Draft Recovery Plan

for the

Sierra Nevada Bighorn Sheep

(Ovis canadensis californiana)

May 2003

Region 1

U.S. Fish and Wildlife Service

Portland, Oregon

Approved: XXXXXXXXXXXXXXXXXXXXXXXXXXX

Manager, California/Nevada Operations Office

Region 1, U.S. Fish and Wildlife Service

Date: 
The Draft Recovery Plan for the Sierra Nevada Bighorn Sheep was developed by

the State of California, Resources Agency, Department of Fish and Game, and the

U.S. Fish and Wildlife Service in cooperation with:

National Park Service

U.S. Bureau of Land Management

U.S. Forest Service

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Date: 

Director, California Department of Fish and Game

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Date: 

Regional Director, National Park Service

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Date: 

Regional Director, U.S. Bureau of Land Management

XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX Date: 

Regional Forester, U.S. Forest Service
i

Primary Author

The primary author of this recovery plan is:

John D. Wehausen, Ph.D.

University of California

White Mountain Research Station

3000 East Line St.

Bishop, CA 93514

The recovery plan was written with the assistance of the Sierra Nevada Bighorn

Sheep Recovery Team (see Acknowledgments).
ii

Disclaimer

Recovery plans delineate reasonable actions required to recover and/or

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

plans, sometime preparing them with the assistance of recovery teams,

contractors, State and other Federal agencies, Tribes, and other affected and

interested 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 of any 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 California/Nevada

Operations Manager as approved. Approved recovery plans are subject to

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

completion of recovery tasks.

Literature citation should read as follows:

U.S. Fish and Wildlife Service. 2003. Draft Recovery Plan for the Sierra Nevada

Bighorn Sheep. U.S. Fish and Wildlife Service, Portland, Oregon. 

xiii + 147 pp. 

An electronic version of this recovery plan is also available at

http://www.r1.fws.gov/ecoservices/endangered/recovery/default.htm.
iii

Acknowledgments

This recovery plan was prepared by the Sierra Nevada Bighorn Sheep

Recovery Team, with important contributions from Mr. Carl Benz, Dr. Vern

Bleich, Dr. Walter Boyce, Ms. Paula Brown, Ms. Diana Craig, Dr. Ben Gonzales,

Dr. David Graber, Mr. Troy Kelly, Dr. Howard Quigley, Dr. Peter Stine, Mr.

Steve Torres, and Dr. John D. Wehausen. The recovery plan benefitted greatly

from numerous discussions with Dr. Holly Ernest, Mr. Mike Lawrence, Ms.

Kathy Noland, Mr. Christopher Papouchis, Ms. Wendy Philpott, Ms. Lynn Sadler,

Mr. Steve Thompson, Mr. John Walter, Mr. Harold Warner, and Dr. David S.

Zezulak who also facilitated preparation and compilation of the recovery plan. 
iv

Sierra Nevada Bighorn Sheep Recovery Team

Stakeholder Team Members

Katie Bellomo, People for Mono Basin Preservation, Lee Vining, California

Bob Bissell, Society for the Conservation of Bighorn Sheep

Paula Brown, Sierra Nevada Bighorn Sheep Foundation, Bishop, California 

Deirdre E. Flynn, California Wool Growers Association, Sacramento, California

Joe Echenique, Echenique Livestock Company, Bakersfield, California

Gary Guenther, Wilderness Watch, Mammoth Lakes, California 

Debbie House, Department of Water and Power, Bishop, California 

Mickey Jarvis, California Cattleman’s Association, Bishop, California 

Ron Keil, Inyo National Forest, U.S. Forest Service, Bishop, California

Brenda Lacey, California Wool Growers Association, Bishop, California 

Mike Lawrence, Bridgeport Ranger District, U.S. Forest Service, Bridgeport,

California 

Ray Lee, Foundation for North American Wild Sheep, Cody, Wyoming 

Craig London, Rock Creek Pack Station, Bishop, California 

Sally Miller, The Wilderness Society, Lee Vining, California

Paul McFarland, Friends of the Inyo, Lee Vining, California

Kathy Noland, Inyo National Forest, U.S. Forest Service, Bishop, California 

Chris Papouchis, Animal Protection Institute, Sacramento, California 

Toni Richards, Bishop Paiute Tribe, Bishop, California 

Lynn Sadler, Mountain Lion Foundation, Sacramento, California 

Steve Thompson, Yosemite National Park, National Park Service, California

Brian Tillemans, Department of Water and Power, Bishop, California 

Todd Vogel, Sierra Mountaineering Center, Bishop, California 

John Walter, The Sierra Club – Range of Light Chapter, Mammoth Lakes,

California 

Harold Werner, Sequoia-Kings Canyon National Parks, National Park Service,

California 

Stakeholder Meetings were facilitated by Dr. John D. Wehausen and 

Dr. David S. Zezulak. 
v

Science Team Members

Mr. Carl Benz, U.S. Fish and Wildlife Service, Ventura, California 

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

Dr. Walter Boyce, University of California, Davis, California 

Ms. Diana Craig, U.S. Forest Service, Pacific Southwest Region, Vallejo,

California

Dr. David M. Graber, Sequoia – Kings Canyon National Park, Three Rivers,

California

Dr. Howard Quigley, Hornocker Wildlife Institute, Bozeman, Montana 

Dr. Peter Stine, Sierra Nevada Research Center, Sacramento, California 

Mr. Steve Torres, California Department of Fish and Game, Sacramento,

California

Dr. John D. Wehausen, University of California, White Mountains Research

Station, Bishop, California 

Science Team Meetings were facilitated by Mr. Troy D. Kelly 

and Dr. David S. Zezulak.
vi

EXECUTIVE SUMMARY

Current Species Status: The population of bighorn sheep in the Sierra Nevada

of California (Ovis canadensis californiana) was listed as an endangered species

on January 3, 2000, following emergency listing on April 20, 1999. In 1995 these

bighorn sheep hit a population low of about 100 total individuals, distributed

across 5 separate areas of the southern and central Sierra Nevada, and had

increased to about 125 in 1999. Since then conditions have been particularly

favorable for population growth, with the total number of individuals reaching

about 250 in 2001.

Habitat Requirements and Limiting Factors: These bighorn sheep use habitats

ranging from the highest elevations along the crest of the Sierra Nevada (4,000+

meters [13,120+ feet]) to winter ranges at the eastern base of the range as low as

1,450 meters (4,760 feet). These habitats range from Great Basin sagebrush scrub

to alpine. Within this range, primary elements of preferred habitats are visual

openness and close proximity to steep rocky escape terrain. Forage resources

vary greatly across habitats used by these bighorn sheep, and plant species eaten

vary accordingly. Of particular importance to population parameters is the

nutrient content of forages eaten. Nutrient quality of diets varies greatly with

season and elevation and is limited primarily by effects of temperature and soil

moisture on plant growth. Because of the relationship between elevation and

temperature, low elevation winter ranges provide an important source of high

quality forage early in the growing season. 

Significant population declines beginning in the late 1980's were

associated with these bighorn sheep avoiding low elevation winter ranges. This

avoidance behavior has been suggested to be linked to increasing predation

pressure from mountain lions on winter ranges during the 1980's. Because of

population collapses that have occurred since this winter range avoidance began,

some of the herds may now be too small to allow the group sizes necessary to

provide bighorn sheep the psychological comfort to make use of winter ranges. 

Longer-term limiting factors have undoubtedly included contact with domestic

sheep leading to pneumonia epizootics in the bighorn sheep; domestic sheep

grazing adjacent to bighorn sheep ranges has continued to be a significant threat
vii

in recent decades. Because almost all bighorn sheep habitat in the Sierra Nevada

is in public ownership, loss of habitat to human use has not been a limiting factor.

Recovery Objective: The objective of this recovery plan is to attain population

sizes and geographic distribution of bighorn sheep in the Sierra Nevada that

assure long-term viability of the overall population and thereby allow its delisting

as an endangered species.

Recovery Priority: The Sierra Nevada bighorn sheep has a recovery priority

number of 3. Recovery priorities for listed species range from 1 to 18, with 1

being the highest priority. The priority system uses the criteria of: (1) degree of

threat, (2) recovery potential, and (3) taxonomy (level of genetic distinctiveness). 

A fourth factor, conflict, is a supplementary element characterizing whether or not

recovery actions are likely to be in conflict with construction or other

development projects. A priority of 3 has been assigned to the Sierra Nevada

bighorn sheep for the following reasons: (1) there is a high degree of threat

because the population is small in size and its distribution is fragmented; (2) there

is a high recovery potential; and (3) the listed entity, as described, is a distinct

population (which receives the same rating level as a subspecies). 

Downlisting Criteria: Potential bighorn sheep habitat in the Sierra Nevada was

divided into 17 herd units, and those herd units were grouped into 4 recovery

units on the basis of natural breaks in habitat distribution. Two criteria will be

used for downlisting.

Downlisting Criterion A1: A minimum of 50 yearling and adult females

exist in the Kern recovery unit (Great Western Divide), 175 in the Southern

recovery unit (Olancha Peak to Coyote Ridge), 75 in the Central recovery unit

(Mount Tom to Laurel Mountain), and 65 in the Northern recovery unit (Mount

Wood to Twin Lakes), for a minimum total of 365 females. These minimum

values will be determined by direct count. To achieve these population numbers

it is expected that the major threats of excessive predation and avoidance of highquality low-elevation winter ranges will have substantially diminished.
viii

Downlisting Criterion A2: The threat of domestic sheep or goats

contacting bighorn sheep in the Sierra Nevada has been eliminated.

Delisting Criteria: Three delisting criteria were developed based on biological

parameters, distribution of the herd units, and research on threats to the

population.

Delisting Criterion B1: The minimum numbers of females by recovery

units required for downlisting have been maintained as an average for one

bighorn sheep generation (6 years) with no intervention. To achieve these

population numbers it is expected that the major threats of excessive predation

and avoidance of high-quality low-elevation winter ranges will have substantially

diminished and remained low over an extended period of time.

Delisting Criterion B2: Bighorn sheep are distributed such that at least 2

herd units are occupied in the Kern recovery unit, 6 in the Southern recovery unit,

3 in the Central recovery unit, and 3 in the Northern recovery unit, for a total of

14 herd units. Currently, seven of these herd units are occupied.

Delisting Criterion B3: Recovery tasks related to monitoring and research

goals have been accomplished, allowing the severity of secondary threats 

(including habitat loss, vegetational succession, recreational disturbance,

competition with elk or deer, acid rain, and climate change) to be adequately

assessed. Threats have either been ameliorated or have been determined not to

pose a significant risk to the population. 

Actions Needed: Immediate actions involve helping small herds increase to sizes

that allow adequate use of winter ranges in order to achieve positive population

growth values. Key elements that may be involved are: (1) predator

management; (2) augmentation of small herds with individuals from larger ones;

and (3) elimination of the threat of a pneumonia epizootic resulting from contact

with domestic sheep or goats.

Longer term actions concern reintroducing bighorn sheep to vacant herd

units and maintaining genetic variation. Reintroductions require the development

of sufficient sources of translocation stock.
ix

Good monitoring of bighorn sheep herds and some predators are also

actions important to the success of this recovery effort, as are some key research

projects.

This recovery plan calls for separate implementation plans on the

following subjects: (1) bighorn sheep monitoring; (2) bighorn sheep

translocation; (3) predator management; (4) genetic management; and (5) how to

deal with a pneumonia outbreak.

Recovery Costs: Cost estimates of all recovery (Part II) tasks but task 1.1 are

made in the Implementation Schedule (p. 69), totaling $21,730,000 over 20 years. 

Additional costs to identify and acquire important habitat not in public ownership

(Task 1.1) will be determined as parcels are identified and acquired.

Date of Recovery: With optimal population growth rates, recovery criteria might

be met to allow downlisting within 10 years (2013) and delisting within another

10 years (2023). Under less than optimal scenarios, including unexpected

catastrophes, one or more additional decades may be needed.
x

TABLE OF CONTENTS

I. INTRODUCTION ...............................................1

A. BRIEF OVERVIEW . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1. LISTING OF BIGHORN SHEEP IN THE SIERRA NEVADA

..............................................1

2. ORIGIN, MORPHOLOGY, AND TAXONOMY ..........1

B. ECOLOGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

1. HABITAT . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

2. FOOD HABITS AND NUTRITION ....................4

3. BEHAVIOR .......................................5

4. METAPOPULATION STRUCTURE . . . . . . . . . . . . . . . . . . . 7

a. Inbreeding and Small Populations ................7

b. The Balance between Extinction and Colonization . . . 8

5. REPRODUCTION ..................................9

6. MORTALITY FACTORS . . . . . . . . . . . . . . . . . . . . . . . . . . . 10

7. DISEASE AND PARASITISM . . . . . . . . . . . . . . . . . . . . . . . 12

8. INTERSPECIFIC COMPETITION AND HUMAN

DISTURBANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

C. ABUNDANCE AND DISTRIBUTION . . . . . . . . . . . . . . . . . . . . . . 16

1. HISTORICAL DISTRIBUTION, ABUNDANCE, AND

TRENDS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

2. RECENT DISTRIBUTION, ABUNDANCE, AND TRENDS

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

D. REASONS FOR LISTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24

1. THE PRESENT OR THREATENED DESTRUCTION,

MODIFICATION, OR CURTAILMENT OF ITS

HABITAT OR RANGE . . . . . . . . . . . . . . . . . . . . . . . . . . 25

2. OVERUTILIZATION FOR COMMERCIAL,

RECREATIONAL, SCIENTIFIC, OR EDUCATIONAL

PURPOSES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 25

3. DISEASE OR PREDATION . . . . . . . . . . . . . . . . . . . . . . . . . 25

4. THE INADEQUACY OF EXISTING REGULATORY

MECHANISMS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
xi

5. OTHER NATURAL OR MANMADE FACTORS AFFECTING

ITS CONTINUED EXISTENCE . . . . . . . . . . . . . . . . . . 28

E. PAST AND CURRENT MANAGEMENT AND CONSERVATION

ACTIVITIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

1. FEDERAL AGENCIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

a. U.S. Department of the Interior - Fish and Wildlife

Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 28

b. U.S. Department of the Interior - National Park Service

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31

c. U.S. Department of Agriculture - Forest Service . . . . . 33

2. STATE AGENCIES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 35

II. RECOVERY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

A. CONSERVATION PRINCIPLES USED IN DEVELOPING THIS

RECOVERY PLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

1. POPULATION DYNAMICS . . . . . . . . . . . . . . . . . . . . . . . . 39

2. GENETIC CONSIDERATIONS . . . . . . . . . . . . . . . . . . . . . . 41

3. ECOSYSTEM INTEGRITY . . . . . . . . . . . . . . . . . . . . . . . . . 43

B. OBJECTIVES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44

1. CONSERVATION CHALLENGE AND GOALS . . . . . . . . . 44

2. RECOVERY CRITERIA . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45

a. Downlisting Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . 45

b. Delisting Criteria . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

c. Recovery Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

C. RECOVERY STRATEGY . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

D. NARRATIVE OUTLINE OF RECOVERY ACTIONS . . . . . . . . . . 53

III. IMPLEMENTATION SCHEDULE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 69

IV. LITERATURE CITED . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 76

V. APPENDICES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

APPENDIX A. PACK LLAMAS AS POTENTIAL SOURCES OF

DISEASES FOR SIERRA NEVADA BIGHORN SHEEP . . . . . 94
xii

APPENDIX B. RISK ASSESSMENT REGARDING DOMESTIC

SHEEP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101

APPENDIX C. TRANSLOCATION CONSIDERATIONS FOR SIERRA

NEVADA BIGHORN SHEEP . . . . . . . . . . . . . . . . . . . . . . . . . 106

APPENDIX D. MONITORING OF BIGHORN SHEEP POPULATION

PARAMETERS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124

APPENDIX E. CONSIDERATIONS FOR A PREDATOR

MANAGEMENT PLAN . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 132

APPENDIX F. PUBLIC INFORMATION AND OUTREACH PLAN

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 137

APPENDIX G. SUMMARY OF THREATS AND RECOMMENDED

RECOVERY ACTIONS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 145

FIGURES

Figure 1. Sierra Nevada bighorn sheep Recovery Units, herd units, and group

sightings (1974-2000) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Figure 2. Minimum population sizes (1978-2001) . . . . . . . . . . . . . . . . . . . . . . . 21

Figure 3. Mountain lion depredation permits issued in Inyo and Mono Counties,

1972-99, and bighorn sheep winter range census results for the Mount

Baxter herd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21

TABLES

Table 1. Causes of known bighorn sheep mortalities in the Sierra Nevada by

population since 1975 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Table 2. Probable locations of historic bighorn sheep herds in the high Sierra

Nevada based on historic records and habitat characteristics . . . . . . . . . 18

Table 3. 1999 population data for Sierra Nevada bighorn sheep . . . . . . . . . . . . 24

Table 4. Herd Units and Recovery Units used as the basis of recovery goals . . 47
xiii

Table 5. Population criteria for downlisting and delisting of Sierra Nevada

bighorn sheep by recovery units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Table C-1. Potential sites for bighorn sheep wintering groups in the central and

southern Sierra Nevada grouped by recovery unit . . . . . . . . . . . . . . . . . 112
1

I. INTRODUCTION

A. BRIEF OVERVIEW

1. LISTING OF BIGHORN SHEEP IN THE SIERRA NEVADA

In 1878, State legislation provided temporary protection from hunting for

all bighorn sheep in California; in 1883, that protection became permanent, a

status that remains for bighorn sheep in the Sierra Nevada (Wehausen et al.

1987). In 1972, the California subspecies, as defined by Cowan (1940) and

including surviving native herds in the Sierra Nevada, was listed as rare under the

1970 California Endangered Species Act (California Department of Fish and

Game 1974); that category was changed to threatened in 1984. In 1999, the

California Fish and Game Commission upgraded the status of these bighorn sheep

to endangered. On April 20, 1999, we (the U.S. Fish and Wildlife Service)

granted emergency endangered status to bighorn sheep inhabiting the central and

southern Sierra Nevada of California as a distinct population segment and,

simultaneously, published a proposed rule to list the species as endangered (U.S.

Fish and Wildlife Service 1999 [64 FR19333]). The final rule granting

endangered status to that population segment was published on January 3, 2000

(U.S. Fish and Wildlife Service 2000 [65 FR 20]).

2. ORIGIN, MORPHOLOGY, AND TAXONOMY

Wild sheep crossed the Bering land bridge from Siberia during the

Pleistocene and, subsequently, spread through western North America as far south

as Baja California and northern mainland Mexico (Cowan 1940). Divergence

from their closest Asian ancestor (Siberian snow sheep; Ovis nivicola) occurred

about 600,000 years ago (Ramey 1993). In North America, wild sheep have

diverged into two extant species -- thinhorn sheep (Ovis dalli) that occupy Alaska

and northwestern Canada, and bighorn sheep (Ovis canadensis) that range from

southern Canada to Mexico. The seven subspecies of bighorn sheep proposed by

Cowan (1940) have come under recent taxonomic scrutiny, and most have not

been consistent with new genetic (Ramey 1993, 1995; Boyce et al. 1997,
2

Gutierrez-Espeleta et al. 1998) or morphological data (Wehausen and Ramey

1993, 2000) or the reanalysis of Cowan’s (1940) original data (Ramey 1993).

Lack of support for the traditional taxonomy includes the classification of

bighorn sheep from the Sierra Nevada. Based on only four immature specimens

collected in the Sierra Nevada, Grinnell (1912) designated Sierra Nevada bighorn

sheep a distinct subspecies (Ovis cervina sierrae). Cowan (1940) failed,

however, to find support for Grinnell's Sierra Nevada subspecies. He included

sheep from the Sierra Nevada instead under the California bighorn (O. canadensis

californiana) subspecies, the distribution of which extended north to British

Columbia between the Cascade and Rocky Mountains and extended south to the

southern Sierra Nevada. Cowan (1940) considered bighorn sheep immediately

east of the southern Sierra Nevada to belong to a different subspecies (O. c.

nelsoni); he noted, however, that he could not statistically distinguish bighorn

sheep in the Sierra Nevada from those to the east or to the north and suggested

that they represented intergrades (Wehausen 1991a). Nevertheless, they were

classified as California bighorn sheep for over half a century (Shackleton 1985)

and have received State rare, threatened and, eventually, endangered status under

the California Endangered Species Act as this taxon since 1972.

In contrast to Cowan’s (1940) classification, recent genetic research based

on mitochondrial DNA has found wild bighorn sheep from the Sierra Nevada to

be allied with those occupying the adjacent desert region (Ramey 1993, 1995). 

However, Sierra Nevada bighorn sheep were found to be the only distinctive

group in the desert region that extended eastward to Utah and New Mexico and

southward into Baja California, Mexico (Ramey 1993, 1995). They exhibit

reciprocal monophyly (no shared mitochondrial haplotypes with desert bighorn

sheep), which qualifies them as an “evolutionary significant unit” (Moritz 1994). 

Recent morphometric analyses (Wehausen and Ramey 2000) have corroborated

these genetic results and found bighorn sheep from the Sierra Nevada to be

distinguishable from those immediately to the east and north. On that basis,

Wehausen and Ramey (2000) determined that O. c. californiana was limited to

the central and southern Sierra Nevada, and they reassigned more northern

populations previously considered to be the same subspecies to other taxa because

of an absence of distinguishing characters. 
3

B. ECOLOGY

1. HABITAT

Two adaptations of bighorn sheep substantially define their basic habitat

requirements. The first is their agility on precipitous rocky slopes, which is their

primary means of evading predators. The second is their keen eyesight, which is

their primary means of detecting predators. Relatively short legs and a stocky

build allow agility on rocks but preclude the fleetness necessary to outrun

coursing predators in less rocky terrain. Consequently, bighorn sheep select open

habitats that allow detection of predators at sufficient distances to allow adequate

lead time to reach the safety of precipitous terrain. In short, optimal bighorn

sheep habitat is visually open and contains steep, generally rocky, slopes. Forests

and thick brush usually are avoided to the extent possible, but bighorn sheep will

use open woodland habitats on rocky slopes. Fire can play an important role in

creating or improving bighorn sheep habitat in some ecosystems by increasing the

visibility of predators. Large expanses lacking precipitous escape terrain, such as

the Owens Valley, can represent substantial barriers to movement. Even within

mountain ranges like the Sierra Nevada, bighorn sheep habitat is patchy and the

population structure is one of natural fragmentation (Bleich et al. 1990a).

Bighorn sheep in the Sierra Nevada utilize a wide range of elevations,

from alpine peaks in excess of 4,000 meters (13,120 feet) to the base of the

eastern escarpment as low as 1,450 meters (4,760 feet) (Wehausen 1980). Within

this elevational range there exists a wide variety of vegetation communities,

including (from lowest to highest): (1) Great Basin sagebrush-bitterbrushbunchgrass scrub; (2) pinyon-juniper woodland and mountain mahogany scrub;

(3) mid-elevation and subalpine forests, woodlands, and meadows; and (4) alpine

meadows and other alpine habitats varying from cliffs to plateaus. Because of the

overall aridity of this region, meadow habitats are patchy in distribution and occur

only where the water table is predictably high due to factors like snow

accumulation. The Great Basin scrub and alpine communities offer the most

desirable habitats for bighorn sheep in terms of visual openness. However,

because of the aridity of the eastern slope of the Sierra Nevada, many of the midelevation vegetation communities have some locations near precipitous rocks
4

with sufficiently sparse plant cover to allow use by bighorn sheep (Wehausen

1980). Because of their extreme visual openness and steep rocky nature, alpine

environments in the Sierra Nevada provide large expanses of habitat broken only

by canyons containing forests and willow stands, which bighorn sheep may avoid. 

In contrast, low elevation winter habitat has been limited to small areas where

topographic and visual features are suitable (Riegelhuth 1965; McCullough and

Schneegas 1966; Wehausen 1979, 1980). High elevation habitat in the Sierra

Nevada has been noted for its aridity relative to other alpine habitats because

precipitation is scant and unpredictable during the summer season when

temperatures permit plant growth (Major and Bamberg 1967). As a result, the

vegetation depends substantially on snow melt for moisture. Snow and resulting

soil moisture show great spatial variation (Major 1977). Vegetation patterns vary

concomitantly with moisture, ranging from meadow patches to areas almost

devoid of plants (Major and Taylor 1977).

2. FOOD HABITS AND NUTRITION

Bighorn sheep are ungulates that possess a large rumen and reticulum

relative to body weight (Krausman et al. 1993), which permits flexibility in plants

consumed and, notably, allows the digestion of graminoids (grasses, sedges, and

rushes) in all phenological stages (Hanley 1982). This flexibility in food

consumption, in turn, allows flexibility in feeding habitats utilized. Wehausen

(1980) and Moore (1991) provided detailed information on the species

composition of diets of bighorn sheep on different seasonal ranges in the Sierra

Nevada. Those authors found great variation in diets, from those dominated by

graminoids to those dominated by non-graminoid species. Wehausen (1980)

provided nutritional data on plant species in different phenological stages and

noted that bighorn sheep altered their diets on the basis of what provided the best

nutrition at the time. Wehausen (1980, 1992), Wehausen and Hansen (1988), and

Moore (1991) provided curves of fecal crude protein, which indexes digestibility

of the forage consumed and, thus, general diet quality (Wehausen 1995). 

Analyses of these patterns over 14 years indicated that timing of the first soaking

winter storm (2.5 centimeters or about an inch of precipitation) that initiated plant

growth most affected winter-spring diet quality for bighorn sheep utilizing low

elevation winter ranges. Earlier initiation of plant growth resulted in improved
5

diet quality. In addition, warmer winter temperatures aided plant growth and

thereby improved diet quality (Wehausen 1992). Summer range diet quality

appeared to be influenced positively by the amount of snowfall the previous

winter, presumably through the influence of summer snowpack on soil moisture

for alpine plants (Wehausen 1980); overall, summer diet quality was higher

following a heavy winter.

Phosphorus may be somewhat lacking in the diets of bighorn sheep in the

Sierra Nevada. Klickoff (1965) found alpine soils in the region of Yosemite

National Park consistently deficient in this mineral, which may reflect leaching of

soils by snowmelt (Major and Bamberg 1967). Wehausen (1983) found notably

lower levels of phosphorus relative to crude protein (a covariate correcting for

phenological stage) for alpine graminoids in the central and southern Sierra

Nevada when compared to the nearby White Mountains. The species analyzed

were potential forages of bighorn sheep in the Sierra Nevada, and Wehausen

(1980) found bighorn sheep there consistently to select alpine forages of higher

phosphorus content, sometimes at the cost of higher protein levels. It is not

known if lower phosphorus levels in the Sierra Nevada have population-level

effects on bighorn sheep there.

3. BEHAVIOR

Bighorn sheep exhibit a variety of behavioral adaptations to avoid

predation. One such adaptation is group living (Hamilton 1971, Alexander 1974);

groups provide more eyes and ears, allowing members to spend less time

surveying for predators and more time feeding. Studies of this phenomenon have

found that increases in group size of up to six (or more) bighorn sheep confer an

advantage in the proportion of time allocated to feeding (Berger 1978,

Risenhoover and Bailey 1985). The selfish herd concept of Hamilton (1971)

suggests that yet greater group sizes may confer further behavioral comfort. Such

comfort may be an important factor enabling bighorn sheep to utilize habitats

with greater risks of predation, notably low elevation winter ranges in the Sierra

Nevada. 
6

Bighorn sheep are primarily diurnal (Krausman et al. 1985). Coupled

with their strong reliance on keen eyesight to detect predators, diurnal behavior

minimizes predation risks. Nights generally are spent on rocky slopes, but

bighorn sheep may venture a short distance away from rocky escape terrain to

feed during daylight. How far they venture from safer habitat varies and is

apparently influenced by visual openness (both habitat and weather influences),

wind, gender, season (e.g. whether vulnerable young are present), and abundance

of predators.

Bighorn sheep commonly exhibit seasonal changes in habitat use that

reflect various resource needs. Surface water, although important in many desert

ranges, rarely is utilized by bighorn sheep in the Sierra Nevada. Instead, these

bighorn sheep obtain needed moisture from forage or occasional consumption of

snow. Because of relationships between elevation and temperature (Major 1977)

and their influences on plant growth (Wehausen 1980, 1983), altitudinal

migration in high mountain ranges like the Sierra Nevada allows bighorn sheep to

maximize nutrient intake (Hebert 1973, Wehausen and Hansen 1988, Wehausen

1996). In past years, bighorn sheep in the Sierra Nevada used low elevation

ranges extensively in winter and early spring, alpine ranges in summer and fall,

and some intermediate ranges during transition periods (Wehausen 1980). During

the second half of the 1980's, this seasonal pattern changed to one of avoidance of

low elevation winter ranges (Wehausen 1996).

Male and female bighorn sheep commonly live in separate groups during

much of the year, and often occupy different habitats (Geist and Petocz 1977,

Wehausen 1980, Bleich et al. 1997). In the Sierra Nevada, both sexes may share

common winter ranges, but they show progressive segregation from winter to

spring (Wehausen 1980). During summer, the two sexes utilize different habitats,

with females restricted largely to alpine environments along the crest and males

often at somewhat lower elevations in subalpine habitats west of the crest

(Wehausen 1980). Males again join females during the breeding season in late

fall.

Bighorn sheep have developed conservative philopatric behaviors

(reluctance to disperse from their home range) that make them slow to colonize
7

unoccupied habitat (Geist 1967, 1971). These behaviors are likely an adaptation

to the naturally fragmented habitats that bighorn sheep commonly occupy, but

they have necessitated the capture and translocation of bighorn sheep to historic

ranges in order to speed up and assure re-occupancy.

4. METAPOPULATION STRUCTURE

a. Inbreeding and Small Populations

The naturally fragmented distribution of bighorn sheep has led to the

application of a broad landscape approach to their population ecology. This

approach groups geographically distinct herds into metapopulations, which are

networks of interacting herds (Schwartz et al. 1986, Bleich et al. 1990a, 1996,

Torres et al. 1996). Thus this approach considers long-term viability not of

individual herds, per se, but rather of entire metapopulations; consequently, both

genetic and demographic factors are considered. Increasing coefficients of

inbreeding and genetic drift accompany decreasing population sizes and, over

time, can lead to decreasing levels of heterozygosity that may have negative

demographic effects through inbreeding depression (Soulé 1980) and loss of

adaptability. At some level, inbreeding and associated low genetic variation are

likely to be a conservation problem for bighorn sheep, but that level is not known

and will be influenced by their general history of inbreeding and other factors that

challenge them. Lamb survival and horn growth in bighorn sheep both have been

suggested to be influenced by inbreeding (Sausman 1982, Stewart and Butts 1982,

Fitzsimmons et al. 1995). Moreover, there is growing evidence that disease

resistance is related to levels of heterozygosity (Carrington et al. 1999, Coltman

et al. 1999).

A small amount of genetic exchange among herds via movements by

males can counteract inbreeding and associated increases in homozygosity that

might otherwise develop within small, isolated populations (Schwartz et al.

1986). In essence, an entire metapopulation is a single gene pool, albeit

somewhat subdivided. Males have a much greater tendency than do females to

explore new ranges, which they may do in search of other females to breed with. 

If geographic distances between groups of females within metapopulations are not
8

great, gene migration via males occurs readily. In the absence of such a

metapopulation structure, populations will be isolated and may benefit from

genetic enrichment via induced migration by individuals translocated between

herds.

Substructuring also can occur within what are often designated as single

herds of bighorn sheep (Geist 1971, Holl and Bleich 1983, Festa-Bianchet 1986,

Wehausen 1992b, Jaeger 1994, Andrew et al. 1997, Rubin et al. 1998). Such

substructuring is defined by separate home range patterns. Although more

evident in females, it can occur in both sexes. Because separate female groups

often reflect matrilines (Festa-Bianchet 1986), differences in (maternally

inherited) mitochondrial DNA profiles between them may be detectable (Bleich et

al. 1996, Boyce et al. 1999). Population substructuring has been recognized in

Sierra Nevada bighorn sheep (Wehausen 1979) and was incorporated in a

previous conservation plan for these bighorn sheep (Sierra Nevada Bighorn

Interagency Advisory Group 1984). What was once known as the Mount Baxter

herd is now recognized as two herds: the Mount Baxter and Sawmill Canyon

herds. Bleich et al. (1996) suggested that separate female groups are the

fundamental building blocks of bighorn sheep metapopulations. 

b. The Balance between Extinction and Colonization

The other important long-term process in metapopulation dynamics is the

balance between rates of natural extinction and colonization among constituent

populations. Colonization rates must exceed extinction rates for a metapopulation

to persist (Hanski 1991). Certainly, this balance has not occurred for Sierra

Nevada bighorn sheep since about 1850 due to the high rate of anthropogenic

extinctions that resulted in an increasingly fragmented distribution. The recent

reintroduction program itself added some new isolated herds (Bleich et al. 1996). 

Additionally, the recent collapse of all herds resulted in mostly small groups of

bighorn sheep that winter at high elevations and that are more vulnerable to

extinction because of small size and more severe winter climates than may be

encountered at lower elevations.
9

5. REPRODUCTION

Bighorn sheep generally give birth to single young, but there is a low

incidence of twins (Buechner 1960). Bighorn sheep occupying many desert

mountain ranges have protracted lambing seasons covering many months, while

those living under colder winter temperature regimes give birth during short

periods in late spring and early summer (Thompson and Turner 1982, Bunnell

1982; but, see Rubin et al. 2000). Bighorn sheep in the Sierra Nevada fit this

latter pattern (Wehausen 1980). The birthing season can begin as early as April

20, and end as late as early July (Wehausen 1991a), with most births occurring in

May and June (Wehausen 1996). Timing of births correlates with the nutritional

regime of females; later birthing appears to be a consequence of lower annual

nutrient intake (Wehausen 1996). The gestation period for bighorn sheep is

approximately 174 days (Shackleton et al. 1984, Hass 1995). The breeding

(rutting) season in the Sierra Nevada, therefore, occurs during late fall and early

winter (mostly November and December), when bighorn sheep are usually at high

elevations.

Nutrient intake also can influence birth rates (Wehausen 1984), including

the frequency with which adult females produce young and the age at which

young females first bear offspring. Two years of age is the youngest that females

in the Sierra Nevada have been known to give birth. Age at first lambing may be

as high as 4 years under poor nutritional circumstances, as has been recorded for

Dall sheep (Ovis dalli; Bunnell and Olson 1981). Measuring the actual

proportion of females producing young is difficult because of possible unrecorded

losses soon after birth. The upper range of summer ratios of lambs to females

recorded shortly after the birthing season in the Sierra Nevada has been 75 to

83:100 (Wehausen 1980, Chow 1991), while the lowest reported value was

30:100 (Wehausen 1980).

Survivorship of lambs to yearling age also varies with environmental and

nutritional factors. For the Mount Baxter and Sawmill Canyon herds in the Sierra

Nevada during 1965 to 1979, 73 percent of the variation in winter lamb to female

ratios could be explained by variation in precipitation 8 to 12 months prior to

conception (Wehausen 1980). That model suggested that variation in the
10

production of young, rather than offspring survival, was the primary variable

affecting winter recruitment ratios during that time period. However, with recent

winter range avoidance, lamb survival in this population declined considerably

(Wehausen 1996); thus, this model does not apply to recent habitat use patterns.

6. MORTALITY FACTORS

Bighorn sheep die from a variety of causes, including disease, predation,

and accidents. Of particular interest relative to the conservation of endangered

populations are factors that remove animals at younger ages when considerable

reproductive potential remains. There is substantial documentation of the

devastating effects of various diseases on bighorn sheep populations. Of

particular note is pneumonia. Pneumonia epizootics can lead to massive all-ages

die-offs that decimate or extirpate entire populations and may have played a

major role in early losses of herds in the Sierra Nevada. Mortality resulting from

disease is discussed further below in section I.B.7. under “Disease and

Parasitism”.

Various predators kill wild sheep in North America, including wolves,

mountain lions, coyotes, bears, bobcats, wolverines, and eagles (Kelly 1980,

Berger 1991, Nichols and Bunnell 1999, Bleich 1999). Wolves are not known to

have occurred in the central and southern Sierra Nevada in the original range of

bighorn sheep (Young and Goldman 1944). In the Sierra Nevada, mountain lions

have been the primary predator of bighorn sheep, accounting for 96 percent of

losses attributed to predation (Table 1). Of 147 bighorn sheep deaths recorded in

the Sierra Nevada in the past quarter century, 54.5 percent have been attributed to

predation (Table 1). That predators take some bighorn sheep does not imply that

these losses will limit bighorn sheep populations.

During recent years, bighorn sheep in the Sierra Nevada have incurred

major winter losses while avoiding low elevation winter ranges, apparently in

response to predation pressure (Wehausen 1996). Those losses have included

poor lamb survival over winter (Wehausen 1996), losses of all sex and age classes

in snow avalanches, and many undocumented losses during the winter and spring 
11

Table 1. Causes of known bighorn sheep mortalities in the Sierra Nevada by population since

1975. Sources include data in Andaloro and Ramey (1981), Chow et al. (1993), Wehausen

(1996) and many unpublished records. Data include radio collared individuals and remains of

uncollared individuals encountered during field surveys. Baxter includes the Mount Baxter

and Sawmill Canyon herd units, and Lee Vining includes the Mount Warren and Mount Gibbs

herd units.

Herd Predation Avalanche/

Accidents

Post 

Release

Exposure

Highway

Collision

Not

Known

Lion Coyote Bobcat

Langley 7 4

Williamson 5 2

Baxter 50 1 27

Wheeler 3 15 2

Lee Vining 12 2 1 3 5 1 7

Totals 77 2 1 19 5 1 42

Percent 52.4 1.4 0.7 12.9 3.4 0.7 28.6

when bighorn sheep failed to use winter ranges. The recent collapse of the Lee

Vining Canyon population can be attributed almost entirely to losses at high

elevations during certain severe winters. Bighorn sheep accounted for during

summer and fall one year have been missing the following summer. A minimum

of 77, and possibly as many as 86 bighorn sheep, could be accounted for between

Lee Vining and Lundy Canyons in the summer of 1993 (Chang 1993). An

apparently less-than-complete count the following summer yielded a minimum of

43 for that area, and a potential maximum of only 69 (Jensen 1994). Following

the severe winter of 1995, however, repeated thorough counts of this herd

produced consistently only 29 bighorn sheep (Wehausen and Chang 1995),

representing a loss of possibly 50, or more, individuals. Additional overwinter

declines occurred in 1998 and 1999 (Wehausen and Chang 1998, Wehausen

1999). Somewhat baffling has been a lack of carcasses of these missing
12

individuals; of the dozens of bighorn sheep that disappeared in this area, the

remains of only two have been found.

7. DISEASE AND PARASITISM

Numerous diseases of bighorn sheep have been documented (Bunch et al.

1999), of which pneumonia and psoroptic scabies have had the greatest

population-level effects. Bighorn sheep show a high susceptibility to pneumonia,

usually caused by bacteria of the genus Pasteurella (Posts 1971). Pneumonia

caused by Pasteurella alone, or in combination with other pathogens, is the most

significant disease threat for Sierra Nevada bighorn sheep (Bunch et al. 1999). 

Exposure of bighorn sheep to some strains of pneumophilic Pasteurella

commonly carried by healthy domestic sheep usually causes fatal pneumonia in

bighorn sheep and constitutes a major management concern (Onderka and

Wishart 1988, Foreyt 1989, Callan et al. 1991, Foreyt et al. 1994, Sweeney et al.

1994, Martin et al. 1996). The strains of Pasteurella that cause disease in bighorn

sheep are much more toxic to certain white blood cells in bighorn sheep than they

are to those in domestic sheep or domestic goats (Silflow et al. 1994). Domestic

goats appear not to carry such strains regularly (Foreyt 1994). However, during a

Pasteurella pneumonia outbreak in bighorn sheep in Hells Canyon (Oregon,

Washington, and Idaho border region), a feral goat found with bighorn sheep

carried strains of Pasteurella haemolytica and P. multocida that were genetically

identical to those in the bighorn sheep associated with it, including a strain

cytotoxic to the bighorn sheep, but not to the goat (Cassirer et al. 1996). Whether

the feral goat was the source of those strains in the bighorn sheep is not entirely

clear (Cassirer et al. 1996), but this event demonstrates that domestic goats can

carry such strains. Goats may carry strains of Pasteurella if they have been in

recent contact with domestic sheep.

Domestic sheep once were grazed in very high numbers throughout the

southern and central Sierra Nevada (Vankat 1970). While particulars of past

population losses for bighorn sheep in the Sierra Nevada are mostly lacking,

contact with domestic sheep and consequent disease problems probably played a

major role (Wehausen 1985). Domestic sheep and goats in or near bighorn sheep

habitat remain the greatest disease threat to the persistence and restoration of
13

bighorn sheep in the Sierra Nevada. The history of bighorn sheep is replete with

examples of major die-offs following contact with domestic sheep (Goodson

1982, Foreyt and Jessup 1982), and these pneumonia epizootics can extirpate

entire populations (Martin et al. 1996). Contact can occur via stray domestic

sheep entering bighorn sheep habitat, or when bighorn sheep come into contact

with domestic sheep.

While early domestic sheep grazing in the Sierra Nevada probably

included all accessible areas at high elevations, it has recently been limited

primarily to lower elevations immediately east of the mountains. All current

bighorn sheep herds have been at risk of contact in recent decades due to a

combination of stock driveways, on which domestic sheep are driven north

through the Owens Valley in spring during some years, and summer grazing

allotments along the eastern base or slopes of the mountains in other areas. In

1974, a large number of domestic sheep escaped from the driveway through

Owens Valley north of Independence, and the 25 that remained were discovered

and removed from the Mount Baxter winter range just as bighorn sheep were

beginning to occupy that winter range in late December. In 1988, a single stray

domestic sheep was discovered in Lee Vining Canyon as it was entering an area

frequently used by bighorn sheep. In 1995, 22 domestic sheep from the Bloody

Canyon allotment were discovered in late October and removed from Mount

Dana in Yosemite National Park, where they overlapped the range of a small

group of bighorn sheep near Mount Gibbs. Undoubtedly, numerous other stray

domestic sheep have gone unrecorded. Fortunately, no stray domestic sheep have

been documented to contact bighorn sheep and cause a pneumonia die-off in the

Sierra Nevada in the past quarter century.

Despite their strong herding behavior, history indicates that domestic

sheep have an inherent tendency to stray. While better husbandry may help limit

this tendency, sheep herders cannot be expected to control it entirely. Bighorn

sheep, especially males, have also been known to move into domestic sheep

herds. Consequently, it has been recognized that the safest solution where

bighorn sheep are at risk is to provide large buffer distances between the two

species. The Bureau of Land Management guidelines for desert regions

suggested that buffer distances as great as 13.5 kilometers (9 miles) may be
14

necessary for adequate protection in some cases. Those guidelines also

recommended that "extraordinary precautions" be taken to protect listed taxa from

the threat of contact with domestic sheep (Bureau of Land Management 1992).

Threats from domestic goats currently concern the use of goats as pack

stock in the back country. Pack goats should be assumed to harbor disease

organisms of pathogenic consequence to bighorn sheep. Horses, mules, burros,

and llamas are not considered disease threats to bighorn sheep (Miller et al. 1995,

Foreyt and Lagerquist 1996; Appendix A).

Lungworms of the genus Protostrongylus can be important contributors to

pneumonia in bighorn sheep in the Rocky Mountains (Forrester 1971, Woodard et

al. 1974), and methods have been developed to control these nematode parasites

in some wild populations (Schmidt et al. 1979). Bighorn sheep in the Sierra

Nevada carry Protostrongylus lungworms, but parasite loads have been too low to

be considered a management concern (Wehausen 1979, 1980).

Many early die-offs of bighorn sheep, including some in the Sierra

Nevada, were attributed to scabies contracted from domestic sheep (Jones 1950,

Buechner 1960). Over the past 20 years, this disease has been a significant

mortality factor among bighorn sheep in the San Andres Mountains of New

Mexico (Lange et al. 1980, Hoban 1990, Rominger and Weisenberger 2000). 

Scabies also has been found recently in bighorn sheep in California east of the

Sierra Nevada (Clark et al. 1988). In a large sampling of bighorn sheep in the

Sierra Nevada during 1979 to 1988, however, no clinical evidence of scabies was

noted. Similarly, serum samples from those sheep showed no evidence of

exposure to Psoroptes (Mazet et al. 1992).

Other infectious diseases may be of concern for bighorn sheep in selected

instances. For example, bluetongue virus was responsible for die-offs of bighorn

sheep in the Lava Beds enclosure in California (Blaisdell 1975) and at the Red

Rock facility in New Mexico (Singer et al. 1998). For the Red Rock facility, a

comparative study of bluetongue exposure in adjacent cattle indicated that those

bovids likely were not the source of infection (Singer et al. 1998). Similarly,
15

Singer et al. (1997), found that neither deer nor cattle were implicated in the Lava

Beds die-off. 

8. INTERSPECIFIC COMPETITION AND HUMAN DISTURBANCE

Interspecific competition occurs when a resource shared by two species is

in short supply for at least one of those species (Krebs 1972). For bighorn sheep

exhibiting altitudinal migration, questions of competition commonly have focused

on winter ranges, where grazing animals are more concentrated and forage is

more limited (Stelfox 1976). Both native deer (Odocoileus hemionus) and

introduced tule elk (Cervus canadensis nannodes) have overlapped winter ranges

used by bighorn sheep in the Sierra Nevada (Riegelhuth 1965). Nonetheless,

quantitative studies of utilization of key forage species on the Mount Williamson

and Mount Baxter winter ranges did not suggest any competition (Wehausen

1979, 1980). Wehausen (1992a) attributed limitations on nutrient intake by

bighorn sheep on these ranges to nutritive quality, rather than quantity, of forage. 

Further, the potential for forage competition has greatly decreased since the

studies of the 1960's, 1970's and 1980's due to behavioral changes by the bighorn

sheep as well as their potential competitors. The Goodale tule elk population that

utilized the Mount Baxter herd winter range abandoned that portion of Owens

Valley about 1990, and use of winter ranges by bighorn sheep has declined to a

small proportion of what it was when competition studies were carried out.

Leopold (1933) considered bighorn sheep to be a wilderness species

because they fail to thrive in contact with urban development. Human

disturbance has been suggested to be detrimental to bighorn sheep in a variety of

situations (Graham 1980, MacArthur et al. 1982, Etchberger et al. 1989,

Papouchis et al. 2001). Similarly, Dunaway (1971) hypothesized that disturbance

of bighorn sheep in the Sierra Nevada by humans was a factor limiting

populations. Results of subsequent research did not support that hypothesis

(Wehausen et al. 1977, Hicks and Elder 1979, Wehausen 1980). Bighorn sheep

have habituated to human activity in many places in the Rocky Mountains, and

occasionally in desert habitats. Any conclusions about the effects of human

disturbance, however, must be limited to the situations studied. Thus, the

question should be revisited as situations change in a direction that suggests
16

disturbance could be detrimental, such as increased presence of humans in

bighorn sheep habitat.

C. ABUNDANCE AND DISTRIBUTION

1. HISTORICAL DISTRIBUTION, ABUNDANCE, AND TRENDS

At one time, bighorn sheep herds were scattered along and east of the

alpine crest of the Sierra Nevada from the Sonora Pass area south to Olancha

Peak (Figure 1). They also occurred in similar habitat west of the Kern River as

far south as Maggie Mountain, with concentrated use in the regions of Mineral

King, Big Arroyo, and Red Spur (Jones 1950). Additional evidence suggested

that herds utilized nonalpine habitat farther south near Walker Pass (Jones 1949,

Garlinger 1987, Wehausen et al. 1987). Whether these southernmost herds were

taxonomically the same as those which occurred farther north in the Sierra

Nevada is unknown.

The total population in the Sierra Nevada prior to settlement is unknown,

but it may have exceeded 1,000 individuals. In some cases, early records provide

details on the occurrence of now extirpated populations. However, the overall

historical record is incomplete and may lack records of some herds that might

have disappeared early in recorded history. Wehausen (1988) postulated some

additional areas that might have supported populations of bighorn sheep, but for

which records are lacking.

Population losses for bighorn sheep apparently began shortly after the

immigration of Europeans to the Sierra Nevada in the mid-1800's, and those

losses continued through most of the twentieth century (Wehausen et al. 1987). 

Of 16 areas in the Sierra Nevada that likely had separate bighorn sheep herds

(excluding the southernmost nonalpine region), only 9 are known to have

persisted to the beginning of the twentieth century (Table 2). Another half

century had reduced the number of areas to five by 1948 (Jones 1950). Jones

(1950) documented bighorn sheep in 3 areas and postulated their existence in 2

other regions based on sign and reported observations; he also produced a

subjective 
17
18

Table 2. Probable locations of historic bighorn sheep herds in the high Sierra Nevada

based on historic records and habitat characteristics.

Region/Population Last Records

of Viable

Native Herds

Sources for Sightings, Skulls,

or other Data

KERN RIVER

Mineral King 1800's Jones 1950

Big Arroyo, Kaweah Peaks 1800's Jones 1950

SOUTHERN

Olancha Peak 1920's Jones 1949

Mount Langley 1960's Wehausen 1979

Mount Williamson Extant Wehausen 1980, 1999

Mount Baxter Extant Wehausen 1980, 1999

Sawmill Canyon Extant Wehausen 1980, 1999

Taboose Creek, Birch Mountain 1920's Ober 1914, Jones 1949

CENTRAL

Mount Tom to Mount Emerson 1920's Ober 1914, 1931; Wolfe 1979

Pine Creek to Rock Creek 1920's Jones 1949

McGee Creek to Convict Creek 1940's Jones 1949

NORTHERN

Mount Ritter to Dana Plateau 1870's Muir 1894, Jones 1949

Mount Warren, Tioga Crest,

Mount Conness

skulls only Bailey 1932, Jones 1949

Shepherds Crest skulls only Jones 1949

Matterhorn Peak area skulls only Jones 1949

Sonora Pass 1878 Grinnell and Storer 1924
19

estimate of 390 bighorn in those 5 herds. By the 1970's, sheep remained in only

two of those areas, but the one known as the Mount Baxter herd was found later

to represent two distinct herds (Mount Baxter and Sawmill Canyon in Table 2;

Wehausen 1979, 1980).

Specific causes of most population losses in the Sierra Nevada are

unknown. Market hunting for mining towns may have played a role in some

areas. A die-off in the 1870's west of the Kern River was attributed to scabies

(Jones 1950), presumably contracted from domestic sheep. Die-offs from

pneumonia contracted from domestic sheep may have been the most important

cause of losses, but have not been documented. Beginning in the 1860's, and

extending into the twentieth century, large numbers of domestic sheep were

grazed seasonally in the Sierra Nevada (Austin 1906, Vankat 1970). While

grazing by domestic sheep has declined greatly and no longer includes ranges

occupied by bighorn sheep, the potential for domestic sheep to come into contact

with bighorn sheep continued through the twentieth century and persists today.

2. RECENT DISTRIBUTION, ABUNDANCE, AND TRENDS

Bighorn sheep persisted in only two areas in the Sierra Nevada by the

1970's, constituting three herds (Wehausen 1979, 1980). Intensive field studies

during 1975 to 1979 provided accurate census data for those herds. The Mount

Williamson population was found to contain only 30 bighorn sheep, while the

Mount Baxter and Sawmill Canyon herds totaled 220 and generally were

increasing (Wehausen 1980). Detailed annual monitoring of the Mount Baxter

and Sawmill Canyon herds up to 1986 repeatedly verified large numbers. Good

winter census opportunities in 1983 and 1985 found the Mount Williamson

population to be static at 30 individuals.

Because of large size and productivity, the Mount Baxter and Sawmill

Canyon herds were used as sources of reintroduction stock beginning in 1979,

with subsequent removals in 1980, 1982, 1986, 1987, and 1988, totaling 103

individuals. These individuals were used to reestablish populations at Wheeler

Ridge (1979, 1980, 1982, 1986), Mount Langley (1980, 1982, 1987), Lee Vining

Canyon (1986, 1988), and the south Warner Mountains in northeastern California
20

(1980) (Bleich et al. 1990b). The Warner Mountains population died out in 1988,

following contact with domestic sheep (Weaver and Clark 1988), but the other

three persist (Figure 1).

The Wheeler Ridge and Mount Langley herds began increasing soon after

they were reintroduced. In contrast, the Lee Vining Canyon population declined

initially due to post-release mortality from particularly inclement weather,

followed by reductions due to mountain lion predation while on winter-spring

range in Lee Vining Canyon (Chow 1991). Following supplementation in 1988

and removal of one mountain lion from Lee Vining Canyon in each of three

consecutive winters (Bleich et al. 1991), this population increased rapidly (Chow

1991; Figure 2). 

Mountain lions have become an increasing source of direct and indirect

mortality for Sierra Nevada bighorn sheep populations. Wehausen (1996)

reported evidence of rapid increases in mountain lion activity and kills on the

winter ranges of the Mount Baxter and Sawmill Canyon herds between 1976 and

1988, with documented kills totaling 49 bighorn sheep. Mountain lion

depredation problems along the eastern Sierra Nevada in Inyo and Mono Counties

also increased notably during the 1980's, especially beginning in 1986 (Figure 3).

In addition to the direct effects of predation, all bighorn sheep populations

in the Sierra Nevada abandoned regular use of low elevation winter ranges during

the 1980's, as a possible response to the threat of predation by mountain lions

(Wehausen 1996). Of the native herds, the Mount Williamson herd was last

recorded using its escarpment base winter range in 1985, while winter range use

by the Mount Baxter herd (also sometimes referred to as the Sand Mountain herd)

declined steeply between 1987 and 1991 to negligible levels and has remained at

these low levels through 2000 (Wehausen 1996, Figure 3). Avoidance of low

elevation winter ranges has exacted a high cost from herds throughout the Sierra

Nevada due to poor nutrition in late winter and spring, exposure to extreme cold

and wind throughout winter, and deep snows and avalanches in heavy winters. 

For the Mount Baxter and Sawmill Canyon herds, the consequences were

manifested in later lambing and poor lamb survival, which led to recruitment well 
21

1970 1975 1980 1985 1990 1995 2000

0

20

40

60

80

100

120

140

160

0

5

10

15

20

YEAR

SHEEP

PERMITS

sheep

permits

Figure 3. Mountain lion depredation permits issued in Inyo and

Mono Counties, 1972-99, and bighorn sheep winter range

census results for the Mount Baxter herd (Wehausen 1996,

unpubl.).

1975 1980 1985 1990 1995 2000

0

50

100

150

200

250

300

350

YEAR

TOTAL SHEEP

Total

Baxter

Williamson

Wheeler

Langley

Mono Basin

Figure 2. Minimum population sizes, 1978-2001 (from

Wehausen 1999, 2001). Baxter includes the Mt. Baxter and

Sawmill Canyon herd units, and Mono Basin includes the Mt.

Warren and Mt. Gibbs herd units (see Figure 1).
22

below that needed to balance adult mortality. This diminished recruitment

resulted in a major population decline (Wehausen 1996), with a low of about 17

females in the reproductive base in 1995 (Wehausen and Chang 1995), just 15

percent of its peak level. Summer field surveys in the Mount Williamson herd

range since 1996 have suggested that this population may have reached a low of

as few as only three to four females and three males. Both of these native

populations appear to be increasing slowly (Figure 2).

Reintroduced herds have suffered similarly while avoiding low elevation

winter ranges. The heavy winter of 1995 took a notable toll. Winter losses in the

Wheeler Ridge herd included 12 individuals that died in a single snow avalanche;

only 18 were recorded to have survived that winter. Earlier surveys of that herd

(Ramey and Brown 1986, Wehausen 1991b) suggest that it may not have

exceeded 40 individuals between the time of its establishment in 1979 and 1998. 

Since 1995, this herd has been increasing steadily. During 1995 to 1997 the herd

remained back in Pine Creek throughout the winter. During the winter of 1999,

the majority of the herd was documented to move to low-elevation winter range

above Round Valley, and in the winter of 2000, all known females used that lowelevation winter range. Wehausen (2000) suggested that this migratory pattern

may have begun in 1998. Numbers of female bighorn sheep counted in Pine

Creek declined by two from 1997 to 1998. However, reconstructed population

sizes (based on 1999 counts) showed that the number of females actually

increased that year, leaving seven females unaccounted for in Pine Creek, at least

some of which may have been using low elevation winter ranges that were not

surveyed. Correlated with this use of low-elevation winter range, reproductive

output was 60 percent higher when compared to the previous 4 years, and the herd

subsequently showed a more rapid rate of increase (Figure 2; Wehausen 2000). A

minimum of 41 individuals was known to exist in this herd in 1999, and it has

continued to grow rapidly; it is now the largest herd in the Sierra Nevada.

The population in Lee Vining Canyon suffered great losses to weather and

predation after its introduction, but the herd exhibited strong recovery following

supplementation with eight females and three males and the removal of three

mountain lions during 1988 to 1990 (Chow 1991). This herd totaled at least 85

individuals in 1993 (Chang 1993). However, beginning in the mid 1990's, a

decline in the use of the Lee Vining Canyon winter range became apparent. 
23

During the winter and spring of 1995, few bighorn sheep used low-elevation

winter range and many disappeared; the population declined to 29 between Lee

Vining and Lundy Canyons, with an additional 4 surviving on Mount Gibbs in a

separate herd. Two subsequent years of population recovery were followed by a

second major collapse during the winter of 1998. Further mountain lion predation

was documented in the spring of 1998. The reproductive base of the two female

groups numbered only two females on Mount Gibbs and six on Mount Warren

and Tioga Crest in 1998, and the latter further declined to only three females in

1999. Twelve males were confirmed in 1999, with an additional four on Mount

Gibbs probably present, but not seen that year (Table 3).

The Mount Langley herd also appears to have suffered a major reduction

in 1995. Repeated census efforts have accounted for only 6 females and 11 males

that survived that winter (Wehausen 1999), in contrast to 42 bighorn sheep

counted there in the summer of 1990 (Moore and Chow 1990). This herd, unlike

the one at Mount Warren, has been increasing slowly since 1995. Its reproductive

base had increased to at least 10 females in 1998 but only 9 were counted in 1999. 

Only seven males could be accounted for in 1999, but recent data suggest as many

as twice that number exist (Table 3).

A reconstructed population approach has been used for many years to

improve minimum population values for Sierra Nevada bighorn sheep (Wehausen

1980). With this method, bighorn sheep of various sex and age classes observed

in one year, but not accounted for the previous year, are added to the minimum

number known the previous year. For instance, 214 different bighorn sheep could

be accounted for in the Mount Baxter and Sawmill Canyon herds in 1978, but

counts the following year determined that more males existed in 1978, bringing

the total to at least 217 (Wehausen 1980).

The total population of bighorn sheep in the Sierra Nevada increased from

250 in 1978 to about 310 in 1986 during the first phase of the reintroduction

program. Since then it has declined substantially. Only about 100 adult bighorn

sheep could be accounted for in 1998, but this number increased to 117 to 129 in

1999 (Wehausen 1999). Reconstructed population values indicate that a low

point of about 100 total bighorn sheep was reached following the winter of 1995. 
24

Table 3. 1999 population data for Sierra Nevada bighorn sheep (from Wehausen

1999). Baxter includes the Mount Baxter and Sawmill Canyon herd units, and

Lee Vining includes the Mount Warren and Mount Gibbs herd units.

 VERY

PROBABLE POSSIBLE

 

 

BIGHORN SEEN

1999

OTHER

BIGHORN

1999

ADDITIONAL

BIGHORN 

1999

Population Ewes Rams Adults Lambs Adults Lambs Adults Lambs

Langley 9 7 16 5 3 5

Williamson 1 1 6 2 2

Baxter 15 9 24 5 6 2 5 1

Wheeler 19 18 37 8 3 9

Lee Vining 5 12 17 4 4

TOTALS 49 46 95 22 22 4 12 10

Overall, the total has been increasing since then, despite the recent declines in and

near Lee Vining Canyon (Figure 2; Wehausen 1999). Including young-ofthe-year, the total population could have been as high as 165 in 1999 (Table 3). 

Continued favorable conditions since 1999 have allowed steady high reproductive

output and recruitment, resulting in about 250 total sheep in 2001 including

young of the year (Wehausen 2001; Figure 2).

D. REASONS FOR LISTING

The following discussion is organized according to the listing criteria

under section 4(a)(1) of the Endangered Species Act.
25

1. THE PRESENT OR THREATENED DESTRUCTION,

MODIFICATION, OR CURTAILMENT OF ITS HABITAT OR RANGE 

Almost all of the historical and currently occupied habitat of bighorn

sheep in the Sierra Nevada is in public ownership and administered by the U.S.

Forest Service, National Park Service, or Bureau of Land Management. While

there are some small parcels owned by the Los Angeles Department of Water and

Power or that are patented mining claims, they amount to a very small fraction of

the habitat. Thus, habitat throughout the historic range of Sierra Nevada bighorn

sheep remains essentially intact; it is neither fragmented nor degraded.

Consequently, habitat loss was not a reason for listing.

2. OVERUTILIZATION FOR COMMERCIAL, RECREATIONAL,

SCIENTIFIC, OR EDUCATIONAL PURPOSES

While unregulated hunting may have played a role in early population

declines (Wehausen 1988), there is no evidence that commercial, recreational,

scientific, or educational activities currently are significant threats. Further,

poaching of these bighorn sheep has not been documented in recent decades. 

Effects of recreational use should be further evaluated but currently appear to be

minor.

3. DISEASE OR PREDATION

The potential for the transfer of virulent disease organisms from domestic

sheep to bighorn sheep in the Sierra Nevada was a key factor in listing these

bighorn sheep. Diseases transferred through contact with domestic sheep can be

particularly devastating to bighorn sheep populations (see section I.B.7), and are

suspected to have played a major role in the disappearance of certain bighorn

sheep herds in the Sierra Nevada beginning around 1870. 

Stray domestic sheep from nearby allotments contacting bighorn sheep has

been a continuing threat. Domestic sheep have been known to escape allotments

and wander into bighorn sheep habitat in the Sierra Nevada (Sierra Nevada

Bighorn Sheep Interagency Advisory Group 1997). Given the susceptibility of
26

bighorn sheep to pathogens contracted from domestic sheep, disease poses a

continuing and significant threat to the survival of Sierra Nevada bighorn sheep.

Mountain lion predation of bighorn sheep on winter ranges has accounted

for the majority of documented mortalities since the late 1970's. This predation

increased from the 1970's to the 1980's and has been hypothesized to be the cause

of a coincident and marked decrease in winter range use by bighorn sheep in the

Sierra Nevada. Subsequent population declines have been attributed to this 

change in winter habitat selection. During 1982 to 1990, four mountain lions that

preyed on bighorn sheep in two winter ranges were removed to help protect those

sheep herds. In 1990 the people of California passed an initiative (Proposition

117) that made mountain lions a specially protected mammal, and thereby

removed the authority of the California Department of Fish and Game to control

this species for the benefit of bighorn sheep herds. Federal endangered status

returned the ability to engage in control of mountain lions to benefit these sheep

through Federal law superseding State law. 

4. THE INADEQUACY OF EXISTING REGULATORY

MECHANISMS

In 1883, an earlier moratorium on the take of bighorn sheep in California

was extended indefinitely (Wehausen et al. 1987), and bighorn sheep in the Sierra

Nevada remain a fully protected species. In 1972, California listed the California

bighorn sheep as “rare.” The designation was changed to “threatened” in 1984 to

standardize the terminology of the amended California Endangered Species Act

(Sierra Nevada Bighorn Sheep Interagency Advisory Group 1997), and the

California Fish and Game Commission upgraded the species' status to

“endangered” in 1999.

In 1971, Inyo National Forest established sanctuaries totaling about

16,500 hectares (41,000 acres) for the Mount Baxter and Mount Williamson herds

of Sierra Nevada bighorn sheep and called them the California Bighorn Sheep

Zoological Areas (Wehausen 1979; Inyo National Forest Land Management Plan

1988). Those sanctuaries were designated to regulate human use in some areas

(Hicks and Elder 1979), and reduce domestic sheep/wild sheep interaction by
27

constructing a fence below the winter range of the Mount Baxter herd along the

U.S. Forest Service and Bureau of Land Management boundary (Wehausen

1979). Adjacent summer range on National Park Service land also was

designated to reduce human disturbance (Wehausen 1979), and those restrictions

continue.

Numerous efforts for the conservation of bighorn sheep in the Sierra

Nevada have taken place in recent decades including, but not limited to: (1)

intensive field studies; (2) reestablishment of three additional populations in

historical habitat; (3) creation, in 1981, of the Sierra Nevada Bighorn Sheep

Interagency Advisory Group, including representatives from Federal, State, and

local resource management agencies, which has produced the Sierra Nevada

Bighorn Sheep Recovery and Conservation Plan (1984) and a Conservation

Strategy for Sierra Nevada Bighorn Sheep (1997); and (4) removal of four

mountain lions that were taking Sierra Nevada bighorn sheep, which played a

significant role in efforts to reestablish the Mount Warren herd (Chow 1991).

Despite these efforts, the bighorn sheep population has shown a

significant decline in the past 15 years (Figure 2). This decline has been

attributed to mountain lion predation and its hypothesized role in the avoidance of

low elevation winter ranges by bighorn sheep (Wehausen 1996). Also, significant

threats of contact with domestic sheep persisted. Existing regulatory mechanisms

were inadequate to correct those problems. First, although efforts had been

underway for many years, the U.S. Forest Service was unable to eliminate, or

even reduce, the threat of contact between domestic sheep and Sierra Nevada

bighorn sheep by eliminating or modifying grazing allotments. Second, as a

result of the passage of Proposition 117 in 1990 by the California Legislature, the

California Department of Fish and Game lost the authority to remove mountain

lions to protect the Sierra Nevada bighorn sheep. However, between the Federal

emergency and final listings, the California State Legislature enacted AB 560,

which amended Proposition 117 and allowed the California Department of Fish

and Game to remove mountain lions that are a threat to bighorn sheep in

California.
28

5. OTHER NATURAL OR MANMADE FACTORS AFFECTING ITS

CONTINUED EXISTENCE

At the time of its listing, the Sierra Nevada bighorn sheep population was

very small, with only about 125 adults known to exist among 5 geographic areas,

with little probability of interchange among those areas. Additionally, multiple

independent groups of females, defined by distinct home range patterns, were

known in some of those areas and resulted in yet smaller population units. 

Evidence has suggested that many of these contained five or fewer females in

recent years. Thus, small population effects alone made these bighorn sheep

vulnerable to extinction. These effects might be random naturally occurring

population fluctuations (see section II.A.1), loss of genetic variation (see section

II.A.2), or both.

E. PAST AND CURRENT MANAGEMENT AND CONSERVATION

ACTIVITIES

1. FEDERAL AGENCIES

a. U.S. Department of the Interior - Fish and Wildlife Service

The Endangered Species Act of 1973, as amended (Act) (16 U.S.C. 1531

et seq.), requires us to identify taxa of wildlife and plants that are endangered or

threatened, based on the best available scientific and commercial information. As

part of the program to accomplish this purpose, we maintain a list of taxa

regarded as candidates for listing. We maintain this list for a variety of reasons,

including: to provide advance knowledge of potential listings that could affect

decisions of environmental planners and developers; to solicit input from

interested parties to identify those candidate taxa that may not require protection

under the Act or additional taxa that may require the Act’s protections; and to

solicit information needed to prioritize the order in which taxa will be proposed

for listing. 

On September 18, 1985, we published a Notice of Review in which we

designated the Sierra Nevada bighorn sheep as a Category 2 candidate and
29

solicited status information (50 FR 37958). Category 2 candidate species include

taxa for which we had information indicating that proposing to list as endangered

or threatened was possibly appropriate, but for which sufficient data on biological

vulnerability and threats were not currently available to support a proposed rule. 

Category 1 candidates were those species for which we had sufficient information

on file to support issuance of proposed listing rules. In our January 6, 1989

(54 FR 554), and November 21, 1991 (56 FR 58804), Notices of Review, we

retained the Sierra Nevada bighorn sheep in Category 2. Beginning with our

February 28, 1996, Notice of Review (61 FR 235), we discontinued the

designation of multiple categories of candidates, and we now consider only

species that meet the definition of former Category 1 as candidates for listing. At

that point, the Sierra Nevada bighorn sheep was not identified as a candidate.

Nevertheless, we remained in contact with the California Department of

Fish and Game and the Sierra Nevada Bighorn Sheep Interagency Advisory

Group regarding the status of the species. In 1998, as new information became

available regarding the continual decline in the Sierra Nevada bighorn sheep

population, we initiated a status review. On April 20, 1999, we published an

emergency rule to list the Sierra Nevada distinct population segment of California

bighorn sheep as endangered (64 FR 19300), as well as a proposed rule (64 FR

19333) to list the species as endangered. The emergency rule provided Federal

protection pursuant to the Act for a period of 240 days. After a thorough review

of all comments received on the proposed rule, we published a final rule listing

the Sierra Nevada bighorn sheep as endangered in accordance with section 4 of

the Act on January 3, 2000 (65 FR 20).

Section 4 further directs us to develop and implement recovery plans for

listed species; this recovery plan was developed according to that direction and

following “Guidelines for Planning and Coordinating Recovery of Endangered

and Threatened Species” (U.S. Fish and Wildlife Service 1990). Once a species

has recovered and is removed from the list, we must, in cooperation with State

government, “effectively monitor for not less than 5 years” the species’ status,

and we must be prepared to restore the species to the list if necessary. Section 5

of the Act authorizes the Department of the Interior to acquire habitat essential to

preserving listed species, and section 6 directs us to cooperate with the States to
30

maintain adequate programs for their conservation. Through section 7 of the Act,

Federal agencies are required to use their authorities to carry out programs for the

conservation of listed species and to consult with us when a Federal action may

have an effect on listed species. Section 9 of the Act provides for protection of

listed species, and section 10 permits exceptions to the protections granted under

section 9. The exceptions are permitted in the form of scientific, recovery, and

incidental take permits, and other circumstances as detailed in section 10.

During the period of Federal protection provided by the emergency rule,

we worked with the Inyo National Forest and the California Department of Fish

and Game regarding measures to protect the bighorn sheep. Predation from

mountain lions and associated abandonment of winter habitat are thought to be

major factors contributing to the decline of the population. We assumed the lead

agency role in the development of a Final Environmental Assessment, Predator

Damage Management to Protect the Federally Endangered Sierra Nevada Bighorn

Sheep (USDA Wildlife Services 1999). This document was prepared by the U.S.

Department of Agriculture, Wildlife Services, and identified the cooperating

agencies: the California Department of Fish and Game, U.S. Forest Service, and

National Park Service. This environmental assessment was for the proposed

program to protect the bighorn sheep from predation on and around its current

range. 

In response to the threat of disease transfer from domestic sheep to Sierra

Nevada bighorn sheep and to facilitate a consistent and comprehensive approach

to consulting on the taking of Sierra Nevada bighorn sheep under the Act, we

organized an interagency team of biologists and rangeland management

specialists from the Bureau of Land Management, California Department of Fish

and Game, U.S. Forest Service, and Los Angeles Department of Water and Power

to develop a grazing strategy for domestic sheep for the Owens Valley. This 

strategy (U.S. Fish and Wildlife Service 2001) analyzes the risk of disease

transmission between domestic sheep and bighorn sheep for each of the

allotments/leases within the Owens Valley on the Inyo National Forest (seven

allotments and one trail), Humboldt-Toiyabe National Forest (one allotment),

Bureau of Land Management (one allotment and one trail), and Los Angeles

Department of Water and Power (three leases). Domestic livestock grazing
31

within the Owens Valley has been modified by the Bureau of Land Management,

U.S. Forest Service, and Los Angeles Department of Water and Power, including

a July 2000 Environmental Assessment and Decision Notice that closed two

grazing allotments on the Inyo National Forest.

Pursuant to section 7 of the Act, we have been in formal and informal 

consultation with the Inyo National Forest, Humboldt-Toiyabe National Forest,

and the Bureau of Land Management on their grazing operations. All agencies

are working cooperatively throughout the consultation process to identify high

risk areas and address unacceptable risks, so that domestic sheep grazing does not

threaten the existence of the bighorn sheep. 

b. U.S. Department of the Interior - National Park Service

Historical Management

A significant portion of the historic summer range of the Mount Baxter

herd occurred, and to some extent still does occur in Kings Canyon National Park.

Since reestablishment in 1979, the Mount Langley herd has utilized a limited part

of the Sequoia National Park during the summer. Males of the reestablished Lee

Vining herd have occasionally visited Yosemite National Park, and it is surmised

that should the herd recover fully, parts of the crest in the national park will be

included in summer range. Lastly, to replace the herd that once occupied the

Great Western Divide, an eventual reintroduction is planned to occur entirely

inside Sequoia National Park.

During the early 1960's, biologists from Sequoia and Kings Canyon

National Parks conducted surveys along the crest, trying to locate remaining

bands of bighorn sheep (Riegelhuth 1965). The National Park Service was a

substantial sponsor of the definitive research conducted by Dr. John Wehausen

from 1976 through 1979 (Wehausen 1980).

Following the lead of the U.S. Forest Service, Sequoia and Kings Canyon

National Parks in the early 1970's closed “the female/lamb range of the Sierra

Nevada bighorn sheep . . . to all pack animals and to off-trail travel by humans [in
32

the national park].” This closure was later codified in the Superintendent’s

Compendium. The associated map identified an area representing the known

range of females and lambs within King Canyon National Park. Because off-trail

travel by pack stock is impractical along the crest of the Sierra Nevada and the

occasional use by mountaineers and climbers does not pose a significant threat to

bighorn sheep, and also because the areas used by bighorn sheep will be in a state

of flux for the indefinite future, the permanent closure was terminated in 2001.

Representatives of the National Park Service have participated in the

Sierra Nevada Bighorn Sheep Interagency Advisory Group since its inception in

1981. In addition to the Recovery and Conservation Plan authored by that group

(Sierra Nevada Bighorn Sheep Interagency Advisory Group 1984), Sequoia and

Kings Canyon National Parks produced a “Bighorn Sheep Management Plan” for

those parks (National Park Service 1986) that outlined steps to recover

populations, such as the Great Western Divide herd, that historically used the

national parks.

In 1985, the Yosemite Association solicited funds from the Goldman Fund

and the Sacramento Safari Club that were paid to the Lee Vining Canyon grazing

allotment holder in exchange for vacating the allotment, which was then later

terminated by the U.S. Forest Service. Subsequently, the National Park Service

conducted follow-up monitoring and research after bighorn sheep were

translocated there in 1986 (Chow 1991, Moore 1991).

During the late 1980's, the National Park Service sponsored and conducted

aerial and ground surveys to establish the availability of winter and summer

habitat in the Great Western Divide and Kern River as a necessary precursor to

eventual translocations there.

Current Management on National Park Service Lands

National Park Service biologists from Sequoia, Kings Canyon, and

Yosemite National Parks participated in preparation of this recovery plan and will

participate in its implementation, particularly by sponsoring the use of National

Park lands by existing herds of Sierra Nevada bighorn sheep and the
33

reestablishment of Sierra Nevada bighorn sheep in the Great Western Divide area

of Sequoia National Park.

c. U.S. Department of Agriculture - Forest Service

Historical Management

Much of the historic habitat of the Sierra Nevada bighorn sheep occurs on

National Forest System lands within the Pacific Southwest Region (Inyo,

Sequoia, Sierra, and Stanislaus National Forests) and the Intermountain Region

(Humboldt-Toiyabe National Forest). The current populations primarily occupy

the Inyo National Forest, although some of the herds seasonally use

Sequoia/Kings Canyon National Park, Yosemite National Park, and the Sierra

National Forest.

The U.S. Forest Service is authorized by Acts of Congress and by

regulations issued by the Secretary of Agriculture to administer, manage, and

protect National Forest System lands for multiple uses, including the provisions

of habitat for fish, wildlife, and plants. Typically, the U.S. Forest Service is

responsible for managing habitats (e.g., food, water, and cover) on National

Forest System lands and coordinates with the appropriate State agency regarding

management of the animal populations. 36 CFR 219.19 directs the U.S. Forest

Service to manage fish and wildlife habitat to maintain viable populations of

existing native and desired nonnative vertebrate species. One way this mandate is

met is through the Forest Service Sensitive Species Program, under which each

Region establishes a list of sensitive plant and animal species that are given

special consideration under the multiple use mandate, with the objectives to

ensure the continued existence of viable, well-distributed populations and to

prevent a trend toward listing under the Endangered Species Act of 1973. Each

National Forest is required to develop a Land and Resource Management Plan,

which sets the framework for multiple use management of the Forest and

incorporates management strategies to maintain viable populations within the

Forest and to promote recovery of federally listed species. In addition, the U.S.

Forest Service, like other Federal agencies, has responsibilities under the Federal

Endangered Species Act (section 7a). Accordingly, the U.S. Forest Service
34

coordinates and consults with us on activities it conducts, funds, or authorizes that

may affect federally listed endangered, threatened, or proposed species and

designated or proposed critical habitat. 

Concern about bighorn sheep in the Sierra Nevada (Dixon 1936) prompted

the National Park Service and Sierra Club in 1940 jointly to propose the creation

of a sanctuary on Inyo National Forest land for the Mount Baxter population

(Colby 1940a, b; Blake 1940). This proposal was rejected by the U.S. Forest

Service and California Department of Fish and Game on grounds that insufficient

information existed to justify the need, as well as concern that the publicity of

such a sanctuary might exacerbate poaching, rather than having the opposite

effect (Blake 1941).

The U.S. Forest Service became active in the management of Sierra

Nevada bighorn sheep in 1971, when the Inyo National Forest created two

Bighorn Sheep Zoological Areas (Mount Baxter and Mount Williamson Units)

for the two surviving native herds (Dunaway 1971). These areas, totaling 1,823

hectares (4,505 acres) outside designated wilderness areas, were created to give

top priority to the requirements of the bighorn sheep through protection and

maintenance of their habitat and through the regulation of human use in certain

sections of the bighorn range to minimize human disturbance; similar restrictions

were applied to adjacent habitat of these herds under National Park Service

management (Wehausen 1985). The U.S. Forest Service has been a member of

the Sierra Nevada Bighorn Sheep Interagency Advisory Group since its inception

in 1981, and assisted in the funding and development by that group of a Recovery

and Conservation Plan in 1984 and the Conservation Strategy in 1997. California

bighorn sheep were classified as a Regional Forester’s Sensitive Species in

California in 1982. In 1985, the Inyo National Forest facilitated, in cooperation

with the California Department of Fish and Game and other members of the

Interagency Advisory Group, the reintroduction of bighorn sheep to the Lee

Vining Canyon area. On November 25, 1998, due to the rapid decline of Sierra

Nevada bighorn sheep, the Pacific Southwest Region Regional Forester issued a

letter directing the Forest Supervisors of the National Forests within the historic

range of the Sierra Nevada bighorn sheep to take specific actions to provide

habitat and other assistance contributing to the viability of the Sierra Nevada
35

bighorn sheep. Various management actions were initiated by this letter; these

included providing funding to U.S. Department of Agriculture Wildlife Services

to monitor mountain lion activity within occupied bighorn sheep habitat, working

with permittees to modify grazing management to eliminate the risk of disease

transmission, initiating informal consultation with us, and using prescribed fire to

improve winter range.

Current Management on National Forest System Lands

Since the emergency listing of the Sierra Nevada bighorn sheep on April

20, 1999, the U.S. Forest Service, primarily the Inyo National Forest, has been

consulting with us on various Federal actions allowed under their Forest Land and

Resource Management Plan with the potential to affect Sierra Nevada bighorn

sheep or their habitat. These actions include term grazing permits for domestic

sheep allotments adjacent to occupied bighorn sheep habitat, recreational use of

occupied bighorn sheep habitat, helicopter use within and adjacent to bighorn

habitat, prescribed fire, normal fire suppression activities, and special use permits

for outfitter guides and packers. In May 2000, a temporary Emergency Forest

Order was issued, which prohibited dogs and domestic goats from entering key

Sierra Nevada bighorn sheep habitat areas on the Inyo National Forest. The final

version of this Forest Order is currently being prepared.

The Inyo National Forest continues to use prescribed fire within bighorn

sheep winter range in an attempt to open up habitats, decrease hiding cover for

mountain lions, and potentially allow bighorn sheep increased access to areas

with highly nutritional food sources.

2. STATE AGENCIES

The first management action for Sierra Nevada bighorn sheep was full

protection from hunting. Decimation of native sheep occurred quickly following

the influx of gold miners in the mid-1800's, and declines of native game led the

State Legislature to enact legal protections beginning in the 1870's. For wild

sheep, legal protection first occurred in 1876, when a law of 1872 that provided

seasonal protection for elk, deer, and pronghorn was amended to include all
36

bighorn sheep. Two years later this law was further amended to establish a 4-year

moratorium on the taking of any pronghorn, elk, mountain sheep, or female deer;

in 1883 the moratorium was extended indefinitely for bighorn sheep (Wehausen

et al. 1987). Sierra Nevada bighorn sheep remain fully protected.

In 1972, the California subspecies, as defined by Cowan (1940) and

including surviving native populations in the Sierra Nevada, was listed as rare

under the 1970 California Endangered Species Act (California Department of

Fish and Game 1974). This category was changed to threatened in 1984. 

Through the listing process, the Fish and Game Commission recommended

development and implementation of a recovery plan, including field research and

reintroductions. Intensive field study began in 1975, and the results of those

investigations led to a series of translocations beginning in 1979. A conservation

and recovery plan was completed in 1984 (Sierra Bighorn Interagency Advisory

Group 1984). The goals of that plan were: (1) to create 2 additional populations

numbering at least 100 bighorn sheep that could serve as translocation stock in

the event of catastrophic decline of the Mount Baxter herd, and (2) to reestablish

bighorn sheep populations throughout historic ranges in the Sierra Nevada where

it was biologically and politically feasible. To date, no reintroduced population

has met the first goal, while unforeseen ecosystem level changes have resulted in

a major reduction of the Mount Baxter population. 

It is the responsibility of the California Department of Fish and Game

(Fish and Game Code Section 1802) to conserve, protect, and manage fish,

wildlife, native plants, and habitat necessary for biologically sustainable

populations of those species. It also is the policy of the State to conserve, protect,

restore, and enhance endangered or threatened species and their habitats. The role

of the California Department of Fish and Game, as trustee for fish and wildlife

resources, includes working with other State, Federal, and private entities to

further conservation and recovery of threatened and endangered species on their

lands. Conservation goals for bighorn sheep (California Department of Fish and

Game 1983) are to:

1. Maintain, improve, and expand bighorn sheep habitat where possible or

feasible.
37

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 as rare or fully protected.

4. Provide for aesthetic, educational, and recreational uses of bighorn

sheep. 

The California Department of Fish and Game supports the concept of

regional management for the long-term viability of bighorn sheep populations. In

support of this strategy, the California Department of Fish and Game’s Bighorn

Sheep Conservation Program maintains an inventory of the distribution of

bighorn 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 recolonization of vacant

habitats, and the need for interagency coordination of land management. The

concept of regional populations considers not only vegetative and geographic

boundaries, but also man-made barriers that define distributions and which have

resulted in the fragmentation of habitat. Given the need to understand the status

and dynamics of regional populations of bighorn sheep, this type of inventory

should provide an index for documenting regional population changes over time

and a basis for evaluating the success or failure of management actions at a

meaningful level.

Although a metapopulation approach is an important biological principle

for understanding the long-term survival of bighorn sheep populations, it is

equally important as a management concept that establishes a priority for regional

coordination for bighorn sheep population and habitat management. For example,

data regarding extinction and recolonization are limited, and we therefore have an

incomplete biological justification for considering some regions as true

metapopulations. Nevertheless, given the need for regional management of

bighorn sheep populations, the California Department of Fish and Game has
38

defined the metapopulations based on the best information available for the

regions, and utilizes this regional strategy for the management of bighorn sheep

throughout the State.

In 1997, a conservation strategy was produced for bighorn sheep in the

Sierra Nevada that reflected the significant changes in the status of those animals

(Sierra Nevada Bighorn Sheep Interagency Advisory Group 1997). 

Unfortunately, funding constraints encountered by the California Department of

Fish and Game limited the recovery efforts identified in this conservation

strategy. We and the Fish and Game Commission took emergency action in 1999

to list the Sierra Nevada bighorn sheep as endangered under the State and Federal

Endangered Species Acts. This action was in response to a significant decline in

the population size, from approximately 310 in 1985 to an estimated 125 adults in

1999. With the small population of Sierra Nevada bighorn sheep in decline, the

threat of this unique population becoming extinct was great. 

Due to the high level of public attention and concern, the California

Department of Fish and Game was provided funding (in 1999) through a

legislative member’s request to implement a population recovery program for

bighorn sheep in the Sierra Nevada. This funding resource is needed to meet the

mandate of the California Department of Fish and Game, and the public’s demand

for endangered species recovery. This funding will support the start of a longterm comprehensive population recovery program, and the recovery potential for

Sierra Nevada bighorn sheep populations is high if conservation actions are taken

immediately. Elements of the recovery program include monitoring the

population, intensively reducing mortality, reestablishing additional populations

in historic range, and preparing for and potentially implementing captive breeding

efforts to increase population size and maintain genetic diversity.
39

II. RECOVERY

A. CONSERVATION PRINCIPLES USED IN DEVELOPING THIS

RECOVERY PLAN 

The following sections apply general conservation principles in the

context of our current knowledge regarding Sierra Nevada bighorn sheep and

outline the relationship of these principles to the recovery criteria for this species. 

Conservation theory recognizes that population dynamics and genetic issues need

to be addressed in species conservation. Although threats to population

persistence are of more immediate importance to Sierra Nevada bighorn sheep,

potential loss of genetic variation also has implications for the long term

conservation of this taxon (Lande 1988). Fundamentally, the recovery strategy

revolves around three main conservation issues: population dynamics, genetic

variation, and ecosystem integrity.

1. POPULATION DYNAMICS 

Demographic processes are especially important considerations in the

conservation of small populations (Gilpin and Soulé 1986). Variation in birth,

death, immigration, and emigration rates, as well as the age and sex structure of

populations, 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 was an inadequate emphasis on the implications of such

population parameters for recovery and cautioned that, for many wild

populations, risks concerning population parameters are of more immediate

importance than genetic concerns. 

Spatial distribution of animals across the landscape is an important

consideration. Sierra Nevada bighorn sheep, like other forms of bighorn sheep

and many other taxa, are distributed as a collection of subpopulations, each

occupying a patch of suitable habitat within a matrix of otherwise less suitable or

unsuitable habitat. The complex topography and the vegetation structure of the

southern and central Sierra landscape, coupled with the intrinsic biology and

behavior of these bighorn sheep, has resulted in a naturally fragmented
40

distribution of animals, a metapopulation (Bleich et al. 1990a). This

metapopulation is composed of multiple subpopulations that interact

intermittently to varying degrees, depending on site-specific geography,

movement characteristics of males (occasional) and females (rare), and chance.

Metapopulation structure has profound implications for the conservation

of Sierra Nevada bighorn sheep. Conservation objectives for this taxon must

simultaneously address all levels of population organization to achieve recovery

goals. Recovery units, herd units, and separate female groups within herd units

are all relevant to overall recovery of Sierra Nevada bighorn sheep. For further

detail on the definitions of these terms refer to the discussion of recovery

objectives (section II.C.2).

Metapopulations typically are assumed to exist in a state of balance

between population extinctions and colonizations (Hanski and Gilpin 1991). 

However, bighorn sheep are relatively slow colonizers (Geist 1967, 1971, Bleich

et al., 1996) and, therefore, metapopulation extinction-colonization processes

must be considered over appropriate time periods. Although bighorn sheep

typically have a naturally fragmented distribution (Bleich et al. 1990a), any

external factor that further fragments existing populations poses a heightened

threat to persistence (Schwartz et al. 1986, Bleich et al. 1996). Hanski and Gilpin

(1991) cautioned that species subject to accelerated habitat and/or population

fragmentation must be managed carefully, as they may not necessarily be able to

function as a metapopulation in equilibrium. This situation may be exacerbated in

the Sierra Nevada because the metapopulation is largely linear in geographic

distribution, resulting in fewer populations that could serve as sources of

colonists.

There is little threat to Sierra Nevada bighorn sheep due to habitat loss. 

Virtually all land that provides habitat for this taxon is managed by the Federal

government and is likely to remain in a wild condition for the indefinite future. 

Population fragmentation due to random natural fluctuations in population

parameters or deleterious effects of disease or predation could, however, affect

overall metapopulation dynamics.
41

The small number of Sierra Nevada bighorn sheep (an estimated 250

individuals in 2001) mandates that population processes be of primary concern in

the conservation of this taxon. Furthermore, Sierra Nevada bighorn sheep occur

as discrete female groups with significance to the distributional structure of the

population (Wehausen 1979). Because these female groups are independent

segments of populations, they are the fundamental demographic units and should

be treated as the basic conservation units (Soulé 1987). Some of these groups

comprise fewer than five females, making them highly vulnerable to chance

variation in birth and death events.

In the southern Sierra Nevada, most herds of bighorn sheep have been

reduced to such low levels that random natural variation in population and

environmental factors pose serious immediate threats. Therefore, recovery efforts

for Sierra Nevada bighorn sheep must entail actions that increase the sizes of

individual female groups (by decreasing adult mortality rates, increasing

recruitment, and possibly augmenting them through translocations) and increasing

overall distribution through reintroductions to historic ranges. 

2. GENETIC CONSIDERATIONS

The Sierra Nevada bighorn sheep was recently recognized as a unique

subspecies (see Section I of this recovery plan). As such, this taxon appears to

have distinctive genetic characteristics that may include adaptations to conditions

in the Sierra Nevada. One of the fundamental objectives of this recovery program

is the conservation of the unique gene pool embodied in the remaining animals of

this metapopulation.

Maintaining genetic variation is an important conservation goal because

loss of genetic variability can result in inbreeding depression (a loss of fitness)

and the inability of populations to respond to long-term environmental changes

(Gilpin and Soulé 1986, Ralls et al. 1988, Lande 1988, Meffe and Carroll 1994,

Fitzsimmons et al. 1995). Rate of evolutionary change in a population is

proportional to the amount of genetic variation available (Fisher 1958), and loss

of genetic diversity reduces future evolutionary options (Meffe 1999). By
42

reducing the fitness of individuals, loss of genetic variation also can reduce the

growth rates and resilience of populations (Lacy 1997).

Loss of genetic variation is a special concern among small populations

because heterozygosity is lost more quickly in small populations than in large

ones (Meffe and Carroll 1994). In the past, movements of males in the Sierra

Nevada once maintained gene flow, but it is unclear to what extent such

movements now occur. The current, fragmented distribution of populations of

these animals likely reduces connectivity among groups. In small herds of

bighorn sheep, random natural variability in population parameters can be an

overriding determinant of population survival and is mitigated by immigration of

both sexes. If small herds become isolated and stay small, they face an increased

loss of genetic variability, in addition to the risks to persistence associated with

random naturally occurring events.

Even if gene flow is maintained among female groups throughout the

Sierra Nevada, the overall small population size (approximately 250 individuals

in 2001) is of concern. The effective population size (Ne, the number of

individuals actually reproducing; Crow and Kimura 1970), which determines the

rate at which heterozygosity is lost, is even smaller than the total number of adults

in the population. An effective population of 500 individuals has been suggested

as the minimum necessary for genetic variation to ensure future evolutionary

change (Franklin 1980, Lande and Barrowclough 1987, Franklin and Frankham

1998), and the actual number may be even higher. Thus, an important goal of this

recovery plan is to increase the abundance of Sierra Nevada bighorn sheep to

maintain as much of the existing genetic variation as possible.

Although genetic variation among bighorn sheep herds in the Sierra

Nevada is not known to confer adaptive advantage in local environments, genetic

theory holds 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). Adaptation to

future changes in the environment, such as may occur through global climate

change, may depend on maintenance of genetic diversity within this taxon. 
43

Because the most immediate problem facing bighorn sheep in the Sierra

Nevada concerns depleted population sizes, the potential implications of loss of

genetic heterozygosity implied by genetic theory should not override management

objectives to maintain and expand the number and size of herds throughout the

Sierra Nevada. Nonetheless, as more is learned about the actual genetic diversity

in the remaining individuals, it may be necessary to incorporate genetic

management, such as moving males between some populations.

3. ECOSYSTEM INTEGRITY

Loss of habitat is recognized as the primary cause of species

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 of many bighorn sheep populations (Bleich et al. 1996). However,

habitat loss, per se, is not considered a proximate threat to the conservation of the

Sierra Nevada bighorn sheep. Virtually all habitat used by this taxon is managed

by the Federal government.

A stable and functional ecosystem is of paramount concern. For Sierra

Nevada bighorn sheep, a primary emphasis is continued access to suitable habitat. 

Habitat conditions within the range of Sierra Nevada bighorn sheep generally are

not subject to obvious human-induced changes. What is primarily at stake for

these animals is continuing, safe access to preferred habitats, notably winter

ranges. Recent declines in population sizes have been linked to the decreased use

of key resources on winter ranges. This change is believed to be the result of

predator avoidance by Sierra Nevada bighorn sheep in these locations (Wehausen

1996). A basic premise of the recovery strategy, therefore, is to sufficiently

reduce factors that inhibit the ability of Sierra Nevada bighorn sheep to utilize

fully all components of their habitat. However, such actions need to take place in

the context of all ecosystem components; potential effects of actions to enhance

bighorn sheep herds on other components of the ecosystem must be considered.

Maintaining ecosystem integrity for the Sierra Nevada bighorn sheep

should revolve around providing suitable habitat conditions and safe access to

those habitats. Safe access implies that exposure to exotic diseases and
44

unsustainable levels of predation are prevented. Exposure to lethal diseases

carried by domestic sheep is a significant threat that could have catastrophic

effects on recovery efforts for this taxon. All habitat, both summer and winter,

must be available with no risk of direct contact with domestic sheep or goats. 

Similarly, predation should be managed within herds that are still at low levels. 

Biologists suspect that bighorn sheep in the Sierra are especially vulnerable to

predation when herds are low in number, and that small group size may preclude

the use of important foraging areas. As long as the populations of this taxon

remain below viable levels, special predator management actions are warranted to

ensure adequate use of important foraging habitat. However, it is also important

to recognize that top predators play a crucial and irreplaceable role in maintaining

the integrity of a variety of ecosystems (Terborgh et al. 1999), including,

potentially, the ecosystem inhabited by Sierra Nevada bighorn sheep.

Habitat factors, such as visual openness, that may have been influenced by

past management practices, also must be addressed. Since recovery is contingent

on full use of the nutritional resources available to these bighorn sheep, the

vegetative structure of some winter ranges needs to be considered with respect to

the recovery strategy. Fire suppression of lands within some winter ranges has

been a common management practice over the last century. The implications of

fire suppression for vegetational succession and the loss of visual openness in

some winter range habitat are not fully understood. Thus, consideration should be

given to how the habitat changes induced by fire suppression might affect use of

some winter ranges by bighorn sheep.

B. OBJECTIVES

1. CONSERVATION CHALLENGE AND GOALS

The challenges and objectives of this recovery plan are (1) to define a

desired future size and distribution of the overall bighorn sheep population in the

Sierra Nevada, at which point continued protection under the Federal and

California Endangered Species Acts is no longer needed and, (2) to outline steps

necessary to reach that condition. From a species perspective, the conservation

challenges of these bighorn sheep concern long-term viability of the overall
45

population and preservation of this unique gene pool. From an ecosystem

standpoint, the challenge involves finding the long-term population viability of

bighorn sheep relative to other elements of the ecosystems involved, as well as

returning this large native herbivore to those regions of the Sierra Nevada from

which it has been extirpated. Thus, the conservation goal of this recovery plan is

to restore Sierra Nevada bighorn sheep in a geographic distribution throughout

their native range with a genetic representation that assures their long-term

viability as a unique life form.

What might be considered a situation of adequate long-term viability may

not require reestablishment of bighorn sheep throughout their native range, and

might require the establishment of one or more isolated and protected captive

breeding populations as a buffer against extinction or as sources of translocation

stock. However, the ultimate goal of this recovery plan is recovery of these

bighorn sheep to population sizes and distribution where long-term viability will

not require active intervention.

2. RECOVERY CRITERIA

A species is considered to be endangered when it is likely to become

extinct in the foreseeable future, and it is considered to be threatened when it is

likely to become endangered in the foreseeable future. Downlisting criteria

identify the conditions at which point the status of the species has improved such

that it is no longer endangered, and may be proposed to be reclassified as

threatened. Delisting criteria represent the minimum conditions necessary to

propose removing the taxon from the endangered species list.

a. Downlisting Criteria

The taxonomic affinities of bighorn sheep that once inhabited the very

southern Sierra Nevada in the vicinity of Walker Pass are unknown. Therefore,

this recovery plan concerns the bighorn sheep only in the southern and central

Sierra Nevada from near Olancha Peak and the Great Western Divide north to the

vicinity of Twin Lakes, near Bridgeport. In this region, 17 herd units have been

identified (Table 4, Figure 1). These herd units are areas that are known or 
46

Table 4. Herd Units and Recovery Units used as the basis of recovery goals

(see Figure 1).

Herd Units and Recovery Units Minimum Elevation

(ft)

Kern Recovery Unit

1. Laurel Creek 6800

2. Big Arroyo 6900

Southern Recovery Unit

3. Olancha Peak 4800

4. Mount Langley 4800

5. Mount Williamson 6200

6. Mount Baxter 4900

7. Sawmill Canyon 4800

8. Taboose Creek 6800

9. Coyote Ridge 5600

Central Recovery Unit

10. Mount Tom 6400

11. Wheeler Ridge 5600

12. Convict Creek 7900

Northern Recovery Unit

13. Mount Gibbs 7600

14. Mount Warren 7600

15. Lundy Canyon 8000

16. Green Creek 9000

17. Twin Lakes 7200
47

suspected to have been occupied historically, and that have a high potential to

support herds of these bighorn sheep. These herd units are defined primarily on

the basis of the location and abundance of suitable habitat for low elevation

winter ranges, because that habitat is considerably more limited than suitable high

elevation habitat.

Seven of the herd units currently support bighorn sheep. Herds to be

reestablished in the remaining units are expected to support geographically

distinct groups of females. It is possible, however, that some may support more

than a single group of females exhibiting distinct home range patterns.

There are 3 natural breaks in the distribution of the 17 herd units, which

separate them into 4 distinct regions. These four larger regions are termed

recovery units, and are treated as the basic units for recovery of this taxon. 

Within a recovery unit, males are expected to move between herd units, while

movement by males between recovery units likely will occur less frequently. 

Movements by males is likely to be the primary source of gene flow.

The rate at which females in the Sierra Nevada colonize vacant habitat is

unknown, but dispersal between adjacent herd units within a recovery unit will

occur with considerably higher probability than across the gaps that define the

recovery units, and thus has implications for the natural recolonization of herd

units that become extirpated. However, movements between herds can also

spread diseases (Dobson and May 1986, Bleich et al. 1990a, 1996). Unoccupied

areas between recovery units are, therefore, potentially important zones of

isolation that may limit the spread of epizootics throughout the range of Sierra

Nevada bighorn sheep.

Downlisting Criterion A1: Downlisting will require a minimum total of

365 females that are at least 1 year of age. At least 50 of those females

must be in the Kern recovery unit, 175 females in the Southern recovery

unit, 75 females in the Central recovery unit, and 65 females in the

Northern recovery unit (Table 5). To achieve these population numbers it 
48

Table 5. Population criteria for down- and delisting of Sierra Nevada bighorn

sheep by recovery units. Minimum total females by recovery units are required

for downlisting, while geographic distribution, in terms of herd units occupied

by females within recovery units, is a criterion for delisting.

Herd Units Occupied

Recovery

Unit

Current Potential Delisting Minimum Total

Females

Kern 0 2 2 50

Southern 4 7 6 175

Central 1 3 3 75

Northern 2 5 3 65

 is expected that the major threats of excessive predation and avoidance of

high-quality low-elevation winter ranges will have substantially

diminished. 

Justification: The relative numbers of requisite females for each of the

four recovery units are based on differences in habitat quantity and quality

among the herd units. Herd units that approached carrying capacity in the

past 25 years were used as benchmarks for subjective comparisons with

other nearby unoccupied herd units to evaluate overall habitat quality. 

These comparisons were made largely on the basis of winter ranges

because, in most cases, that is the most limited seasonal habitat. 

Conservative carrying capacities for each herd unit were derived from

these comparisons. These were summed for each recovery unit, and that

sum was halved to arrive at the number of females needed for downlisting. 

This 50 percent rule reflected the recognition that: (1) considerable error

might exist in these subjective carrying capacities, (2) dynamics of

populations may not be synchronous, (3) data used as the basis of

downlisting will be minimum counts and will likely be less than actual

sizes of some herds, and (4) these criteria need to be realistic and

attainable.
49

Downlisting can occur upon reaching these thresholds, which will

minimize extinction risk through: (1) considerable geographic

distribution; (2) sufficient numbers to provide multiple sources of bighorn

sheep for translocation to help any faltering herds and/or to establish

bighorn sheep in unoccupied areas; and (3) minimal loss of genetic

variation through drift. Occupation of all four recovery units is necessary

to develop sufficient numbers of bighorn sheep, and have bighorn sheep in

enough isolated areas to make it highly unlikely that all would go extinct

simultaneously. Because of the expectation of natural, independent

dynamics among these herds, minimum sizes were set for each of the

recovery units, but not for any individual herd units.

Downlisting Criterion A2: The threat of domestic sheep or goats

contacting bighorn sheep in the Sierra Nevada has been eliminated.

Justification: Any contact between domestic sheep and bighorn sheep

could lead to the loss of entire herds of bighorn sheep in the Sierra

Nevada. Hence, potential for contact between bighorn sheep and domestic

sheep must be eliminated to avoid the possibility of a catastrophic

epizootic. Bighorn sheep and domestic sheep can potentially come into

direct contact through the movements of either species. As recovery

proceeds, and the numbers and geographic distribution of bighorn sheep

increase, the potential for contact will increase. Strong, decisive actions

must be taken to prevent contact from occurring now or in the future. 

b. Delisting Criteria

Delisting Criterion B1: The number of females required for downlisting

by recovery units (Table 5) has been maintained as an average for at least

6 years (one generation) without intervention. Herd status for delisting

must entail at least three censuses, one at the beginning of the period

(qualifying for downlisting), one at the end of the period, and one

intermediate count for each herd unit. To achieve these population

numbers it is expected that the major threats of excessive predation and

avoidance of high-quality low-elevation winter ranges will have
50

substantially diminished and remained low over an extended period of

time.

Delisting Criterion B2: Bighorn sheep of both sexes are present in a

minimum of 14 herd units, distributed as follows: 2 in the Kern recovery

unit, 6 in the Southern recovery unit, 3 in the Central recovery unit, and 3

in the Northern recovery unit.

Justification: The target number of occupied herd units for delisting

(Table 5) was based on realistic expectations. There is uncertainty about

whether it will be possible to establish herds of bighorn sheep in three of

the herd units (Coyote Ridge, Green Creek, and Twin Lakes; Figure 1,

Table 4); thus, those three were not included in the delisting criteria.

These criteria result in a total requirement of 14 occupied herd units and

365 females at least 1 year of age necessary for delisting (Table 5). With

a natural adult sex ratio of about 70 males:100 females (Wehausen 1980),

the minimum total population at both downlisting and delisting will be

about 620 adults. Because this number is based on minimum requirements

for each recovery unit, the total population will almost certainly be higher.

The time requirement of one generation will assure the maintenance of

these population and distribution conditions across all recovery units

while much of the population is replaced through mortality and

recruitment. Also, it is recognized that a period of substantial population

growth will necessarily precede the initial attainment of conditions

necessary for delisting. Thus, a period of favorable population conditions

encompassing multiple generations will precede delisting.

Delisting Criterion B3: Recovery tasks related to monitoring and research

goals have been accomplished, allowing the severity of secondary threats 

(including habitat loss, vegetational succession, recreational disturbance,

competition with elk or deer, acid rain, and climate change) to be

adequately assessed. Threats have either been ameliorated or have been

determined not to pose a significant risk to the population. 
51

Justification: Before we determine that the bighorn sheep warrants

delisting, additional information is needed regarding which threats

significantly endanger the population. Research is needed on the threats

noted above, which, although they are not as immediately critical as

disease, predation, and winter range usage, may have potential for longterm adverse effects on the population. Research and monitoring tasks

should assess which threats are significant and if necessary identify

appropriate management actions to be implemented.

c. Recovery Units

The delisting criteria include only 14 of the 17 herd units because of

uncertainty as to whether viable bighorn sheep herds can be established in 3 of

those units (numbers 9, 16, and 17 in Table 4). The area defined by those 14 core

herd units (Figure 1) is considered habitat necessary to the recovery of the species

for the following reasons. First, it may be necessary for all 14 herd areas to be

occupied to attain the minimum total population size of 365 females. Given the

likelihood that the four recovery units will function largely as independent

metapopulations, it is important to develop sufficient distribution in each to buffer

them against catastrophic losses of individual herds. These recovery units also

span a variety of ecological settings. Second, the recovery units may function

largely as separate metapopulations. It is, therefore, necessary to have as many

bighorn sheep in each as possible to prevent genetic drift from eroding genetic

diversity within recovery units. Similarly, there is a need for geographic

continuity in the distribution of herds in order to maximize genetic interchange

among herds, as well as occasional interchange among recovery units. 

C. RECOVERY STRATEGY

Because bighorn sheep are naturally slow to disperse and colonize new

habitat, recovery of Sierra Nevada bighorn sheep within a reasonable time frame

will ultimately depend on translocations of bighorn sheep to reintroduce them to

herd units from which they are absent, or to aid in the recovery of existing herds

where necessary. A translocation program will require one or more sources of
52

Sierra Nevada bighorn sheep. Identifying and developing those sources from the

current limited herds is one of the greatest challenges to recovering this

subspecies. The rate of recovery will, in part, be tied to the number of herds

capable of producing bighorn sheep for translocation. The protection and

enhancement of existing herds to maximize population growth is the first step.

The major threats to existing herds have been decreased survivorship and

reproductive success associated with their avoidance of high-quality winter

ranges at low elevations (likely in response to predation by mountain lions) and

potential outbreaks of disease contracted from domestic sheep. Therefore,

predator management (to reduce direct mortality and encourage use of lowelevation wintering ranges) and changes in domestic sheep grazing practices (to

prevent contact and disease transmission) are key aspects of the recovery strategy. 

The strategy will necessarily be supplemented by habitat management (to

promote open habitat where predators are readily visible) and perhaps

establishment of a captive breeding facility. A genetic management plan is also

necessary because the small size and isolation of existing populations threatens to

reduce the variability of their unique gene pool. Because maintaining a viable

metapopulation will require a broad, minimally fragmented spatial distribution of

subpopulations over the landscape, recovery criteria will be defined on the basis

of population sizes and occupied herd units within specified recovery units

(section II.C.2). 

Monitoring and research are necessary to provide the basis for adaptive

management and, as such, are critical aspects of this recovery plan. Recovery

actions for the bighorn sheep will depend on regularly updated information on

population parameters and habitat use patterns for each herd. Similarly, a detailed

assessment of the genetic population structure of each herd will be necessary as

the basis of a genetic management plan. Monitoring of mountain lions in the

vicinity of bighorn sheep winter ranges will greatly enhance efforts to protect

herds. Finally, outreach to enlist public support for recovery efforts will be

important to the success of this plan.
53

D. NARRATIVE OUTLINE OF RECOVERY ACTIONS

1. Protect bighorn sheep habitat.

1.1 Identify and acquire important habitat not in public ownership from

willing landowners.

While the vast majority of historic bighorn sheep range in the

Sierra Nevada is in public ownership, a small number of in-holdings exist. 

A list of all private land holdings that might affect bighorn sheep should

be developed and prioritized relative to importance to bighorn sheep. Key

parcels should be acquired or protected under a conservation easement.

1.2 Maintain and/or enhance integrity of bighorn sheep habitat.

Although the vast majority of bighorn sheep habitat in the Sierra

Nevada is under Federal ownership, that does not guarantee maintenance

of habitat integrity. Habitat integrity might be compromised by fire

suppression that affects vegetation succession (see Task 2.2.3), or a

variety of human uses (see Task 2.4). Although these issues are both

considered with respect to bighorn sheep behavior and population

parameters, they also are important to structural attributes of the habitat. 

All proposed Federal actions in the vicinity of bighorn sheep habitat

should be analyzed relative to influences on that habitat. 

2. Increase population growth by enhancing survivorship and reproductive output

of bighorn sheep. 

 Recovery of these bighorn sheep requires an overall population increase.

Enhancing survivorship and reproduction wherever possible will speed recovery. 

To the extent that these parameters are enhanced through increased nutrient intake

by more extensive use of habitat, the carrying capacity of herd units also will be

increased.
54

2.1 Prepare and implement a management plan to temporarily protect

Sierra Nevada bighorn sheep herds from predation losses, where needed,

until viable herd sizes are reached.

 The management plan must address the immediate needs for

selective predator management while allowing for a long range approach

that restores and maintains the health of the larger predator-prey system. 

Known predation losses have been primarily attributed to mountain lions

(Table 1). Thus, efforts to prevent further losses should focus on this

predator, but not ignore other potential predators.

 Individual mountain lions can vary in behavior, including whether

they prey on bighorn sheep and whether immigrating lions become

potential threats for each herd when resident lions are removed. 

Therefore, this management plan should attempt to set up criteria to

remove only lions that are a threat. Radio-collaring and careful

monitoring of mountain lions in the vicinity of bighorn sheep winter

ranges will help with selective removal (see Task 5.2 and Appendix E). 

Additionally, the need to protect bighorn sheep should be carefully

balanced with concerns for the viability of the mountain lion population. 

Potential effects of mountain lions on winter habitat selection by bighorn

sheep should be included in this predator management plan; this aspect is

addressed below in Task 2.2.

 Predator management should be viewed as a temporary measure. 

It should be terminated when herd units reach a reproductive base of 25

females, with the possible exception of herd units serving as sources of

translocation stock. It should be reinstated if a herd unit subsequently

declines below 20 females and predators are preventing recovery of that

herd unit. 

2.2 Increase use of low elevation winter ranges.

Increased use of low elevation winter ranges will increase nutrient

intake and thereby enhance reproductive output and success. Increased
55

low elevation winter range use will also decrease mortality associated with

the use of high elevations during severe winters. 

2.2.1 Reduce influences of predation on winter habitat selection

by Sierra Nevada bighorn sheep.

Adult survivorship and recruitment can be negatively

affected when bighorn sheep avoid low elevation winter ranges. 

Winter habitat selection may influence population dynamics more

than direct losses from predation. Reducing influences of

predators on winter habitat selection may, therefore, be important. 

Until some herds build sufficient numbers, it could be necessary to

remove mountain lions that frequent key winter range areas or

aversively condition mountain lions to cause them to avoid those

areas (see Task 6.4). If aversive conditioning is successful, the

maintenance of home ranges by conditioned resident lions may

discourage immigration of unconditioned lions and thereby reduce

the number of lions that need to be removed. Biologists familiar

with bighorn sheep have independently arrived at a threshold of 25

females considered a minimum number for herd viability (Sierra

Nevada Bighorn Sheep Interagency Advisory Group 1997, Fisher

et al. 1999, U.S. Fish and Wildlife Service 2000).

2.2.2 Supplement small female groups where appropriate to attain

a threshold herd size that will encourage behavioral attributes

favorable to winter range use.

Because bighorn sheep find security in groups, habitat

selection during winter may be affected by the number of bighorn

sheep available to form groups. Adding females to small female

groups may produce significant increases in uses of winter ranges

and, thereby, increase adult survivorship as well as recruitment

rates. Further, behavior of bighorn sheep previously translocated

in the Sierra Nevada indicates that females translocated from

populations that use low elevations will initially attempt to do the
56

same on new ranges. The ability to augment small herds is

currently limited by the lack of sources of bighorn sheep that can

be moved. The development of sources of bighorn sheep to move

is fundamental to achieving this task and is addressed in task 3.2.

2.2.3 Enhance bighorn sheep winter range habitat to increase

visibility where appropriate.

Favorable attributes of bighorn sheep habitat are steepness,

rockiness, and visual openness. Although steepness and rockiness

cannot be changed, openness can be modified via management of

vegetation. In the past, fires may have burned in bighorn sheep

habitat much more frequently than has occurred over the past

century. In opening up habitats, fire can decrease the effectiveness

of mountain lions as ambush predators and, perhaps, allow bighorn

sheep greater access to low elevation winter ranges that provide

nutritious forage. Policies to let fires burn in bighorn sheep

habitat, coupled with prescribed fire or other methods of habitat

manipulation, should be used to enhance winter ranges where

visibility for bighorn sheep needs to be increased.

2.3 Minimize probability of bighorn sheep contracting diseases causing

mortality and morbidity.

Introduced diseases have probably been the primary cause of

extirpation of bighorn sheep herds in North America. They represent one

of the greatest threats.

2.3.1 Eliminate the risk of contact between bighorn sheep and

domestic sheep or goats.

Allotments in the vicinity of bighorn sheep habitat should

be reviewed by an expert task force and appropriate actions taken

to eliminate the risk of contact between domestic sheep and

bighorn sheep. This task force should consist of rangeland
57

managers and independent experts, including at least one

veterinarian familiar with bighorn sheep and a scientist versed in

mathematical modeling and risk assessment.

The Interagency Domestic Sheep Management Strategy

(U.S. Fish and Wildlife Service 2001) provided risk assessment

criteria for allotments (see Appendix B for a summary). Reviews

of allotments should recognize that management of domestic sheep

allotments may not be sufficient to prevent contact between

domestic sheep and bighorn sheep over the long term if it is

possible for domestic sheep to get to the west side of Highway

395. Allotment reviews should occur in three timeframes. The

first should consider existing bighorn sheep herds and lead to

immediate actions necessary to eliminate the threat of contact with

bighorn sheep. The second should anticipate future conflicts with

domestic sheep grazing in relationship to unoccupied bighorn

sheep ranges within essential habitat and develop a plan to

alleviate those conflicts as needed when bighorn sheep range

expands through translocations or natural colonizations. Third

should be consideration of domestic sheep allotments that are

likely to conflict with bighorn sheep herd units outside of essential

habitat. While occupation of some of these herd units by bighorn

sheep may prove necessary to meet recovery criteria, attempts to

restore bighorn sheep to these herd units outside of essential

habitat are unlikely to occur until those within essential habitat are

occupied. Consequently, resolution of conflicts with domestic

sheep grazing near those herd units will not be necessary until the

more distant future, if at all. Because it is not possible to know or

control whether domestic goats have recently been in contact with 

domestic sheep, and thereby carry strains of pneumophilic bacteria

that are pathogenic to bighorn sheep, domestic goats should

likewise be prevented from utilizing areas near bighorn sheep

populations.
58

2.3.2 Develop an action plan in the event that a pneumonia

outbreak occurs.

History is replete with examples of decimation and

extirpation of bighorn sheep herds from pneumonia epizootics. 

Quick and decisive actions may save part of a herd, or other nearby

herds, in such an event. The development of an action plan prior

to such an occurrence may be critically important to taking timely

actions. This plan should include actions needed if a bighorn

sheep is found in contact with domestic sheep.

2.4 Manage human use locally where it is found to cause bighorn sheep to

avoid important habitat and, thereby, compromises survivorship or

reproductive success.

This action will take place only if research (see Task 6.3) results in

a recommendation to limit human use in some areas; at present there

appear to be few locations where recreational disturbance has the potential

to significantly affect bighorn sheep. Focused research on effects of

human activities on bighorn sheep will determine whether any limitations

on human use are required. If it is concluded that limitations will be

beneficial, appropriate actions should be taken to limit human use that is

found to be detrimental. Disturbance by humans (or possibly by off-trail

domestic dogs) will be significant to bighorn sheep if nutrient intake of a

herd is compromised by avoiding key foraging areas because of human

activity. Both quality and quantity of forage vary greatly across the

landscape, and bighorn sheep visit key locations where more nutritious

forage is available. If bighorn sheep are regularly displaced from such

areas and cannot procure equivalent nutrient intake at an alternative site,

population parameters of the herd will be negatively affected. If they

frequently flee encounters with humans, there may also be an unnecessary

waste of energy that can have population-level effects. 
59

3. Increase the number of herds, and thereby the number of bighorn sheep.

 It will be necessary to increase the geographic distribution and overall

numbers of bighorn sheep in the Sierra Nevada to attain criteria necessary for

downlisting and delisting. Because of the slow rate of natural colonization of

bighorn sheep, this action will require active management.

3.1 Develop and implement a strategy for translocations.

Because of the slow rates of natural colonization by bighorn sheep,

recovery can be accelerated by translocations to originate herds in vacant

ranges and to augment those in existing ones. It will be important to

utilize the limited number of bighorn sheep available for translocations in

a way that maximizes recovery of these bighorn sheep in the shortest time

period. A strategy is needed that clearly identifies issues, options, and

tradeoffs, and analyzes different herd units as potential recipients of

translocated bighorn sheep (See Appendix C).

3.2 Develop sources of translocation stock.

Availability of bighorn sheep to be translocated has been, and

continues to be, the primary factor limiting recovery of bighorn sheep in

the Sierra Nevada. Only one source of stock was available for previous

restoration efforts (see section I.C.2). The vulnerability of that situation

led to the proposal to develop additional such sources as the primary goal

of an earlier conservation plan for these bighorn sheep (Sierra Nevada

Bighorn Interagency Advisory Group 1984). Additional sources of

translocation stock will continue to be a fundamental need.

3.2.1 Manage wild herds as sources of stock.

Developing sources of translocation stock will depend on

sufficient recovery of at least one existing herd to the point where

bighorn sheep can be removed. All, or most, of the first available

translocation stock should be used to develop one or more
60

additional sources of such stock. This strategy is analogous to

compounding interest and will, thereby, increase the rate of

recovery of these bighorn sheep.

3.2.2 Develop criteria for and, if appropriate, implement a captive

breeding program.

In addition to wild populations as a source of translocation

stock, a captive breeding facility should be considered. Such a

facility may produce bighorn sheep more rapidly, but it could also

pose risks. Aspects of captive breeding as a potential program

should be investigated in detail, including criteria that would

trigger implementation of such a program (Appendix C).

4. Develop and implement a genetic management plan to maintain genetic

diversity of Sierra Nevada bighorn sheep. The plan must use data on genetic

variation developed in Task 6.1.

Restoration of bighorn sheep to vacant habitats in the Sierra

Nevada will be accomplished largely through translocations. However,

translocation may not maximize conservation of the genetic variation that

currently exists. There is a need to consider long-term genetic

management in conjunction with the translocation strategy to distribute

genetic variation throughout the range of these bighorn sheep.

Because translocation will be the primary method of genetic

management, a genetic management plan should be developed in

conjunction with the translocation strategy to address needs at the level of

the population.

5. Monitor status and trends of bighorn sheep herds and their habitat.

 Recovery of bighorn sheep in the Sierra Nevada will require an adaptive

approach, one in which decisions made will depend on current information about
61

key resources. Consequently, monitoring of those resources is a fundamental

component of this recovery plan.

5.1 Develop and implement a monitoring plan for population abundance

and distribution of bighorn sheep herds in the Sierra Nevada.

Management actions will be dependent on the best possible data on

the population status of each herd. Downlisting and delisting criteria also

are dependent on that information and were developed in part with the

recognition that minimum counts will be the most conservative data to use

as the basis of management decisions. Appendix D considers further

details of this monitoring.

Recent population dynamics of Sierra Nevada bighorn sheep

indicate that recovery to adequate population levels will occur only with

increased use of winter ranges. Trends in the use of winter ranges need to

be monitored in conjunction with population monitoring. Trends in winter

range use will be useful in projecting future population trends. They will

also allow efforts to focus on herds that are reluctant to use winter ranges. 

5.2 Monitor key predators in the vicinity of winter ranges.

Efforts toward the recovery of Sierra Nevada bighorn sheep

necessarily take place in a larger ecosystem context. Because

management of predators, especially mountain lions, is a component of

this recovery plan, careful monitoring of these predators near bighorn

sheep populations is important. Such monitoring will provide data on how

individual mountain lions, and mountain lions in general, use habitat in

the vicinity of each population of bighorn sheep, and will allow an

assessment of which mountain lions pose the greatest threats to bighorn

sheep, and when those threats are greatest (see Appendix E).
62

5.3 Monitor vegetation structure and composition changes likely to affect

bighorn sheep population parameters.

In the absence of regular fires, vegetational succession can slowly

decrease openness in bighorn sheep habitat. Vegetation structure and its

concomitant effects on visibility should be monitored on a long term basis.

5.4 Monitor exposure to disease organisms of concern.

Exposure to disease organisms can be monitored indirectly by

testing blood serum and directly by testing for the organisms. When

bighorn sheep in the Sierra Nevada are captured for management

operations, appropriate sampling and testing of those animals should take

place to develop a continuing database that will potentially detect changes

over time. A large database already exists from captures beginning in

1979.

6. Continue or initiate needed research.

An adaptive approach to management will require development or

continuation of existing research.

6.1 Investigate genetic population structure of existing herds.

Genetic population structure can play a potentially large role in the

long-term viability of bighorn sheep in the Sierra Nevada. The

conservation of the gene pool of bighorn sheep in the Sierra Nevada will

depend on a detailed understanding of the distribution of genetic variation

and the dynamics within that genetic population structure. There is need

to develop a genetic database and to use it as the foundation for a genetic

management plan (see Task 4). Specific data needs concern: (1) current

amount of genetic variation compared with other metapopulations of

bighorn sheep; (2) distribution of genetic variation among the different

herds; and (3) population genetic changes in each herd to determine if

future erosion of genetic diversity is likely to be a problem. These studies
63

are possible with modern laboratory techniques by using a variety of

sources of DNA. 

6.2 Further investigate habitat use patterns of bighorn sheep herds.

A large database of sightings of bighorn sheep in the Sierra

Nevada has been accumulated by researchers over the past 25 years

(Figure 1). Population substructuring of female groups also has been

identified and hypothesized on the basis of naturally marked bighorn

sheep. However, because of sampling limitations, these data do not

provide details of habitat use throughout the year or the degree of

separation of female groups. Radio telemetry studies can help fill in that

detail. Global positioning system collars may provide an efficient method

of developing detailed, accurate information on the seasonal distribution

and habitat selection patterns of these bighorn sheep.

 

6.3 Investigate and analyze human use patterns relative to habitat use

patterns of bighorn sheep.

Earlier investigations of hypotheses concerning human disturbance

(Dunaway 1971) dismissed it as not important for the Mount Baxter herd,

but possibly a factor for the Mount Williamson herd (Wehausen et al.

1977, Hicks and Elder 1979, Wehausen 1980). Bighorn sheep have been

reintroduced to three additional areas since the earlier studies, but these

new herds have not been investigated to determine the possible impacts of 

human disturbance. There is a need to investigate patterns of use by

humans and domestic dogs including intensity, trends, and types of use in

and near existing bighorn sheep habitat to identify areas of possible

conflict. If areas of concern are identified, intensive studies to investigate

whether human disturbance may be displacing bighorn sheep from

favorable habitat can be initiated. Potential reintroduction sites also

should be investigated to identify areas of possible conflict.
64

6.4 Investigate the potential for altering habitat use patterns of mountain

lions on bighorn sheep winter ranges by aversive conditioning.

Altering the behavior or distribution of mountain lions through

aversive conditioning may provide an alternative to temporary

management involving removal of mountain lions that may kill bighorn

sheep. If effective, this approach may allow the recovery of bighorn sheep

with less intervention. Aversive conditioning of mountain lions is an

untested concept, and it can be investigated in situations that minimize

risks to bighorn sheep.

6.5 Investigate future introduction sites relative to predator and domestic

sheep problems and other potential conflicts.

Like the genetic management plan, this investigation should be

coordinated with the translocation strategy. One product of a

translocation strategy (see task 3.1) will be the identification of priority for

future reintroduction sites that is based on habitat characteristics and

spatial relationship to existing herds. Once this priority is established,

sites of top priority should be investigated for potential problems with

predators, domestic sheep, or other concerns.

6.6 Investigate and, if appropriate, develop a plan for decreasing the

mortality of sheep remaining at high elevations in extreme winters.

The bighorn sheep on Mount Warren have experienced major

population declines during recent severe winters while attempting to live

at high elevations during that season. While an emphasis of this plan is to

attempt to develop more low elevation winter range use, it also is

important to maintain numbers of bighorn sheep until such changes in

habitat use patterns take place. Supplemental feeding of bighorn sheep at

high elevations during severe winters could be crucial to their survival. 

This subject should be explored in detail and an action plan developed as

appropriate.
65

6.7 Attempt to develop long-term data to elucidate predator-prey

dynamics of this ecosystem as they affect bighorn sheep.

During the 1980's, bighorn sheep in the Sierra Nevada began to

avoid low elevation winter ranges, a pattern of behavior that has, in turn,

led to major declines in the population. This dynamic appears to reflect

predator-prey processes that are not fully understood but that clearly can

affect the bighorn sheep population. A better understanding of the larger

predator-prey system is needed and will require long-term information. 

Some of the components of this system (bighorn sheep, mountain lions,

and possibly other predators) will be tracked as part of the monitoring for

this recovery effort. Mule deer, the primary prey of mountain lions, are a

key component of this ecosystem. Monitoring the dynamics of the mule

deer population is basic to developing an understanding of this predatorprey system. Other potentially important components that are not

currently monitored should be identified and efforts should be made to add

them to the monitoring scheme to aid future efforts to understand the

dynamics of this system.

6.8 Investigate effects of climate change on bighorn sheep habitat and

environmental contaminants, such as mining wastes or acid rain, on the

health of Sierra Nevada bighorn sheep.

If acid rain increases in the southern Sierra Nevada, profound

changes in soil chemistry may occur in bighorn sheep habitat. Such

changes can affect plant uptake of minerals, such as selenium, that are

important to bighorn sheep. Mining wastes, including pollutants in

aerosol form, also have the potential to affect the health of these bighorn

sheep. Climate change may cause significant habitat changes. 

7. Engage in public outreach and sharing of information.

The overriding purpose of the Sierra Nevada bighorn sheep public

information and outreach effort is to build understanding, respect, and concern for

this species, and understanding of and support for conservation measures and
66

recovery actions. A number of recovery actions outlined in this recovery plan

will directly affect public use in the eastern Sierra Nevada and, conversely,

human activities may affect recovery actions. It is therefore imperative that

strong public information and awareness programs be implemented. The public

needs to be informed of the reasons why specific recovery actions are being

taken. Conservation efforts are more likely to succeed if efforts are understood

and supported by the populace. Enlisting public support for recovery efforts will

require an information and outreach program on the ecology of Sierra Nevada

bighorn sheep, the threats this species is currently facing, and how recovery

actions will reduce those threats. Imparting that knowledge to the public will help

build respect and concern for this species and its larger ecosystem, as well as

support for conservation measures. Appendix F contains a detailed plan for

developing an effective outreach and information program.

Public information and outreach on Sierra Nevada bighorn sheep has been

occurring and is ongoing. The Sierra Nevada Bighorn Sheep Interagency

Advisory Group, the Sierra Nevada Bighorn Sheep Foundation, the Inyo National

Forest, and the Interagency Domestic Sheep Grazing Strategy Working Group

have conducted media interviews and hosted public meetings focused on Sierra

Nevada bighorn sheep ecology, management, and threats. However, additional

efforts are possible and desirable. In addition, there should be a higher degree of

coordination among individual programs and other recovery activities. Increased

coordination would not only allow each program to present the most accurate and

updated information, but it would also let the general public see that the recovery

of Sierra Nevada bighorn sheep is a collaborative effort supported by multiple

agencies, organizations, and individuals. Specific recovery actions to accomplish

the identified goals are as follows.

7.1 Conduct a survey of public uses of Sierra Nevada bighorn sheep

habitat and public attitudes regarding Sierra Nevada bighorn sheep. 

Results of the survey will be used to (1) prioritize the public

information and outreach action items, (2) determine the best methods to

accomplish the action items with the highest likelihood of meeting the

recovery plan goals, and (3) establish a baseline from which the success of
67

the action items in meeting the recovery plan goals can be measured by

comparing to a resurvey 1 year after implementation.

7.2 Develop and distribute information related to recovery efforts.

The results of the public survey (7.1) should be used to determine

the specific topical information and most effective method(s) of

disseminating this information to target audiences. This information

should be available from the key agencies involved in this recovery effort. 

A general brochure or information sheet should be developed that contains

a brief overview of the status of Sierra Nevada bighorn sheep, as well as

specific suggestions on what people can do to help the species. In

addition, information on a variety of topics germane to the recovery of

Sierra Nevada bighorn sheep should be summarized and made available to

the public in booklet form.

During implementation of recovery efforts, the public should be

fully informed as early as possible regarding actions required or restricted

while in Sierra Nevada bighorn sheep habitat. Further, the finalized

recovery plan, along with a cover letter, should be widely distributed to

affected and interested people, including hikers and other recreationists,

ranchers, ranchette owners with domestic sheep or goats, commercial

packers, environmental groups, mountain lion and bighorn sheep

advocacy groups, and affected local, State, and Federal agencies. 

Moreover, the recovery plan should reach people who would not typically

be exposed to traditional programs (i.e., individuals who might not

frequent visitor’s centers or who do not have school-aged children).

7.3 Continue, update, and coordinate existing informational and outreach

programs and develop further programs as needed.

The results of the public survey (7.1) should be used to develop the

most effective informational and outreach programs. However, there is a

more immediate need to update existing programs to provide an accurate

view of our current knowledge regarding Sierra Nevada bighorn sheep. 
68

Information should strive to highlight not only how the activities of each

individual agency or organization contribute to the recovery of Sierra

Nevada bighorn sheep, but how these activities complement those of other

agencies or organizations. Further, existing bighorn sheep curricula

should be reviewed and modified to be applicable to Sierra Nevada

bighorn sheep. Further, a variety of education materials on bighorn sheep

exist that target school-aged children and could be incorporated into a

Sierra Nevada bighorn sheep curriculum.

8. Establish an implementation advisory team for coordination and

communication.

Numerous Federal, State, and private agencies share responsibility for

bighorn sheep in the Sierra Nevada along with stakeholders. Efforts to recover

these bighorn sheep will require considerable coordination and communication

among these different entities. This coordination will be greatly enhanced

through the formation of an advisory team that meets at least twice annually. This

team should include agency representatives, appropriate specialists, and key

stakeholders.
69

III. IMPLEMENTATION SCHEDULE

The Implementation Schedule that follows outlines actions as identified in

the Narrative Outline of Recovery Actions (section II.D) and estimates costs for

the recovery of Sierra Nevada bighorn sheep. It is a guide for meeting the

objectives discussed in Part II of this recovery plan. This Schedule indicates task

priority, task numbers, task descriptions, duration of tasks, 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

the lead responsibility for each task are indicated in the table. Initiation of these

actions is subject to the availability of funds.

The Implementation Schedule indicates speculative, future costs

(preparation of additional plans, or research programs, etc.) as “to be

determined.” Indirect costs, such as those incurred by: (1) agencies and groups

contributing of time and materials, or (2) public agencies performing

administrative or regulatory functions are not included in cost totals. Costs of

continuous tasks are estimated assuming a 20-year time to recovery. Though the

Implementation Schedule does not distinguish between public and private costs,

no identifiable or specific expenditures by the private sector are likely to be

necessary, other than voluntary efforts contributed by nonprofit conservation

organizations and citizen groups. Priorities (column 1 of the following table) are

assigned as follows:

Priority 1 - An action that must be taken to prevent extinction or to prevent the

species from declining irreversibly in the foreseeable future.

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 of the

species.
70

Abbreviations used in the Implementation Schedule:

TBD To be determined

cont. Continuous

† Continued implementation of task expected to be necessary after

delisting.

‡ Task expected to be necessary until delisting of species.

* Lead responsible agency

Agencies and Organizations

BLM Bureau of Land Management

CDFG California Department of Fish and Game

CT CalTrans

LADWP Los Angeles Department of Water and Power

FWS U.S. Fish and Wildlife Service

FS U.S. Forest Service

NPS National Park Service

UC University of California, White Mountain Research Station

USGS U.S. Geological Survey, Biological Resources Division
71

RECOVERY PLAN IMPLEMENTATION SCHEDULE FOR SIERRA NEVADA 

Priority

#

Task

#

Task Description

Task

Duration

(Years)

Responsible

Agencies

Total Estimated

Cost

($1,000s)

E

FY 03 FY 

1 2.1 Prepare and implement a

management plan that addresses theimmediate needs for predatormanagement while developing along-range approach that concernsthe larger predator-prey system.

cont. CDFG* 7,000 350 3

1 2.2.1 Reduce potential predator

influences on winter habitatselection where appropriate

cont. CDFG* 1,000 50 

1 2.2.2 Supplement small female groups

where appropriate to attainthreshold herd sizes that willencourage behavioral attributesfavorable to winter range use

cont. CDFG* 300

(estimated cost

$3,000 per

animal captured;

number captured

per year TBD)

TBD T

1 2.3.1 Eliminate risk of contact between

bighorn sheep and domestic sheepor goats

cont.† FS*, FWS,

BLM, DWP,

CDFG

50 2.5 2

1 3.1 Develop and implement a strategy

for translocations

cont. FS, NPS,

FWS, CDFG*

600 30 
Priority

#

Task

#

Task Description

Task

Duration

(Years)

Responsible

Agencies

Total Estimated

Cost

($1,000s)

E

FY 03 FY 

72

1 3.2.1 Manage wild herds as sources of

stock

cont. CDFG* costs included in

other tasks

1 5.2 Monitor key predators in the

vicinity of winter ranges

cont.‡ CDFG* included in 2.2.1

2 1.2 Maintain and/or enhance integrity

of bighorn sheep habitat

cont.‡ NPS*, FS*,

FWS, CDFG

TBD TBD T

2 2.2.3 Enhance bighorn sheep winter

range habitat to increase visibilitywhere appropriate

cont. FS*, NPS*,

CDFG

600 30 

2 2.3.2 Develop an action plan in the event

that a pneumonia outbreak occurs

1 CDFG* 10 

2 3.2.2 Develop criteria for and, if

appropriate, implement a captivebreeding program

cont. FS, FWS,

CDFG*

5,000 250 2

2 5.1 Develop and implement a

monitoring plan for populationabundance and distribution ofbighorn sheep herds in the SierraNevada

cont.† CDFG*, UC* 4,000 200 2

2 5.4 Monitor exposure to disease

organisms of concern

cont.‡ CDFG* 75 3.75 3

2 6.1 Investigate genetic population

structure of existing herds

5 CDFG, UC* 200 40 
Priority

#

Task

#

Task Description

Task

Duration

(Years)

Responsible

Agencies

Total Estimated

Cost

($1,000s)

E

FY 03 FY 

73

2 8. Establish an implementation

advisory team for coordination andcommunication

cont.‡ CDFG* 20 1 

3 1.1 Identify and acquire important

habitat not in public ownershipfrom willing landowners

cont. FS*, FWS,

CT, CDFG

TBD TBD T

3 2.4 Manage human use locally where it

is found to cause bighorn sheep toavoid important habitat and,thereby, compromises survivorshipor reproductive success.

1 FS*, NPS*,

FWS, CDFG

5

3 4 Develop and implement a genetic

management plan using data ongenetic variation developed inTask 6.1

cont.‡ CDFG* 20

Implementation

costs included in

3.1

3 5.3 Monitor vegetation structure and

composition changes likely to affectbighorn sheep populationparameters

10 FS*, NPS*,

CDFG

100 10 

3 6.2 Further investigate habitat use

patterns of bighorn sheep herds

20 CDFG* 400 20 

3 6.3 Investigate and analyze human use

patterns relative to habitat usepatterns of bighorn sheep

cont. FS, NPS,

CDFG*

100 5 
Priority

#

Task

#

Task Description

Task

Duration

(Years)

Responsible

Agencies

Total Estimated

Cost

($1,000s)

E

FY 03 FY 

74

3 6.4 Investigate the potential for altering

habitat use patterns of mountainlions on bighorn sheep winterranges by aversive conditioning

10 CDFG* 100 10 

3 6.5 Investigate future reintroduction

sites relative to potential predatorand domestic sheep problems andother potential conflicts

cont. FS, NPS,

CDFG*

200 10 

3 6.6 Investigate and, if appropriate,

develop a plan for decreasingmortality of bighorn sheepremaining at high elevation inextreme winters

1 FS, CDFG* 20 

3 6.7 Attempt to develop long term data

that will help elucidate predatorprey dynamics of this ecosystem asthey affect bighorn sheep

cont. FS, NPS,

UC*, CDFG

1,550 30 

3 6.8 Investigate effects of climate

change on bighorn sheep habitatand environmental contaminants,such as mining wastes or acid rain,on the health of bighorn sheep

TBD FS, NPS,

USGS*,

CDFG

120 TBD T

3 7.1 Conduct a survey of public uses of

bighorn sheep habitat and publicattitudes regarding bighorn sheep

1 FS*, NPS*,

FWS, CDFG

30 
Priority

#

Task

#

Task Description

Task

Duration

(Years)

Responsible

Agencies

Total Estimated

Cost

($1,000s)

E

FY 03 FY 

75

3 7.2 Develop and distribute information

related to recovery efforts

cont.‡ FS, NPS,

FWS*,

CDFG*

110 10 

3 7.3 Continue, update, and coordinate,

existing informational and outreachprograms and develop furtherprograms as needed

cont.‡ FS, NPS,

FWS*,

CDFG*

100 5 

Total estimated cost (over 20 year timeframe): $21,730,000 + additional costs that cannot be determined 
76

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136. 

Bailey, N. T. 1951. On estimating the size of mobile populations from recapture data. 

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Blake, A. H. 1940. Conference on Sierra bighorn planned. Sierra Club Bull. 25(6):7.

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Bleich, V. C. 1999. Mountain sheep and coyotes: patterns of predator evasion in a

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Bleich, V. C., J. D. Wehausen, and S. A. Holl. 1990a. Desert-dwelling mountain sheep:

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Bleich, V. C., J. D. Wehausen, K. R. Jones, and R. A. Weaver. 1990b. Status of bighorn

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survival, and mortality in south central Colorado. Journal of Wildlife Management

38:771-774.

Young, S. P. and E. A. Goldman. 1944. The wolves of North America. Dover

Publications, New York, NY.
93

V. APPENDICES

A. Pack llamas as potential sources of diseases for Sierra Nevada bighorn sheep

B. Risk assessment regarding domestic sheep

C. Translocation considerations for Sierra Nevada bighorn sheep

D. Monitoring of bighorn sheep population parameters

E. Monitoring of mountain lions near bighorn sheep winter ranges

F. Public information and outreach plan
94

APPENDIX A. PACK LLAMAS AS POTENTIAL SOURCES OF DISEASES

FOR SIERRA NEVADA BIGHORN SHEEP

Abstract: The interspecies transmission of infectious pathogens is dependent on

characteristics of the two species, the disease agents, and the environment and requires

effective contact between the host species. The requirements for transmission of diseases

potentially shared by pack llamas and Sierra Nevada bighorn sheep are not satisfied in the

context of the epidemiology of known diseases of new world camelids in the United States,

the management of pack llamas in the back country, and the ecology and natural history of

free ranging Sierra Nevada bighorn sheep. Current scientific evidence suggests that llamas

utilized as pack animals present minimal risk of transmission of known pathogens to Sierra

Nevada bighorn sheep and does not support the exclusion of llamas from Sierra Nevada

bighorn sheep habitat due to the risk of disease transmission. Prevention of overuse of trails

by llama packers, requirement of evidence of preventive health programs in llama herds for

issuance of trail use permits, and good sanitation and husbandry practices by llama packers

on the trail will further reduce the already very small risks and further protect the endangered

Sierra Nevada bighorn sheep.

Literature Review: The transmission of infectious disease agents from one species to

another depends on characteristics of the host species, (susceptibility and infectiousness),

characteristics of the pathogen (infectivity, virulence and environmental stability) and

effective contact between the host species (Thrusfield 1995). In order for a llama (Llama

glama) to transmit a pathogenic virus, bacterium or parasite to a bighorn sheep, the agent

must be present in the llama in a form and quantity adequate for successful transmission, the

disease agent must be infective enough to be passed between species either by direct contact

or indirectly via a vector or inanimate physical vehicle, and there must be effective contact

with the bighorn sheep adequate to allow transmission. The agent must be able to survive

environmental conditions during the transmission and the bighorn sheep must in turn be

susceptible to the pathogen. 

A review (Thedford and Johnson 1989) and a standard text (Fowler 1998) on the

infectious diseases of new world camelids indicated that llamas in the United States are

basically healthy and that most medical problems are management or environment related. 

Many disease agents that are infectious to both new world camelids and bighorn sheep are

rare in llamas in the United States, are more easily acquired from the environment or

sympatric wildlife than from the llama, are not present at adequate levels in the environment
95

to infect bighorn sheep, or are unlikely to survive environmental conditions during indirect

transmission.

Due to their high intrinsic economic value, pack llamas are generally tethered or

otherwise kept close to their owners on the trail (Fowler 1998). In the unlikely event that a

llama would escape into a free ranging situation, it would be unable to keep up with Sierra

Nevada bighorn sheep in the steep, rocky terrain they frequent. Also, Sierra Nevada bighorn

sheep naturally keep a wide flight distance from humans, making direct physical contact

between pack llamas and bighorn sheep highly unlikely and reducing the opportunity for

transmission of infectious disease. Depending on the number and size of llama pack strings

and their distribution, indirect transmission of disease agents including common

gastrointestinal parasites, contagious ecthyma virus, and others from contaminated pastures,

artificial feed, and standing water sources is theoretically possible. A few disease agents

warrant individual discussion as they have demonstrated pathogenicity in bighorn sheep:

Pasteurella hemolytic pneumonia; Mycobacterium paratuberculosis (Johne’s disease);

Contagious ecthyma virus (CE, soremouth); and Psoroptes spp. (Scabies). 

Pasteurella hemolytica pneumonia

Pasteurella pneumonia is a major cause of epizootic disease outbreaks in captive and free

ranging bighorn sheep populations resulting in high adult mortality with poor lamb

survivorship in subsequent years. In separate trials, Rocky Mountain bighorn sheep were

placed in direct contact with llamas, domestic sheep, exotic mouflon sheep (Ovis musimon),

domestic goats, mountain goats (Oreamnos americana), domestic cattle (Foreyt 1994), elk

(Cervus elaphus), and deer (Odocoileus virginianus and Odocoileus hemionus hemionus)

(Foreyt 1992) and domestic horses and cattle (Foreyt and Lagerquist 1996) to determine if

contact with other wild and domestic ungulate species exposed bighorn sheep to Pasteurella

pneumonia. Except for the llamas and horses, essentially all the ungulates including the

bighorn sheep were phanyngeal carriers of isolates of Pasteurella hemolytica when the

experiment started. Foreyt tested a total of 17 llamas to use as Pasteurella carriers in the

trials but found none that were culture positive. All bighorn sheep exposed to the domestic

sheep and the mouflon (Foreyt 1994), and one exposed to domestic cattle (Foreyt and

Lagerquist 1996), succumbed to Pasteurella pneumonia while those exposed to the other

ungulates including the llamas remained normal. Pasteurella multocida infection can cause

a hemorrhagic septicemia-like disease in old world camels (Thedford and Johnson 1989).

However, Pasteurella pneumonia in new world camelids has not been reported in the
96

literature. Based on available data, there is no scientific evidence that contact with llamas

will result in respiratory disease from Pasteurella spp. in bighorn sheep (Foreyt 1994).

Mycobacterium paratuberculosis (Johne’s Disease)

Much controversy surrounds the potential for transmission of Johne’s disease

(Mycobacterium paratuberculosis) from llamas to free ranging bighorn sheep (Fowler

1998). Johne’s disease is considered a disease of confinement, usually requiring intense

sustained exposure to feces of infected, shedding animals as seen in domestic livestock and

captive wild ungulates. Generally, adult ungulates are much less susceptible to infection and

require greater exposure than juveniles. Mycobacterium paratuberculosis infection has been

documented in several species of free ranging ungulates in the United States (Chiodini et al.

1983, Shulaw et al. 1986, Riemann et al. 1979, Jessup et al. 1981). Williams et al. (1979)

reported on cases of Johne’s disease in bighorn sheep and in a mountain goat (Oreamnos

americana) in the Mount Evans area of Colorado. The source and epizootiology of the

disease were not clear in these cases. In a followup study, M. paratuberculosis was isolated

from tissues and/or feces from nine of nine bighorn sheep/domestic sheep hybrids

experimentally inoculated with an M. paratuberculosis isolate from the Mount Evans cases

and two of three bighorn sheep hybrids exposed to runoff from contaminated animal pens

(Williams et al. 1983).

Johne’s disease has been documented in new world camelids in England (Fowler 1998) and

in Australia (Ridge et al. 1995) but is rarely diagnosed in llamas in the United States, with

only four cases documented in Colorado (2), Oklahoma (1) and Minnesota (1) (Fowler

1998). Casual contact with the feces from a subclinically infected pack llama shedding

Mycobacterium paratuberculosis is considered unlikely to provide adequate exposure to

infect a bighorn sheep. The rare occurrence of this disease in llamas in North America

makes it highly unlikely that any exposure will occur. There is no scientific evidence that

llamas present a risk of transmission of Johne’s disease to bighorn sheep.

Contagious ecthyma virus (CE, soremouth)

Contagious ecthyma is a cause of painful scabs and lesions on the mouths and faces of

bighorn lambs and on the teats of bighorn females, and can result in difficulty in nursing and

stunted growth of lambs. Clinical cases of contagious ecthyma have been diagnosed in

bighorn sheep in Nevada, New Mexico, Colorado, Canada and California (Jessup 1993) and
97

serologic evidence of exposure is not uncommon in desert bighorn (Ovis canadensis nelsoni)

and Peninsular bighorn sheep (Ovis canadensis cremnobates) in California (California

Department of Fish and Game, unpublished data). Clark et al. (1993) surveyed Sierra

Nevada bighorn sheep sera retrospectively for contagious ecthyma exposure and found 2 of

14 (14 percent) seropositive accessions. More recent data from five Pine Creek animals

captured in 1999 showed one of five negative and four of five inconclusive results on

contagious ecthyma complement fixation tests (California Department of Fish and Game,

unpublished data).

Transmission can be direct or indirect, as contagious ecthyma virus can be transmitted by

insect vectors and may survive for years in scabs and soil. Contagious ecthyma is seen in

camelids in Peru, and at least one case is documented in the United States. The natural

reservoir for contagious ecthyma infecting llamas is probably the domestic sheep (Fowler

1998). Direct transmission of contagious ecthyma virus is highly unlikely due to lack of

physical contact with bighorn sheep. While the contamination of pastures with contagious

ecthyma virus is theoretically possible, the rare occurrence of contagious ecthyma in llamas

in the United States makes it highly unlikely. Closely managed pack llamas, kept under

good husbandry and sanitation conditions and with no evidence of clinical contagious

ecthyma, present little or no risk to Sierra Nevada bighorn sheep.

Psoroptes spp. (Scabies)

Psoroptes scabies is an ectoparasitic disease that has caused declines in bighorn sheep

populations throughout the west from the late 19th century to the present. Serologic

evidence of exposure is not uncommon in desert bighorn sheep in California (Clark et al.

1993), and clinical cases have been observed in several desert mountain ranges in California

(California Department of Fish and Game, unpublished data). Of 110 Sierra Nevada bighorn

sheep tested retrospectively, none showed evidence of previous exposure to Psoroptes spp.

(Clark et al. 1993). Two llamas, a cria and his dam (offspring and mother), are the only

documented cases of Psoroptes in new world camelids in the United States. Based on

morphological and epidemiological studies, the authors determined that the potential for

transmission of Psoroptes from llamas to other hosts is present (Foreyt et al. 1992). 

Considering the rarity of this disease in llamas in the U.S. and the unlikely nature of direct

contact between llamas and Sierra Nevada bighorn sheep, the risk for interspecies

transmission of this disease is extremely low.
98

Conclusion

Scientific evidence suggests that llamas utilized as pack animals present minimal risk of

transmission of known pathogens to Sierra Nevada bighorn sheep. Diseases reported in new

world camelids but not discussed here (e.g. tuberculosis, brucellosis) are rare or nonexistent

in the United States in llamas, are environmentally related (anthrax, clostridial diseases), or

require conditions of contact that do not exist in the context of Sierra Nevada bighorn sheep

and llama management. Due to the endangered status of the Sierra Nevada bighorn sheep,

land managers may desire a conservative approach to further reduce the already small risk of

disease introduction from llamas. The following measures could be implemented:

• Prevent overuse by private and commercial llama packers. This measure will limit

contamination of pastures, pens, and standing water sources. Limitations placed on

numbers due to potential forest and trail impacts may be adequate to address disease

considerations.

• Require evidence of adequate herd health care before issuance of permits. Evidence

of herd examinations by a licensed veterinarian, regular diagnosis and treatment of

gastrointestinal parasites, and exclusion of animals showing signs of infectious

disease from the pack string can be reflected in a health certificate that is renewed on

a periodic (annual) basis.

These additional precautions impose little if any additional burden on either land managers

or llama packers, and will further protect the small and endangered populations of Sierra

Nevada bighorn sheep.
99

References Cited

Chiodini, R. J., H. J. Van Kruiningen. 1983. Eastern white-tailed deer as a reservoir of

ruminant paratuberculosis. Journal of the American Veterinary Medical Association

182(2):168-169.

Clark, R. K., W. M. Boyce, D. A. Jessup, and L. F. Elliot. 1993. Survey of pathogen

exposure among population clusters of bighorn sheep (Ovis canadensis) in

California. Journal of Zoo and Wildlife Medicine 24(1):48-53.

Foreyt, W. J., L. G. Rickard, and W. M. Boyce. 1992. Psoroptes sp. in two llamas (Lama

glama) in Washington. Journal of Parasitology 78(1)153-155.

Foreyt, W. J. 1992. Experimental contact association between bighorn sheep, elk and deer

with known Pasteurella haemolytica infections. Biennial Symposium of the

Northern Wild Sheep and Goat Council. 8:213-218.

Foreyt, W. J. 1994. Effects of controlled contact exposure between healthy bighorn sheep

and llamas, domestic goats, mountain goats, cattle, domestic sheep, or mouflon

sheep. Biennial Symposium of the Northern Wild Sheep and Goat Council. 9:7-14.

Foreyt, W. J., and J. E. Lagerquist. 1996 . Experimental contact of bighorn sheep (Ovis

canadensis) with horses and cattle, and comparison of neutrophil sensitivity to

Pasteurella haemolytica cytotoxins. Journal of Wildlife Diseases 32(4) 594-602.

Fowler, M. E. 1998. Infectious Diseases In Medicine and Surgery of South American

Camelids. 148-194. Iowa State University Press, Ames, IA.

Jessup, D. A. 1981. Paratuberculosis in tule elk in California. Journal of the American

Veterinary Medical Association 179(11):1252-1254.

Jessup, D. A., and W. M. Boyce. 1993. Diseases of Wild Sheep. In M. E. Fowler, ed Zoo

and Wild Animal Medicine: Current Veterinary Therapy 3. M. E. Fowler, Ed. pages

554-560.
100

Ridge, S. E., J. T. Harkin, R. T. Badman, A. M. Mellor and J. W. A. Larsen. 1995. Johne’s

disease in alpacas (Lama pacos) in Australia. Australian Veterinary Journal 72(4)

150-153.

Riemann, H. R., M. R. Zaman, R. Ruppanner, O. Aalund, J. B. Jorgensen, H. Worsaae, and

D. Behymer. 1979. Paratuberculosis in cattle and free-living exotic deer. Journal of

the American Veterinary Medical Association 174:841-843.

Shulaw, W. P., J. C. Gordon, S.Bech-Nielsen, C. I. Pretzman, and G. F. Hoffsis. 1986.

Evidence of paratuberculosis in Ohio’s white-tailed deer, as determined by an

enzyme-linked immunosorben assay. American Journal of Veterinary Research

47(12):2538-2542.

Thedford, T.R., and L. W. Johnson. 1989. Infectious disease of new-world camelids. In

Veterinary Clinics of North America: Food Animal Practice. Llama Medicine. 5(1):

145-157.

Thrusfield, M. 1995. The transmission and maintenance of infection. Chapter 6 in

Veterinary Epidemiology. Blackwell Science, Malden, MA

Williams, E. S., T. R. Spraker and G. G. Schoonveld. 1979. Paratuberculosis (Johne’s

Disease) in bighorn sheep and a rocky mountain goat in Colorado. Journal of

Wildlife Diseases 15:221-227.

Williams, E. S., S. P. Snyder, and K. L. Martin. 1983. Experimental infections of some

North American wild ruminants and domestic sheep with Mycobacterium

paratuberculosis: clinical and bacteriological findings. Journal of Wildlife Diseases

19(3):185-191. 
101

APPENDIX B. RISK ASSESSMENT REGARDING DOMESTIC SHEEP

The probability that stray domestic sheep will contact bighorn sheep might be

modeled as the product of three probabilities: (1) the probability of strays occurring near the

bighorn sheep population; (2) the probability of those strays entering bighorn sheep habitat;

and (3) the probability of those strays that reach bighorn sheep habitat contacting bighorn

sheep. The overall probability of contact between a bighorn sheep and a stray domestic

sheep in the Sierra Nevada over time will be the product of the above three probabilities for

each population summed across years and across populations. Assigning values to the three

basic probabilities would be difficult at best. Because probabilities must be summed across

many years and populations, it is essential that the product of the three basic probabilities be

very close to zero to assure that this larger sum over future years also will be as close to zero

as possible. The probabilities that can be influenced by management are the occurrence of

strays and the probability of these strays finding bighorn sheep habitat. The second of these

will be greatly influenced by the distance between domestic sheep and bighorn sheep

habitat, potential barriers to domestic sheep movement toward bighorn ranges, and various

aspects of the grazing procedures of each allotment. Detailed monitoring of domestic sheep

also may reduce the probability of strays reaching bighorn habitat through the timely

knowledge that strays are missing from a flock. While the third probability cannot be altered

by management actions, it should be recognized that it will increase as the bighorn sheep

herds increase; the more bighorn sheep there are, the more likely it will be that a stray

domestic sheep in their habitat contacts one.

The question of contact between bighorn and domestic sheep is further complicated

by the possibility that bighorn sheep males might seek out and contact domestic sheep

females in estrous and then return to the mountains, thereby serving as the vector of

pathogenic strains of pneumophilic bacteria. 

Below is a method developed by an interagency team to evaluate the risks to bighorn

sheep of nearby domestic sheep grazing operations in the eastern Sierra Nevada. This group

included individuals familiar with the behavior and ecology of Sierra Nevada bighorn sheep

and the behavior of domestic sheep in wildland grazing situations. Other scientists and

specialists were consulted during the development of this method of risk assessment. The

group identified nine risk factors associated with the likelihood of interspecies contact

(U.S. Fish and Wildlife Service 2001).
102

The first purpose of this risk assessment approach was to apply it to individual

allotments so as to arrive at an overall risk rating (high, medium, or low/insignificant). The

second purpose was to investigate key factors responsible for the rating and determine if

they could in some way be mitigated to lower the risk rating to an acceptable level. The

following risk levels were identified and assigned to each allotment/lease based on a

subjective analysis of all the risk factors evaluated, including mitigation measures identified.

• LEVEL 1: Domestic sheep may escape or wander from their permitted grazing area,

and at least one contact between stray domestic and bighorn sheep may occur over a

10-year period. This level requires formal consultation with us because the grazing

operation is likely to adversely affect the Sierra Nevada bighorn sheep.

• LEVEL 2: It is unlikely that domestic sheep may escape from their permitted

grazing area. There is no reasonable risk that they would contact bighorn sheep. 

This level requires only informal consultation with us because the grazing operation

is not likely to adversely affect the Sierra Nevada bighorn sheep.

• LEVEL 3: There is no risk that domestic sheep that stray from their permitted

grazing area will contact bighorn sheep. This level represents a no effect

determination, which does not require consultation with us.

Risk Factors

a. Distance between grazing area and bighorn sheep habitat and presence or absence of

physical barriers to prevent domestic sheep from moving into bighorn sheep range

and bighorn sheep moving into domestic sheep areas. For example, barriers that

would prevent domestic sheep travel include the following: cliffs, canyons, large

bodies of water, and sheep proof fencing. Barriers that would only discourage

domestic sheep travel include the following: rocky or broken terrain, dense

vegetation (mountain mahogany, thick aspen, coniferous forest), and boundary

barbed wire fences. Barriers that would discourage bighorn sheep from moving into

domestic sheep areas include the following: large, flat areas without rocky escape

cover, large areas of dense vegetation that may harbor predators, large bodies of

water, and human settlements.

High: Inconsistent natural and man-made physical barriers
103

Low: Natural physical barriers continuous with unnatural physical barriers 

(such as fences)

b. Proximity of bighorn sheep to allotment/lease during time domestic sheep are

present. 

For example, overlapping seasons of use where bighorn sheep are occupying

summer range adjacent to domestic sheep grazing areas being used May-October.

High: Bighorn sheep are known sometimes to be at low elevations during

the grazing season (October 10 to June 1)

Medium: It is conceivable that bighorn sheep are at low elevations during

the grazing season (September 15 to October 10)

Low: Bighorn sheep are known to be at high elevations during the grazing

season (July 1 to September 15)

c. Potential condition of domestic sheep to attract bighorn males. 

High: Yes, females in estrus

Low: No females in estrus 

d. Physical ability of domestic sheep to move freely

High: Yes, normal physical condition

Low: No, they are in their third trimester of pregnancy

e. Condition of terrain that can hinder: 1) visibility of the entire herd, or 2)

detection/capture of escaped domestic sheep.

High: Area includes shrubs, trees, or boulders
104

Low: Pasture grazed domestic sheep

f. Grazing practices such as "trailing" that require movement to new watering

spots/bedgrounds that offer more opportunities for individuals or groups of domestic

sheep to wander off.

High: Yes

Low: No

g. Number of domestic sheep each herder must account for. The norm is about 1,000-

2,000 animals per herder.

High: Over 1,500 individual animals (including lambs)

Medium: From 800–1,500 individual animals (including lambs)

Low: Fewer than 800 individual animals (including lambs)

h. Length of time when domestic sheep are present within 10 kilometers (6 miles) of

bighorn sheep habitat. This factor is important because the longer domestic sheep

are on the allotment/lease, the greater risk there is for a stray.

High: Over 2 months

Medium: From 1-2 months

Low: Less than 1 month

i. Known escaped or stray domestic sheep originating from the allotment, lease, or

driveway.

High: Yes

Low: No
105

References Cited:

U.S. Fish and Wildlife Service. 2001. Interagency Domestic Sheep Management Strategy. 

Unpublished report. U.S. Fish and Wildlife Service, Ventura, CA.
106

APPENDIX C. TRANSLOCATION CONSIDERATIONS FOR SIERRA

NEVADA BIGHORN SHEEP

The future of bighorn sheep in the Sierra Nevada hinges on the use of translocations

for reintroductions and herd augmentations, and possibly for genetic management. The

translocation plan called for in Task 3.1 is therefore critical to the recovery effort for these

bighorn sheep. This appendix lays out some of the elements and issues that should be in that

plan and a discussion of both occupied and unoccupied bighorn sheep habitat in the southern

and central Sierra Nevada.

A. Sources of translocation stock

In the 1970's and 1980's, only a single herd existed in the Sierra Nevada that was 

large and productive enough to be tapped for reintroduction stock. That vulnerable situation

was a primary concern addressed in the Sierra Nevada Bighorn Sheep Recovery and

Conservation Plan (Sierra Nevada Bighorn Sheep Interagency Advisory Group 1984). The

same vulnerable situation exists today. Solving this problem has to be one of the key

elements of the translocation strategy. Among the options that need to be explored are the

establishment and maintenance of one or more wild source herds; and the conditions under

which a captive herd should be developed in parallel to produce stock for translocation

needs to be addressed as well. The advantages of captive breeding lie with being able to

control factors affecting survivorship and reproductive output. A captive herd could be

managed to have optimum reproduction and survivorship without the environmental

variation that is present in wild populations, thereby maximizing production of bighorn

sheep. 

A captive breeding contingency plan will need to be developed to facilitate decisions

relating to the captive breeding of bighorn sheep. The final product of a captive breeding

herd should be healthy, behaviorally normal individuals capable of surviving and

reproducing in the wild. The concept of captive breeding in general, along with the history

of bighorn sheep captive breeding attempts, will need to be reviewed. A theoretical decision

tree should be constructed to help facilitate captive breeding decisions and identify the point

at which captive breeding is considered essential to prevent extinction and accelerate

recovery.
107

Selection guidelines for a captive breeding site need to be developed, and potential

sites should be identified and evaluated. Also, guidelines and recommendations for

constructing and maintaining a facility for captive breeding, selection of founder breeding

stock, husbandry, veterinary care, and a summary of diseases that may affect a captive herd

needs to be carefully developed. Development of this information prior to an actual decision

to enter into a captive breeding program will greatly expedite the development of such a

facility if and when it is needed. 

Population models can help in evaluating how captive breeding may facilitate

recovery goals. The integrity of these models will depend on the input of demographic data

on age- and cause-specific mortality, reproductive success, and census numbers. Such

models also can help assess the effects that the bighorn sheep removal and augmentation

associated with captive breeding could have on extinction probabilities in populations. These

initial models may help guide decision-making and the construction of future models.

B. Management of wild herds for translocation stock

Issues that should be addressed in a translocation plan are: (1) how such herds are to

be managed differently from other herds; (2) what demographic criteria will be used to

determine when and how many bighorn sheep will be removed from a herd; (3) what

tradeoffs and benefits are associated with waiting until a herd has grown larger before

removing bighorn sheep for translocation; and (4) what potential behavioral implications for

the source herd may be associated with frequent captures, and how these may relate to

logistical difficulties of capturing bighorn sheep.

C. Translocation strategy

The optimal use of bighorn sheep available to translocate is a complex question. 

While a short term plan can be developed based on current population information, it is

important to recognize that it will need to change as the status of herds change, recovery

goals are met, and new information on habitat is developed. Ideally, the plan will

incorporate needed flexibility. The alternative will be to revise the plan as needed. Below

are some of the key issues to be addressed in the plan.
108

1. Prioritization of locations to receive available stock

• Should available stock be used only for augmentations to assure recovery to

all existing herds before unoccupied ranges are considered? 

• Should the first bighorn sheep available for translocation be used only to

create at least one more source of translocation stock, or should a mixed

strategy be considered? 

• Should the goal of the translocation strategy be to minimize the time to

downlisting? Does such an optimization have any associated risks? In

developing a long term strategy, it will be important to estimate the minimum

number of bighorn sheep that will need to be moved for reintroductions to

meet recovery goals.

2. Translocation group size

Minimum numbers that will be moved for augmentations versus

reintroductions need to be established. Moving smaller numbers will risk fewer

bighorn sheep and may be desirable for some reintroductions, with the idea that the

initial group can be augmented at a later date. Because herd augmentations can

generally be accomplished with far fewer individuals than reintroductions, it may be

difficult to justify engaging in reintroductions until existing herds have reached sizes

that afford some comfort in terms of viability.

It has been recommended that reintroduced herds of bighorn sheep be created

with at least 20 individuals (Wilson and Douglas 1982), and this approach has been

the common practice, including past reintroductions in the Sierra Nevada. 

Establishing sufficient genetic variation in isolated herds has been one reason for this

approach. In contrast, a new group of females established within a metapopulation

where males will find them might be created with a small number of females and

perhaps one male to assure breeding until other males discover them. This practice

will better mimic natural colonization in bighorn sheep, where new female groups

sometimes arise from a single dispersing female (Bleich et al. 1996). Males explore
109

nearby habitat considerably more than females and in general find suitable habitat

patches before females.

There are other considerations regarding numbers of females to translocate. 

Regardless of how much research may be allocated to choosing release sites,

uncertainties will always remain. Therefore, it will be important to proceed with an

experimental approach to translocations so that different scenarios can be evaluated

to optimize future efforts. Even for a reintroduction, an initial translocation of a

relatively small number of individuals will allow an assessment of site suitability. 

An augmentation can follow if deemed appropriate to boost numbers and assure

sufficient genetic diversity, but the failure of a reintroduction of many bighorn sheep

due to unforeseen circumstances will be an irretrievable loss of a rare resource. Also

considered should be the advantages that bighorn sheep obtain from group living,

including better predator detection and feeding efficiency. Group sizes of five to six

are common, and feeding efficiency shows little gain beyond that size (Berger 1978,

Risenhoover and Bailey 1985). Thus, releases in new areas should attempt to

provide a group of at least five bighorn sheep if possible.

3. Timing of translocations

The intent of most or all translocations will be the establishment or

augmentation of herds using low elevation winter ranges. Since the peak in such use

of this habitat historically has been in late winter and early spring, this period

(especially March) would be the ideal time to translocate bighorn sheep to these

sites. There are several reasons for this assessment. First, these bighorn sheep have

a natural tendency to descend to such sites at that time of year. Second, forage

quality will be high during this period, which may help hold translocated bighorn

sheep near the release site. Third, for augmentations, there are likely to be herds

present on these winter ranges that translocated animals can join, which should also

serve to help hold translocated bighorn sheep near the release site. Finally, bighorn

sheep can be caught most readily at this time of year. The translocation strategy

should consider whether there is any other time of year at which translocations might

be successfully done.
110

4. Potential areas to receive bighorn sheep

Below is a discussion of locations that might support herds of bighorn sheep. 

It combines habitat attributes with historical data. These locations are grouped by

recovery units and by herd units within recovery units. The following attributes

were considered in developing a list of potential areas that might support female

groups (Table C-1): (1) known past use by bighorn sheep; (2) extent of high

elevation snow-free winter habitat; (3) availability of lower elevation south or eastfacing habitat and its lowest elevation and quality in terms of visual openness; and

(4) availability of high elevation summer habitat. Winter habitat is the most limited

habitat available in general and was the primary focus.

Recent herd histories have indicated that some use of low elevations in late

winter and spring is essential for herds to maintain viable sizes. Table C-1 lists

minimum elevations for each area. Lower elevations are correlated with warmer

temperatures, earlier initiation of forage growth, and potentially higher overall

nutrient intake by bighorn sheep. Wehausen (1980) found that each 17.8-meter

(58.4-foot) increase in elevation equated to a 1-day delay in initiation of forage

growth and associated increases in diet quality. This relationship translates to a 17-

day delay per 1,000 feet, or 28 days per 500 meters. The large size attained by the

Mount Baxter herd prior to changes in winter habitat use apparently resulted from

high nutrient intake obtained on its low elevation winter range; this herd declined to

about 15 percent of its former size while avoiding low elevation winter range habitat

(Wehausen 1999). While lower minimum elevations allow greater nutrient intake by

bighorn sheep herds using them, it is not known what the upper limit of this

minimum elevation is relative to supporting a viable herd.

Northern Recovery Unit

Bighorn sheep were recorded historically as far north as the Sonora Pass

region (Grinnell and Storer 1924). Some patches blown free of snow exist near and

east of Sonora Pass. However, these patches included little rocky escape terrain and

were not considered suitable for reintroduction. It is not yet evident what sort of

habitat use patterns the native bighorn sheep in this area might have had, but viable

habitat may have included the Walker River Gorge and even the Sweetwater
111

Mountains. It is questionable whether bighorn sheep will ever be returned to this

area.
112

Table C-1. Potential sites for bighorn sheep wintering groups in the central and southern Sierra Nevada groUnit.Location Current Bighorn

Sheep Use

Minimum WinterHabitat Elevation (m)

Winter RConditio

Northern Recovery UnitTwin Lakes (Victoria Peak) no 2,200 openGreen Creek (Crater Crest) no 2,750 openDunderberg Peak no 3,050 openLundy Canyon males 2,450 mixedLee Vining Canyon (Mount Warren) yes 2,300 mixedTioga Crest yes 2,900 openBloody Canyon (Mount Gibbs) yes 2,775 openParker Canyon (Mount Lewis) males 2,700 openAlger Creek (Mount Wood) males 2,300 openCentral Recovery UnitConvict Creek (Laurel Mountain) no 2,400 openMcGee Creek (McGee Mountain) no 2,450 openNevahbe Ridge no 2,600 openWheeler Ridge yes 1,700 openMount Tom males 1,950 open
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Southern Recovery UnitShannon Canyon (Coyote Ridge) no 1,700 openBirch Mountain/Kid Mountain no 2,800 openTaboose Creek no 1,950 openGoodale Creek no 2,100 openSawmill Canyon yes 1,500 openThibaut Canyon-Sand Mountain yes 1,525 openOnion Valley (Kearsarge Peak) yes 2,300 openShepherd Creek-Pinyon Creek yes 2,075 mixedGeorge Creek - N. Bairs Creek no 1,900 mixedLone Pine Creek-Hogback Creek no 2,075 mixedCarroll Creek -Tuttle Creek yes 1,750 mixedCottonwood Creek - Slide Canyon males 1,450 openFalls Creek - Ash Creek no 1,450 openKern Recovery UnitBig Arroyo no 2,100 mixedRattlesnake Creek no 2,075 mixedLaurel Creek no 2,075 mixed
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Nine areas were considered to have potential habitat for bighorn sheep in this

recovery unit (Table C-1). Three of these currently are inhabited by both sexes, and three

more receive at least occasional use by males.

Mount Warren Herd Unit: The Mount Warren area north of Lee Vining Canyon

has a good combination of high elevation and low elevation winter habitat and

supported a large concentration of bighorn sheep prior to 1995. Tioga Crest is

included in the herd unit because of close connectivity. However, since 1995 data

have suggested that a separate female group occupies Tioga Crest. 

Lundy Canyon Herd Unit: Immediately north, Lundy Canyon has good low

elevation south-facing winter range that rivals Lee Vining Canyon in its lowest

elevation (Table C-1). In contrast, Lundy Canyon has very little high elevation

winter habitat. Farther north, much of Dunderberg Peak is substantially blown free

of snow in winter, but it does not connect to low elevation winter range. It is,

however, connected to the Lundy Canyon range in summer. 

Green Creek Herd Unit: Farther north is Crater Crest, which has some high areas

free of snow in winter and connects to some potential low elevation habitat in Green

Creek, but the minimum elevation is somewhat high at 2,743 meters (9,000 feet)

Twin Lakes Herd Unit: Immediately north of Twin Lakes there are south-facing

slopes at relatively low elevation that are blown free of snow, as is an area around

Victoria Peak. It is not clear whether there would always be a connection between

these sites for bighorn sheep except in late winter and spring when snow firms up. 

The south-facing slopes above Twin Lakes, while steep and open, appear to lack

areas of rock outcrops. In contrast, the Crater Crest range provides such outcrops in

the Green Creek drainage. Dunderberg Peak, Crater Crest, and Victoria Peak

probably all had bighorn sheep use historically, but these areas should be considered

for translocations only after all other more suitable areas have been filled. Lundy

Canyon is one of those more suitable areas.

Mount Gibbs Herd Unit: South of Lee Vining Canyon, the region from Mount

Wood to Mount Dana has high potential for expansion of bighorn sheep range in this

recovery unit. There is considerable high elevation habitat blown free in winter,
115

which connects well to south-facing slopes that drop to lower elevations. Males are

already known to move between Mount Warren and this area. With the recruitment

of a yearling female in the Mount Gibbs herd in 1997, its known reproductive base

increased to two females. Beginning in 1999, a third female has been documented in

this group (Wehausen 2000). It is possible that, left alone, this little group will grow

and eventually expand south to Mount Wood. This process could be greatly

accelerated by translocating some females into this area. It is noteworthy that just

west of Parker Peak lies Koip Peak, which means bighorn sheep in the Paiute

language. 

While many details on seasonal habitat use are lacking, the current herd in

the region apparently uses only Mount Gibbs and part of Mount Dana during

summer. Mount Lewis has habitat that appears to receive use only by males

currently. The south-facing side of this mountain is steep and holds little snow in

winter. It may be capable of supporting a small group of females. The Mount Wood

area appears to be the best habitat in this unit. The slopes above Silver Lake provide

low elevation east-facing winter range down to 2,316 meters (7,600 feet) that

probably once received use by bighorn sheep, perhaps including birthing in spring in

some years.

Central Recovery Unit

Wheeler Ridge Herd Unit: The Central recovery unit currently has one herd on

Wheeler Ridge, which had grown to about 70 individuals in 2000. In the winter of

1998, there was a reported sighting of three females above Wells Meadow, the first

known use of this low elevation winter range in many years. In subsequent years,

this excellent winter range showed a steep increase in use by that herd in late winter. 

The herd is increasing very rapidly and is the one prospect for a source of

translocation stock in the near future.

Mount Tom Herd Unit: Immediately south of Wheeler Ridge is Mount Tom,

which had a native herd of bighorn sheep that persisted into the 1930's. Ober (in litt.

1911) said of them: "on Mount Tom, twenty miles west of the city of Bishop, there

ranges in winter and summer a beautiful herd numbering forty head; they course

from Mount Tom on over the summit to the west and around the head waters of Pine
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Creek". Three years later Ober also noted that this herd numbered "about forty or

fifty head; they follow the snow line in winter, and, as a matter of fact come very

close to the little farming community of Round Valley (Ober 1914).” Males from

Wheeler Ridge have been known to visit Mount Tom occasionally since they were

reintroduced in 1979, and Mount Tom is the likely first site for range expansion in

this region via translocation. Mount Tom offers multiple habitat options. Low

elevation winter-spring habitat extends down to 1,950 meters (6,400 feet) in

Elderberry Canyon. High elevation winter habitat is extensive on the west side of

the north ridge of Mount Tom, and there are even some narrow ridges that can be

blown free of snow on the south side of the mountain. Further, the summit plateau

between Basin Mountain and Mount Humphreys remains snow free in winter and is

accessible to bighorn sheep traversing ridge lines from Mount Tom via Four Gables

and along the crest. Early sighting records indicate that the bighorn sheep that

inhabited this area used the crest in summer at least as far as Mount Emerson, and

males certainly ranged farther. Reestablishment of this herd might go a long ways

toward increasing total numbers of bighorn sheep in this recovery unit and thereby

enhancing its viability.

Convict Creek Herd Unit: Farther north are three areas that were probably all used

historically by bighorn sheep to some degree: Nevahbe Ridge, McGee Mountain,

and Convict Creek. A native herd inhabited the Convict Creek area into the 1950's

(Jones 1950). Traditional south-facing winter-spring habitat that melts off quickly

after winter storms occurs above Convict Lake down to 2,407 meters (7,900 feet) 

This area is connected to extensive high elevation wind swept patches on Laurel and

Bloody Mountains. Of these three northern sites, Convict Creek is the most

favorable due to this combination. McGee Mountain has excellent south-facing

winter habitat down to about 2,438 meters (8,000 feet) that is equivalent to the slope

above Convict Lake, but has only a small amount of high elevation winter habitat. 

Nevahbe Ridge has more windblown habitat than McGee Mountain, but the low

elevation habitat is east-facing and occurs down to only 2,590 meters (8,500 feet); 

thus it is much more delayed in snow melt.

In 1989, 11 males from Wheeler Ridge were photographed by a hiker near

Rosy Finch and Laurel Lakes, which is a considerable distance northwest from

Wheeler Ridge and indicative of the potential for gene exchange with the northern
117

portion of this recovery unit if it can be established via translocation. There was

probably also once some gene exchange between this recovery unit and the Northern

recovery unit via San Joaquin Ridge. 

Numerous sightings of bighorn sheep on San Joaquin Ridge were recorded

between 1954 and 1957 including a male killed by a deer hunter. Connectivity

across this region is less likely in the future because of human developments.

Southern Recovery Unit

As many as 13 or more distinct female groups may have once occupied the

area from Olancha Canyon to Coyote Flat. Of those areas listed on Table C-1, five

currently contain female groups and another four are known to have been visited by

males. These areas are discussed below as six general herds.

Coyote Ridge Herd Unit: East above the south fork of Bishop Creek there are

multiple high elevation patches of habitat on Coyote Ridge and the Inconsolable

Range that remain snow-free in winter. There is a paucity of historical evidence that

bighorn sheep occupied this area, but this lack of evidence could reflect an

incomplete record. Bighorn sheep using this area might have used low elevation

habitat along Bishop Creek and/or crossed over Coyote Flat to excellent south and

east-facing winter range as low as 1,706 meters (5,600 feet) in the Shannon Canyon

area. Bishop Creek is currently treated as a break between the Central and Southern

Recovery Units because of uncertainty about former use of the region of Coyote

Ridge and the Big Pine Creek drainage. A Coyote Ridge herd would serve

substantially as a link between these two recovery units. It is likely that historically

there was gene flow through the bighorn sheep herds along the entire east side of the

Sierra Nevada. It is noteworthy that a number of recent reported sightings on Coyote

Ridge, the Inconsolable Range, and the west side of the Palisades region suggest the

possibility of a small number of bighorn sheep currently occupying this area. 

Taboose Creek Herd Unit: Jones (1950) listed a Birch Mountain herd just south of

Big Pine that he estimated at 15 bighorn sheep. His evidence for these bighorn sheep

was tracks of six animals. Clyde (in litt. 1971) noted that he had never seen bighorn

sheep sign on Birch Mountain in numerous ascents but had once seen deer (does and
118

fawns) well above timberline on its slopes. Nevertheless, Ober (1914) mentioned

bighorn sheep living from Birch Creek to Big Pine Creek, and Clyde (in litt. 1971)

noted evidence on a variety of occasions of bighorn sheep in the upper Big Pine

Creek drainage. Whether females were present is unknown. There are some

significant areas of high windblown habitat on Birch and Kid Mountains that might

have supported bighorn sheep. However, available low elevation south or eastfacing habitat to complement these sites is limited to relatively high elevations unless

the animals moved farther south to Red Mountain and Taboose Creeks. 

Alternatively, they might have dropped as low as 2,194 meters (7,200 feet) on the

northeast side of Kid Mountain.

The Inyo National Forest Fish and Game Reports in 1921 and 1923 listed a

Goodale-Birch Mountain herd; the 1921 report described it as "A considerable

number ranging from Goodale Mountain to Birch Mountain, and wintering along the

foothills in the Black Rock region during heavy snow.” Ober (in litt. 1911) noted,

"In the winter season they range low on Taboose Creek and along the snow line to

Goodale and Red Mountain.” Coincident with increasing mountain lion predation

on bighorn sheep in the early 1980's, bighorn sheep were found wintering in Goodale

Creek, where they had not been recorded for decades. As numbers of bighorn sheep

wintering in Sawmill Canyon declined, the number wintering in Goodale Creek

increased to a peak of 25 in 1981 and 24 in 1982, but then declined steadily. It is

possible that members of the Sawmill Canyon herd were attempting to find a new

safer area to winter. Lion predation on these bighorn sheep was also recorded at

Goodale Creek in this period, which may have accounted for the decline in use there

also. No use of this winter range has been known for some years. This area offers

some patches of high elevation winter habitat, and excellent south-facing low

elevation habitat, especially in Taboose Creek, where it occurs as low as 1,950

meters (6,400 feet).

Mount Baxter and Sawmill Canyon Herd Units: What was once referred to as

the Mount Baxter herd is now known to be multiple herds. The northernmost is the

Sawmill Canyon herd, which ranges as far north as Mount Pinchot. South of

Sawmill Canyon is the Mount Baxter herd proper. South of Oak Creek there appears

to be a third independent female group that developed after abandonment of winter

range use in the late 1980's. Its range extends south to Kearsarge Peak and Mount
119

Gould. The herd that utilized the ridges and drainages of Mount Baxter in the 1970's

and 1980's was large and productive, and it provided most of the reintroduction stock

used in the Sierra Nevada. Bighorn sheep removed from the Sawmill Canyon herd

made up the remainder. Of existing herds currently existing in the Sierra Nevada,

the Mount Baxter herd has the highest prospect for becoming a second wild source

of translocation stock in addition to the Wheeler Ridge herd, due to its history. 

Augmentation of this herd with members of the Wheeler Ridge herd could accelerate

that prospect.

Mount Williamson Herd Unit: Females from the Mount Williamson herd ranged

from Georges Creek to Shepherd Creek prior to its recent decline (Wehausen 1980)

associated with avoidance of winter ranges. Of the four canyons previously used as

winter range, only Shepherd Creek is still known to be used. Males were previously

known to use the Sambas Creek and Pinyon Creek drainages in addition during

summer, as well as areas west of the crest. Clyde (in litt. 1971) recorded

considerable use farther south on Mount Russell, where he once encountered four

males. This greater range of use may have reflected a much larger herd at that time,

which Jones (1950) estimated subjectively at 125. Recent surveys of the herd have

suggested that its range is currently farther north than it was up to 1985 when all

winter range areas were used (Wehausen 2000). Any attempts to expand its current

range through augmentation should attempt to reestablish South Bairs Creek as a

winter range. Females established there will likely use Georges Creek.

A small amount of historic evidence suggests that females may have once

used Sambas and Pinyon Creeks to the north, where only males could be found in

the 1970's (Wehausen 1979). 

Mount Langley Herd Unit: Prior to its recent decline, females from the Mount

Langley herd used the area from Carroll Creek to Lone Pine Peak. It is not clear

whether Tuttle Creek currently receives other than occasional use by females. South

of Carroll Creek are Slide Canyon, which contains the road to Horseshoe Meadows,

and then Cottonwood Creek, the top of which is also traversed by that road. Both of

these canyons offer excellent low elevation open winter range, with Cottonwood

Canyon notably more extensive. These winter ranges are better than those currently

used from Carroll Creek to Diaz Creek, but would require greater distance traveled
120

to connect them to alpine ranges. From Slide Canyon and the top of Cottonwood

Canyon, it would be natural for bighorn sheep to cross a short stretch of open southfacing forest via Wonoga Peak to reach the large open plateau country currently used

by this herd. It is hard to imagine that Cottonwood Canyon did not once support a

large bighorn sheep herd. Males have begun using Cottonwood Canyon. The

carrying capacity of this herd could probably increase dramatically if a female group

used Cottonwood Canyon every winter. An alternative home range pattern for

bighorn sheep using Cottonwood Creek would be a summer range to the south

immediately east of the Kern Plateau at top elevations of only about 3,048 meters

(10,000 feet). While this habitat would not provide the vast open expanses of higher

alpine habitats in the Mount Langley area, it would be nutritionally quite suitable and

likely to support a large bighorn sheep herd.

Olancha Peak Herd Unit: South of Cottonwood Creek, from north to south, are

Ash, Braley, Cartago, Olancha, and Falls Creeks, all of which are potential bighorn

sheep habitat. The southern three of these creeks are more favorable because they

readily connect to Olancha Peak, which reaches 3,695 meters (12,123 feet) and

provides some alpine summer habitat (the southernmost alpine habitat in the Sierra

Nevada). Olancha Canyon is the most direct connection to this alpine habitat. The

Olancha Peak herd would be the most southern herd in this recovery unit. Winter

range would be traditional low elevation south-facing slopes, of which there is an

abundance of excellent habitat reaching low elevations that will ensure high winter

and spring diet qualities. Jones (1950) considered this region part of his Mount

Langley herd, presumably because of reported sightings in that region at that time.

Kern River Recovery Unit

There is good historical evidence of bighorn sheep on the Great Western

Divide. They occurred in the Mineral King and Kaweah Peaks area, with notable

concentrations on Red Spur and in Big Arroyo (Jones 1950). A die-off was reported

in the Kaweah Peaks in the 1870's that was attributed to scabies (Jones 1950). 

Big Arroyo and Laurel Creek Herd Units: Bighorn sheep would have moved

readily along the east-facing cliff areas of the Kern River Canyon in winter, but Big
121

Arroyo, Rattlesnake Creek, and Laurel Creek would have been particularly attractive

due to south-facing exposures on which snow melts faster and forage grows earlier. 

These sites are probably the best ones for reintroductions. Since there are no high

elevation wind-swept areas west of the Kern River, the issues in comparing these

three winter range sites are: (1) elevation; (2) visual openness; (3) amount of southfacing range; and (4) access to alpine ranges. Minimum elevations differ little

among the sites (Table C-1). Big Arroyo may have the largest amount of low open

habitat, but there appears to be ample habitat at each site, and all three are

substantially open with some scattered trees. The Chagoopa Plateau largely blocks

access to alpine habitat from Big Arroyo, but bighorn sheep can be expected to find

access to the Kaweah Peaks at the upper end of the drainage. Alternatively, Red

Spur can be immediately accessed from the Kern River canyon. In contrast,

Rattlesnake and Laurel Creeks provide immediate access to summer ranges. One

alternative would be to release bighorn sheep along the Kern River near Red Spur

and let them ultimately find Big Arroyo as a preferred winter range. Laurel Creek

has the potential advantage of having no trails and, thus, probably the least human

use.
122

Literature Cited

Berger, J. 1978. Group size, foraging, and antipredator ploys: an analysis of bighorn sheep

decisions. Behav. Ecol. and Sociobiol. 4:91-99.

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 D. R.

McCullough, ed. Metapopulations and wildlife conservation. Island Press, Covelo,

CA.

Grinnell, J., and T. I.. Storer. 1924. Animal life in the Yosemite. University of California

Press, Berkeley, CA. 752pp.

Jones, F. L. 1950. A survey of the Sierra Nevada Bighorn. Sierra Club Bull. 35(6):29-76.

Ober, E. H. 1914. Fish and game conditions in the "land of little rain". Biennial Report of

the State of California Fish and Game Commission. 23:123-126.

Risenhoover, K. L., and J. A. Bailey. 1985. Foraging ecology of mountain sheep:

implications for habitat management. J. Wildl. Manage. 49:797-804.

Sierra Nevada Bighorn Interagency Advisory Group. 1984. SNBS Recovery and

Conservation Plan. Inyo National Forest, Bishop, CA. 17 pp.

Wilson, L. O., and C. L. Douglas. 1982. Revised guidelines for capturing and reestablishing desert bighorns. Trans. Desert Bighorn Counc. 26:1-7.

Wehausen, J. D. 1979. Sierra Nevada bighorn sheep: an analysis of management

alternatives. Admin. Report. Inyo National Forest and Sequoia, Kings Canyon, and

Yosemite National Parks.

Wehausen, J. D. 1980. Sierra Nevada bighorn sheep: history and population ecology. 

Ph.D. thesis, Univ. of Michigan, Ann Arbor, MI.
123

Wehausen, J. D. 1999. Sierra Nevada Bighorn Sheep: 1999 population status. 

Unpublished report, University of California, Mountain Research Station, Bishop,

CA.

Wehausen, J. D. 2000. Sierra Nevada Bighorn Sheep: 2000 population survey results, a

report to the California Department of Fish and Game. Unpublished report,

University of California, White Mountain Research Station, Bishop, CA.

In Litt. References

Clyde, N. 1971. The bighorn in the Southern Sierra. Mostly half a century of casual

recollections. Letter to game warden Vernon Burandt. March 23, 1971. 

Ober, E. H. 1911. Letter to the California Fish and Game Commission. November 20,

1911.
124

APPENDIX D. MONITORING OF BIGHORN SHEEP POPULATION

PARAMETERS 

Downlisting and delisting goals (section II.C.2) were formulated in conjunction with

monitoring criteria. Those goals recognized that females were key to population success,

and monitoring criteria are similarly focused on that sex. Downlisting and delisting goals

also recognized that minimum counts were desirable as the basis of management decisions

because: (1) there is certainty in the numbers as compared with population estimators of

potentially poor precision and (2) minimum counts can have the benefit of a built-in buffer

of additional individuals not accounted for.

History of Monitoring Efforts

Monitoring the sizes of bighorn sheep herds in the Sierra Nevada has always posed a

challenge because of the difficulty of accessing most of the habitat they inhabit, coupled

with the high elevations they occupy much of the year. Prior to the late 1970's, most

information consisted of subjective population estimates that used unclear methods to derive

estimates from very limited data (Wehausen 1980). A different approach has been used to

develop data on population sizes over the past 25 years. These efforts have relied on

understanding the behavior of different herds and conducting counts when the bighorn sheep

have been most concentrated in regions that are most accessible, either low elevation winter

ranges or along the crest in summer, to derive minimum counts that account for a high

proportion of the herds. Initially, direct counts were made for the two native herds when

bighorn sheep concentrated on low-elevation winter ranges in late winter. This method

involved multiple such counts each year when bighorn sheep numbers appeared highest.

(Wehausen 1980, 1981, 1982, 1983, 1987, 1996). After those bighorn sheep began avoiding

winter ranges beginning in the mid 1980's (Wehausen 1996), data on population sizes

became considerably more difficult to obtain and required efforts at high elevations during

summer, where bighorn sheep can be more dispersed. Nevertheless, with sufficient

persistence, predictable patterns of habitat use in summer also can be used to develop good

counts in some situations. For the Mount Langley, Mount Warren, and Mount Gibbs herds,

summer counts have always produced the best data (Brown and Ramey 1987, Moore and

Chow 1990, Hammett and Thompson 1992, Jensen 1993, Chang 1994). For most herds,

attempts to develop regular data on sizes were resumed only beginning in 1995 because of

concern about herd declines (Wehausen and Chang 1995, 1997, 1998; Wehausen 1999). 
125

The development of data on minimum numbers at high elevations in summer for some of

these herds has been possible only because of a combination of small herd sizes,

substructuring into separate female groups, and recognition of some individual bighorn

sheep.

All population data on Sierra Nevada bighorn sheep over the past 25 years have been

minimum numbers present by sex and distinguishable age classes. Such figures always beg

the question of how many were missed. Reconstructed population values have allowed an

evaluation of at least some previously uncounted individuals for some herds (see section

I.C.2), and consistency from one year to the next has similarly provided a means of

assessment. For the Mount Baxter, Sawmill Canyon, and Mount Williamson herds prior to

winter range abandonment, counts were notably more complete in winters of heavy snowfall

(1978, 1983, and 1986), and only in such winters was it possible that essentially every

individual might have been accounted for (Wehausen 1987). During 1977 to 1987, counts

of females in the Mount Baxter and Sawmill Canyon herds in years of less snowfall varied

from 70 to over 90 percent of numbers expected in the population based on a recruitment

model that treated counts in those heavy winters as complete counts (Wehausen 1987). A

second major influence on these census results was nutritional level of the winter range

forage. Analysis of diet quality data from 14 winters showed that the timing of the first

soaking storm had the greatest influence on forage nutritional value for bighorn sheep

feeding on the Mount Baxter and Sawmill Canyon herd winter ranges (Wehausen 1992). 

The lowest winter range counts occurred during years of delayed forage growth, i.e. the

benefit to risk ratio for these bighorn sheep appears to have influenced their use of winter

ranges. A multiple regression analysis using the date of the first soaking storm and April 1

snow pack (inches of water) on Sawmill Pass as independent variables explained 91 percent

of the variation in the proportion of expected females counted in the Mount Baxter herd

(Wehausen 1987).

Recent herd size information from summer ranges has been supplemented with the

interpretation of sign left by bighorn sheep, where it suggested that some individuals had not

been counted, to provide an assessment of possible additional individuals present (Wehausen

1999). This method of supplementing counts has been possible also only because of small

herd size, and has relied on information such as sizes of lamb fecal pellets to indicate that the

sign probably represented additional individuals.
126

Future Monitoring

Future monitoring of bighorn sheep population dynamics in the Sierra Nevada needs

to utilize as many tools as possible to develop the best possible data. Recent direct counts

have relied on knowing the habitat use patterns of bighorn sheep, recognizing some

individual bighorn sheep, and making usually multiple attempts to find them when they are

most accessible and concentrated. Such methods should continue, but they should be

augmented to the extent possible with other methods and aids that may supplement these

counts, make them easier and more efficient, or serve as an independent check on data.

Helicopter Counts

The remoteness and ruggedness of much of this habitat limit the methods that can be

employed. For instance, previous attempts to use a helicopter at high elevations in the Sierra

Nevada have found no bighorn sheep or only a small proportion of those known to exist. 

Because of the atmospheric conditions at high elevations and related high speeds and

distances that helicopters must fly for safety, it is unlikely that adequate data will be obtained

on sex and age composition of what few bighorn sheep might be found by this method.

In 1981, a helicopter census took place on the low elevation winter ranges of the

Mount Baxter and Sawmill Canyon herds. This census was carried out with simultaneous

ground observers to produce a double survey estimate (Magnusen et al. 1978) and evaluate

the use of such helicopter counts (Wehausen 1981). This approach was never repeated

because the results were poor compared with data that a single experienced investigator

could produce with repeated ground surveys.

Nevertheless, helicopter surveys may prove useful to supplement winter ground data. 

For instance, under conditions of high snow cover, helicopters may be particularly effective

in finding bighorn sheep via tracks. Helicopter surveys will be most effective in late winter

(first half of March) when bighorn sheep are most likely to be at low elevations. At this time

a helicopter survey can help focus ground efforts by checking locations that are more

difficult to access on the ground. Ground work can then focus on areas containing bighorn

sheep that had not been recorded in ground work prior to the helicopter survey. 
127

Telemetry Collars 

Radio collars have been used to great effect in the past to aid in monitoring the three

reintroduced herds in the Sierra Nevada and can similarly aid future population monitoring. 

Radio collars can be added to herds through capture of existing members or by translocating

bighorn sheep to these populations from a larger and more productive herd. Captures will

be limited largely to low elevation winter ranges because of logistical constraints. 

Consequently, the option of translocating bighorn sheep to add radio collars will have the

advantage of not putting members of small herds through the major disturbance of capturing

them during brief visits to winter ranges that these bighorn sheep are hesitant to utilize. If

efforts to capture members of such small groups cause winter range avoidance, these efforts

will trade off recovery for easier information. There exist some herds or subgroups of herds

in the Sierra Nevada that are not currently known to visit any low elevation winter ranges. 

For these groups it is likely that the only way to have radio-collared bighorn sheep will be to

translocate some to those areas. Because of the fundamental importance of females as the

reproductive base of each herd, a greater return in monitoring can be expected by radio

collaring that sex. 

Radio collars will have the extra benefit of adding data on mortality and habitat use

patterns. Such data will be limited by the number of radio collars that can be placed in each

herd. Determination of causes of death will require finding dead bighorn sheep a short time 

following death. Given the remote nature of much of the habitat that Sierra Nevada bighorn

sheep occupy, it should be recognized that a significant time lag often will occur between

when an animal dies, when the mortality signal is detected (often only from an airplane), and

when a biologist can get to the location to investigate the mortality. This time lag may be

particularly problematic for winter mortalities that occur at higher elevations. For instance,

the death of a radio collared female in the Mount Warren area in 1998 was first detected

probably 2 months post-death and then could not be investigated for 4 months until snow

had melted. Consequently, radio collars may produce only limited data on cause-specific

mortality. The best data will come from low elevation winter ranges where detection of

mortality and investigation will be rapid, but these ranges are used for only a small fraction

of the year.

Collars might also be used to generate mark-resight population estimates if herds can

be sampled in an approximately random manner. Multiple sampling approaches are possible
128

for such estimates (Bailey 1951, Chapman 1951, Caughley 1977, Neal 1993). Such

estimates have the advantage of providing measures of precision in the form of confidence

limits. However, because of the difficulty of developing large sample sizes and the

relatively low proportion of the population likely to be collared, such estimates can be

expected to yield confidence limits too large to be of much use. The inefficiency of such

sampling compared with a minimum known population approach was demonstrated by

Wehausen (1996) for a small population of desert bighorn sheep in the Granite Mountains of

California. The requirement of random sampling for such estimation procedures precludes

the use of telemetry signals from radio collars to aid in finding bighorn sheep. In the Sierra

Nevada, this effect will eliminate the primary benefit of radio telemetry for herd monitoring

– greater efficiency in finding bighorn sheep and an aid in finding otherwise missed

individuals. Consequently, mark-resight estimation procedures should be used only under

sampling conditions that will clearly provide useful results.

Two fundamental question should be asked about radio-collaring bighorn sheep in

the Sierra Nevada: (1) what information will be gained with radio collars beyond what has

been obtained without them and (2) what tradeoffs may occur in terms of potential adverse

behavioral or other effects on the bighorn sheep. The recovery of these bighorn sheep will

require many to be captured and moved to new locations. If capture efforts result in

undesirable changes in habitat use patterns of the bighorn sheep and make future captures

more difficult, it may be preferable to limit capture efforts to the extent possible to

translocations.

Genotyping from Feces

Genotyping bighorn sheep from DNA extracted from fecal samples (Taberlet et al.

1996, 1997, 1999) is the most promising tool to help assess how many individuals are not

accounted for in minimum counts. This procedure can be carried out in conjunction with

studies of genetic variation. Sampling can be done in conjunction with field work to develop

minimum population values. When field evidence of bighorn sheep is found that is thought

to be from individuals not yet seen, this hypothesis can be tested via analysis of fecal

samples from those individuals and the ones already seen. There are also sex-specific genes

that can be used to determine the sex of the animal from which the sample originated. 

Because of the major expense of lab work, this approach is currently most appropriate for
129

small herds that are difficult to census directly. As this technology develops further it may

have more applications and prove to be an integral part of monitoring these bighorn sheep.

Frequency of Monitoring

A. Herds considered potential sources of translocation stock. Monitor minimum

numbers of females, yearlings, and lambs yearly to provide data on recruitment and

herd size. Any population to be used as translocation stock will undoubtedly make

concentrated use of low elevation winter habitat where the best population data will

probably be obtained. Data on population parameters should be developed on winter

ranges unless opportunities for better data occur in a different season. Attempt to

develop data on the number of males, including age distribution, every 1-2 years.

B. Herds not used as translocation stock containing 1-15 females. Gather yearly

data on size and recruitment for each female group. Attempt to count males every 2-

3 years.

C. Herds not used as translocation stock containing 15-25 females. Attempt to

assess size and recruitment every 1-2 years for each female group. Count males

every 2-4 years if possible.

D. Herds not used as translocation stock containing more than 25 females.

Attempt to assess size and recruitment every 2-3 years for each female group and

every 3-5 years for males if possible until delisting. After delisting, attempt to

develop population data every 5 years or more often if severe environmental

conditions occur (e.g. a very severe winter) that raise concerns for the welfare of the

bighorn sheep.
130

Literature Cited

Bailey, N. T. 1951. On estimating the size of mobile populations from recapture data. 

Biometrika 38:293-306.

Brown, L. M., and R. R. Ramey II. 1987. The results of the Mount Langley bighorn sheep

census, summer 1987. Report to Inyo National Forest, Bishop, CA. 12 pp.

Caughley, G. 1977. Analysis of vertebrate populations. John Wiley and Sons, New York.

Chang, K. D. 1993. Report on the status of the Lee Vining Canyon bighorn sheep

reintroduction, summer 1993. Unpublished Report, Yosemite Nat. Park. 10 pp.

Chapman, D. G. 1951. Some properties of the hypergeometric distribution with application

to zoological sample censuses. University of California, Press. Stat. 1:131-160.

Hammet, L., and S. C. Thompson. 1992. Report on the status of the Lee Vining Canyon

bighorn sheep reintroduction. Unpublished report, Yosemite Nat. Park.

Jensen, M. 1994. Report on the status of the Lee Vining Canyon bighorn sheep

reintroduction, summer 1994. Unpublished report, Yosemite Nat. Park. 8 pp.

Magnusson, W. E., G. J. Caughley, and G. C. Grigg. 1978. A double-survey estimate of

population size from incomplete counts. J. Wildl. Manage. 42:174-176.

Neal, A. K., G. C. White, R. B. Gill, D. F. Reed, and J. H. Olterman. 1993. Evaluation of

mark-resight assumptions for estimating mountain sheep numbers. J. Wildl.

Manage. 57:436-450.

Taberlet, P., S. Griffin, B. Goossens, S. Questiau, V. Manceau, N. Escaravage, L. P. Waits,

and J. Bouvet. 1996. Reliable genotyping of samples with very low DNA quantities

using PCR. Nucleic Acids Research 24(16):3189-3194.

Taberlet, P., J. J. Camarra, S. Griffin, E. Uhres, O. Hanotte, L. P. Waits, C. Dubois-Paganon,

T. Burke, and J. Bouvet. 1997. Noninvasive genetic tracking of the endangered

Pyrenean brown bear population. Molec. Ecology. 6: 869-876.
131

Taberlet, P., L. P. Waits, and G. Luikart. 1999. Noninvasive genetic sampling: look before

you leap. Trends in Ecology and Evolution 14:323-327.

Wehausen, J. D. 1981. The Mount Baxter bighorn herd: past and future censuses. 

Unpublished report. 8pp.

Wehausen, J. D. 1982. 1982 Mount Baxter herd census. Unpublished report. 7 pp.

Wehausen, J. D. 1983. Sierra Nevada bighorn herds: 1983 status. Unpublished report.

18 pp.

Wehausen, J. D. 1987. Mount Baxter bighorn population: 1987 Status. Unpublished

report. 8 pp.

Wehausen, J.D. 1992. The role of precipitation and temperature in the winter range diet

quality of mountain sheep of the Mount Baxter herd, Sierra Nevada. Bienn. Symp.

North. Wild Sheep and Goat Counc. 8:279-292.

 

Wehausen, J. D. 1996. Effects of mountain lion predation on bighorn sheep in the Sierra

Nevada and Granite Mountains of California. Wildlife Soc. Bull. 24:471-479.

Wehausen, J. D. 1999. Sierra Nevada bighorn sheep: 1999 population status. Unpublished

report. University of California, White Mountain Research Station, Bishop, CA.

Wehausen, J. D., and K. D. Chang. 1995. 1995 status of three bighorn sheep populations in

the Sierra Nevada. Sierra Nevada Bighorn Sheep Foundation Tech. Report No. 1.

Wehausen, J. D., and K. D. Chang. 1997. Sierra Nevada bighorn sheep: 1995-97 status.

Sierra Nevada Bighorn Sheep Foundation Tech. Report No. 2.

Wehausen, J. D., and K. D. Chang. 1998. Sierra Nevada bighorn sheep: 1998 survey

results. Sierra Nevada Bighorn Sheep Foundation Tech. Report No. 3.
132

APPENDIX E. CONSIDERATIONS FOR A PREDATOR MANAGEMENT

PLAN

Predators are an integral ecological component of the community occupied by Sierra

Nevada bighorn sheep. Sierra Nevada bighorn sheep will not be recovered until population

objectives are attained, at which point Sierra Nevada bighorn sheep will be able to withstand

naturally occurring predation without intervention. Coyotes and bobcats are known to prey

on bighorn sheep; however, mountain lions, because of their larger size, are better adapted to

kill larger prey, such as deer and bighorn sheep. Predation is a natural component of the

system. But predation, like disease, represents another vehicle of bighorn sheep mortality,

and all mortality must be minimized until full recovery is attained. The goal of the predator

management plan is to temporarily protect bighorn sheep from adverse effects of predators

while preserving an intact ecosystem.

A predator management plan (Task 2.1) should be prepared that ties together the

multiple tasks concerning predators called for in section II.D of this recovery plan and lays

out specifics of how they will be accomplished and when they will be ended. These tasks

include monitoring, research, and selective, humane predator removal where needed. Of

potential predators, mountain lions have been implicated as the primary predator of Sierra

Nevada bighorn sheep, and they may affect population dynamics of those bighorn sheep

through direct losses or by influencing habitat selection by the bighorn sheep. Below is a

brief discussion of some of the elements that should be included in this plan.

1. Experimental approaches in an ecosystem context.

The primary objective of the predator management plan should be to protect small

herds of bighorn sheep to prevent further extirpations and to restore populations to a level at

which the natural predator-prey interactions can be allowed to occur without human

intervention. Predators, and their potential direct and indirect effects on these bighorn sheep,

are part of the ecosystem inhabited by these bighorn sheep, and management of predators

needs to recognize the role of these species in an ecological system. 

The one sure way of protecting endangered Sierra Nevada bighorn sheep from the

potential negative effects of predation would involve long-term, indiscriminate removal of

predators in the vicinity of bighorn sheep herds. There is little question that such a control
133

program would also result in the unnecessary removal of some predators that had little or no

influence on the population dynamics of bighorn sheep. Further, such a program would

undoubtedly have unforeseen effects on other aspects of the ecosystem that might ultimately

negatively affect bighorn sheep. Therefore, this approach is undesirable in that it has

unacceptable consequences.

Finding a balance in which the minimum of predator management is practiced will

take creative and experimental approaches. Management prescriptions will evolve as they

are tried and evaluated and conditions change. Balanced predator management will entail

using different approaches for different bighorn sheep herds and will take into account the

vulnerability of each herd to extirpation. Finding the optimal prescription(s) for minimal

predator management while still recovering bighorn sheep will entail risk to some individual

bighorn sheep. At the same time, though, those risks will be allowed only where the bighorn

herds are large enough to be able to withstand such a loss.

2. Protection of bighorn sheep translocation stock.

The ultimate success of population recovery hinges on the development and use of

sources of translocation stock. Past reintroduction efforts occurred only because of the prior

size and productivity of the Mount Baxter and Sawmill Canyon herds. The decline and

inability of those herds to serve as further sources of translocation stock was associated with

widespread changes in winter habitat use patterns that Wehausen (1996) suggested were

linked to increased predation pressure from mountain lions during the 1980's. Predation

pressure from mountain lions that developed in the 1980's may have been exceptional, and

differed substantially from the current situation of lower lion densities. Nevertheless, the

predator management plan should address how herds serving as sources of translocation

stock might be treated, given their key role in the recovery of these bighorn sheep.

3. Protection of translocated bighorn sheep.

Bighorn sheep may be translocated to augment existing herds or to create new ones. 

Translocation stock has been, and will likely continue to be, a rare and precious resource. 

The predator management plan needs to address questions of how translocated bighorn

sheep will be treated relative to predators compared with other herds, and why. Among the

tasks to be considered will be investigations of potential predator conflicts at sites considered
134

for reintroductions (Task 6.5). Results of such investigations may influence decisions on

where available translocation stock will be used. For instance, reintroduction sites that have

higher potentials for predator problems may be a lower priority for translocation projects. 

Those areas may be stocked later when, presumably, greater numbers of bighorn sheep will

be available and that will allow larger initial releases to compensate for potential losses to

predators.

4. Monitoring of mountain lions in the vicinity of winter ranges (Task 5.2).

 It is well known that mountain lions vary in their behavior toward different prey

species. Research in Canada, New Mexico, and California (Ross et al. 1997, K. Logan and

L. Sweanor 2001, H. Ernest, unpubl.data) indicates that one or a small number of individual

mountain lions often are responsible for a disproportionate number of bighorn sheep kills. 

Radio-collaring of lions in the vicinity of winter ranges will allow the details of habitat use

patterns to be elucidated, thereby identifying potential problem animals.

In the Sierra Nevada, mountain lions range long distances as a response to the

availability of prey (Pierce et al. 1999). Radio-collaring lions will allow predator

management teams to monitor their locations precisely in relation to areas used by bighorn

sheep. Although physical evidence of the presence of mountain lions is important when

evaluating degree of threat to bighorn sheep, tracks of individual lions are not always

distinguishable from each other (Grigione et al. 1999). Collared lions will remove most

guesswork in reading sign (i.e., distinguishing individual lions via track measurements),

provide more reliable data on which lions are of concern, and allow predator management

specialists to be most efficient in the use of their time. In the absence of the use of radio

collars on lions, efforts to protect bighorn sheep in the Sierra Nevada will likely result in the

deaths of some lions that might have been spared if telemetry data were available. It is

possible to collar most lions near bighorn sheep winter ranges, but it is unlikely that more

than a small proportion of the bighorn sheep population can be collared. Monitoring of

collared lions can provide considerable data regarding bighorn sheep and predator dynamics. 

The success of this approach ultimately will lie with the schedule of monitoring of collared

and uncollared lions in conjunction with monitoring of populations of bighorn sheep.

Through the collaring of mountain lions, detailed information also can be gathered

on lion population dynamics, allowing assessment of the impacts of removals of mountain
135

lions on their populations and, thereby, helping to put recovery efforts for these sheep in a

larger ecosystem context.

5. Attempting to alter habitat use patterns of mountain lions on bighorn sheep winter ranges

by aversive conditioning (Task 6.4).

Aversive conditioning has not been attempted before with mountain lions. It is a

potentially useful tool that, if successful, could afford a reduction of mortality for both Sierra

Nevada bighorn sheep and mountain lions. Experiments should be carried out when and/or

where they do not jeopardize bighorn sheep. To be effective, these efforts will need to occur

during fall and early winter, prior to the usual appearance of bighorn sheep on winter ranges. 

These experiments will require the development of data on activity patterns of the subject

mountain lions that will allow an adequate evaluation of the effectiveness of this

intervention.

6. Development of long-term data to elucidate predator-prey dynamics of this ecosystem as

they affect bighorn sheep (Task 6.7).

The predator-prey situation that unfolded in the eastern Sierra Nevada during the

1980's was unexpected and is not sufficiently understood. Those dynamics are not likely to

be adequately explained unless similar circumstances recur and key elements are monitored

over many years. Of primary interest will be the dynamics of deer herds, which are the

primary prey of mountain lions, and the distributions and densities of which are important

factors determining the abundance of lions (Pierce et al. 2000). Monitoring of

mesopredators, such as coyote or bobcat, to ascertain population fluctuations relative to

mountain lion populations should also be considered. Careful monitoring of key elements of

this ecosystem will help elucidate whether the events of the past two decades were simply

part of a cyclical phenomenon, or whether these events constitute an exceptional

circumstance that is not likely to be repeated; in either situation, however, future efforts to

conserve wild sheep will be enhanced through the acquisition of such knowledge.
136

Literature Cited

Grigione, M. M., P. Burman, V. C. Bleich, and B. M. Pierce. 1999. Identifying individual

mountain lions (Felis concolor) by their tracks: refinement of an innovative

technique. Biological Conservation 88:25-32.

Logan, K., and L. Sweanor. 2001. Desert Puma. Island Press, Covelo, CA. 390pp. 

Pierce, B. M., V. C. Bleich, and R. T. Bowyer. 2000. Social organization of mountain lions:

does a land-tenure system regulate population size? Ecology 81:1533-1543.

Pierce, B. M., V. C. Bleich, J. D. Wehausen, and R. T. Bowyer. 1999. Migratory patterns of

mountain lions: implications for social regulation and conservation. Journal of

Mammalogy 80:986-992.

Ross, P. I., M. G. Jalkotzy, and M. Festa-Bianchet. 1997. Cougar predation on bighorn

sheep in southwestern Alberta during winter. Can. J. Zool. 74:771-775.

Wehausen, J. D. 1996. Effects of mountain lion predation on bighorn sheep in the Sierra

Nevada and Granite Mountains of California. Wildlife Society Bulletin 24:471-479.
137

APPENDIX F. PUBLIC INFORMATION AND OUTREACH PLAN

Abstract

The Sierra Nevada bighorn sheep Public Information and Outreach Program is based

on the overarching principle that understanding and appreciation of the natural history and

ecology of the Sierra Nevada bighorn sheep and concern for its future are vital to building

public support for conservation measures and recovery actions. A number of recovery

actions will directly affect the public using the eastern Sierra Nevada. Conversely, human

activities may affect recovery. Knowing how Sierra Nevada bighorn sheep live and survive

and the threats they face will help people understand the need for regulatory actions. 

Delegating Public Information and Outreach Plan responsibilities to one agency and

one or two individuals within that agency will eliminate confusion and ensure that a uniform

and timely message gets out to the public.

An initial survey to assess the present level of public understanding of Sierra Nevada

bighorn sheep and the situation threatening the survival of the species can be used as a tool

to create the most effective public information and outreach program. The survey data will

be used to establish and prioritize the steps that are needed to inform the public and build

support. The program will not only seek to build an appreciation and understanding of the

species, but also to make the public aware that the Sierra Nevada bighorn sheep recovery

effort is a collaborative effort supported by multiple agencies, organizations, and individuals. 

A second survey will be taken 1 year later and compared to the initial survey in order

to measure the success of the program and to identify areas where the program needs to be

strengthened or otherwise modified. 

Certain information projects should be initiated concurrently with the activities to

design a Sierra Nevada bighorn sheep Public Information and Outreach Program. The

public needs to be made aware as soon as possible about required actions and restrictions

while in Sierra Nevada bighorn sheep habitat. The recovery plan will also be released to the

public, and wide distribution should be ensured. Funding to support future programs and

broadened public information campaigns should be sought.
138

1. INCREASING AWARENESS

Using Understanding as a Foundation for Support

The public needs to have a foundation upon which to build concern for the situation

facing the Sierra Nevada bighorn sheep and an interest in its recovery. The words

"endangered species" frequently carry a negative connotation for a significant segment of the

public. In the absence of more information, the public may interpret the words to mean that

a rather hopeless situation exists that will limit human activities in order to save a remote

species of unknown importance. The Public Information and Outreach Plan should provide

information about the unique qualities of the Sierra Nevada bighorn sheep, its historic

significance to American Indians, its decline with the settlement of the west, its ecology, and

its natural history. This information will offer the public an alternative picture to

conceptualize when hearing about the Sierra Nevada bighorn sheep, the threats to the

survival of the species, and the recovery program underway.

Assigning Program Duties

To be optimally effective, an information campaign needs to be coordinated,

accurate, timely, and consistent in the message it delivers. Deliberate steps need to be taken

to ensure that a uniform message reaches the public. Numerous agencies have been and will

continue to be involved in the recovery efforts. The responsibility for overseeing the Sierra

Nevada bighorn sheep Public Information and Outreach Program should be delegated to one

agency or organization and a single or small number or persons within the organization. 

Restricting oversight of outreach efforts will ensure that a consistent message is delivered to

both the public and agency personnel who are not directly involved in the recovery effort. It

will also ensure that a message is getting out to the public, rather than setting up a situation

that could lead to misunderstandings and confusion about which agency is undertaking a

given information or outreach activity. Finally, it will provide some assurance that the

importance of communicating with the public and building public support will not be

forgotten or minimized amid the urgent and intriguing biological questions attendant to the

recovery of Sierra Nevada bighorn sheep. 
139

2. DESIGNING A PUBLIC INFORMATION AND OUTREACH PLAN

Objectively Assessing Current Public Perceptions

An objective assessment of current public knowledge and attitudes toward the Sierra

Nevada bighorn sheep needs to be made. Identifying the target audience and a baseline use

of Sierra Nevada bighorn sheep habitat, key messages, and methods for disseminating

information can all be achieved through the use of a survey. The survey should be

conducted similarly to the effort currently underway for Peninsular bighorn sheep and could

be conducted by one of the partner agencies or a university.

Surveying for Target Audiences

The survey will be used to identify target audiences. Recreationists, commercial

packers, local residents, range allotment permittees, and domestic sheep and or goat owners

all conduct activities that take place in or near Sierra Nevada bighorn sheep habitat. Other

target audiences would need to be identified as part of the process of determining how

people receive their information (see Methods of Disseminating Information below). The

identification of target audiences would include information about how these individuals and

businesses use Sierra Nevada bighorn sheep habitat and important surroundings areas.

Defining and Prioritizing Key Messages

The survey will establish public knowledge of the natural history and ecology of

Sierra Nevada bighorn sheep. It will also provide insight into the public perception of the

threats to Sierra Nevada bighorn sheep and the seriousness of the situation, as well as

attitudes about conservation efforts related to Sierra Nevada bighorn sheep. The data, in

turn, will provide direction for defining key messages. Specific information should include:

an overview of the ecology of Sierra Nevada bighorn sheep, current threats to population

viability, and recovery actions; effects of mountain lion predation on recovery of Sierra

Nevada bighorn sheep and the larger role of predators in ecosystems; threats to Sierra

Nevada bighorn sheep due to disease transmission from domestic sheep and goats; threats to

bighorn sheep recovery from domestic dogs in bighorn sheep habitat; threats to bighorn

sheep from disturbance by human recreational activities; actions needed to achieve recovery

objectives; and opportunities to learn more about Sierra Nevada bighorn sheep. This
140

approach will encourage the full spectrum of business people, recreationists, students,

seniors, and local residents to behave in ways that promote the recovery of Sierra Nevada

bighorn sheep populations. 

Disseminating Information

The survey will provide data that identify the most effective means of conveying

information. The survey could query individuals about how they receive their information

and which media outreach efforts could then be channeled through the media that are most

effective at delivering the message. The survey will also be used to identify other target

audiences, including opinion leaders such as local elected officials and national and local

media. The means and methods of distributing information include but are not limited to:

printed material (press releases, handouts, brochures, newspaper articles, signage); electronic

media (radio and television interviews, public service announcements, web sites); person to

person delivery (presentations for service organizations, elected officials, as well as school

programs and field trips, interpretive programs, campfire talks); and the merchandising of

consumer goods with an educational theme (t-shirts, posters, postcards, notepaper). The

information should be updated regularly and kept current regarding the status of Sierra

Nevada bighorn sheep and recovery actions.

Distributing Information

Identifying the most effective method of message delivery would also guide the

identification and prioritization of points of distribution. Printed matter could be distributed

at a variety of locations, including visitor’s centers, agency offices, chambers of commerce,

web sites, email, and conventional mail. Links to a single web site would assure that the

information is up-to-date and would eliminate duplicative efforts. 

Information should be specifically distributed to members of the general public that

are directly affected by recovery actions, such as hikers, ranchers, ranchette owners with

domestic sheep or goats, commercial packers, and off-road vehicle users.
141

3. ASSESSING THE EFFECTIVENESS OF AND MODIFYING THE PLAN

Second Survey

Approximately 1 year after the initial survey is undertaken and a formal Sierra

Nevada bighorn sheep Public Information and Outreach campaign is launched, a second

survey should be undertaken. Comparisons of the results with the initial survey would

provide the basis for modifying the information and outreach efforts.

Stakeholder and Recovery Team Meeting

A meeting of the Recovery Plan Team and Stakeholders Group should be convened

to critique the Sierra Nevada bighorn sheep Public Information and Outreach Plan. 

Broadening the outreach should also be considered. Interviews on national radio and

television should be considered to maximize the number of people reached. Videotapes or

audio tapes of the programs could be used as tools for further outreach. 

4. USING CONCURRENT INFORMATION PROJECTS

Disseminating Information on Multiple Fronts

Certain information projects should be initiated concurrently with the activities to

design a Sierra Nevada bighorn sheep Public Information and Outreach Program. The

public needs to be made aware as soon as possible about required actions and restrictions

while in Sierra Nevada bighorn sheep habitat. The recovery plan will also be released to the

public, and broad distribution should be ensured. Existing outreach programs need to be

updated to incorporate the most current information.

During implementation of recovery efforts, the public should be fully informed as

early as possible regarding actions required or restricted while in Sierra Nevada bighorn

sheep habitat. For example, signs or flyers explaining trail closures (in such places as the

Zoological Area) or restrictions (such as areas where dogs or pack goats are not allowed)

should be located so that users are aware of these restrictions while planning their trip and/or

when they are still able to modify their visit. 
142

Affected members of the public should be contacted in other ways, such as through

presentations to commercial packers or campers. Information regarding restrictions and 

requirements while in Sierra Nevada bighorn sheep habitat should also be included in

sources of information that attract visitors to the area, such as commercial advertising,

chamber of commerce publications, and web sites.

A master calendar that lists all specific recovery actions requiring public

involvement should be developed (such as seasonal trail closures). This calendar should

indicate the dates that publicity should begin, as well as the outreach message and method. 

Distributing the Recovery Plan

The final recovery plan, along with a cover letter, should be widely distributed to

affected and interested people, including hikers and other recreationists, ranchers, ranchette

owners with domestic sheep or goats, commercial packers, environmental groups, mountain

lion and bighorn sheep advocacy groups, and affected local, State and Federal agencies. 

Distribution of the recovery plan can be facilitated through the Recovery Plan Stakeholders

Working Group. At a minimum, recovery plans should be distributed to everyone on our

mailing list of people interested in the Endangered Species Act listing of Sierra Nevada

bighorn sheep as well as the local news media.

Updating and Coordinating Existing Informational and Outreach Programs

There is an immediate need to update existing programs to provide an accurate view

of our current knowledge regarding Sierra Nevada bighorn sheep. Information should strive

to highlight not only each agency’s or organization's contributions to the recovery of Sierra

Nevada bighorn sheep, but how these activities complement those of other agencies and

organizations. 

The bighorn sheep exhibit at the Mono Basin Scenic Area Visitor's Center should be

updated and upgraded. 

The California Watchable Wildlife Viewing Guide site at Lee Vining/Tioga Lake

should include interpretive information on bighorn sheep.
143

National Park Service, U.S. Forest Service, Bureau of Land Management, and

California Department of Fish and Game interpretive talks at visitor centers and

campgrounds should include segments on bighorn sheep.

Using Educational Programs for Students

If an educational program targeting local schools is developed, the goals of the

program should be for students to: understand the ecology of Sierra Nevada bighorn sheep;

develop a respect, appreciation and concern for this species; become aware of the threats

this species is currently facing and how recovery actions will reduce these threats;

understand the role of Sierra Nevada bighorn sheep within the ecosystem and the value of

bighorn sheep recovery to the ecosystem; become aware of specific actions they must take

while in Sierra Nevada bighorn sheep habitat and why they are important to recovery; and

become aware that the Sierra Nevada bighorn sheep recovery effort is a collaborative effort

supported by multiple agencies, organizations, and individuals.

Existing bighorn sheep curricula should be reviewed and modified as needed to be 

applicable to Sierra Nevada bighorn sheep. Existing activities or curricula include: 

! "Murder Ewe Wrote" (level: Grades 6-8) 

(http://www.sd5.k12.mt.us/glaciereft/wild8-12.htm)

! “Bringing bighorn into the classroom” (Cunningham, S. C. 1993. Desert

Bighorn Council Trans. 37:33-36).

In addition, a variety of educational materials on bighorn sheep exist that target

school-aged children and could be incorporated into a Sierra Nevada bighorn sheep

curriculum. They could be incorporated as is or modified to be made specific to Sierra

Nevada bighorn sheep. These materials include:

! National Bighorn Sheep Center's Traveling Trunk Exhibit

(http://www.bighorn.org/exhibit.html)

! National Bighorn Sheep Center's A Year in the Life of the Whiskey Creek

Bighorn Sheep (Level: Grade 6)

(http://www.bighorn.org/Exhibit.html)
144

! Foundation for North American Wild Sheep's Wild Sheep Journal

5. IDENTIFYING FUNDING AND PARTNERSHIPS TO SUSTAIN SIERRA NEVADA

BIGHORN SHEEP PUBLIC INFORMATION AND OUTREACH PROGRAMS

Finding New Partners and New Funding 

An effort should be made to identify new partners in the Sierra Nevada bighorn

sheep Public Information and Outreach Plan such as the Paiute Shoshone Tribes, The

Independence Civic Club, the Yosemite Association, and others. Funding to support future

programs and broaden public outreach campaigns should be sought. In addition to grants, a

partnership with the Eastern Sierra Interpretive Association might be explored. As referred

to in section 2 above, marketing t-shirts, posters, and other informational consumer goods

would not only raise awareness about the Sierra Nevada bighorn sheep program but could

also provide a source of income to sustain or augment the program. 

Conclusion

An effective Sierra Nevada bighorn sheep Public Information and Outreach Plan will

enhance the success of recovery efforts for the Sierra Nevada bighorn sheep. The program

needs to celebrate the uniqueness and majesty of the species along with delivering a message

about the threats facing the Sierra Nevada bighorn sheep and how recovery efforts are

addressing those threats. With opportunities for innovative partnerships, the Sierra Nevada

bighorn sheep campaign can be the source of regional pride not only for residents of the

eastern Sierra Nevada but also the agencies that are collaborating on the recovery plan.
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APPENDIX G. SUMMARY OF THREATS AND RECOMMENDED

RECOVERY ACTIONS

LISTING

FACTOR

THREAT RECOVERY

CRITERIA

TASK NUMBERS

A Habitat loss [considered a

minor threat]

B3 1.1, 1.2, 6.2

B Hunting [historical in 19th

century; not currently

considered a substantial

threat]

N/A N/A

C Disease (pneumonia and

other epizootics contracted

from domestic sheep)

A2 2.3.1, 2.3.2, 5.4, 6.5, 7.1, 7.2, 7.3

C Disease (lungworm

infestation) [considered a

minor threat]

B3 5.4

C Direct mortality from

predation (by mountain lions

and other predators)

A1, B1 2.1, 5.2, 6.4, 6.5, 6.7, 7.1, 7.2, 7.3

C

Reduced nutritional condition

and lamb survival due to use

of poor-quality winter range

at high elevations, perhaps

indirectly resulting from

excessive predation 

A1, B1 2.1, 2.2.1, 2.2.2, 2.2.3, 5.1, 5.2, 5.3, 6.2, 6.4, 6.5,

6.6, 6.7, 7.1, 7.2, 7.3

D Limited effectiveness of

management by State and

Federal agencies

B3 1.2, 2.3.1, 2.3.2, 7.1, 7.2, 7.3, 8

E Random variation in

population characteristics

(e.g., sex ratio) due to small

population size

A1, B1, B2 2.2.2, 3.1, 3.2.1, 3.2.2, 5.1, 6.5, 6.6

E Loss of genetic variability

due to small population size

A1, B1, B2 2.2.2, 3.1, 3.2.1, 3.2.2, 4, 5.1, 6.1, 6.5, 6.6
LISTING

FACTOR

THREAT RECOVERY

CRITERIA

TASK NUMBERS

146

E Increased vulnerability to

naturally occurring

environmental events

(avalanches, prolonged or

severe winters) due to small

population size

A1, B1, B2 2.2.2, 3.1, 3.2.1, 3.2.2, 5.1, 6.5, 6.6

E Competition with elk or deer

for winter range resources

[considered a minor threat]

B3 6.7

E Disturbance from

recreational use [not currently

considered a substantial

threat; may be reevaluated if

warranted in future]†

B3 1.2, 2.4.1, 2.4.2, 6.3, 7.1, 7.2, 7.3

E Mortality from automobile

strikes

B3 7.3

E Vegetation succession

decreasing openness in

habitat†

B3 1.2, 2.2.3, 5.3, 6.2

E Broad environmental factors

(climate change, acid rain,

mining wastes)[potential

threat, needs research]†

B3 1.2, 6.8

† Not identified as a threat in the original listing rule.

Listing Factors: 

A. The Present or Threatened Destruction, Modification, or Curtailment Of Its Habitat or Range 

B. Overutilization for Commercial, Recreational, Scientific, Educational Purposes (not a factor)

C. Disease or Predation 

D. The Inadequacy of Existing Regulatory Mechanisms 

E. Other Natural or Manmade Factors Affecting Its Continued Existence

Recovery Criteria

Downlisting

A1: A minimum total of 365 females at least 1 year of age, distributed among the Kern (50), Southern (175),

Central (75), and Northern (65) Recovery Units.

A2: Threat of domestic goats and sheep contacting bighorn sheep is eliminated.
147

Delisting

B1: Downlisting population levels maintained for 6 years without intervention.

B2: Bighorn sheep of both sexes present in 14 herd units, distributed among the Kern (2), Southern (6), Central (3),

and Northern (3) Recovery Units.