General Distribution
Peninsular bighorn sheep occur in the Peninsular Mountain Ranges of southern California from the San
Jacinto Mountains in Riverside County south to the desert ranges of Anza-Borrego Desert State Park and
Baja California (U.S. Fish and Wildlife Service 1998). Peninsular bighorn sheep populations in
California currently consist of eight distinct subpopulations that occur in the San Jacinto Mountains, the
northern and southern Santa Rosa Mountains, Coyote Canyon, the northern and southern San Ysidro
Mountains, the Vallecito Mountains, and Carrizo Canyon (U.S. Fish and Wildlife Service 1998).
The Peninsular Ranges' metapopulation is composed of eight distinct populations (Boyce 1995). Three
of the eight ewe groups occur within the area of the San Jacinto Mountains and northern and southern
Santa Rosa Mountains (Stephenson and Calcarone 1999, U.S. Fish and Wildlife Service 2000).
Most of the habitat available to peninsular bighorn sheep outside National Forest System lands in
southern California occurs on state park lands (41 percent) and Bureau of Land Management lands (29
percent). Additionally, some private land contains important lambing habitat for this taxon (Stephenson
and Calcarone 1999). Systematics
There were previously four recognized subspecies of bighorn sheep collectively designated as desert
bighorn sheep: Nelson's bighorn sheep (O. c. nelsoni), Mexican bighorn sheep (O. c. mexicana),
peninsular bighorn sheep (O. c. cremnobates), and Weems bighorn sheep (O. c. weemsi) (Manville
1980). However, these subspecific classifications have been challenged on the basis of morphometric
and genetic analysis. Wehausen and Ramey (1993) placed the peninsular subspecies with the Nelson
subspecies; this is the currently recognized taxonomy (U.S. Fish and Wildlife Service 2000a).
Nevertheless, peninsular bighorn sheep is considered a Distinct Population Segment under the federal
Endangered Species Act because the population is geographically separated from all other populations
of desert bighorn sheep. Habitat Requirements
Peninsular bighorn sheep are able to exist in areas of extreme environmental conditions where average
annual precipitation is less than 4 inches (10 centimeters) and summer season daily temperatures
average 104 ° F (40 ° C). As a result, distribution of individuals during dry periods is largely influenced
by the availability of water (U.S. Fish and Wildlife Service 2000b).
Within its range, peninsular bighorn sheep occurs along a narrow band of habitat that varies in elevation
from below 3,600 feet (1,100 meters) in the northern portion of the range to an elevation of 4,000–5,000
feet (1,219–1,524 meters) in the southern portion of the range.
Mountain slope and canyon bottoms are the two general habitats utilized by peninsular bighorn sheep.
Mountain slopes provide peninsular bighorn sheep with escape, thermal, and lambing habitat, while
canyon bottoms provide travel corridors, seasonal forage, and sources of water (Welles and Welles
1961). Escape cover consists of precipitous cliffs and steep slopes. Lambing areas are associated with
ridge benches or canyon rims adjacent to escape cover. Peninsular bighorn sheep often use canyon
bottoms, specifically washes and alluvial fans, as travel corridors linking geographically separate areas
(Cochran and Smith 1983). Canyon bottoms provide sources of water that can be critical to the survival
of peninsular bighorn sheep (U.S. Fish and Wildlife Service 2000a).
Vegetation associated with peninsular bighorn sheep habitat includes brittlebush, desert lavender, cholla,
burrow-weed, creosote, and other creosote associations (U.S. Fish and Wildlife Service 2000b). Reproduction
The breeding season of peninsular bighorn sheep begins with the rutting season, which occurs in the fall
(generally in November). Ewes have a gestation period of six months and give birth to a single lamb
(occasionally twins) from late April through early July. During the first few weeks after giving birth,
ewes occupy steep terrain and live solitarily with lambs until the two join a nursery group. Lambs are
weaned at 1–7 months, and juveniles remain with ewes until reaching sexual maturity (U.S. Fish and
Wildlife Service 2000b). Rams are believed to be sexually mature at 6 months of age (U.S. Fish and
Wildlife Service 2000a). Daily/Seasonal Activity
Peninsular bighorn sheep are diurnal and exhibit daily patterns of feeding and resting (Jones and Gard
1957). In general, bighorns feed in the early morning, at midday, and in the evening, lying down and
chewing their cud at other times and bedding down for the evening. Foraging and bedding spots may be
used for years (McMahon 1985). Daily foraging and resting cycles also vary depending on forage
quality (U.S. Fish and Wildlife Service 2000a).?Seasonal activity depends on availability of water, forage, and escape cover. Peninsular bighorn sheep
typically congregate near dependable water sources from May through October, when temperatures are
highest. Young peninsular bighorn sheep learn locations of escape terrain, water sources, and lambing
habitat from older individuals in the group (U.S. Fish and Wildlife Service 2000b).
From birth, ewes remain together in "ewe groups." Their gregarious and philopatric behavior limits their
dispersal. The most extensive recorded movement of a ewe was 18.6 miles (30 kilometers), when a
radio-collared ewe temporarily joined a second ewe group. However, genetic data suggest that
movement of ewes among groups, while rare, has occurred in the evolutionary past (U.S. Fish and
Wildlife Service 2000a).
Young rams, upon reaching sexual maturity (6 months–2 years), follow older rams away from their birth
group during the rut, returning only when the breeding period is over. Genetic and observational data
suggest that ram movements among ewe groups are common (U.S. Fish and Wildlife Service 2000a). Diet and Foraging
Peninsular bighorn sheep are grazers that occasionally browse on woody vegetation when nutritious
forms are available. Variations in dietary composition depend on time of year. One study determined
that the peninsular bighorn sheep diet consisted of 57 percent shrubs, 32 percent herbaceous annuals and
perennials, 8 percent cacti, and 2 percent grasses (Cunningham 1982). Territoriality/Home Range
Young ewes learn home range boundaries from their mothers and/or older females and demonstrate a
high degree of philopatry to these traditional home ranges throughout their lives (Geist 1971). Rams do
not exhibit the same site fidelity as ewes and tend to move among ewe groups. Home ranges in one
study were found to average 9.8 square miles (25.5 square kilometers) and 7.8 square miles (20.1 square
kilometers) for rams and ewes, respectively (U.S. Fish and Wildlife Service 2000a). Predator-Prey Relations
Recently, mountain lion predation has become a threat to some ewe groups in the Peninsular Ranges.
Predation by other species (coyotes and bobcats) may also reduce lamb recruitment (U.S. Fish and
Wildlife Service 2000a). Literature Cited
Cochran, M.H.; Smith, E.L. 1983. Intermountain movements by a desert bighorn ram in western
Arizona. Desert Bighorn Council 1983 Transactions.
Cunningham, S.C. 1982. Aspects of ecology of peninsular bighorn sheep (Ovis Canadensis cremnobates)
in Carrizo Canyon California. Tempe: Arizona State University. M.S. thesis.
Geist, V. 1971. Mountain sheep–a study in behavior and evolution. Chicago: University of Chicago
Press.
Jones, F.L.; Flittner, G.; Gard, R. 1957. Report on a survey of bighorn sheep in the Santa Rosa
Mountains, Riverside County. California Fish and Game. 43(3): 170–191.
King, M.M.; Workman, G.W. 1986. Response of desert bighorn sheep to human harassment:
Management implications. Transaction 51st N.A. Wildlife and National Resource Conference.
Manville, R.H. 1980. The origin and relationships of American wild sheep. In: Monson, G.; Sumner, L.,
eds. The desert bighorn: Its life history, ecology, and management. Tucson: University of Arizona Press;
1-6.
McMahon, J.A. 1985. The Audubon Society nature guides: Deserts. New York: Alfred A Knopf.
Stephenson, J.R.; Calcarone, G.M. 1999. Southern California mountains and foothills assessment:
Habitat and species conservation issues. General Technical Report GTR-PSW-172. Albany, CA: Pacific
Southwest Research Station, Forest Service, U.S. Department of Agriculture.
U.S. Bureau of Land Management, USDA Forest Service, U.S. Fish and Wildlife Service, California
Department of Fish and Game, and California Department of Parks and Recreation. 1996. Peninsular
Ranges' bighorn sheep coordinated management plan – final draft. Unpublished report on file and the
San Bernardino National Forest, San Bernardino, CA.
USDA Forest Service. 2000. Southern California conservation strategy province consultation package.
Unpublished document submitted to the U.S. Fish and Wildlife Service. 15 December 2000.
U.S. Fish and Wildlife Service. 1998. Final rule: Endangered status for Peninsular bighorn sheep.
March 18, 1998. 63 Federal Register: 13134-13150.
U.S. Fish and Wildlife Service. 2000a. Recovery plan for bighorn sheep in the Peninsular Ranges,
California. Oct. 25, 2000. U.S. Fish and Wildlife Service, Portland, OR.
U.S. Fish and Wildlife Service. 2000b. High priority biological opinion on activities related to trails,
dispersed recreation, and developed recreation on the peninsular bighorn sheep.
U.S. Fish and Wildlife Service. 2001. Final rule to designate critical habitat for the peninsular bighorn
sheep distinct population segment. Feb 02, 2001. 66 Federal Register: 8649-8677.
Wehausen, J.D.; Ramey, R.R., II. 1993. A morphometric reevaluation of the peninsular bighorn
subspecies. Desert Bighorn Council Transactions 37: 1-10.
Welles, R.E.; Welles, F.B. 1961. The bighorn of Death Valley. U.S., National Park Service, Fauna Series
No. 6.
Information gathered from California DFG - California Interagency Wildlife Task Group
