and alluvial fans within the home range ofeach ewe group.

Consequently, the distribution of forage plants does not appear to limit sheep

distribution, though it can influence seasonal habitat use patterns.

156
The primary habitat components that limit the distribution ofbighorn sheep in the

Peninsular Ranges may be those associated with predator evasion. Unobstructed

visibility is recognized as an important habitat characteristic by many researchers

(e.g., Geist 1971, Risenhoover and Bailey 1985, Fairbanks et at. 1987, Etchberger

et at. 1989). Bighorn sheep rely on their keen vision and climbing ability to detect

and evade their predators (Geist 1971). The presence ofescape terrain and an

unobstructed view are, therefore, key habitat requirements (Geist 1971).

All bighorn sheep habitat models recognize escape terrain as a key habitat

component. However, the definition of“escape terrain” varies widely (McCarty

and Bailey 1994). Some researchers defined it by a minimum slope (e.g., Andrew

et at. 1999, Dunn 1996) or slope plus a qualitative measure ofruggedness (e.g.,

Holl 1982, Risenhoover and Bailey 1985, Armentrout and Brigham 1988), while

others have described escape terrain with word models that incorporate a

qualitative description ofslope and ruggedness(e.g., Hansen 1 980b, Elenowitz

1983, Gionfriddo and Krausman 1986, Fairbanks et at. 1987, Cunningham 1989).

The difficulty in determining a universal definition may be because bighorn sheep

in different mountain ranges have access to different habitat (in terms ofslope and

ruggedness), and/or because use ofescape terrain varies with group size

(Risenhoover and Bailey 1985), group composition, and season (Cunningham and

Ohmart 1986, Bleich et a!. 1997). Furthermore, escape terrain has been described

as habitat used “for escape from perceived danger” (Van Dyke et at. 1983). This

definition recognizes that escape terrain is based on a bighorn sheep’s perception,

something that apparently differs among individuals and populations. Desert

bighorn sheep frequently have been found at slopes of21 to 50 percent (Elenowitz

1983), slopes greater than or equal to 20 percent (Andrew et at. 1999), and slopes

averaging 13 to 34 percent (Bleich et at. 1997). A minimum slope of 20 percent

was used (in combination with canopy cover) to define bighorn sheep habitat in

New Mexico (Dunn 1996). A slope of greater than or equal to 20 percent was

adopted asthe minimum required as escape terrain for bighorn sheep in the

Peninsular Ranges. The first step ofthe habitat mapping process was, therefore,

to identify all patches ofland having a slope of greater than or equal to 20 percent

(see following methods).

157
Bighorn sheep are closely associated with mountainous habitat and often are

hesitant to venture far from escape terrain (Geist 1971). Although they have been

documented to move great distances from escape terrain on rare occasions

(Schwartz et at. 1986), it is not uncommon to observe animals moving a short

distance from escape terrain in search of forage or water sources, or moving

between neighboring mountain masses. Washes and alluvial fans often support a

higher diversity, quality, and quantity offorage species than less productive rocky

slopes (Leslie and Douglas 1979), seasonal and perennial water sources (Wilson

et al. 1980, Holland and Keil 1989), bedding and thermal cover (Andrew 1994),

alternative forage sources in times ofdrought, resource scarcity, and stress (Leslie

and Douglas 1979, Bleich et a!. 1997), and a source offorage with higher

nutritional value during the lambing and rearing season (Hansen and Deming

1980). Also refer to section I.B. 1. Since temperature varies inversely with

elevation, the earliest winter forage growth occurs at lower elevations (Wehausen

1980, 1983), and sheep often seek this early source ofnutrients. The critical

importance to bighorn ofaccess to a variety of feeding habitats was demonstrated

in the Whipple Mountains when reintroduced sheep were confined to an enclosure

containing what was considered ample forage. At lambing time, both ewes and

their new lambs began dying ofmalnutrition (Berbach 1987), apparently because

they were not free to seek out habitats containing more nutritious forage.

Researchers have documented animals ranging at a variety of distances from

mountainous terrain, e.g., 1.6 kilometers (0.80 mile) (Denniston 1965), 0.8

kilometer (0.50 mile) (MeQuivey 1978), 1.3 kilometers (0.70 mile) (Leslie and

Douglas 1979), greater than 1 kilometer (1.6 miles) (Burger 1985), greater than

1.6 kilometers (1 mile) (Bleich eta!. 1992), and greater than 2.5 kilometers (1.6

miles) (Andrew eta!. 1997). Jones et at. (1957) reported bighorn sheep foraging

as far as 2 kilometers (1.2 miles) from the base ofthe Santa Rosa Mountains.

Elsewhere in the Peninsular Ranges, bighorn sheep were frequently observed

within 0.8 kilometer (0.5 mile) from mountainous habitat feeding in or moving

across washes and alluvial fans (DeForge and Scott 1982; E. Rubin and M.

Jorgensen, pers. comm.). Accordingly, the second step ofthe mapping process

was to include habitat within 0.8 kilometers (0.50 mile) ofslopes greater than or

equal to 20 percent.

158
To identify slopes of 20 percent or greater, 7.5’ digital elevation models (DEMs)

were merged together over the entire study area. These digital elevation models

are 30-meter by 30-meter (98-foot by 98-foot) cell grids with a vertical accuracy

of 7 meters (23 feet). All grid cells were then aggregated into slope classes. Next,

the slope classes were analyzed to select habitat within 0.8 kilometer (0.5 mile) of

slopes of greater than or equal to 20 percent. This selection was accomplished by

first lumping slopes greater than or equal to 20 percent into one class in a

derivative grid. A buffer of 0.8 kilometer (0.5 mile) was then applied to the

perimeter of all areas ofslope in the derivative grid.

In the Peninsular Ranges, bighorn sheep habitat is delimited at upper boundaries

by dense vegetation associations (primarily chaparral) that reduce visibility and

likely increase susceptibility to mountain lion predation. Measuring visibility (by

actual fieldmeasurements) to delineate the upper boundary ofhabitat would

require study because it is currently not known what visibility threshold is

acceptable to bighorn sheep in the Peninsular Ranges. Fire frequency and its

effect on plant succession changes visibility thresholds over time (refer to section

I.D). Therefore, to determine the upper boundary ofbighorn sheep habitat, the

westernmost areas used by bighorn sheep within the past 25 to 30 years were

identified and the vegetation associations in these areas were applied rangewide

where detailed vegetation analyses were available. Because a detailed vegetation

map was not available rangewide, a team of biologists experienced with

Peninsular bighorn sheep flew the entire upper/western boundary line in a

helicopter and visually assessed vegetation associations. The path ofthe flight

was determined by consensus among the biologists and was recorded via a Global

Positioning System (GPS). The antenna of a Trimble Navigation, LTD., Global

Positioning System was mounted in the helicopter and position data were

recorded every 10 seconds. A total of228 kilometers (142 miles) were flown. A

base station Global Positioning System, located in the Anza-Borrego Desert State

Park, was run during the entire flight. Trimble Navigation Pathfinder Office

software was used to post process the collected Global Positioning System data

using base station information. Trimble Navigation Pathfinder Office (IM) was

then used to export the data as an ESRI NRC/INFO Geographic Information

Systems (GIS) readable file. Only corrected data were used to build the resulting

Geographic Information System layer. Because this line is dynamic in response to

159
fire frequency and likely has shifted to a lower elevation with the advent offire

suppression, a 0.8 kilometer (0.5 mile) extension was added to the westside of

this line.

The resulting line in Anza-Borrego Desert State Park was checked against detailed

Geographic Information System mapping of vegetation associations within the

park (Keeler-Wolf et at. 1998). Vegetation associations not typically used by

bighorn sheep in the Peninsular Ranges were excluded from essential habitat.

These associations primarily included Muller’s oak (Quercus cornelius-rnutteri),

sugarbush (Rh us ova ta), chamise (Adenostomafascicutatum), and manzanita

(Arctostaphvlos spp.) associations. Associations encompassed within bighorn

sheep habitat included brittlebush (Encetiafarinosa), desert lavender (Hyptis

emo,yi), cholla (Opuntia spp.), burro-weed (Ambrosia dumosa) and creosote

(Larrea tridentata), and other creosote associations. The resulting line supported

the habitat boundary that was derived during the helicopter flight along the

western margin ofcurrent bighorn sheep habitat.

To validate the choice ofgreater than or equal to 20 percent slope and 0.8

kilometer (0.5 mile) distance from this slope as model parameters, Recovery

Team members experienced with Peninsular bighorn sheep flew the easternmost

line ofbighorn sheep habitat in a northern portion ofthe range (San Jacinto

Mountains and Santa Rosa Mountains). The path ofthis flight was determined by

consensus among the team members, based on theirobservations ofbighorn sheep

in these ranges, and was believed to represent the low elevation (easternmost)

boundary ofhabitat commonly used by Peninsular bighorn sheep. The path ofthis

flight, which was recorded via Global Positioning System, supported the choice of

the greater than or equal to 20 percent slope plus 0.8 kilometer (0.5 mile) distance

from this slope as the eastern, lower elevation habitat boundary.

The resulting habitat boundaries were reviewed by Recovery Team members who

have studied bighorn sheep in the Peninsular Ranges to verify whether those areas

known to be used by sheep in the recent past (within the past 25 to 30 years) were

included within the modeled habitat boundaries. This review included a

comparison of bighorn sheep sighting locations against the map and verified that

160
most areas used by sheep within the past 25 to 30 years were included within the

modeled habitat boundaries (Figure 6).

Mapping Refinement

Upon further review by Recovery Team members, it was determined that the

modeled habitat included a habitat type not likely to be used by Peninsular

bighorn sheep. This habitat type, classified as mud hills (Augustine and Ward

1995) was found in the Borrego Badlands and Camzo Badlands ofAnza-Borrego

Desert State Park. Much ofthis soil type was removed from the delineated map

because it did not correspond with known bighorn sheep habitat use patterns.

Conversely, the preliminary habitat boundaries excluded several small islands of

“nonhabitat” (defined by the modeling ofslope and distance from slope). Because

Recovery Team members familiar with the areas considered these islands to be

bighorn sheep habitat on the basis of known sightings in nearby or comparable

areas, these islands were included in delineated habitat.

A small number of known observations fell outside the delineated boundaries at

lower elevations on relatively flat terrain, such as Clark Dry Lake and Coyote

Canyon. These observations support previously published reports ofbighorn

sheep occasionally moving away from mountainous areas. However, the relative

rarity ofrecords beyond the 0.8 kilometer (0.5 mile) distance from slope was

judged to indicate that such habitat was not essential to population recovery if the

habitat delineated within the 0.8 kilometer (0.5 mile) distance from slope were

protected. In other areas, the opposite process was required to minimize the

habitat edge to area ratio consistent with sound tenets ofresource management

and preserve design. Along some segments, the 0.8 kilometer (0.5 mile) distance

from slope was expanded slightly to capture “nonhabitat” areas that would have

represented deep but narrow intrusions into an otherwise stable and manageable

essential habitat boundary.

Further modifications were deemed necessary along the urban interface in the

Coachella Valley. The 0.8 kilometer (0.5 mile) distance from slope largely has

been lost to urban development. Much ofthe remaining valley floor and alluvial

habitat within the 0.8 kilometer (0.5 mile) distance is highly fragmented and

161
degraded with marginal or detrimental value to bighorn conservation (e.g., vacant

lots along Highway 111, parcels bordered on three sides by urban development).

A series ofmeetings with affected jurisdictions and majorland owners was

convened under the auspices ofthe Coachella Valley multiple-species planning

effort to discuss and refine the delineation of essential habitat along the urban

interface. Lands without long-term conservation value were excluded from

essential habitat (Figures 7, 8, 9). The larger fragments that still remain were

included within essential habitat where they were contiguous with mountain slope

habitat and ofa configuration amenable to effective management. Subject to

implementation ofrequired conservation measures, the essential habitat boundary

does not include development projects previously reviewed and approved by us.

Finally, pursuant to Secretarial Order 3206 June 5, 1997, we have entered into

government to government discussions with the various American Indian tribes

that possess lands in bighorn sheep habitat. We coordinated with the tribes to

encourage their participation in delineating essential habitat and developing the

Peninsular bighorn sheep Recovery Plan in a way that promotes recovery ofthe

species and minimizes the social, cultural, and economic impacts on tribal

communities. We worked with and supported the efforts ofthe Torres-Martinez

Desert Cahuilla Indians to obtain data on the value ofReservation lands to

bighorn sheep conservation but the Tribe has not agreed that sufficient

information is available to demonstrate that theirlands are essential to recovery.

Based on coordination with the Morongo Band of Mission Indians, tribal lands

within the essential habitat boundary will be included for sheep conservation. The

Agua Caliente Band of Cahuilla Indians has coordinated with us in the delineation

and have agreed that a reservation-wide habitat conservation planning effort will

determine appropriate land management issues at a finer scale within the essential

habitat boundary.

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sheep in the East Chocolate Mountains, Imperial county, California. M. S.

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162
Andrew, N. G., V. C. Bleich, P. V. August, and S. G. Torres. 1997. Demography

of mountain sheep in the East Chocolate Mountains, California.

California Fish and Game 83(2):68-77.

Andrew, N. G. and V. C. Bleich. 1999. Habitat selection by mountain sheep in

the Sonoran desert: Implications for conservation in the United States and

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Armentrout, D. J. and W. R. Brigham. 1988. Habitat suitability rating system for

desert bighorn sheep in the Basin and Range province. U.S. Department

ofthe Interior, Bureau ofLand Management. Technical Note 384. l8pp.

Augustine, S. and K. Ward. 1995. Geomorphology Mapping Project, Calif.

Depart. Parks and Recreation and Cesar Lab, San Diego State Univ.

Berbach, M. W. 1987. The behavior, nutrition, and ecology ofa population of

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Bernardino County, California. M.S. Thesis, Calif, State Polytechnic

University, Pomona, l3Spp.

Bleich, V. C., M. C. Nicholson, A. T. Lombard, and P. V. August. 1992.

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information system. Biennial Symposium ofthe Northern Wild Sheep and

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Bleich, V. C., J. D. Wehausen, R. R. Ramey II, and J. L. Rechel. 1996.

Metapopulation theory and mountain sheep: implications for conservation.

Pages 353-373 in Metapopulations and Wildlife Conservation. D. R.

McCullough, ed. Island Press, Washington, D.C. 4.29pp.

Bleich, V. C., R. T. Bowyer, and J. D. Wehausen. 1997. Sexual segregation in

mountain sheep: resources or predation? Wildlife Monographs No. 134.

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Broyles, B. 1995. Desert wildlife water developments: questioning use in the

southwest. WildI. Soc. Bull. 23(4):663-675.

Bureau ofLand Management. 1980. Santa Rosa Mountains Wildlife Habitat

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Burger, W. P. 1985. Habitat use by desert bighorn sheep on Desert National

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California. Q3pp.

Cunningham, 5. 1989. Evaluation ofbighorn sheep habitat. Pages 135-160 in

The desert bighorn sheep in Arizona. R. M. Lee, ed. Arizona Game and

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Cunningham, S. C. and R. D. Ohmart. 1986. Aspects ofthe ecology of desert

bighorn sheep in Carrizo Canyon, California. Desert Bighorn Council

Transactions 30:14-19.

DeForge, J. R. and J. E. Scott. 1982. Ecological investigations into high lamb

mortality. Desert Bighorn Council Transactions 26:65-76.

Denniston, A. 1965. Status of bighorn in the River Mountains ofLake Mead

National Recreation Area. Desert Bighorn Council Transactions 9:27-34.

Dunn, W. C. 1996. Evaluating bighorn habitat: a landscape approach. U. S.

Department ofthe Interior, Bureau ofLand Management. Technical Note

395. 4lpp.

Elenowitz, A. 5. 1983. Habitat use and population dynamics oftransplanted

desert bighorn sheep in the Peloncillo Mountains, New Mexico. M.S.

thesis. New Mexico State University, Las Cruces. lS8pp.

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Etchberger, R. C., P. R. Krausman, and R. Mazaika. 1989. Mountain sheep

habitat characteristics in the Pusch Ridge Wilderness, Arizona. Journal of

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Management 51(4):912-915.

Geist, V. 1971. Mountain sheep: a study in behavior and evolution. The

UniversityofChicago Press, Chicago, Illinois. 383pp.

Gionfriddo, J.P. and P.R. Krausman. 1986. Summer habitat use by mountain

sheep. J. WildI. Manage. 50:33 1-336.

Hansen, C. G. 1980a. Habitat. Pages 64-79 in The desert bighorn: it life history,

ecology, and management. G. Monson and L. Sumner, eds. The

University of Arizona Press. Tucson. 370pp.

Hansen, C. G. 1980b. Habitat evaluation. Pages 320-335 in The desert bighorn:

its life history, ecology, and management. G. Monson and L. Sumner, eds.

The University of Arizona Press. Tucson. 370pp.

Hanson, C G. and 0. V. Deming 1980. Growth and Development. Pages 152-

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ecology, and management. The Univ. OfArizona Press, Tucson, 370 pp.

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Jones, F. L., G. Flittner, and R. Gard. 1957. Report on a survey of bighorn sheep

in the Santa Rosa Mountains, Riverside County, Calif. Fish and Game

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Department of Parks and Recreation. Prepared by the Natural Heritage

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c433000.

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Mountains, Nevada. Wildlife Monographs No. 66. 56pp.

McCarty, C. W. and J. A. Bailey. 1994 Habitat requirements ofdesert bighom

sheep. Colorado Division of Wildlife, Terrestrial Wildlife Research.

Special report number 69. Z7pp.

McQuivey, R. P. 1978. The desert bighorn sheep ofNevada. Nevada

Department of Fish and Game. Biological Bulletin No. 6. 8lpp.

Risenhoover, K. L. and J. A. Bailey. 1985. Foraging ecology of mountain sheep:

implications for habitat management. Journal ofWildlife Management

49:797-804.

Schwartz, 0. A., V. C. Bleich, and S. A. Holl. 1986. Genetics and the

conservation of mountain sheep (Ovis canadensis nelsoni). Biological

Conservation 37:179-190.

Van Dyke, W. A., A. Sands, J. Yoakum, A. Polenz, and J. Blaisdell. 1983.

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Oregon. General Technical Report PNW- 159, USDA Forest and Range

Exp. Sta., Portland, Oregon. Y7pp.

Wehausen, J. D. 1980. Sierra Nevada bighorn sheep: history and population

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Yoakum, M. Hinks, J. Turner, and J. DeForge. 1980. Desert bighorn

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167
APPENDIX C. GUIDELINES FOR DEVELOPING A LONG-TERM

STRATEGY FOR REINTRODUCTION, AUGMENTATION, AND

CAPTIVE BREEDING OF BIGHORN SHEEP IN THE PENINSULAR

RANGES

The purpose ofthis appendix is to provide guidelines for developing a long-term

strategy for reintroduction, augmentation, and captive breeding ofbighorn sheep

in the Peninsular Ranges, as identified in the recovery plan (task 1.4). This

appendix is organized into two sections. The first section outlines some ofthe

preliminary steps needed to identify cases in which reintroductions,

augmentations, and captive breeding may be appropriate, and highlights some

important considerations in the development of a long-term strategy. The second

section presents protocols for captive breeding and release ofcaptive animals, and

represents guidelines prepared by the Bighorn Institute for an existing captive

breeding and release program. This section addresses many ofthe issues

identified in our Policy Regarding the Controlled Propagation ofSpecies Listed

Under the Endangered Species Act (65 FR 56916; September 20, 2000).

I. Considerations in developing a long-term strategy for reintroductions and

augmentations

A number ofdecisions must be made when developing a long-term strategy for

augmentation and reintroduction ofbighorn sheep in the Peninsular Ranges.

Important preliminary steps are presented here in outline form:

1) Identify the general goals ofthe long-term strategy in relation to the overall

recovery effort. These goals should consider the viability ofthe population

with respect to population dynamics and genetics.

2) Determine if existing ewe groups should be augmented or new groups

established. A population model, using estimated population parameters (e.g.,

abundance, recruitment, survivorship, dispersal), should be used to evaluate

the effectiveness of various options (including the option of no augmentation

or reintroductions) on the viability ofthe metapopulation.

168
3) Identify and prioritize sites for augmentations and reintroductions. This

assessment must evaluate not only the site’s importance to the viability ofthe

entire population, but also must address the following questions:

a) What is/was the cause of extinction or endangerment in this location?

b) Has this cause been minimized or removed?

c) Is reintroduction or augmentation the best conservation option for this

particular situation? Have other necessary measures, such as habitat

restoration or protection, been taken?

4) Determine augmentation and reintroduction techniques. The success of

previous bighorn sheep augmentation and reintroduction projects has been

mixed, and a number ofquestions remain (Desert Bighorn Council 1996). In

reintroducing or augmenting Peninsularbighorn sheep, the following issues

need to be evaluated:

a) Determine whether to use captive or free-ranging animals. For the

following reasons, caution should be exercised when using captive

animals:

i) Ifmultiple, consecutive generations ofanimals are bred in captivity,

they may undergo “domestication selection”; that is, captive

individuals may have behavioral or morphological phenotypes that

perform well in captivity but not in the wild. In addition, captive

animals may have been raised in an overly protective environment

where selection against deleterious genes was relaxed (Brambell 1977,

Campbell 1980, Elliott and Boyce 1992, Bush et a!. 1993).

ii) Captive animals may be disease vectors to wild populations if they

have been exposed to novel diseases during ex situ (outside the

original site, or captive) propagation (Campbell 1980, Woodford and

Kock 1991, Bush et at. 1993), or ifthey have continued to harbor

pathogens that have been “purged” from wild populations.

iii) The use of captive animals during augmentations can reduce or

increase the effective population size ofthe wild population (Ryman

and Laikre 1990, Elliott and Boyce 1992).

Part 11 ofthis appendix provides protocols by which these concerns may be

minimized. Releases offree-ranging animals are typically more successful

169
than are those ofcaptive animals (Griffith eta!. 1989, Gordon 1991,

Stanley Price 1991); however, an advantage ofusing captive animals is

that their genetic profiles typically are known. In addition, the potential

effects on population (Stevens and Goodson 1993) and genetics of

removing animals from the wildpopulation must be considered. Currently

the small size ofewe groups within the peninsular Ranges limits the

availability offree-ranging animals for translocation. Additional genetic

studies may help identify sources within the Peninsular Ranges or

elsewhere. Future projects could involve both captive and free-ranging

bighorn sheep.

b) Ifcaptive animals are to be used in reintroductions and augmentations,

determine the desired size ofthe captive herd, and optimum facilities and

management techniques. One alternative is to establish a large captive

herd that is housed in a larger enclosure and managed less intensely than

the existing captive herd. An approach similar to this is used by the New

Mexico Department ofGame and Fish (1997) at theirRed Rock Wildlife

Area, where bighorn sheep are housed in a fenced area ofover 500

hectares (1,235 acres). Potential advantages ofsuch a facility are that

released animals may have traits more characteristic offree-ranging

animals (as opposed to animals raised in a more confined environment),

and a larger captive population may lessen genetic concerns associated

with small founder populations. As with any captive breeding program,

however, the source ofanimals for this captive population would have to

be considered, and both population and genetic management guidelines

would have to be addressed (see part II ofthis appendix).

c) Determine the best population composition ofreleased groups. This

consideration applies whether captive orfree-ranging animals are used.

The number, age/sex composition, and experience ofreleased animals are

important considerations (Lenarz and Conley 1980, Wilson and Douglas

1982, Kleiman 1989). The gregarious behavior of bighorn sheep suggests

that larger groups are desirable (Wilson and Douglas 1982). However,

smaller group sizes more likely mimic natural re-colonization events. The

sex ratio should maximize the reproductive potential ofthe released group

170
orthe wild population during reintroductions and augmentations

respectively. For bighorn sheep, this typically means a low ram to ewe

ratio (Lenarz and Conley 1980). Young animals have high reproductive

value (Gotelli 1995) and have a strong tendency to integrate with existing

herds when used as release stock (Ostermann et al, in press), anl thus are

desirable for augmentation programs. Lenarz and Conley (1980)

suggested that the optimum age for released bighorn sheep is 3 years.

However, inclusion ofa small number ofolder orfree-ranging, and

presumably more experienced, individuals increasesthe likelihood of

success ofa reintroduction. The effect ofthese variables needs to be

considered not only with respect to how they will influence success ofthe

release, but also how the removal ofthese animals will affect the source

stock from which they came (Stevens and Goodson 1993).

d) Identify appropriate release animals based on pedigree and proximity to

the intended release area. Though based solely on genetic theory, this

approach is conservatively designed to: (1) preserve the potential for

genetic adaptations to local conditions, (2) prevent outbreeding depression,

and (3) maintain the existing genetic structure currently found among

Peninsular bighorn ewe groups (Brambell 1977, Boyce et a!. 1999).

However, other options are available to prevent loss ofheterozygosity in

the wild population (May 1991). In general, the preservation ofthe gene

pool ofthe entire metapopulation (wild and captive populations included)

should be the primary concern (Foose 1991). Therefore, when

reintroducing or augmenting animals, care must be taken to avoid genetic

swamping ofnative populations (Kleiman 1989, Ryman and Laikre 1991,

Foose 1991, Elliott and Boyce 1992). Furthermore, during any

reintroduction or augmentation, the number and sex ratio ofreleased

animals must be considered, as it will affect effective population size

(Crow and Kimura 1970, FitzSimmons et at. 1997). The second section of

this appendix discusses the genetic considerations ofcaptive breeding and

release of captive animals in detail.

171
e) Determine the most effective means ofreleasing animals. These

considerations, which applyto both the release ofcaptive and free-ranging

animals, should include:

i) Whether to use a ‘soft’ or‘hard’ release (Berbach 1987, Moore and

Smith 1991).

ii) How far to move free-ranging animals during reintroductions and

augmentations. The philopatric behavior ofbighorn sheep may result

in animals attempting to return to their natal home range. Research on

dispersal and movement patternsmay guide these decisions (refer to

section II.D.2 ofthis recovery plan).

iii) During which time of year to conduct releases.

iv) What specific release site to use. For instance, how far should release

sites be from other bighorn sheep (Bleich et at. 1996) or from human

development? This question may be assessed by releasing and

monitoring a small number ofsentinel animals during a feasibility

study (Kleiman 1989, Chivers 1991).

5) Determine methods for monitoring and assessing the success ofreintroduction

or augmentation programs, in relation to the goals ofthis recovery effort

(Stanley Price 1991), and identify a specific schedule for future review and

possible revision ofthe long-term strategy.

II. Captive breeding and release ofcaptive bighorn sheep

While it is not a long-term solution (Snyder et a!. 1996), captive breeding is a

powerful tool for rescuing species threatened with extinction (Caughley 1994,

Philippart 1995, Caughley and Gunn 1996). Captive breeding can also be used to

delay extinction while the agents of a decline are investigated (Caughley and

Gunn 1996). Other advantages ofcaptive propagation include the ability to

moderate environmental variance, manage genetic diversity, increase the effective

population size, and expand animal numbers to provide stock for wild populations

(Foose et at. 1995). Releasing captive-born animals into the wild to support weak

populations is an increasingly common practice (Griffith et a!. 1989, Kleiman

1989, Snyder etat. 1996).

172
Although there are benefits ofcaptive propagation programs forreleasing animals

into the wild (Griffith et at. 1989, Kleiman 1989, Caughley 1994, Foose et at.

1995), these programs can be costly, labor intensive, and their effectiveness has

been questioned (Campbell 1980, Philippart 1995, Caughley and Gunn 1996,

Snyder et a!. 1996). Additionally, there are a number ofpotential risks associated

with captive breeding and release programs. Our Policy RegardingControlled

Propagation of Species Listed Under the Endangered Species Act (65 FR 56916;

September 20, 2000) identified the following risks that must be addressed when

planning controlled propagation and reintroduction programs: (1) removal of

natural parental stock that may result in an increased risk ofextinction by

reducing the abundance of wild individuals and reducing genetic variabilitywithin

naturally occurring populations; (2) catastrophic events that can cause the loss of

some or all ofthe captive population; (3) potential for inbreeding or other adverse

genetic effects that mayresult from increasing only a portion ofthe gene pool; (4)

potential erosion of genetic differences between populations; (5) exposure to new

selection regimes in controlled environments that may diminish capacity to

survive and reproduce in the wild; (6) genetic introgression; (7) increased

predation or competition for food, space, and/or mates; and (8) disease transfer.

Adhering to established criteria and upholding standardized protocols will

contribute to the success ofreintroduction and augmentation programs and reduce

the accompanying risks. In this appendix, generalized criteria and guidelines for

reintroduction and augmentation programs are combined with knowledge of

desert bighorn sheep ecology to create more specific guidelines for Peninsular

bighorn sheep captive breeding and release programs.

In this appendix, reintroduction is defined as the movement of wild or captive

animals into formerly occupied habitat, while the release ofanimals into currently

occupied habitat is termed “augmentation” or “restocking.” The ultimate

objective ofthese guidelines is to establish wild, free-ranging herds that no longer

rely on captive breeding. Separate guidelines should be developed for captive

breeding programs with other primary goals.

173
Before commencing a captive breeding program, a feasibility study should be

conducted to determine its necessity and potential for success. The following

general criteria should be considered (Kleiman et a!. 1994): the wild population’s

need for support with respect to genetic diversity and population structure, the

availability ofstock, removal ofthe original cause ofdecline, protection of

sufficient habitat, local politics, governmental and nongovernmental agency

support, reintroduction/augmentation technology, knowledge ofspecies biology,

and sufficient financial resources. A summary ofthese criteria, which are grouped

into four categories, is provided below.

Needfor population and/or genetic support

Because captive breeding and reintroduction/augmentation programs

require large financial and logistical commitments, the need for population

and/or genetic support must first be clearly established (Kleiman 1989,

Phillipart 1995, Snyder eta!. 1996). The International Union for the

Conservation ofNature and Natural Resources (1995) guidelines for

reintroduction and augmentationsrecommend conducting a population and

habitat viability workshop before initiating a program. A population

viability analysis may also facilitate the design and objectives ofthe

program by providing direction on the number ofanimals needed, and

hence the size ofthe facility needed, and whether restocking (augmenting

populations) or reintroduction (establishing new groups) is preferred.

Captive breeding is often expensive and not always the most cost-efficient

conservation strategy (Kleiman 1989, Kleiman et at. 1991, Snyder et at.

1996). It must be conducted in conjunction with other conservation

measures, and should be based on specific recommendations within a

recovery or management plan so that it does not unjustlypreempt other

recovery techniques (Snyder et a!. 1996).

Environmental conditions

Captive breeding should only be undertaken ifsuitable, unsaturated habitat

is available (Brambell 1977, Kleiman 1989, Ounsted 1991) and release

sites have sufficient carrying capacity to support the expansion ofthe

reintroduced or augmented population. Ideally, release sites should be

174
legally protected (Kleiman et a!. 1994). Removing or controlling the

original cause(s) ofdecline is an essential step, as failure to do so is a

primary reason that reintroduction and augmentation efforts are

unsuccessful (Brambell 1977, Ounsted 1991, Kleiman et a!. 1994).

However, in some situations, augmenting a population while investigating

the cause ofdecline is an acceptable practice (Caughley and Gunn 1996).

The philopatric behavior ofbighorn sheep (Geist 1971) suggests there are

advantages to augmenting a population to retain traditional herd

knowledge, rather than reintroducing animals after extirpation, particularly

ifthis would allow research into the cause ofdecline.

Biopolitical conditions andfunding

Although no breeding program can be successful without knowledge of

the species’ biology orreintroduction/augmentation technology, nonbiological factors such as long-term funding, project administration, and

communication among participating organizations have been found to be

important determinants for program success (Stanley Price 1991, Beck et

a!. 1994, Kleiman et a!. 1994). Feasibility studies should include

investigating prospects for long-term funding and obtaining the support of

all relevant governmental and non-governmental agencies. Inadequate

funding could severely limit the progress and success ofthe program.

Therefore, programs should not be initiated until funding is secured to

ensure that all phases (disease testing, research, post-release monitoring,

etc.) will be accomplished. Because captive breeding programs are a

multidisciplinary undertaking involving people drawn from a variety of

backgrounds (International Union for the Conservation ofNature and

Natural Resources 1995), the decision making structure, as well as the

authority and responsibility ofeach group involved should be clearly

delineated (Kleiman et a!. 1994).

Knowledge ofthe species and reintroduction/augmentation technology

Knowing the ecological requirements ofa species is necessary for a

successful breeding and release program. For many species, the lack of

basic information and release technology necessitates detailed studies

examining the species behavior and biological needs before establishing a

175
breeding program (Kleiman 1989, Stanley Price 1991). However, past and

ongoing captive propagation programs for desert bighorn sheep (Calkins

1993, New Mexico Department of Game and Fish 1997, Ostermann et al.

in press) have demonstrated the potential for establishing self-sustaining

captive populations and the techniques developed for translocations

(Rowland and Schmidt 1981, Wilson and Douglas 1982) provide

information that can be applied to releasing captive-reared animals into the

wild.

Husbandry

Large, predator-proofenclosures with native vegetation, natural habitat features,

and adequate food, salt, mineral, and water resources are needed. Native

vegetation should be retained in the enclosure, and supplemental feed may be

required to prevent over-browsing. An enclosure that contains a variety of habitat

types and topographic relief will allow captive animals to exhibit natural behavior,

such as using escape terrain in response to disturbance. Presumably, housing

captive animals in conditions as similarto the release site as possible will ease

their transition to a wild environment. During the nonbreeding season, adult

males and females should be separated or have ample room to naturally segregate.

To reduce disease transmission risks, captive populations should be maintained

within the natural range ofthe animal, in single-species facilities that do not

regularly exchange stock (Snyder et a!. 1996). The design ofthe enclosure should

allow forthe safe capture ofanimals for sampling and/or release. Enclosure

fencing should be greater than or equal to 3 meters (10 feet) in height above

ground and extend aminimum of 0.61 meter (2 feet) underground, or employ

other options to exclude predators. Mountain lions have entered enclosures and

killed captive bighorn sheep on several occasions (Blaisdell 1971, Sandovol 1979,

Winkler 1977). Monitoring consisting of at least daily checks ofthe enclosure

and animals is necessary for detecting health concerns, causes ofmortalities, and

disturbances.

Disease prevention and screening

Disease prevention is ofprimary importance for desert bighorn sheep captive

breeding programs. Of all North American wild ungulate species, wild sheep are

possibly the most sensitive to common livestock diseases and parasites (Jessup

176
1985). Disease outbreaks terminated reintroduction efforts at both the Lava Beds

National Monument in California (Blaisdell 1982) and the Sierra Diablo pensin

Texas (Brewer 1997), two initially successful desert bighorn sheep breeding

operations. Disease in the captive animals and poorreintroduction success led to

the release ofall bighorn sheep from the Zion National Park captive propagation

enclosure (McCutchen 1978). Outbreaks ofblue-tongue reduced the Red Rock

population by approximately 18 animals in 1985 and 25 animals 1991 (New

Mexico Department ofGame and Fish 1997). See section I.E.3 for information

on the captive population at Bighorn Institute.

Disease considerations for augmentation programs include the potential of

introducing disease to the wild population when releasing captive-reared stock

and the impact ofdiseases endemic in the wild population on released animals

(Viggers eta!. 1993). The prevalence ofdisease in the wild and captive

population will determine the need to eradicate pathogens in animals brought into

or released from captivity and whether to release or breed certain animals.

Elimination ofall pathogens from captive animals is not expected or

recommended (Bush et a!. 1993, Viggers et a!. 1993), as this may reduce their

immunity to disease and place them at risk ofdiseases endemic in the wild

population. Regular,standardized disease monitoring ofboth the wild and captive

populations is strongly recommended.

Diseaseprevention measures

Captive breeding facilities should be closed to the public and the staff

should practice rigorous disease prevention measures, including avoidance

of potential disease transmission from other captive stocks as well as

between wild and captive bighorn sheep. All potential routes for disease

transmission from domestic livestock should be anticipated and avoided.

For example, when purchasing hay, care should be taken to avoid dealers

who rotate their crops with domestic livestock grazing.

Separate quarantine facilities should be available to house incoming stock;

however, animals known to be sick should not be brought into captivity. It

is important to determine the cause of death for all animals that die in

captivity or soon afterrelease into the wild. Fresh carcasses should be

177
refrigerated and transported to a veterinary diagnostic laboratory for full

necropsy.

Disease-free certification

Disease screening (hematology, serum chemistry, serology, virus isolation,

ova and parasite tests, and bacterial culture) should be performed on

greater than or equal to 25 percent ofthe captive animals at least annually,

and on all pre-release animals within 30 days prior to their release into the

wild. Health screening of pre-release bighorn sheep helps prevent the

introduction ofdisease into the free-ranging population and optimize the

released animal’s chances for survival in the wild. Screening of wildcaught breedstock reduces the chance ofintroducing disease to the captive

population. All bighorn sheep entering or leaving the captive breeding

program should be certified as “disease-free.” Disease-free certification

requiresthat within 30 days prior to release: (1) the animals appear

healthy and shows no signs of active infection upon visual examination by

an U.S. Department of Agriculture accredited veterinarian familiar with

bighorn sheep, (2) recent laboratory results (from testing described above)

do not indicate active infection or other health concerns, (3) the animal

tests negative for Ovine Progressive Pneumonia (AGlID test), and (4) the

animals have not been exposed to diseased animals in the captive breeding

facility.

Treatment ofsick animals in captivity

Animals showing signs ofillness (e.g., drooping ears, nasal discharge,

coughing, lethargy, weight loss) should be closely observed and

biologically sampled to attempt to determine the cause ofillness. Bighorn

sheep in poor condition, needing frequent treatment, or exhibiting signs of

infectious or contagious disease should be placed in quarantine.

Treatment should be provided under veterinary supervision ifthe

condition is life threatening, unless research needs dictate otherwise.

Principles guiding genetic management

Genetic management strives to minimize the loss of naturally occurring genetic

variability by preserving genes offounders who represent a gene pool ofinterest

178
(Ballou and Lacy 1995). Goals for the genetic management of captive populations

usually include retaining genetic variation for future evolutionary potential,

minimizing genetic changes that may occur while a species is in captivity, and

avoiding inbreeding (Foose and Ballou 1988, Hedrick and Miller 1992, Foose

1991, Foose et a!. 1995). Concerns about the fitness, evolutionary potential, and

locally adapted gene pools of natural populations require that conservation efforts

also consider intraspecific genetic variation (Soul~ 1986, Millar and Libby 1991,

Hedrick and Miller 1992, Cronin 1993). Molecular markers (allozymes,

restriction fragment length polymorphisms, microsatellites, mitochondrial DNA)

can aid in identifying current and historic levels ofpopulation subdivision, gene

flow, and population characteristics (Milligan et a!. 1994, Avise 1995). However,

it is important to note that molecular markers identify only a small portion ofthe

genome and arenot specifically or necessarily tied to traits involved in either

adaptation or fitness.

Identifying the genetic structure ofthe population being augmented is considered

a first step towards assuring that appropriate subpopulations are targeted for

propagation and release (Brambell 1977, Lyles and May 1987). Peninsular

bighorn sheep are distributed in a metapopulation comprising approximately eight

subpopulations, although the degree to which this structure reflects anthropogenic

forces is unknown (Torres et a!. 1994, Boyce et a!. 1997, Rubin et a!. 1998, Boyce

eta!. 1999).

The genetic effects ofpopulation subdivision are quantified by the fixation index

(F; Wright 1951), which describes the proportion ofgenetic variation within

bighorn sheep subpopulations relative to the total variation in the population. The

fixation index can also be used as an index of genetic differentiation among

populations. A high fixation index value indicates significant genetic

substructuring ofthe population. Moderate values (defined as F of0.05 to 0.15,

ST

Wright 1978) for mean F were found for six populations within the Peninsular

ST Ranges using nuclear DNA markers (micro-satellite loci [F equals 0.113] and

the major histocompatibility complex loci [F equals 0.120]). They suggest

ST

there are relatively high levels ofmale-mediated gene flow among populations

(Boyce et a!. 1997). When managing a group ofclosely related subpopulations

migration should be maintained while also allowing for genetic differentiation

179
among demes in response to local selective pressure (Nelson and Soul~ 1987,

Ryman eta!. 1995).

Other factors to consider in reintroduction or augmentation programs are effects to

the native gene pool, including introgression, and an increase in the variance in

family size or the number of offspring per individual (Ryman et a!. 1995).

Introgression occurs when populations with different genetic characteristics are

mixed. It may cause the loss oflocally adapted genes through interbreeding, loss

ofentire gene pools as a result ofdisplacement, and/or homogenization of a

previously genetically structured population through swamping with a common

gene pool. Factors relating to introgression that should be considered include: the

amount ofgenetic divergence between the captive and wild populations, the

genetic population structure ofthe wild population, and the number of animals to

be released relative to the size ofthe recipient population (Ryman eta!. 1995).

Without knowledge ofthe genetic characteristics ofthe natural population, it is

nearly impossible to predict the occurrence orimportance ofchanges in the

genetic structure ofthe augmented population. Although problems with

outbreeding depression usually involve populations that are distinct subspecies,

the effects ofgenetic mixing are difficult to predict, ranging from no effect to

outbreeding depression even within the same species under similar circumstances

(Ryman et a!. 1995). There are some circumstances when introgression can be

beneficial, for example, when a natural population has been genetically depleted

over an extended period due to small population size (Ryman et al. 1995).

A second problem with captive or supportive breeding programs is the potential to

increase the variance in family size or number ofoffspring produced per

individual (Ryman et a!. 1995). Taking a fraction ofthe wild population into

captivity for enhanced reproduction and survival may increase population

numbers, but it can reduce genetic variation by inflating the variance in family

size, a parameter that is inversely related to the genetically effective size ofthe

population (Ryman and Laikre 1991). Pedigree analysis, rotation ofbreeding

stock, and genetic management ofthe captive and wild populations can help

lessen concerns associated with introgression and variance in family size. For

example, in the northern Santa Rosa Mountains, the origin (captive or wild-born)

ofall animals in this herd is known and the sire and/or dam ofmost individuals is

180
known (Ostermann and DeForge 1996). In this case, particular wild-born bighorn

sheep native to the gene pool can be targeted for captive propagation if necessary.

This situation presents a unique opportunity to use high intensity genetic

management (Lacy et a!. 1995) to improve or maintain the genetic variability in a

free-ranging population.

Se!ection ofbreeding stock

Even when the main goal of an augmentation project is to provide population

support, Kleiman (1989) recommended first considering the genetic

characteristics of potential release animals. Animals released into the wild should

be similar to the native animals ofthe region because over evolutionary time,

successful populations are expected to become morphologically, physiologically,

and behaviorally adapted to the local environment (Brambell 1977, Kleiman 1989,

Lynch 1996). Obtaining locally adapted stock for captive breeding and release

into the wild is proposed as a method to approximate the correct, locally adapted

genotype, although this may add relatively little genetic variability to the wild

population (Lyles and May 1987). However, given the habitat fragmentation and

small size ofseveral demes in the Peninsular Ranges, genetic exchange to avoid

inbreeding depression should be considered.

Only bighorn sheep less than 1 year of age are recommended for capture for

breeding stock if animals are to be placed in small enclosures (approximately less

than 2 hectares [5 acres]) for quarantine. Young bighorn sheep adjust more

readily to a captive environment than adult bighorn sheep (J. DeForge, pers.

comm.), which have died from colliding with fences while in captivity (Montoya

1973, Sandoval 1981). Larger enclosures would reduce this risk.

Matingstrategies

Appropriate level of genetic management ofcaptive populations depends on the

information available, intended intensity ofmanagement, and goals ofthe

program (Lacy et a!. 1995). Breeding programs for bighorn sheep vary from small

populations receiving high-intensity genetic management to large herds where

only low-intensity genetic management is possible. Several low-intensity mating

strategies based on maximizing the effective population size and maximum

avoidance ofinbreeding have been developed (Princee 1995). This document

181
focuses on concepts for intensive genetic management, which applies mainly to

small captive populations.

The genetic importance of an animal is defined as a measure ofthe probability

that it carries founder genes that are currently at risk ofbeing lost (MacCluer et al.

1986, Ballou and Lacy 1995, Thompson 1995), though this value may be

compromised by the presence ofdeleterious genes. Although animals with many

living relatives in a population may be less genetically valuable than animals with

few relatives, this larger group ofrelatives may be more successful due to superior

fitness. “Mean kinship”, one ofseveral methods used to identify genetically

important individuals, is defined as the average ofthe kinship coefficients

between an individual and all living individuals including itself (Ballou and Lacy

1995). Animals with low mean kinship values are genetically important. Because

mean kinship is insensitive to the age structure ofa population, the concept of

kinship value was introduced. “Kinship value” considers the age and reproductive

value ofanimals when calculating mean kinship (Ballou and Lacy 1995). Kinship

values will exceed mean kinship for animals whose relatives are ofprime

reproductive age.

Both theory and computer simulation studies suggest that mating strategies based

on mean kinship (and therefore kinship value) retain the highest level ofgene and

allele diversity (Ballou and Lacy 1995, Miller 1995). To the extent possible, a

strategy based on kinship value (Ballou and Lacy 1995) should be used to arrange

matings in the captive population, precluding matings between relatives. Target

founder representation and kinship value can be used to assess the genetic

importance of animals and help direct rotation ofbreeding stock. Rams will

generally contribute genes faster than ewes and will therefore need to be rotated

more frequently than ewes.

Genetic evaluation

Captive breeding programs should include provisions for genetic testing,

including mitochondrial DNA sequence analysis and microsatellite typing on all

founders in the captive population. Genetic testing of captive-born offspring is

particularly important in populations with low intensity genetic management or in

cases where paternity is unknown. Molecular genetic analyses can be used to

182
determine the genetic similarity between captive-reared and free-ranging sheep, as

well as to construct pedigrees for captive or wild populations.

Population management

General objectives for population management oflarge captive populations with

multiple generations in captivity are: (1) establishment of a self-sustaining

captive population, (2) expansion ofthe population to a predetermined carrying

capacity as quickly as possible within genetic management guidelines, (3)

stabilization ofthe population at a given capacity, with an age and sex ratio that

will achieve the goals ofthe program (such as production ofsurplus stock for

release) (Foose and Ballou 1988). For small captive breeding programs,

population management is most relevant to the behavioral stability ofthe captive

population and minimizing the impact ofstock rotation. In most cases bighorn

sheep should be released into the wild by 10 years of age, to prevent an

accumulation ofold-age animals. Ewes that fail to recruit a lamb for 3

consecutive years should be considered forrelease because they are not

contributing to the goal of producing stock for release into the wild.

Surplusor unfit animals

Healthy animals displaying abnormal behavioral or physiological

characteristics should be evaluated. Preferably, ifthe characteristic has

potential to be altered to allow release into the wild, the animal should be

retained in captivity until suitable forrelease. Ifan animal’s genetic

characteristics cause it to be unfit forrelease into target populations, that

animal can be released into a nontarget subpopulation so long as

deleterious traits are not introduced to the wild. Because the primary goal

of captive propagation is reintroduction or augmentation, bighorn sheep

should be released into the wild whenever possible. As a last resort,

animals may be transferred to a zoo facility in cooperation with the

American Zoological and Aquarium Association.

183
Release and Monitoring

Research and data collection on the captivepopulation

Captive populations can provide an ideal control population for

experimental or developmental studies. Data on the population

characteristics, behavior, physiology, nutrition, and diseases ofthe captive

population should be collected to the extent possible without risking the

animals’ survival or ability to be released into the wild. Handling or

continuous observation at close range should be minimized to avoid

habituation. The captive population at Bighorn Institute has been used in

severalstudies (Castro et al. 1989, Jessup et al. 1990, Borjesson et a!.

1996) that required little or no additional handling.

A SPARKS (Single Population Analysis and Records Keeping System;

International Species Information System [ISIS] 1989) orsimilar format

studbook should be maintained to record the identification, sex, parentage,

date ofbirth, release date, release location, and date as well as cause of

death for each individual born or brought into captivity. Marking of

animals to facilitate data collection may be necessary in large captive

populations. Locations ofbirths within enclosures and individual ewe

reproductive success should also be recorded. Notes recording the feeding

rations, general health, and behavior of captive animals, and unusual

environmental conditions should be collected at least once daily.

Research and data collection on released bighorn sheep

Each release should be designed as an experiment to test various

techniques related to factors such as release site and time (May 1991).

Monitoring post-release animals is one ofthe most critical components of

a reintroduction or augmentation program because it allows for the

assessment of methods, use ofadaptive management, and can provide a

framework for theoretical studies. All released bighorn sheep should be

fitted with a radiocollar and eartag and monitored as frequently as possible

(more than weekly) to record their integration process, habitat use,

behavior, health, survivorship, and reproductive success. At a minimum,

monitoring should be designed to document survival and reproductive

184
rates, cause-specific mortality, habitat use ofreleased bighorn sheep

though their first year in the wild, and key biotic and abiotic factors, such

as habitat quality and weather. Most importantly, post-release studies

should provide data to evaluate the success ofthe program. Long-term

(greater than or equal to 3 years) monitoring on at least amonthly basis of

greater than or equal to 50 percent ofreleased animals in a subpopulation

should be included in all programs. Monitoring ofpost-release animals

should include planned studies comparing captive-reared and wild-reared

sheep (e.g., reproductive success, survivorship, vigilance, maternal

behavior, reactions to disturbance, etc.), and theoretical studies (May

1991, Sarrazin and Barbault 1996).

Peer-reviewedProgram Assessment

Guidelines forreintroductions (Kleiman 1989, Stanley Price 1991, Chivers 1991)

suggest an assessment phase in which the experiences, results, and conclusions of

a reintroduction or augmentation program would be published at intervals or at the

completion ofthe study. Short-term success ofsuch programs can be evaluated

by: 1) the survival and/or reproductive rates ofreleased animals, or 2) the amount

of genetic diversity retained and/or habitat preserved, or 3) public education and

research interest generated, or 4) the time gained to allow continued research into

the problems suppressing the population (Kleiman 1989; Caughley and Gunn

1996). The multi-faceted nature of captive breeding and release programs

requires that assessments examine both the captive breeding and release phases, as

well as the indirect benefits generated from the program. Reporting failures

encountered in captive breeding and release programs is ofequal or greater value

than reporting successes, although it is done much less frequently.

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194
APPENDIX D. GUIDELINES FOR SAFELY CAPTURING. HANDLING,

AND MONITORING BIGHORN SHEEP

Standard research methods, including surveys (foot, helicopter, and fixed wing

aircraft), field capture, biological sampling, and radiotelemetry monitoring have

been used for assessing abundance and abundance trends (DeForge et a!. 1995,

1997; Rubin et a!. 1998), recruitment patterns (Wehausen et a!. 1987, DeForge et

a!. 1995, DeForge et a!. 1997, Rubin et a!. 2000, Ostermann et a!. in press), adult

survivorship and cause-specific mortality (Hayes et a!. 2000, DeForge et a!. 1997,

DeForge and Ostermann 1 998b, Ostermann et a!. in press), health status and

disease exposure (DeForge eta!. 1982; Clark eta!. 1985, 1993; Jessup and Boyce

1993; Elliott eta!. 1994; Boyce 1995; Crosbie et a!. 1997), genetic profiles

(Boyce eta!. 1997, Boyce eta!. 1999), and spatial distribution ofthe population

(Rubin et a!. 1998) in specific subpopulations ofbighorn sheep within the

Peninsular Ranges. Adaptive management (Holling 1978) will require the

continued use ofthese field research methodsto achieve recovery of Peninsular

bighorn sheep.

As with any human intervention, these research methods are not without risks and

consequences for free ranging bighorn sheep. Low-level helicoptersurveys

provide an effective method for estimating population size and distribution.

However, alterations in behavior, movement, and distribution ofbighorn sheep

resulting from helicopter disturbance (Bleich et a!. 1990a) could potentially

introduce bias into those estimates or adversely affect survivorship and

reproduction in bighorn sheep populations (Bleich eta!. 1994). Jessup et a!.

(1984) compared the relative risks and benefits of different capture methods,

including drop-netting, drive-netting, darting from helicopters, stationary corraltrapping and the use ofa hand-held net gun operated from a helicopter. Some

methods were found to be inherently safer than others. All methods presented

some risk to individual animals, and no single method ofcapture was best for all

situations. Bleich et a!. (199Gb) documented chronic injuries to the mandibles

and necks of bighorn rams from ill-fitting radiotelemetry collars and proposed

potential adverse effects on foraging behavior and decreased fitness ofthese

otherwise dominant males.

195
Through constant critical re-assessment ofresearch activities, risks can be

recognized and addressed to minimize the impact ofthese activities on bighorn

sheep populations. In the past, epidemiological analysis ofcapture data

documented the relative safety ofdrop net and helicopter net gun capture of

bighorn sheep over other methods including drive-net, chemical immobilization,

and corral trapping (Jessup et a!. 1988). Recommendations on collar tightness

(Bleich et a!. 1 990b) have reduced jaw and neck injuries in bighorn rams in recent

years. Risks associated with future research activities can be minimized by

requiring: (1) adequate justification for the activity, (2) thorough planning, (3)

selection ofappropriate survey and capture methods, experienced personnel, and

proper equipment for the activity, and (4) constant critical re-assessment of

research activities to recognize and address problems arising from these activities.

Guidelines for specific research activities

Surveys

Fixed-wing aerial surveys have a very low probability ofaffecting bighorn sheep

because aircraft are typically flown at high altitude. During these flights,

telemetry locations ofradio-collared animals are obtained but visual observations

are not usually attempted. The risk ofdisturbance to bighorn sheep is greater

during helicopter and foot surveys.

Helicopter surveys may temporarily disrupt normal bighorn sheep behavior and

may negatively affect bighorn sheep if not conducted properly. Helicopter

surveys should be avoided during periods when bighorn sheep may be especially

sensitive to disturbance. These periods include the late winter through early

summer months, when the majority ofewes give birth, and the summer months,

when bighorn sheep are dependent on scant water sources. During surveys, the

helicopter should only remain above a group ofanimals long enough to determine

group size and composition. Ifthe group appears to be running excessively, if

terrain conditions are potentially dangerous for the animals, or if young lambs are

observed in a group, the safety ofthe animals should take priority over data

collection, and the survey crew should continue moving to the next portion ofthe

survey area. During surveys, the location ofroads should be considered, and

196
flight paths should proceed from roads into habitat, so as to avoid driving animals

towards automobile traffic.

Foot surveys are not typically considered a risky research activity but the

following considerations will further reduce any negative impact on bighorn

sheep. Bighorn sheep appear to be more comfortable when they are able to

remain higher than their human observers and watch them from a distance.

Observers should approach bighorn sheep from below and avoid approaching too

closely. Care should be taken to avoid startling bighorn sheep by appearing

suddenly around a corner or over a ridge. Time near springs and guzzlers should

be kept to a minimum to avoid displacement ofanimals from water sources,

especially during the summer.

Capture

The active management ofbighorn sheep may require: (1) marking or tagging to

determine population numbers, range usage, movement patterns, behavior,

reproduction, survival, and cause-specific mortality; (2) treating orsampling

diseased individuals; (3) sampling ofhealthy bighorn sheep forresearch; and (4)

relocation (Jessup et al. 1984). In skilled, experienced hands, the use ofa net gun

from a helicopter has been shown to be a safe method ofcapture, with fewer stress

related complications and lower injury and mortality rates than other methods

(Jessup et a!. 1988). Due to the steep, rough terrain and the scattered distribution

ofbighorn sheep found in the Peninsular Ranges, net gun capture appears to be

the most practical and cost-effective capture technique. The use of drop nets and

tangle nets may also be necessary on the rare occasion when an animal hasto be

captured within or on the fringes ofthe urban environment. The safe use ofthese

techniques requires careful planning and adequate numbers of experienced

personnel trained in handling net-captured bighorn sheep. Thorough discussions

ofcapture methods and veterinary medical concerns can be found in The Wi!d!fe

Restraint Handbook (California Department ofFish and Game 1996), and the

Wild!~fe Restraint Series (International Wildlife Veterinary Services 1996).

The most common veterinary problems occurring during the helicopter net gun

capture of bighorn sheep are physical injury, capture stress/capture myopathy

(disorder ofmuscle tissue or muscles) and hyperthermia. Physical injury can

197
occur when a netted animal tumbles on rough, rocky terrain, takes a fall down a

steep slope, or when the net tangles around the animal’s neck and compromises

respiration. The risk ofphysical injury can be minimized by netting the animal as

it runs uphill or capturing animals on relatively flat saddles or in flat sandy canyon

bottoms. Capture stress/capture myopathy occurs when an animal severely

overexerts itself, resulting in pathologic metabolic changes and cellular damage in

muscle tissue and internal organs. Hyperthermia occurs when an animal’s heat

production from muscle activity exceeds its ability to dissipate that heat. Due to

the physical exertion experienced during helicopter pursuit, the rectal temperature

ofmost bighorn sheep at capture will be higher than 38.9 degrees Celsius (102

degrees Fahrenheit), considered normal for resting domestic sheep (California

Department of Fish and Game 1996), and will often reach 39.4 to 40.6 degrees

Celsius (103 to 105 degrees Fahrenheit) or greater. These animals are susceptible

to hyperthermia regardless ofthe ambient temperature. Dousing with water

around the flanks, inguinal region, thorax, head, and neck at capture to cool the

animal should be routine during warm weather and anytime an animal shows an

increasing trend in rectal temperature. Animals with heavy winter pelage also

may have a problem dissipating heat even in cold weather and may require efforts

to cool them. Keeping chase times within conservative limits will prevent most

problems with capture stress/capture myopathy and hyperthermia. A “safe” chase

time will vary with the condition ofthe animal, terrain, environmental conditions,

and the intensity of pursuit. Most individual chase times during California

Department ofFish and Game bighorn sheep captures are under 3 minutes.

Pursuit of a running animal should not exceed 5 minutes. Attention must be paid

to total chase time as animals in a group may be run repeatedly as individual herd

members are captured. Pursuit should be called offif the animal appears

disoriented, exhausted, or injured, or anytime a member ofthe capture crew

determines that there is excessive risk in continuing the capture effort.

Prolonged restraint can also contribute to capture stress/capture myopathy and

hyperthermia. Most bighorn sheep cease struggling when eye covers and hobbles

are applied. Positioning the animal in a normal resting position with its head up

will allow the sheep to belch ruminal gas and minimize bloat and regurgitation.

Vital signs should be taken immediately and monitored continuously to monitor

the need/effectiveness of cooling treatment orto determine if a severely distressed

198
animal should be released. A severelycompromised animal that is not ambulatory

requires aggressive therapy. Jessup (1999) recommended that wild sheep with

rectal temperatures greater than 41.7 degrees Celsius (107 degrees Fahrenheit),

respiration rates of 75 per minute, and/or heart rates greater than 200 per minute

receive intensive treatment for capture stress/myopathy including cooling baths,

balanced intravenous fluids, anti-inflammatory drugs (fast acting corticosteroids),

vitamin and mineral supplements, and possibly intraperitoneal bicarbonate.

Medical treatment of a moderately compromised animal that is ambulatory

involves the trade-offofcontinued stress during the treatment period with the

benefits ofmedication. Some medications themselves may have adverse effects

when administered. For example, pharmacologic doses ofcorticosteroids used in

treating shock may induce parturition in ewes in late stages of pregnancy (Plumb

1995). In a field situation, the decision to treat or release is ajudgement call made

by capture personnel in consultation with an experienced wildlife veterinarian.

Airtransport ofbighorn sheep to base camps should be accomplished in “sheep

bags” (heavyweave plastic mesh bags custom designed for this purpose), which

support the animal in a sternal position. “Air transport ofmountain sheep upside

down suspended by their hobbled legs is inappropriate and unnecessary”

(Jessup 1999). During captures using base camp processing, the capture crew

should be prepared to process animals exhibiting capture stress at the capture site

to reduce the handling time.

Processing (application oftags and collars, collection ofbiological specimens,

administration ofprophylactic medications) should be carried out in a quick,

efficient manner with minimal disturbance to the animal. Prior to release, the

animal should be positioned so that release occurs in the direction with the fewest

physical hazards and that allows the animal to move toward the area from which it

was captured.

Other issues to consider when capturing and handling bighorn sheep include:

Pregnancy status - capture of ewes in the last two months ofpregnancy

should be avoided whenever possible (December through early summer).

199
Caution should be used when capturing ewes with very young lambs

(spring through late summer) due to possible abandonment ofthe lamb or

exposure ofthe lamb to predation in the absence ofthe mother. These

ewes should be processed at the capture site, and should not be transported

to a base camp.

Extreme caution should be used when capturing young lambs. Lambs

should be processed and released at the capture site whenever possible.

Whenever possible, processing at the capture site is preferred to minimize

stress on the animal, However, for adult animals, the choice ofprocessing

at the capture site or transport to a base camp will varywith local

conditions. Very important for ewes and less so for rams, the location and

distance ofbase camps from the capture site should allow direct access

back into the area in which the animal was captured. A general guideline

is that the release site should be within the home range ofthe ewe group

and within 5 kilometers (3.1 miles) ofthe capture location with no

insurmountable or dangerous obstacles separating the animal from its

home range.

Capture personnel should be made aware ofhuman safety and zoonotic

disease concerns.

Key points to consider before capture of bighorn sheep:

A detailed capture plan must be prepared in advance ofthe capture that

outlines goals, methods, potential problems, personnel and safety

procedures (California Department ofFish and Game 1988).

A pre-capture meeting should be mandatory for all participating personnel.

All personnel must be trained in proper animal handling techniques.

Experienced veterinary assistance and emergency medical supplies and

equipment should be readily available to treat a physically distressed or

200
injured animal. Frequent post-capture monitoring ofindividual bighorn

sheep is mandatory to determine effects of capture, tags, and collars on

survivorship, reproduction, and well being.

A written report should be prepared after each capture that documents the

activity, provides a critical assessment ofthe capture, and suggests

improvements for future capture activities.

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International Wildlife Veterinary Services. 1996. Medical concerns. In: Wildlife

Restraint Series. Ed. R. K. Clark, D. A. Jessup. pp. 8.1-8.15. IWVS, Inc.

Publications, P. 0. Box 936, Fort Collins, Colorado 80522.

Jessup, D. A., W. E. Clark, and R. C. Mohr. 1984. Capture ofbighorn sheep:

management recommendations. Wildlife Management Branch

Administrative Report 84-1. California Department ofFish and Game.

Sacramento, California.

Jessup, D. A., R. K. Clark, R. A. Weaver, M. D. Kock. 1988. The safety and cost

effectiveness ofnet-gun capture ofdesert bighorn sheep (Ovis canadensis

ne!soni). Journal of Zoo Animal Medicine 19(4): 208-213.

Jessup, D. A., W. M. Boyce. 1993. Diseases of wild sheep. In: Zoo and Wild

rd

Animal Medicine, 3 Edition. Ed. M. E. Fowler. W. B. Saunders. pp.

554-560.

203
Jessup, D. A.. 1999. Capture and handling ofmountain sheep and goats. In: Zoo

th

and Wild Animal Medicine, 4 edition. Eds. M.E. Fowler, R.E. Miller.

W.B. Saunders Company. pp. 681-687.

Ostermann, S. D., J. R. DeForge, and W. D. Edge. Captive breeding and

reintroduction evaluation critena: a case study ofPeninsular bighorn

sheep. Conservation Biology. In press.

Plumb, D. C. 1995. Glucocorticoid agents, general information. In: Veterinary

Drug Handbook. Iowa State University Press, Ames, Iowa. pp.292-295.

Rubin, E. S., W. M. Boyce, M. C. Jorgensen, S. G. Torres, C. L. Hayes, C. S.

O’Brien, and D. A. Jessup. 1998. Distribution and abundance ofbighorn

sheep in the Peninsular Ranges, California. Wildlife Society Bulletin

26(3):539-55 1.

Rubin, E. S., W. M. Boyce, and V. C. Bleich. 2000. Reproductive strategies of

desert bighorn sheep. J. of Mammalogy 81(3):769-786.

Wehausen, J. D., V. C. Bleich, B. Blong, and T. L. Russi. 1987. Recruitment

dynamics in a Southern California mountain sheep population. Journal of

Wildlife Management 51:86-98.

204
APPENDIX E. PROTOCOLS FOR MONITORING POPULATION

ABUNDANCE

This appendix presents protocols for two methods ofmonitoring the abundance

and population trends of Peninsular bighorn sheep. These two methods are: (1)

waterhole counts and (2) aerial helicoptersurveys. For explanations of

terminology (e.g., ewe group) or reference to specific names oflocations, please

refer to the main body ofthe recovery plan and papers cited therein.

Waterhole counts have been conducted in selected parts ofAnza-Borrego Desert

State Park since 1971 (M. Jorgensen, pers. comm.) and have been used to assess

abundance trends ofPeninsular bighorn sheep (Rubin et a!. 1998). Prior to 1993,

no marked animals were present in the areas in which counts were conducted.

Count data were, therefore, only appropriate for use as an index ofabundance

ratherthan for calculation of an absolute population estimate. Since 1993,

however, collared animals have been present and waterhole count data can be

used to generate population estimates for some ewe groups in Anza-Borrego

Desert State Park.

Waterhole counts are organized and conducted by volunteers under the direction

ofPark staff. Although helicopter surveys provide a more comprehensive

population estimation tool, waterhole counts should be continued. Continuation

for at least 10 more years will allow investigators to determine the correlation

between waterhole count and aerial survey population estimates, which may make

it possible to generate historical population estimates using early waterhole count

data. In addition, waterhole counts provide data that are difficult to determine

from a helicopter (e.g., reproductive status ofindividually marked ewes; refer to

section II.D.2.1 ofthe recovery plan), and provide an opportunity for the

community to participate in Peninsular bighorn sheep conservation projects (refer

to section II.D.3).

Helicopter surveys have been conducted in the Santa Rosa Mountains annually

since 1977 (Wehausen eta!. 1987, DeForge eta!. 1995), the San Jacinto

Mountains in 1983, 1984, and annually since 1987 (DeForge et a!. 1997), and in

some parts of Anza-Borrego Desert State Park in the early 1980’s (M. Jorgensen,

205
pers. comm.). Radio-collared animals have been present in the northern Santa

Rosa Mountains since the early 1980’s (DeForge et a!. 1995) and in the San

Jacinto Mountains since 1992 (DeForge et a!. 1997). In 1994, 1996, and 1998,

radio-collared animals were present throughout the Peninsular Ranges and surveys

covered all parts ofthe ranges for the first time, making it possible to generate

population estimates for the entire range as well as for subregions (Rubin et a!.

1998). Currently, helicopter surveys in the San Jacinto Mountains and the Santa

Rosa Mountains are conducted by California Department of Fish and Game and

the Bighorn Institute, while surveys ofthe remainder ofthe range are conducted

by California Department ofFish and Game and Anza-Borrego Desert State Park.

The following sections outline specific protocols for each monitoring technique.

Aerial Helicopter Surveys

Frequency ofsurveys

Helicopter surveys covering the entire range should be conducted at least every

other year. Recently, the San Jacinto Mountains and Santa Rosa Mountains have

been surveyed annually, while the remainder ofthe range has been surveyed every

other year (1994, 1996, 1998).

Time ofsurvey

Helicopter surveys should be conducted ideally between late September and early

November. This method reduces the risk to bighorn sheep by avoiding periods

when young lambs are present, periods when ewes reach late gestation, and

months ofhigh summer temperatures. In addition, this time period coincides with

part ofthe rut, or breeding season. This approach allows the most accurate

estimate ofthe sex ratio because bighorn tend to congregate during this time.

Areas to be surveyed

All bighorn sheep habitat in the Peninsular Ranges should be surveyed. For

consistency among years, the same predetermined areas should be flown every

year, with the same amount oftime (effort) spent per area during each year. Flight

areas and associated approximate survey times are included in this appendix

(Tables E-l and E-2). Maps are not included here because the geographic

references in the Tables below accurately describe the survey areas and this plan is

206
Table E-l. Approximate polygons flown by Bighom Institute in annual helicoptersurveys ofthe

San Jacinto and Santa Rosa Mountains. Topography and sheep sign influenced the amount of

time spent per area. Flight polygons were developed while the population was at a low, and some

areas where sheep sign (trailing, bed sites, etc.) has not been noted for several consecutive years

are flown less intensely than areas with sign. Ifthe population increases, more time may be

needed to thoroughly survey areas that are only cursorily surveyed now. Flighttimes are actual

time within the polygon.

Polygon Area/Canyons Notes

Number

San Jacinto Mountains:

west fork of Palm Canyon north to

Blaisdell Canyon

2 Santa Rosa Mountains:

Calcite Mine west to Rattlesnake

Canyon

3 Santa Rosa Mountains:

western Santa Rosa Mountains, west of

Rattlesnake Canyon to Buck Ridge and

Rockhouse Canyon

4 Santa Rosa Mountains:

Big Wash north, Wonderstone Wash,

Travertine Palms, and Barton, Alamo,

and southern Sheep Canyons.

5 Santa Rosa Mountains:

north Sheep Canyon, Martinez Canyon

6 Santa Rosa Mountains:

Agua Alta and Toro Canyons

7 Santa Rosa Mountains:

Guadalupe, Devil, andBear Canyons

8 Santa Rosa Mountains:

Coyote, Sheep, Deep, Carrizo, and Dead

Indian Canyons.

9 Santa Rosa Mountains:

Magnesia, Bradley, and Cathedral

Canyons.

Approx.

flight time

(hours)

2.25

2.25

2.25

1.75

Areas south of Andreas and north

ofChino have been flown less

intensely in recent years due to

lack of bighorn sheep sign. It will

be necessary to add survey time if

distribution expands.

Buck Ridge flown cursorily.

Barton, Alamo, and Sheep

Canyons flown cursorily due to

lack ofsign.

1.25

2.00

2.25

2.25

2.00

Polygon should include Indio and

Eisenhower Mountains.

Western Cathedral Canyon

appears to have been abandoned

recently — minimal flight time

spent west ofCathedral Canyon.

Surveys may need to intensify

west ofCathedral Canyon proper

if the population increases.

207
Table E-2. Survey polygons flown inbighorn sheep habitat outside ofthe Santa Rosa and San

Jacinto Mountains. Flight times are actual time within the polygon.

Polygon Area Polygon Description

Number

10

11

12

13

14

15

16

17

18

19

20

21 Carnzo Canyon area

22 ‘‘

23 ‘‘

24 ‘‘

25 Fish Creek

Mountains

26 CoyoteMountains

27 5. ofInterstate 8

Coyote Peak

NE side of Coyote Canyon

SW side ofCoyoteCanyon

N ofCounty Rd 22 (Montezuma Grade)

S ofCounty Rd 22 and Yaqui Ridge

Pinyon Ridge and N side of Sentenac Canyon

Pinyon Mts to Pinyon Canyon

Sunset Mm, Harper Flats,to Harper Canyon

Harper Canyon to Hapaha Flats to Alma Canyon

Alma Canyon to Fish Creek Wash to Split Mm

Whale Peak (Fish Creek Wash to Smuggler

Cyn)

Tierra Blanca Mts to Rockhouse Canyon

W side Carrizo Wash (to Blackwater Canyon)

Camzo Gorge to Tule Cyn, E. to Dos Cabezas

E side ofCarrizo Wash (N of railroad tracks)

Fish CreekMountains

Coyote Mountains

Dos Cabezas to U.S.-Mexico border

Approx. flight

time (hours)

1.25

3.00

2.25

2.75

2.00

1.00

2.25

1.50

1.75

1.25

1.25

2.00

1.25

2.00

1.25

1.75

1.75

2.00

Coyote Canyon

N. San Ysidro Mts

S. San Ysidro Mis

Vallecito Mountains

not intended to represent a comprehensive compendium ofinformation related to

bighorn conservation activities.

Survey techniques

The survey crew consists ofthree observers in addition to the pilot. When

possible, the same pilot and pool ofexperienced observers should be used each

year. The doors ofthe helicoptershould be removed for optimum visibility. Each

polygon should be flown systematically at 40 to 60 kilometers per hour (25 to 35

miles per hour), following topographic contours of 100 to 150-meter (330 to 490-

foot) intervals. The pilot and the observers should not be aware ofthe locations

ofradio-collared sheep, and telemetry should not be used to locate groups or

individuals. The number ofradio-collared animals in each survey polygon should

be determined immediately before or during the helicoptersurvey, by additional

personnel, using aerial fixed-wing or ground monitoring. These animals serve as

“marked” animals in the calculation ofabundance estimates using mark-recapture

methods (see below). The Global Positioning System base station at AnzaBorrego Desert State Park headquarters should be run during the entire survey so

208
that Global Positioning System location data can be corrected by staff at their

General Plan office. All four individuals in the flight crew are considered

observers, and each ofthe three passengers is assigned one ofthe following

additional tasks: (1) to monitor the progress ofthe flight on a topographical map,

advise the pilot of polygon boundaries, and record the location of each observed

sheep on the map, (2) maintain a data sheet onto which the date, time, elevation,

group size and composition, number ofcollared animals, and, possibly,

identification of collared animal is recorded for each group ofanimals, or(3)

record the flight ofthe survey and the location of each observed animal using a

Global Positioning System unit. All observed animals should be classified as

yearling ewe, adult ewe, yearling ram, Class II ram, Class III ram, Class TV ram,

or lamb (classifications modified slightly from those used by Geist 1971). When

possible, simultaneous double-counts should be conducted during each survey,

following the methods ofGraham and Bell (1989), to provide an additional

abundance estimate. All sightings offeral animals and deer should be recorded

during surveys. The location and condition ofsprings, tinaj as, and other water

sources also should be recorded.

Data Ana!yses

Population estimates should be generated using estimators such as Chapman’s

(1951) modification ofthe Peterson estimator (Seber 1982), orthe joint

hypergeometric estimator (e.g., Neal et a!. 1993). Estimates should be calculated

separately for each sex and for the total population (rams and ewes combined). In

the event that low numbers ofcollared rams prevent the estimation ofram

numbers, the ram to ewe ratio and the estimated number ofewes can be used to

generate an estimate of adult numbers. Confidence intervals (95 percent) should

be calculated using methods such as those ofSeber (1982). Simultaneous doublecount data should be used to estimate the number ofgroups missed and to

generate an additional estimate ofthe minimum number of animals present within

the surveyed areas (Graham and Bell 1989). All reported results (e.g., lamb to

ewe or ram to ewe ratios) should clearly state whether or not yearlings are

included.

209
Estimates should be generated for the entire range, as well as for individual ewe

groups. It is important to note that ewe group distribution may change slowly

over time. Monitoring ofradio-collared ewesto determine ewe group structure

will therefore, have to be continued, and stratification ofsurvey data may have to

be modified slightly. Furthermore, ewe group delineations in the Santa Rosa

Mountains south ofHighway 74 and in the Vallecito Mountains still need to be

more clearly resolved.

Further considerations

Initially, a sufficient number ofactive radio-collared animals must be present in

each portion ofthe range for use in mark-recapture estimate calculations. The

number ofcollared animals should be sufficient to achieve an accuracy ofplus or

minus 25 percent with probability of 0.05, following the methods described in

Krebs (1989) and Robson and Regier (1964), or approximately 30 percent ofthe

estimated ewe population should be radio-collared. However, a “sightability”

estimate may be generated after additional multiple surveys are conducted,

thereby eliminating the need to maintain this percentage ofradio-collared animals.

This approach would be especially beneficial if/when population numbers become

large.

As batteries expire, collars become non-functional and the actual number of

marked animals present in the survey area becomes difficult to know. Only those

bighorn sheep with functional collars should be used as marked animals. This

approach will require that bighorn sheep with “functional” collars be

distinguishable from those with “nonfunctional” collars at a glance, from the

helicopter. Therefore, an accurate inventory of all collared animals must be

maintained and the choice ofcollar and eartag color combinations must be

considered during collaring efforts. No newly collared animal should match (in

collar and eartag color combination) an animal that is possibly still present in the

field.

Within a polygon, an attempt should be made to “sweep” across the survey area,

ratherthan flying over an area more than once. This method will reduce the

chance ofdouble counting animals. Helicopter activity at times cause bighorn

sheep to move (Bleich et a!. 1994); therefore, adjacent polygons should, when

210
possible, be flown consecutively so that groups can be recognized and possible

double counts eliminated. The flight polygons delineated in this document were

chosen, in part, so that natural breaks in topography orroadways coincided with

polygon boundaries.

Data should be maintained in an electronic data set that can be used by

investigators in the future. All raw data should be retained. That is, data should

not be summarized before being entered into a data set.

Waterhole Counts

Frequency ofCounts

Waterhole counts should be conducted annually.

Time ofCounts

Counts should be conducted at the same time every year so that yearly

comparisons ofram:ewe ratios, lamb:ewe ratios, group size, and number ofsheep

observed at watersources are most meaningful. In addition, counts should be

conducted during the hottest and driest time ofthe year to maximize the number

of animals coming to drink at water sources. Counts have typically been

conducted during the July 4th weekend, and should continue to be held between

mid June and the first week ofJuly.

Areasto be Counted

Annual counts have been conducted in the southern part ofthe park (Carrizo

Canyon area) during 1973 to 1982, and in the northern part ofthe park (San

Ysidro Mountains, Coyote Canyon, and one site in the south Santa Rosa

Mountains) since 1971. Counts in the southern portion ofthe park were

discontinued after 1982 because ofthe large number ofvolunteers that were

needed to conduct counts at both ends ofthe State park, and the complex logistics

oforganizing and getting teams set up in fairly remote count sites.

In the past, the number ofsites counted in each area has varied slightly across

years because of variation in the number ofavailable volunteers or unexpected

problems (for example, a fire near count sites). The number ofsites did not

211
significantly influence the number ofsheep counted in each portion ofthe range

(Rubin et a!. 1998). However, an attempt should be made to keep the number and

locations ofcount sites constant during future years. Priority sites should be those

that have been counted most consistently in the past. Additional or “secondary”

sites should be counted when additional volunteers are available. Data analyses

can then focus on data collected at “priority” sites, while “secondary” sites can be

used for more cursory monitoring ofsheep presence.

Count Techniques

Teams ofthree to five observers should be assigned to each count site. Each team

should include at least two individuals who are experienced at classifying bighorn

sheep by age and sex. At each count site, the entire team should be stationed at a

location that allows observation of animals coming to a water source, while

minimizing disturbance ofthe animals orinterference with their use ofthe water

source. These locations have been identified by Anza-Borrego Desert State Park

personnel. While at these sites, observers should minimize noise and movement.

Observations should be made during 7 a.m. to 5 p.m. on 2 consecutive days and 7

a.m. to 2 p.m. on the third day. During these periods, observers should

systematically scan all areas within view and record all sheep observations on the

supplied data sheet. Data to be recorded include date, time, temperature, group

size and composition, the presence of collared animals, and, if possible, the

identification ofcollared animals. Additionally, interactions among individuals

(e.g., breeding behavior, lamb nursing bouts) and observations ofother species

(e.g., deer, coyotes, birds) should be recorded. The location ofeach group of

bighorn sheep should be noted on a topographic map.

Repeat sightings ofindividual sheep should be recorded as such, but they should

not be counted. At the end ofeach day, each team should review and discuss their

observations with neighboring teams so that repeat observations can be identified

and eliminated from the final tally.

Data Analysis

The primary use ofdata collected during waterhole counts is to monitor

abundance trends. Rubin et a!. (1998) used count data to assess long-term trends.

In this case, linear regression analysis was used to determine if the number of

212
ewes observed per day showed an increasing or decreasing trend over a period of

10 to 26 years. If a sufficient number ofcollared animals are present in each ewe

group area, abundance estimates can be generated for some ewe groups, using

mark-recapture techniques. Lamb to ewe ratios can be calculated to monitor

reproductive success ofewe groups. Most lambs are 3 to 5 months old during

waterhole counts and these ratios will not be directly comparable to ratios

generated from helicoptersurveys, which represent lamb recruitment to an older

(approximately 6 to 8 months) age. The reproductive status (lamb present versus

not present) ofindividual radio-collared ewes can supplement observational data

collected by biologists monitoring reproductive patterns ofPeninsular bighorn

sheep. Ram to ewe ratios should be generated for comparison among years. The

rut typically peaks after July, so these ratios may underestimate the actual ram to

ewe ratios since some rams may not have joined ewe groups yet.

Further Considerations

To make waterhole count data as useful as possible for future investigators, it is

important for teams to determine the composition ofeach group as accurately as

possible. Given the great distancessometimes involved, an effort should be made

to equip each team with a spotting scope and at least one individual should be

experienced at using it to observe and classify bighorn sheep.

All new observers must complete a one day orientation and training session led by

Anza-Borrego Desert State Park personnel. In addition, all new observers must be

paired with individuals experienced at classifying bighorn sheep in the Peninsular

Ranges (Bleich 1998).

Data should be maintained in an electronic dataset for use in the future. All raw

data should be retained. That is, data should not be summarized before being

entered into a primary data set.

Reinitiation ofwaterhole counts in the Santa Rosa Mountains should be

considered. This approach may enhance the probability ofdetecting relationships

between aerial helicopter data and water hole count data, thereby facilitating a

retrospective interpretation of numbers ofsheep in the Santa Rosa Mountains in

the past.

213
References

Bleich, V.C., R. T. Bowyer, A. M. Pauli, M. C. Nicholson, and R. W. Anthes.

1994. Mountain sheep Ovis canadensis and helicopter surveys:

ramifications for conservation oflarge mammals. Biological Conservation

70:1-7.

Bleich, V. C. 1998. Importance ofobserver experience in classifying mountain

sheep. Wildlife Society Bulletin. In press.

Chapman, D. G. 1951. Some properties ofthe hypergeometric distribution with

applications to zoological sample censuses. University ofCalifornia

Publication in Statistics 1(7): 131-160.

DeForge, J. R., E. M. Barrett, S. D. Ostermann, M. C. Jorgensen, and S. G.

Torres. 1995. Population dynamics ofPeninsular bighorn sheep in the

Santa Rosa Mountains, California, 1983-1994. Desert Bighorn council

transactions 39:50-67.

DeForge, J. R., S. D. Ostermann, C. W. Willmott, K. B. Brennan, and S. G.

Torres. 1997. The ecology of Peninsular bighorn sheep in the San

Jacinto Mountains, California. Desert Bighorn Council Transactions 41:8-

25.

Geist, V. 1971. Mountain sheep: a study in behavior and evolution. University

ofChicago Press, Chicago. 383pp.

Graham, A. and R. B. Bell. 1989. Investigating observer bias in aerial survey by

simultaneous double-counts. Journal of Wildlife Management

53(4):1009-1016.

Jorgensen, M. pers. comm. Calif Dept. Parks and Recreation.

Krebs, C. J. 1989. Ecological Methodology. Harper Collins Publishers. New

York, N.Y. 6S4pp.

214
Neal, A. K., G. C. White, R. Bruce Gill, D. F. Reed, and J. H. Olterman. 1993.

Evaluation of mark-resight model assumptions for estimating mountain

sheep numbers. J. Wildl. Manage. 57:436-450.

Robson, D. S. and H. A. Regier. 1964. Sample size in Peterson mark-recapture

experiments. Transactions ofthe American Fisheries Society 93 :215-226.

Rubin, E. S., W. M. Boyce, M. C. Jorgensen, S. G. Torres, C. L. Hayes, C. S.

O’Brien, and D. A. Jessup. 1998. Distribution and abundance ofbighorn

sheep in the Peninsular Ranges, California. Wildlife Society Bulletin

26(3):539-551.

Seber, G. A. F. 1982. The Estimation ofAnimal Abundance. Charles Griffin

and Company, Limited, London, England.

Wehausen, J.D., V. C. Bleich, B. Blong, and T. L. Russi. 1987. Recruitment

dynamics in a southern California mountain sheep population. Journal of

Wildlife Management 51(1):86-98.

215
APPENDIX F. RECOMMENDED CONSERVATION GUIDELINES

BACKGROUND

Bighorn sheep in the Peninsular Ranges are afforded protection pursuant to the

California Fish and Game Code (sections 4700 as a fullyprotected species and

2050 as a threatened species). Section 4700 ofthe Fish and Game Code does not

allow for issuance ofpermits orlicenses to take fully protected mammals, except

for scientific research, notwithstanding any other provision oflaw; therefore, a

California Endangered Species Act section 2081 permit that would authorize

incidental take ofPeninsular bighorn sheep cannot be issued. This take

prohibition in turn limits the type of mitigation that can be required pursuant to

the California Environmental Quality Act. The sheep also is listed at 50 CFR §

17.11 by the U.S. Fish and Wildlife Service as an endangered species and

protected against take at 50 CFR § 17.21. Regulations that authorize take under

prescribed circumstances are found at 50 CFR Parts 17 and 402.

The California Environmental Quality Act requires that mitigation measures be

identified and implemented for any significant impacts unless a finding ofoverriding considerations is adopted. Section 15370 ofthe California Environmental

Quality Act Guidelines provide five categories ofmitigation measures: “...avoid,

minimize, rectify, reduce or compensate.” These forms ofmitigation are

appropriate for bighorn sheep only to the extent that they avoid take ofthe

species, pursuant to Section 4700 ofthe Fish and Game Code, and avoid take

under 50 CFR § 17.21, unless otherwise authorized by the U.S. Fish and Wildlife

Service under 50 CFR § 17.22. Accordingly, the Fish and Wildlife Service and

California Department ofFish and Game work with lead agencies and project

proponents on a case by case basis to identify which forms of mitigation would be

appropnate.

OBJECTIVES

The objective ofthese guidelines is to provide a set ofconsistent mitigation

measures for project proposals that do not otherwise threaten sustainable bighorn

sheep populations needed for recovery. These mitigation measures are not

216
intended for projects proposed in locations that would fragment habitat or

preclude effective reserve design and management ofthe species because those

adverse effects cannot be offset. In such instances, the Fish and Wildlife Service

and California Department of Fish and Game may recommend additional

avoidance, minimization, and mitigation measures to ensure against the likelihood

ofsignificant adverse effects that would impinge on take and jeopardy thresholds.

Through proper coordination, our agencies will assist local, State, and Federal

governments in identifying whether the adverse effects ofproject proposals can be

mitigated to a level ofinsignificance, based on project location, size, and potential

for indirect effects, which typically are the primary criteria influencing the type

and severity ofimpact. These guidelines may require future modification based

on the availability ofnew information on threats, ecological requirements, species

status, etc.

CONSERVATION MEASURES

I. HABITAT COMPENSATION: Acquisition of off-site habitat may be

appropriate to offset any residual effects after application ofappropriate avoidance

and minimization measures. For projects adjacent to bighorn sheep habitat that

provide infrastructure to support larger humanpopulations, habitat compensation

is generally appropriate because ofthe consequent increased levels ofhumanrelated disturbance in adjoining open space. The cumulative effects of human

disturbance may be mitigated by acquisition ofsheep habitat that would otherwise

be vulnerable to future development. Projects adjacent to sheep habitat that do

not result in indirect effects to adjoining sheep habitat generally lack a mitigation

nexus.

To maintain sustainable subpopulations (ewe groups), compensation habitat

should be acquired within the range ofthe affected ewe group and at an elevation

comparable to the impact. Bighorn sheep in the Peninsular Ranges are mainly

threatened by habitat loss at lower elevations that provide unique resources

unavailable farther up the mountain slopes. Therefore, loss of unique or limiting

resources at lower elevations can not be offset by conservation of different

resources associated with habitats at higher elevations.

217
Habitat acquisition promotes survival and recovery by reducing the potential

future loss ofbighorn sheep habitat through permanent protection ofland

currently available for development. Amount of compensation will be determined

on a case by case basis because the effects ofindividual projects are variable. A

management endowment should accompany all acquired lands so that the

responsible public agency has the ability to effectively manage conserved lands.

II. FENCING: Fencing along the urban interface provides a barrier that separates

bighorn sheep from urbanization threats (e.g., disease and mortality associated

with toxic plants, traffic, parasites, irrigated landscapes, pesticides, etc.). Fencing

also can help mitigate the adverse effects ofincompatible land uses adjoining

sheep habitat. For example, fencing controls human access into habitat that may

otherwise conflict with management objectives to minimize human disturbance,

especially during sensitive time periods, such as lambing. Land uses along the

habitat edge should be designed to not introduce additional human disturbance.

Recreational access should be provided only where access is coordinated with

natural resource agencies and is consistent with management objectives in the

regional trails plan. Fencing does not offset the effects of habitat loss and should

be located along the edge and not within sheep habitat.

A. Fencing should be mandatory for any new development in or

adjacent to sheep habitat, where bighorn sheep have begun or may

begin using urban sources offood and water.

B. Fences should be 2.4 meters (8 feet) high, chain-link or functional

equivalent.

C. Fences should not contain gaps in which sheep can be entangled

[gaps should not be larger than 11 centimeters (4.3 inches)].

III. TOXIC PLANTS: Landscape plants can cause sickness or death. Only local

native plants should be used along the wildland interface. Known and potential

toxic plants should not be used in areas accessible to bighorn sheep. Ornamental

plants currently known to be toxic to sheep include oleander, Prunus species, and

plants in the nightshade (Solanaceae) family.

218
IV. LAMBING SEASON AND HABITAT RESTRICTIONS: Seasonal

restrictions during this period minimize impacts to bighorn sheep at a critical

stage oftheir life cycle. Lambing habitat is often emphasized because ofthe

sensitive nature and behavior ofewes and lambs. Lambing habitat comprises

those areas used for breeding, sheltering, and nurturing oflambs up to the time of

weaning, including those areas occupied by ewes 1 month before giving birth.

Though the lambing season can span the majority ofthe calendar year--from late

winter through summer, January 1 through June 30 encompasses the majority of

the lambing season. Trails that traverse lambing habitat should be managed during

this period or relocated outside ofsensitive habitat areas.

V. SUMMER WATER SEASON: Available water sources during summer

months are highly restricted and bighorn sheep are vulnerable to disturbance in

these areas. Ifsummer rains fail, water may remain scarce until the first winter

rains. Accordingly, interagency cooperation will be needed to adapt trails

management prescriptions to the water requirements ofbighorn sheep. Public

education, signage, rangers, and other forms ofmanagement should be provided at

appropriate locations to control access during this period.

Title 14 ofthe Public Resources Code, Section 550(b)(1) and Sections 630(b)(l I)

and (30) restricts access to water holes on State lands in the Santa Rosa

Mountains. Closure periods are from June 15 to September 15.

VI. WATER FEATURE DESIGN SPECIFICATIONS: Any artificial water

features (e.g. ponds, lakes) in areas adjoining bighorn habitat should be designed

to preclude shallow, vegetated edges that provide breeding habitat for Cu!icoides

midges, an invertebrate disease vector forbluetongue virus. Water bodies should

be designed with steep sides and depths at least 0.6 to 0.9 meters (2 to 3 feet)

along the edge [see: Mullens, B. A. 1989. A quantitative survey of Cu!icoides

variipennis (Diptera: Ceratopogonidae) in dairy wastewater ponds in southern

California. J. ofMedical Entomology 26(6):559-565; and Mullens, B. A. and J.

L. Rodriquez. 1990. Cultural management of bluetongue virus vectors. Calif.

Agriculture 44(l):30-32].

219
WILDLIFE AGENCY RECOVERY AND MANAGEMENT

RESPONSIBILITIES

AUGMENTATION: Augmentation is a potential recovery tool that is addressed

within the context ofthe recovery plan and would be used until a self-sustaining

population is established. The release ofcaptive reared or translocated wild

animals to establish new populations or supplement small populations are not

acceptable mitigation measures because they do not compensate forthe permanent

loss ofhabitat or ensure the continued viability of habitat to support selfsustaining, wild populations.

PREDATOR CONTROL: Predator control is a potential management tool

available to the Fish and Wildlife Service and California Department ofFish and

Game to address specific situations. Bighorn sheep are adapted to survive natural

levels ofpredation, drought, disease, competition, etc., which do not pose

problems in properly functioning ecosystems. Because predator control is a

temporary solution to remedy a short-term problem, it does not constitute

mitigation for the permanent loss ofsheep habitat.

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APPENDIX G. RESPONSE TO COMMENTS

The following issues are a compilation of all substantive comments received by

the Fish and Wildlife Service from technical reviewers, agencies, and the public,

which were not otherwise responded to by directly incorporating changes into the

text ofthe final recovery plan. The issues are organized by general subject matter.

LEGAL ISSUES

Issue.~ Designation ofessentia! habitat i!lega!lv usurps authority over local !and

use p!anning by imposingprohibitions on private property and mandating

erection offences. Ident~fying private !andsfor protection without committing

Federa!funding or conservation incentives exposes !oca! government to property

taking lawsuits because cities and counties lack the wherewithal to cooperate in

implementation of theplan. To avoid representing a moratorium on future

deve!opment, can some deve!opment in essentia! habitat goforward ifadequately

mitigated, and fso, what criteria orstandards would be used?

Response: Essential habitat (in contrast to critical habitat, discussed below) is a

nonregulatory indication ofthose areas we believe to be important to the

conservation of bighorn sheep. The map is intended to provide information that

can advance conservation efforts through the activities of other agencies and the

public. By sharing biological information, we intend to promote public policy

decisions that balance the conservation needs ofbighorn sheep with other

competing land uses. As such, the designation ofessential habitat does not affect

the discretion oflocal and State governments or private land owners over land use

decisions. Given the biological importance ofthe habitat to recovery, limited

development could occur in essential habitat if adequately mitigated and designed

to be compatible with bighorn sheep recovery. Furthermore, the identification of

areas with biological importance can provide a wider range ofpotential land uses

that generate economic opportunity. For example, local governments and private

landowners can structure economic incentives to conserve bighorn habitat by

creating programs whereby developments in other areas can provide a source of

income to land owners with habitat of higher conservation value. This mitigation

bank concept has gained widespread acceptance in numerous other areas where

221
local government has created a mitigation nexus that avoids property taking

lawsuits and promotes regional habitat conservation planning.

Issue: Membership ofthe Recovery Team and peer review team consists of

individuals whose livelihood depends on funding, permits, and recommendations

from the State and Federal government. Therefore, these individua!s are

reluctant to voice criticisms with the recoveryplanningprocessforfear of

retribution. In addition, authors of the draft recoveryplan stand to gain

financially by creating an open checkbook/cash cow with questionable research

projects having no accountability.

Response: At ourinvitation, members agreed to participate on the Recovery

Team for the purpose ofproviding scientific advice to the Fish and Wildlife

Service and cooperating agencies, including assistance in developing and

implementing the recoveryplan. The draft recoveryplan was largely written by

team members who provided the information and opinions needed to complete a

draft plan. Though consensus was achieved on most issues addressed by the team,

we and cooperating agencies judged how best to incorporate various views where

full agreement was not reached. Many ofthe research topics recommended in the

recovery plan are a reflection ofscientific questions that remain unresolved. Any

funding to addressthese research needs will be directed on a competitive basis to

the best qualified individuals available. Funding and permitting actions by us and

cooperating agencies have and will follow applicable laws and regulations that

ensure against preferential treatment and capricious behavior. Recovery Team

members are not dependent upon the Fish and Wildlife Service or the listing of

bighorn sheep for their continued livelihood. Members are under no obligation

whatsoever and do not enjoy economic benefit for their voluntary participation on

the Recovery Team.

Issue: Undue reliance on unpublished informationfails tojustify the spending of

$16Mevery 5 yearsforseveral decades. The conclusions, recovery criteria, and

habitat mapping lack credibility due to theirreliance on over 100 unsupported

citations and that underlying data were intentional4’ withheldfrom public review.

The public has a right to inspect all the unpublished information cited in the draft

plan as an aid to provide informed comments; therefore, thepublic comment

222
period should be extended until after these data have been made available.

Following the response to all comments and correction of many deficiencies, the

draft recoveryplan should be circulated again for public review.

Response: The draft recovery plan was based on the best available data, which

includes personal experience ofcredible researchers. Unpublished information

cited in the draft recovery plan was documented and compiled prior to completion

ofthe final recovery plan and has been available along with published papers, for

public inspection. Any facts or interpretations based on unpublished information

cited in the draft recovery plan for which documentation could not be obtained

have not been included in the final recovery plan. Justification forresearch

recommended in the recovery plan was not based on cited unpublished

information but on consensus recommendations ofthe Recovery Team and

concurrence by the cooperating agencies. Upon reassessing the relative

importance ofthe unpublished information cited in the draft recovery plan to the

findings and conclusions in the recovery plan, we have determined that the

unpublished information unavailable for review in the draft recovery plan did not

materially affect any significant findings or recommendations in the final recovery

plan. As a result, we elected to not reopen the public comment period. In

response to any substantive comments received afterreview ofthe unpublished

information, the recovery plan may be appended, revised or updated.

Issue: The recovery plan is too general to meet the spec~ficcriteria at 16 U S.C.

1533(1). The unusable scale ofthe essential habitat map was intentionally vague

andfails to meet the site speqfic standards for describing management actions

necessaryfor recovery.

Response: Section 4(f) ofthe Act requires that recovery criteria be measurable

and site specific, with estimates ofassociated time frames and costs. We believe

that these requirements have been satisfied. The scale ofthe draft essential habitat

map in the draft recovery plan was designed to portray a specific concept outside

and along the urban interface based on bighorn habitat requirements and

principles ofconservation biology. The draft map was designed to elicit input

from interested parties so that the final map could best reflect the concerns of

local interests. We elected not to depict draft essential habitat in the draft

223
recovery plan at a parcel specific scale because it would have engendered

unnecessary and unproductive controversy and suggested a predetermined

outcome. We scheduled numerous meetings with all local jurisdictions and major

landowners to refine the boundaries along the urban interface. As described

below under the Essential/Critical Habitat section, consensus among Federal,

State, and local governments was achieved along the majority ofthe urban

boundary.

Issue: A recovery plan is unnecessary ~fbighorn sheep in the PeninsularRanges

are synonymous with the Nelson ‘s subspecies.

Response: Section 4(f) ofthe Act requires preparation ofrecovery plans forlisted

species whenever prudent. This comment implies that bighorn sheep in the

Peninsular Ranges do not comprise an entity that can be listed under the Act.

Please refer to the FederalRegister Notice, dated March 18, 1998, as well as

section l.A. 1. ofthe recovery plan, for a discussion ofthe applicability ofour

policy on implementing the Act’s provisions for listing distinct vertebrate

population segments.

Issue: The Fish and Wildlfe Service ‘s authority and intended use ofthe

“Recommended Conservation Guidelines” in Appendix F is not apparent.

Furthermore, the guidelines appear intended to restrict thepower and override

the legislative authority of lead agencies.

Response: The Fish and Wildlife Service and Department ofFish and Game

prepared these guidelines to assist local governments in theirimplementation of

the California Environmental Quality Act and land use decision making, not to

usurp the discretion of other governmental agencies. It is ourintention to provide

consistent guidance as early as possible in the decision making process so that (1)

ourrecommendations do not come as a surprise later on in the planning process,

and (2) projects can be designed to accommodate the habitat requirements of

bighorn sheep.

224
PROCEDURAL ISSUES

Issue: The bibliograpiw contains many blanksfor the authors names, indicating

that such information cannot be relied upon.

Response: The blank lines in place ofthe name ofan author is a bibliographic

convention that indicates the same author asfor the preceding reference. In the

final plan the bibliographic format has been revised to show full references.

Issue. The recoveryplan should describe how thepublic will track agency

implementation ofrecovery tasks, be involved in prioritizing lands to be acquired,

be involved in future modifications to recovery criteria, comment on land

exchanges, etc. Similarly, the draft recoveryplan did not ident~fr how entities,

such as local government, were expected tofulfil! assigned task responsibilities in

the Implementation Schedule. The recovery tasks often lacksite spec~city and do

not ident~fy applicable mechanisms or responsible entitiesfor implementing the

tasks. For example, the habitat protection objectivefor task 1.1 does not describe

who, how, or where the action would be completed. As a result, affectedparties

have beenprevented fromproviding meaningful review ofthe recovery plan.

Response: The public can track implementation by communicating directly with

the agencies assigned to implement specific tasks. Progress and updates should

be incorporated into the public education and outreach programs recommended in

the recoveryplan. The public may also track the extent ofappropriations

allocated by legislative bodies as an indication of agency capability for

implementing the recovery plan. Local governmentsshould interpret the recovery

plan as guidance for contributing to the recovery process. Many ofthe provisions

in the recoveryplan should be implemented through the regional habitat

conservation plan sponsored by the Coachella Valley Association of

Governments. This plan represents a stakeholders group that provides an

opportunity for involvement by all interests. Any ofthe recovery tasks that apply

to respective jurisdictions should be viewed as an opportunity to cooperatively

participate with other agencies in the common goal ofbighorn sheep recovery.

We encourage local governments to use their applicable authorities for

conservation/management ofopen space in the furtherance ofbighorn recovery.

225
Participating agencies can provide more detailed guidance on the roles and

responsibilities oflocal government as case specific questions arise. Ifthe

recovery plan is updated orrevised in the future, the public will be given another

opportunity to comment on the plan.

Issue: The recoveryplan should contain an economic impact analysis to estimate

the costs ofrecovery. The total estimated costs ofrecovery implementation

should be determined and provided to thepublicfor comment before the recovery

plan is approved. Projectedfunding levelsfor monitoring appearinadequate; ~fa

long-term monitoring program is needed, why are costs projectedfor only 5

years.

Response: Though an economic impact analysis is not required by law or

regulation, section 4(f) ofthe Act requires an estimate ofcosts to achieve

recovery. We have projected total costs based on a rough estimate of 25 years to

recovery, with more detailed cost estimates forthe first five years. Certain costs

are difficult to estimate accurately without detailed scopes ofwork, real estate

appraisals, etc. As a result, cost estimates in the Implementation Schedule should

be viewed as approximations that inform the public and participating agencies

about the resource estimates necessaryto achieve the recovery objectives ofthe

recovery plan.

Issue: The recoveryplan should describe the study areasfor allresearch

conducted in the PeninsularRanges.

Response: The reader should refer to the references cited to obtain more detailed

information on the study methods ofliterature cited in the recovery plan. The

purpose ofthis recovery plan is not to compile and summarize all research

conducted in the area at issue.

Issue: Reliance uponforthcomingplanning efforts, such as the Coachella Valley

multispecies plan to address immediate bighorn sheep conservation needs,

unnecessarily defers actions needed to avert the near-term risk of extinction.

226
Response: We are not aware of any such deferrals and intend to use our legal

authorities under sections 4 (designation ofcritical habitat), 7 (interagency

consultation), and 10 (habitat conservation planning) whenever appropriate during

the interim period while the Coachella Valley plan is in preparation.

Issue: The recoveryplan should critically examinepast management mistakes so

that they are not repeated in thefuture.

Response: Much ofthe recovery plan reflects on the past (e.g., section I.D) and

looks to the future (e.g., section II.D). Many ofthe Recovery Team members

have many years ofexperience in the Peninsular Ranges and, therefore, have a

solid historical perspective. A focused, intensive historical inquiry likely would

result in arguable conclusions ofdubious merit that could adversely affect current

interagency cooperation. The purpose ofrecovery plans is to assess the current

situation with a view towards future feasibility ofimplementing needed

conservation actions.

Issue: Many of the tables were not as descriptive as they could have been

because (1) the tables excludedpotentially available data, such asfrom years

before or after those presented in the tables, and (2) statistical analyses were not

conducted.

Response: In some instances, more recent data were not available; in other cases,

data from earlier years were not comparable because of different data collection

methodologies; and in other circumstances, available data have not yet been

compiled and analyzed. In most instances, statistical analyses were not included

because this information was provided in the references cited and because the

purpose ofrecoveryplans is more informative and prescriptive than analytical and

quantitative.

Issue: The recoveryplan should discuss thefinancialsituation ofthe Bighorn

Institute, along with a detailed critique ofoverall operations.

Response: Financial issues associated with the Bighorn Institute are not a concern

ofthe Fish and Wildlife Service or cooperating agencies. Overall operations

227
regarding research and captive rearing have been the subject ofannual reviews by

the California Department of Fish and Game prior to Federal listing and now fall

under the purview ofsection 10(a)(1)(A), not section 4(f) ofthe Act.

Issue: A repositoryfor all data collected on bighorn sheep should be created and

made available to thepublic at large.

Response: Creation ofsuch a repository would not be possible unless agencies

and researchers donated proprietary information and personal property. The

concept poses numerous legal, economic, and administrative issues that exceed

our authorities and those ofcooperating agencies.

Issue: Numerous comments requested the Fish and Wildl~fe Service and

cooperating agencies to conduct additional research andfurther analyze data not

in theirpossession before issuing a recoveryplan.

Response: The Act’s mandate to use the best available information does not

require us to conduct additional research orobtain unavailable data as a

prerequisite to preparing and completing recoveryplans. A court stipulated

settlement agreement required completion ofthe recoveryplan under an

established schedule.

Issue: The draft recoveryplan focuses excessively on habitat conservation

instead ofpopu!ation recovery; the various problems should be dealt with in

order of importance.

Response: As described in the draft and final recovery plans, multiple, apparently

cumulative factors are depressing population levels, with contributing causes

differing among ewe groups. The relative importance offactors affecting

reproduction, recruitment, and adult survival are poorly understood in some ewe

groups, though intensively studied in others. These complexities make it difficult

to determine relative importance and management priority. Therefore, we have

and will address concurrently all probable factors affecting individual ewe groups

to the extent possible. Ifthe habitat base upon which bighorn sheep depend is not

228
protected, sufficient space will not be available to support “recovered” population

levels.

Issue: The Fish and Wildlife Service should list credentials ofRecovery Team

members.

Response: By practice and for consistency, we do not provide this information

regarding team members. Members were selected for a variety ofskills and

experiences that may not be apparent from briefsynopses.

Issue: The Fish and Wildl~fe Service rejected, without explanation, many

comments provided by Recovery Team members themselves. Disagreements

within the team should be discussed in the recoveryplan.

Response: The various views held by members ofthe team were discussed openly

at team meetings until a consensus emerged. Various iterations, including the

final recovery plan, have been reviewed multiple times by team members, and all

comments have been incorporated into the recovery plan directly or after group

discussion where further consideration was warranted. We are unaware ofany

significant scientific disagreement within the team regarding the content ofthe

recovery plan. Regardless, the Fish and Wildlife Service and cooperating

agencies assume ultimate responsibility for the recovery plan, inasmuch as

Recovery Teams function as expert advisorsto the Fish and Wildlife Service.

Issue: The peer reviewprocess ofthe draft recoveryplan wasflawed, failed to

address all the issuesraised and to follow academicprotocol, and therefore,

should not be referred to as peer review. The draft recovery plan misleads the

public into thinking that thepeer reviewers endorse the draft plan.

Response: The peer review processreferred to in the draft recovery plan

represented separate technical and agency reviews prior to public release and was

not intended to follow academic protocols. Though most ofthe comments

received by the technical (peer) reviewers were addressed in the draft recovery

plan, the draft recovery plan did not claim that the reviewers necessarily agreed

with or endorsed the plan. The Recovery Team and Fish and Wildlife Service

229
have included and addressed in this list ofissues and responses all substantive

comments submitted by technical reviewers not otherwise incorporated into the

draft or final recovery plans.

Issue: Research tasks in the recoveryplan should identify testable hypotheses.

Response: The Recovery Team is not a research team; therefore, this recovery

plan represents a general strategy for recovery that identifies major research topics

that should be pursued. It would not be appropriate to propose various

experimental designs and hypotheses at this time because the additional level of

analysis required should more properly occur when detailed research proposals by

individual researchers are prepared.

Issue: The Recovery Team should include a trained land useplannerto improve

the effectiveness ofcoordinating conservation activities with localjurisdictions,

such as the cities and counties.

Response: One ofthe current Recovery Team members has an extensive

background in land use planning, havingworked in that capacity for numerous

jurisdictions for many years. In addition, several other members work routinely

with local government in land use planning matters and have a thorough

understanding oflegal and procedural requirements needed to coordinate effective

interagency conservation programs.

ESSENTIAL/CRITICAL HABITAT ISSUES

Issue: All localjurisdictions should be extended the same opportunity asthe

Indian tribes in determining essential habitat boundaries. Failure to do so will

doom the recoveryplanning effort.

Response: Federally recognized Indian tribes enjoy a special relationship and trust

privileges under numerous executive, legislative, and judicial mandates not

extended to non-Tribal entities. Nonetheless, within the context ofthe Coachella

Valley multispecies planning program, the Fish and Wildlife Service and

California Department ofFish and Game convened numerous meetings with city

230
and county governmentsto discuss and refine essential habitat boundaries in a

process similar to that used with the tribes. The Fish and Wildlife Service,

Department of Fish and Game, and local jurisdictions achieved agreement along

virtually the entire urban boundary except for about six proposed project sites.

The Fish and Wildlife Service and Department of Fish and Game will attempt to

resolve residual differences for each ofthe proposed developments through

individual regulatory actions.

Issue: The suggested 20percentslope delimiting lower elevational boundaries in

most cases lies below the 213-meter (700-foot) lower elevation limit described

elsewhere in the recoveryplan as the lower elevational limit ofsheep distribution.

The essential habitat line should be set along the 213-meter (700-foot) elevation

contourfrom Palm Springsto La Quinta, which would avoid lambing and

watering areas andprovide opportunitiesfor unrestricted hiking. Essential

habitat should not extend onto the valleyfloorfarther than existing wilderness or

theproposed National Monument boundary. The map appears to represent a no

growth effort that would extort extreme mitigationfrom developers.

Response: The 213-meter (700-foot) lower elevational limit ofsheep distribution

typically correspondsto the urban interface at the northern end ofthe Coachella

Valley, whereas in the southern end ofthe valley, the urban interface occurs along

lower elevational contours. As described elsewhere, sheep in the Peninsular

Ranges are adapted to survive at lower elevations and depend on lower elevational

slopes and alluvial habitats for important resources. The extent ofsuitable habitat

is influenced by soils, aspect, and other topographic featuresthat do not

necessarily correspond with fixed elevation contour lines, or wilderness and

proposed monument boundaries, which were established for a variety ofreasons

apart from the habitat needs of bighorn sheep.

Issue. Habitat compensation should not be requiredfor development adjacent to

sheep habitat because development of thesefragmented areas would not affect

sheep.

Response: Most ofthe proposed development along the urban interface occurs

within, rather than adjacent to, sheep habitat. As discussed in the recovery plan,

231
bighorn sheep in the Peninsular Ranges spend much oftheir time at lower

elevations, where otherwise scarce resources, such as food and water, commonly

occur. Flatter topography contains more productive alluvial soils that support

more diverse and nutritional food sources than occurs on steeper, rockier slopes.

Though alluvial habitats are more fragmented by urban development, these

smaller patches still support habitat value, though much reduced from historical

conditions. Development ofhabitat fragments also indirectly affects sheep by

supporting a larger human population that increases the amount ofdisturbance in

adjoining sheep habitat. As long as suitable habitat conditions exist within the

historical range ofthe species and development results in indirect adverse effects

to sheep in nearby habitat, local governments have a mitigation nexus under the

California Environmental Quality Act. Mitigation measures can be designed to

conserve larger patches ofcomparable value habitat by requiring offsite habitat

replacement, thereby contributing to the conservation ofsheep even ifsmaller

habitat fragments are permitted for development. To contribute to recovery, we

recommend that local governments consider offsite habitat replacement for

permitted development ofresidual habitats between the essential habitat boundary

and 800 meters (2,624 feet) from toe of20 percent slope.

Issue: Proposed designation of essential habitat requires adequate legal notice to

landowners in the vicinity of habitat proposedfor conservation so that an

opportunity to comment on theproposal is provided. The public comment period

should be opened indefinitely until essential habitat is displayed on detailed

aerialphotography and has been made availablefor public comment. A more

detailed map ofessential habitat then should be providedfor public comment

before the recovery plan is completed.

Response: The Fish and Wildlife Service broadly announced a 45-day public

comment period on the draft recoveryplan (64 FR 73057; December 29, 1999),

which was extended an additional week as a convenience to the public. This

noticing process fulfilled all legal requirements. As described above, the Fish and

Wildlife Service coordinated with affected interests in soliciting input and

promoting discussion to achieve consensus on the essential habitat boundary.

232
Issue. The draft recoveryplan does not adequately describe the importance ofthe

Mount San Jacinto State Park to sheep recovery.

Response: The park is largely located above the elevation where bighorn sheep

normally occur.

Issue.~ The essential habitat map should modelfood and water resources as was

donefor physiography.

Response: Food and water resources generally are too dynamic to quantify

because their distribution is a function ofunpredictably variable rainfall patterns.

For example, randomly occurring thunderstorms do not provide uniformly

distributed moisture regimens throughout sheep habitat but rather result in

localized green-up following high intensity, short duration precipitation events.

Sheep typically respond to these sporadic events by exploiting ephemeral sources

offood and water. Patterns ofsheep distribution relative to perennial water

sources have been analyzed and discussed in Appendix B.

Issue: The draft recoveryplan did not identify the spec~ficprojects previously

approved by the Fish and Wildl~fe Service that would be excludedfrom areas

mapped as essential habitat. Essential habitat should be designated on areas

previously approved by the Fish and Wildl~fe Service for development Wscient~fic

data indicate these areas should be part ofcritical habitatfor recovery. Essential

habitat should include not yet constructedprojects that have been previously

approved by the Fish and WiIdl~fe Service because these areas are neededfor

sheep recovery.

Response: The Fish and Wildlife Service completed section 7 consultation on the

Ritz-Carlton GolfCourse and Mirada development prior to release ofthe draft

recovery plan, and completed section 7 conferences on the Jimenez Pit, Cahuilla

Zone Reservoir, and Shadowrock projects prior to listing. The Fish and Wildlife

Service and project proponents agreed to reconfiguration ofproject designs and

other conservation measures on the former four projects. Agreement on the latter

project has not been achieved and the affected area is considered essential habitat

233
unless the project is reconfigured to be consistent with the section 7 conference

opinion.

Issue: Critical habitat should be designated even fit divulges locations and

consequently exposes sheep to harm.

Response: On July 5, 2000, the Fish and Wildlife Service published a proposed

rule (65 FR 41405)to designate critical habitat under a separate process pursuant

to a recent settlement agreement with the plaintiffs who challenged our not

prudent finding that accompanied the listing. This topic was discussed in the

proposed rule.

Issue. The recovery plan should describe the relationship ofessential habitat and

critical habitat from a regulatory and proceduralperspective.

Response: Though the two designations are similar in theirfocus on defining

future survival and recovery needs, they differ significantly from a regulatory

perspective. For purposes ofthis plan, essential habitat is an informative

designation intended to provide scientific guidance to cooperating agencies and

the public, while critical habitat is statutorily defined with implementing

regulations that govern Federal agency activity. Critical habitat receives

protection under the Act through the prohibition against destruction or adverse

modification ofcritical habitat asset forth under section 7 ofthe Act with regard

to actions carried out, funded, or authorized by a Federal agency. Aside from the

protection that may be provided under section 7, the Act does not provide other

forms ofprotection to lands designated as critical habitat. Critical habitat

designation does not impose any restrictions to activities on private or other nonFederal lands that do not involve a Federal permit, authorization, or funding. The

process for designating critical habitat is distinct from the process for completing

the recovery plan. A proposal to designate critical habitat for the Peninsular

bighorn sheep was published in the Federal Register on July 5, 2000 (65 FR

41405). The essential habitat mapped in the recovery plan has the same boundary

as the proposed critical habitat, with slight discrepancies introduced by a legal

description for critical habitat along boundaries imposed by a

township/range/section coordinate grid.

234
Issue: Undeveloped butfenced property should not be mappedas essential

habitat.

Response: Areas that can be enhanced orrestored are included as essential habitat

if they are necessary for recovery. Fencing often does not establish an effective

movement barrier to sheep, though it can cause entanglement, injury, and death.

The Fish and Wildlife Service advises that fences constructed to exclude bighorn

sheep could result in take ifbuilt at the wrong location orimproperly designed.

Issue: The recoveryplan shouldprovide more spec{fic guidelines to local

jurisdictionsfor conserving habitat and reducing the effects ofurbanization. For

essential habitat to be effective, the recoveryplan shouldprovide guidance on

future regulation oftake undersections 7 and 10 of the Act, which should

spec(17cally prohibit authorization offuture take fewe grouppopulation levels

drop belowpredetermined thresholds and/or populations increase to a point

suggesting progress towards recovery. For example, the threshold approach used

for predator management also could be applied to habitat loss.

Response: Appendix F was designed to provide general guidelines that would fit

most projects in oradjacent to sheep habitat. More specific guidelines would be

difficult without a case by case analysis ofindividual projects. The Fish and

Wildlife Service can not use recoveryplans to predetermine future regulatory

decisions under sections 7 and 10 because the Act did not envision recoveryplans

as a regulatory mechanism.

Issue: The draft recoveryplan places inordinate importance on land use controls

and too little emphasis on reducingpredationpressure. Byfailing to manage

threats under its control, such as predation, the Fish and Wildl~fe Service unfairli’

shqis onerous regulatory impositions onto privateproperty owners. Another

commenter claimed that the acknowledged lack of understanding concerning

factors limiting population viability undermines the credibility ofthe proposed

land use controls, and that the uncertainty over adverse effects of urban

development eliminates any nexusfor governmental regulation.

235
Response: The Fish and Wildlife Service intends on concurrent implementation

of numerous recovery tasks commensurate with available funding. Completion of

the recoveryplan provides a basis for increased funding allocations to cooperating

agencies. Because numerous factors are depressing population growth, it would

not be appropriate for the Fish and Wildlife Service and cooperating agencies to

attempt to prioritize threats and address only one at a time. Focusing solely on

predator control and allowing continued loss of valuable habitat would be based

on a theory that habitat loss does not adversely affect bighorn sheep. The

available evidence suggests the opposite. The ewe groups adjoining metropolitan

areas historically have declined to a greater degree and currently are more severely

threatened with extirpation than more southerly and remote ewe groups that have

not sustained substantial loss ofhabitat in the past.

Issue: The draft recoveryplan does not adequately identify the specific lands

mapped as essential habitat and targets all available habitat without scientflcalh’

analyzing whetherportions ofthe area support any suitable habitat at all.

Response: Appendix B presents a habitat model that analyzed a variety ofhabitat

characteristics based on information in the scientific literature and distributional

data throughout the Peninsular Ranges. Areas with unsuitable soils and

topographywere excluded, as were areas greater than 800 meters(2,624 feet)

from toe of20 percent slope, though sheep are known to use these areas. Based

on the wide-ranging movements ofsheep in the Peninsular and other ranges

throughout the desert southwest, sheep are known to use a broad range ofhabitats

in desert environments. None ofthe areas mapped as essential habitat contains

soils, vegetation, ortopography that is unsuitable for use by sheep. Though sheep

may not use or occur in certain areas as frequently when population sizes are

small and distribution is more constrained, it is sometimes difficult to track sheep

movements, especially when only a small percentage ofcertain subpopulations

have radio collars. Thus, the known distribution is always an underestimate of

actual distribution.

Issue: The designation of “essential habitat” is an illegalsubterfugefor avoiding

the statutory requirementfor designating critical habitat and analyzing

consequent economic effects.

236
Response: A proposal to designate critical habitat for the Peninsular bighorn

sheep was published in the FederalRegister on July 5, 2000 (65 FR 41405), under

terms ofthe settlement agreement referenced above. A notice ofavailability for

the draft economic analysis on proposed critical habitat designation was published

in the Federal Register on October 19, 2000 (65 FR 62691).

Issue: Numerous land owners requested that their lands be specifically removed

from areas designated as essential habitat because ofthe significant social and

economic impacts thatshould be minimized per existing Fish and Wildlife Service

policy on recoveryplanning.

Response: As discussed above, the Fish and Wildlife Service has met with many

landowners and agencies in an effort to refine the essential habitat boundary so

that social and economic impacts are minimized to the extent that the potential for

recovery is not compromised. These discussions resulted in substantial agreement

with all parties involved over the vast majority ofthe urban interface. The

resulting essential habitat boundary was designed to minimize economic conflict

to the extent consistent with maintaining the likelihood offuture recovery.

Essential habitat differs significantly from critical habitat. Under critical habitat,

exclusions are a procedural outcome ofapplying section 4(b)(2) and/or “special

management” under the Endangered Species Act. Under 4(b)(2), economic and

social impacts are evaluated. However, there is no such process identified for

exclusions for essential habitat because recovery plans are nonregulatory

documents designed to guide, not dictate, recovery ofthe species.

Issue: The draft recoveryplan was deficient because it did not quant~fy the

acreage of diferent landownerships, historical distribution, and extent of

proposed essential habitat.

Response: Acreages were not calculated in the draft recovery plan because an

updated landownership map was not available and a precise boundary along the

urban interface was not delineated. In the final recovery plan, land ownership is

delineated with respect to essential habitat in Figure 4; however, the land

ownership map is somewhat outdated and any acreage figures would be

approximate. Approximate land ownership percentages are summarized in

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Section I.E. ofthe plan. Historical trends along the urban interfaces are

summarized in Section D. 1.

Issue: Lands that historically never were used by sheep should be identified. The

term “unoccupied habitat” is scient~ficallv undefined and inappropriately used to

describe unsuitable habitatfrom which bighorn sheep are absent.

Response: Historical information prior to the use ofaerial surveys and radio

telemetry is oflimited utility because the rugged topography and lack ofroads

throughout the Peninsular Ranges greatly restricted the extent of access on the

ground. Therefore, it is not possible to reliably conclude that certain areas were

not used historically. Similarly, given the relatively small sample size ofradiocollared sheep at present, especially rams (which are far more wide ranging than

ewes), more recent data cannot be properly interpreted to conclude that sheep are

absent from certain areas. Therefore, the remaining undeveloped portions of

historical range constitute the current distribution ofbighorn sheep in the

Peninsular Ranges. Use ofthe terms “occupied~~, “unoccupied~~, “suitable”, and

“unsuitable”, are more conceptual than empirical. Thus, these terms add little to

our understanding ofsheep biology, and as a result, the final recovery plan avoids

use ofthis terminology.

Issue: Given the tendency ofsheep to not venturefarfrom escape terrain,

justification in the recoveryplan is not adequate to support the needfor habitat

up to 0.8 kilometer (0.S mile)from toe of20 percentslope. Twentypercent slope

does not represent effective escape terrain; therefore, a steeperslope should be

usedfor ident{fying habitat in need of conservation. The recoveryplan does not

adequately describe what constitutes a movement corridor on the desert floor. If

sheep avoid human disturbance, thefragmented habitat patches on the desert

floor within the urban matrix would appear to have low habitat valuefor sheep.

Response: Though sheep typically are found in steeperterrain, numerous records

exist in the Peninsular Ranges and elsewhere of occurrences over 0.8 kilometer

(0.5 mile) from escape terrain. The 0.8 kilometer (0.5-mile) distance was selected

to capture the more typical movements onto the alluvial slopes. The 20 percent

slope for escape terrain was taken from the published literature. As discussed in

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Appendix B, a range ofslopes have been recognized by various authors as escape

habitat. Flatter topography encompasses more productive soils that support more

diverse and nutritious forage that is seasonally critical to sheep. Flatter

topography also can be important for dispersal and for sources ofseasonal water.

Sheep in other areas ofthe desert southwest have been known to move many

kilometers across the desert floor to reach neighboring mountain ranges. Given

the limited number ofdocumented movements ofthis kind, not enough is known

to delimit linkage dimensions. Rams are especiallyprone to use flatter areas

farther removed from escape terrain. Ruggedness on flatter topography can

function as escape habitat but has been difficult to measure and account forin

studies published to date. The essential habitat map excludes the less frequently

used and lower value habitats characterized by small patch size and proximity to

human disturbance.

Issue: Designation ofessential habitat asproposed would restrict accessfor

construction and maintenance of infrastructuralfacilities likeflood control and

water supply. Flood controlfacilities should not be included in essential habitat

because any use by sheep is incidental to theprimarypurpose ofthese lands.

Response: Case by case project reviews under the regulatory provisions of

sections 7 and 10 ofthe Act will detennine whether construction ofinfrastructural

facilities are compatible with sheep survival and recovery. Based on discussions

with Riverside County Flood Control and Water Conservation District and

Coachella Valley Water District, normal operations and maintenance ofexisting

facilities would not conflict with the management objectives for essential habitat.

Flood control facilities typically occur in washes and alluvial habitat that have

been most affected by historical habitat losses and often still support the same

important habitat values as the surrounding areas. As such, these facilities are not

defacto unsuitable or detrimental to sheep use. Ifreasonably managed, these

areas can fulfill their intended function while at the same time not conflicting with

sheep use in the area.

Issue: The recoveryplan does not discuss thepossibility thatpast habitat loss

from urbanization in the San Jacinto and northern Santa Rosa Mountains may

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have resulted in irreversible population declines, rendering essential habitat

designation in this area potentially useless.

Response: The recovery plan strives to intensify management efforts to offset the

loss ofhistoric habitat, and thereby maintain functional population levels in the

future. If populations become extirpated and the Recovery Team and cooperating

agencies determine that habitat areas are no longer capable ofsupporting selfsustaining populations, future revisions ofthe recoveryplan may delete essential

habitat and management objectives for those areas.

BIOLOGICAL ISSUES

Issue: One commenter thought that the eyesight ofbighorn equaling that of

humans aided by 8-power binoculars should be emphasized.

Response: According to Geist (1971), scientific evidence is not available to

support this popular myth, which probably originated with the experiences of

hunters with the species.

Issue: The regular sightings ofbighorn sheep in Chino Canyon and Tachevah

Canyon alleged by Fish and Wildlife Service biologists appear inconsistent with

portions of the draft recoveryplan that state bighorn sheep vanishedfrom the

northern San Jacinto Mountains after construction ofthe Palm Springs Aerial

Tramway.

Response: Though rams still range north ofChino Canyon, ewes have not been

documented in the northern San Jacintos (north ofChino Canyon) since the late

1980’s. The tramway was constructed in the early to mid-1960’s.

Issue: The high number ofundetermined causes ofdeath indicates that a better

explanation is needed of how the deaths were discovered and how the causes were

diagnosed.

Response: Most deaths were discovered from radiocollared animals because the

fate ofuncollared animals is far more difficult to ascertain. When dead animals

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are found, the cause ofdeath is sometimes difficult to determine because in many

cases, coyotes and other scavengers have consumed the carcass so thoroughly that

the original cause of death (whether predation or not) can not be determined.

Issue: Some commenters thought the recovery criteria of 25 ewes per 9 ident~fied

regions and an average of 750 adultsfor delisting is too low to assure survival

and recovery, and that the estimated rangewide carrying capacity of 1,000 sheep

appears low. Another commenter thought the criteria requiring a minimum of 25

ewes in each ewe group would be too dfftcult to achieve.

Response: The team and agencies decided that it would be difficult to justify a

higher population level than was known historically, especially given the

extensive habitat loss and fragmentation, and other factors that likely have

reduced carrying capacity over time. Team members most familiar with the

Peninsular Ranges assessed current and historic habitat quality, and made regional

comparisons with other bighorn sheep habitats in estimating current conditions

and carrying capacity. The 9 regions were deemed capable ofsupporting in

excess of 25 ewes, with the carrying capacity in most ofthe regions substantially

exceeding the minimum. Because 750 is an average figure, it would be necessary

forthe population to rise above that level forsome period oftime, likely in

response to changing carrying capacity. The averaging criterion was selected

because it allows natural population fluctuations and management flexibility. If

the long-term carrying capacity exceeds 750 animals, the population likely would

exceed the 750 minimum established in the recovery plan.

Issue: The operations by the Bighorn Institute are contributing to the decline

instead ofthe recovery of bighorn sheep. Alternative methods, such as on-theground surveys, should be used for estimating population size and distribution,

instead ofmore highly disruptive helicopterflights. Helicopter censuses and

captures arefar more stressful to sheep than researchers, hikers, and riders

quietly moving through sheep habitat.

Response: The Bighorn Institute conducts hundreds of days ofon-the-ground

work and only about 6 days ofhelicopter work each year. Conducting on-theground studies is often not feasible on private property and could result in

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significant disruption to sheep if implemented at a level needed to estimate

population distribution and abundance at precision levels comparable to aerial

techniques. Even at current levels, on-the-ground disturbance associated with

research activities could be detrimental if not for rigorous safeguards. For

example, Bighorn Institute biologistsregularly document through radio telemetry

that their presence “bumps” or “pushes” sheep in flight away from them, at which

point the field methodology requires backing off, which often prevents the

recording offield data.

Issue. Why is agricultural use adjoining bighorn sheep habitat considered a

more compatible use, whereasresidential and resort developments are not?

Response: Agricultural activities do not generate the high levels ofsecondary

impacts, such as human recreation in adjoining habitat, as is typically associated

with urban land uses. In addition, agricultural lands can be restored to sheep

habitat, whereas urban land uses can not. Though agricultural lands were

excluded from delineated essential habitat, several Recovery Team members

recommended they be included because oftheirrestoration potential.

Issue: Numerous commenters inquired whetherstudies have been conducted and

evidence existsfor thepresence ofbighorn sheep on theirlands.

Response: We have included a map with known locality records to provide a

better indication ofbighorn sheep distribution. References cited throughout the

recovery plan should be perused to determine study areas and methods. The lack

ofrecords for certain areas does not necessarily indicate that sheep are absent,

only that their presence has not been documented.

Issue: The slow reproductive rate and long-term estimatesfor recovery should be

accelerated by importing sheep to increasepopulation levels.

Response: Unless the factors that limit population growth in the Peninsular

Ranges are addressed, it is unlikely that a program to introduce animals from

outside areas would be successful. However, alleviating in situ decimating factors

would allow the resident population to expand on its own, which would forego the

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need for translocation. Importing animals also poses risks ofdisease

transmission. Regardless, bighorn sheep populations throughout the Mojave

Desert are currently depressed to the extent that surplus animals are not available

for importation.

Issue: Given the history ofpopulation declines in regions adjoining urban areas,

it does not seem plausiblefor the recoveryplan to claim that Peninsular bighorn

sheep have a high potentialfor recovery.

Response: The recoveryplan attemptsto build on past examples and taking

action soon enough to reverse the decline ofsheep in our mountains. The

Recovery Team and cooperating agencies believe that the recovery potential is

high ifthe management recommendations in the recovery plan are implemented.

Issue: Thefurther research andplanning required through the captive rearing

and augmentation guidelines in Appendix C does not recognize or expedite the

immediate recovery needs and issues that must be addressed in the short-term.

After manyyears ofoperation, these issues should already have been addressed

and a plan ready to implement.

Response: The existing operations ofthe Bighorn Institute are reviewed annually

by the agencies and adjustments made if needed. Captive breeding for population

augmentation, population monitoring, and research have been and continue to be

the primary emphases until changes in direction are agreed to by the Institute,

agencies, and Recovery Team.

Issue: One commenter suggested that the draft recovery plan was deficient

because a recent discovery ofa desert bighorn sheep population in Ventura

County was not addressed.

Response: Sheep populations in Ventura County are not included in the distinct

population segment listed in the Peninsular Ranges and, therefore, are not relevant

to the recovery plan.

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Issue: Because bighorn sheep arewilderness animals, more emphasis should be

place on conservation efforts in Anza-Borrego Desert State Park, instead of

urbanizing Coachella Valley, where prospectsfor success are less than in more

remote areas.

Response: Numerous subpopulations are necessary to maintain the larger

Peninsular Ranges metapopulation. Therefore, recovery will require protection of

all areas needed to maintain the constituent subpopulations. This protection will

require increased management emphasis and cooperation among land managers in

urbanized areas.

Issue: The limited dispersal and colonization capabilities contradict statements

elsewhere in the recoveryplan that bighorn sheep arewide ranging animals

dependant upon large tracks ofhabitat.

Response: True, each individual is a wide-ranging animal with a relatively large

home range. This behavior and knowledge ofthese areas is learned by the

offspring, which is transmitted across generations. Though colonizations ofnew

habitat are known to occur, they are not a common event. Rams are more wideranging than ewes and are known to move between mountain ranges and ewe

groups.

Issue: The draft recovery plan does not clearly indicate how or whether models

would be used to assist in gaining a better understanding ofthe interacting

factors thatplace sheep at risk.

Response: Models are a tool that help assimilate knowledge and understand

factors that place bighorn sheep at risk, for later application through management

prescriptions. Models should be used anytime they can help us to better

understand bighorn sheep population dynamics, genetics, or ecosystems. Though

the recovery plan provides examples ofhigh priority issues that should be

examined with models, the points at which amodel would be appropriate are

difficult to predict. Modeling is included in the section on research because it is

an ongoing process that will have to be applied and modified as questions arise

and more databecome available.

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Issue: The recoveryplan is biologically inconsistent, arguing on the one hand

that human disturbance in wildareas causesthem to avoid otherwise important

habitat but on the hand arguing thatfences are needed to preventsheepfrom

being attracted to urban areas.

Response: Bighorn sheep react differently to various kinds ofdisturbance

depending on numerous factors, including location. The northern Santa Rosa

Mountains ewe group is the only herd that has habituated to using the urban

interface, yet when inwild habitat distant from the urban edge, these same sheep

react similarly to nonhabituated herds—that is, individuals revert to normal wild

behavior when away from the urban edge. The reaction is perhaps most

pronounced during the lambing season, when ewes with lambs are frequently

displaced by human disturbance. This effect has been repeatedly documented

through radio telemetry research, where sheep are sometimes inadvertently

“bumped” or “pushed” farther away by researchers, even though the sheep are still

hundreds ofmeters distant and not visible to the researchers. In other words,

behavioral reactions often depend on geographical and seasonal context, with the

spectrum ofcontrasting responses to human stimuli most clearly evident within

this ewe group.

PREDATOR CONTROL ISSUES

Issue: Radiocollars may rendersheep more vulnerable to predation and

therefore should not be used as prevalently as they are today.

Response: We are not aware ofdata that indicatesradiocollared animals are at

greater risk ofpredation than uncollared animals. Nonetheless, cooperating

agencies have attempted to balance the number ofradiocollars to minimize

potential risk without compromising information needed to achieve population

recovery.

Issue: Whereas one commenter assertedthat theproposedpredator management

measures were too lax and should be more aggressive in termns of moving

predatorsfrom the area before they become an issue, another commenter claimed

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that scientflc evidence wassufficient to indicate that mountain lion predation was

not a problem and that management measures, therefore, were not warranted.

Response: This issue was discussed vigorously by the team and agencies.

Because documented mortalities were particularly high in certain ewe groups, the

team and agencies decided the prudent course ofaction dictated a measured

management response, which would be modified as more data became available.

Issue. Predator management should be given higher priority than land

management restriction because mortality to predators is the more likely limiting

factor on bighorn populations.

Response: The draft recoveryplan and available evidence indicate that individual

subpopulations are affected by a variety ofinfluences that affect population levels

and that the combinations and relative strength ofthese influences typically differ

among ewe groups and change over time. Therefore, the recovery plan focuses on

the range ofthreats facing bighorn sheep. The recovery plan prescribes

predetermined criteria for initiating predator management and recognizes the

importance ofhabitat protection so that recovered populations have sufficient

space to inhabit.

Issue: The long-term decline in habitat quality and deer populations in the Santa

Rosa Mountains should be identified as a cause ofhigh levels ofmountain lion

predation on bighorn sheep, with a strategy to reverse the situation. The recovery

plan should more clearly establish the relationship of bighorn sheep to mule deer

by superimposing a deer distribution map.

Response: Mule deer typically occur at higher elevations than bighorn sheep,

though ranges may overlap regionally and seasonally, such as during the winter

when deer in some areas move to lower elevations. Traditional predator/prey

theory holds that predator populations increase and decrease in response to

fluctuating prey populations. However, there are no data indicating that high

levels of predation are due to declines in habitat quality or deer populations, or

whether prey switching may be occurring in the Peninsular Ranges. Because data

on habitat quality, as well as deer and mountain lion populations in the Peninsular

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Ranges are not sufficiently robust to provide insight into these questions, the draft

and final recovery plans propose focused research to address this ecological issue.

Issue: The recoveryplan does not provide compelling evidence that the

predator/prey system is not viable, and therefore, predators should not be

managed unless a cause and effect relationship with bighorn population declines

is established.

Response: The high incidence ofpredation, comparatively lower adult

survivorship rates than in other regions, and long-term population declines

suggest to land managers that predation is a limiting factor to population growth

in some areas ofthe Peninsular Ranges. The cooperating agencies have agreed

that this evidence is sufficient to prompt responsible but cautious management

intervention.

Issue: One commenter argued that counterto claims in the draft recovery plan,

the only available scientflc evidence indicates a declining trend in statewide

mountain lionpopulations.

Response: The evidence presented by the commenter lacked associated statistical

analysis; therefore, the statistical resolution ofthe data cannot be evaluated and no

-conclusion on population trend is possible.

TRAIL ISSUES

Issue: The constantpresence ofbighorn sheep along Highway 111 in Rancho

Mirage indicates human activities, such as hiking andjeep use, may not create

movement barriers, assuggested in the draft recoveryplan. Further information

is requested to support why back roads and trails are detrimental to sheep when

they are known to cross 6-lane highways (e.g. Highway 111 in Rancho Mirage).

Response: The recovery plan cites numerous studies that have documented

avoidance behavior to human related disturbance (see Papouchis et al. 1999 for

example). Numerous records of vehicular related mortality provide further

evidence ofadverse effects. The recovery plan seeks to remedy the maladaptive

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behavior ofhabituation to urban sources offood and water so that sheep are better

able to survive in the wild.

Issue: A trails map to clarfy and accompany Table 10 is needed.

Response: Though a good idea, an accurate trails map is not currently available.

The cooperating agencies are pursing the development ofsuch a map.

Issue: Detailedmaps oflambing, rearing, and watering habitat are needed to

just~fyany decisions to close trails.

Response: The distribution oflambing, rearing, and watering habitat is

incompletely known and, therefore, cannot be accurately mapped. The final

recoveryplan has been modified to include a more complete set ofinformation

upon which trails decisions should be based.

Issue.’ A permit system should be usedfor controlling trail use on all trailsfor

which conflicts were identified in the recovery plan.

Response: The cooperating agencies are working with interest groups in the

formulation ofa range ofalternative trails strategies that include this option.

Issue: The recovery plan should consider that in the San Jacinto Mountains, the

existing trails network appears to provide a passive disturbance boundary that

may control sheep access to the urban interface and prevent exposure to the

urban hazards experienced in the northern Santa Rosa Mountains. Consequently,

seasonal orpermanent trail closures could have unintended adverse effects.

Response: A trails management plan prepared by the land management agencies

and interest groups will consider the merits ofthis comment. Certain adjustments

to the existing trails network and associated monitoring could be implemented to

improve upon this concept.

Issue: More specificity is needed in describing where human disturbance and

other indirect effects ofurbanization is conflicting with sheep conservation.

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Response: Human intrusion and associated disturbance has the potential to extend

wherever access into habitat is provided. Though lambing and watering habitats

are particularly vulnerable, excessive human use throughout the year may also

affect bighorn persistence.

Issue.’ Will mitigation credits be givenfor the eradication ofinvasive non-native

plants?

Response: Conservation measures for proposed projects will be determined on a

case by case basis through regulatory processes oflocal, State, and Federal

agencies.

Issue: The January through June trailconflicts in the San Jacinto Mountains

appear excessive ifthe lambing season there extends only through mid-March.

Response: The draft recovery plan stated on page 12 that DeForge et a!. (1997)

found a similar onset to the lambing season in February in the San Jacintos.

Cunningham found that lambing in Carrizo Gorge extended only to mid-March.

Lambs are critically dependent upon theirmothers for several months after birth.

Issue: Rather than monitoring to ensure compliance with seasonal trail closures

before allowing construction oftrailreroutes out oflambing habitat, the recovery

plan should allow simultaneous construction ofalternative trail routes to enhance

the effectiveness ofseasonal closures on existing trails in lambing habitat.

Response: The finalrecovery plan has been modified to incorporate flexible

approaches that will be provided in more detail in the trails management plan

prepared by the cooperating agencies and interests. Without adequate

management and monitoring, this approach could result in more trails and no

reduction in use ofproblematic trails.

FENCING ISSUES

Issue: The draft recoveryplan does not provide evidencefor the effectiveness of

the proposedfencing as a mitigation measure andfails to address the associated

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financial and visual burdens. Except in areas with vehicular related mortalities,

the needforfencing is questionable, considering the potentially detrimental

effects ofsevering habitat, restricting sheep movement, and rendering sheep more

vulnerable to predation againstfences. Alternativesto fences, such as

nonmotorized trails adjoining development, which would provide a deterrent to

sheep movement into urban areas, warrant more analysis. By imposing the

mandateforfencing on privateproperty without adequatejustification, the draft

recoveryplan acted in an arbitrary manner in excess ofstatutory authority.

Response: The cooperating agencies are open to alternative means ofcontrolling

sheep movements into urban areas. However,some landowners and jurisdictions

have chosen fencing as an affordable and reliable solution to the problem of

behavioral habituation. When installed, fences have proven effective and

aesthetic concerns have been addressed through alternative designs and

alignments. Fencing along the urban interface is intended to benefit sheep by

curtailing movement into areas with unnatural sources ofmortality and help

reduce herd mortality rates to sustainable levels. The demonstrated loss of

animals to vehicular related mortality, poisoning from landscaping plants,

drownings, etc., establish a legal nexus to warrant measures to prevent these

adverse effects.

NON-NATIVE ANIMAL ISSUES

Issue: The recoveryplan needs to establish a bufferzone between bighorn sheep

habitat and cattle grazing, as was donefor domestic sheep grazing, so that the

risk ofdisease transmission is minimized.

Response: There is no conclusive evidence to support a buffer zone for disease

protection from cattle as there is for domestic sheep. The recovery plan

recommends research on disease transmission between livestock and bighorn, and

if a buffer zone is shown to be warranted, future iterations ofthe recovery plan

will be amended accordingly.

Issue: Cattle grazing and associatedfencing should not be allowedfor various

reasons, including disease hazards and risk ofphysical injury to bighorn sheep.

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Response: We agree that fencing should be minimized and eliminated if possible.

Iffencing is necessary, design guidelines have been developed that minimize and

prevent the risk ofinjury. The recovery plan establishes the need to thoroughly

review the appropriateness ofcattle grazing in sheep habitat and take action if

prudent.

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Region 1

U.S. Fish and Wildlife Service

Ecological Services

911 N.E. 11th Avenue

Portland, Oregon 97232-4181

October2000