Peninsular Bighorn Sheep
Peninsular Bighorn Sheep
|Listed||March 18, 1998|
|Description||Bighorn sheep with pale brown coat.|
|Habitat||Open slopes in hot and dry desert regions.|
|Food||Plants, pulp and fruit of cacti.|
|Reproduction||One lamb produced per year.|
|Threats||Effects of disease; low recruitment; habitat loss, degradation, and fragmentation; high rates of predation coinciding with low population numbers.|
The Ovis canadensis cremnobates (Peninsular bighorn sheep) is similar in appearance to other desert associated bighorn sheep. The species' pelage (coat) is pale brown, and its permanent horns, which become rough and scarred with age, vary in color from yellowish-brown to dark brown. The horns are massive and coiled in males; in females, they are smaller and not coiled. In comparison to other desert bighorn sheep, the Peninsular bighorn sheep is generally described as having paler coloration and larger and heavier horns that are moderately divergent at the base.
The bighorn sheep (Ovis canadensis ) is a large mammal (family Bovidae) originally described by Shaw in 1804. Several subspecies of bighorn sheep have been recognized on the basis of geography and differences in skull measurements. These sub-species of bighorn sheep include O. c. cremnobates (Peninsular bighorn sheep), O. c. nelsoni (Nelson bighorn sheep), O. c. mexicana (Mexican bighorn sheep), O. c. weemsi (Weems bighorn sheep), O. c. californiana (California bighorn sheep), and O. c. canadensis (Rocky Mountain bighorn sheep). However recent genetic studies question the validity of some of these subspecies and reveal the need to reevaluate bighorn sheep taxonomy.
From May through October, bighorn sheep are dependent on permanent sources of water and are more localized in distribution. Bighorn sheep populations aggregate during this period due to a combination of breeding activities and diminishing water sources. Summer concentration areas are associated primarily with dependable water sources, and ideally provide a diversity of vegetation to meet the sheep's forage requirements.
Bighorn sheep species are diurnal. Their daily activity pattern consists of feeding and resting periods that are not synchronous either within or between groups, as some sheep will be resting while others are feeding. Browse is the dominant food of desert-associated bighorn sheep. Plants consumed may include brittlebrush, mountain mahogony, Russian thistle, bursage, mesquite, palo verde, and coffeeberry. During the dry season, the pulp and fruits of various cacti are eaten. Native grasses are eaten throughout the year and are important food, especially near water holes.
Bighorn sheep species produce only one lamb per year. The gestation period is about five to six months. Lambing occurs between January and June, with most lambs being born between February and May. Lactating ewes and young lambs congregate near dependable water sources in the summer. Ewes and lambs frequently occupy steep terrain that provides a diversity of slopes and exposures for escape cover and shelter from excessive heat. Lambs are precocial and within a day or so climb as well as the ewes. Lambs are able to eat native grass within two weeks of their birth and are weaned between one and seven months of age. By their second spring, bighorn sheep lambs are independent of the ewes and, depending upon physical condition, may attain sexual maturity during the second year of life.
The Peninsular bighorn sheep occurs on open slopes in hot and dry desert regions where the land is rough, rocky, sparsely vegetated and characterized by steep slopes, canyons, and washes. Most of these sheep live between 300-4,000 ft (90-1,200 m) in elevation where average annual precipitation is less than 4 in (10 cm) and daily high temperatures average 104°F (40°C) in the summer. Caves and other forms of shelter (e.g., rock outcrops) are used during inclement weather. Lambing areas are associated with ridge benches or canyon rims adjacent to steep slopes or escarpments. Alluvial fan areas are also used for breeding and feeding activities.
Peninsular bighorn sheep are biologically and ecologically significant to the species in that they constitute one of the largest contiguous metapopulations (interaction between subpopulations) of desert bighorn sheep. The metapopulation spans approximately 100 mi (160 km) of contiguous suitable habitat in the United States. The loss of Peninsular bighorn sheep in the United States would isolate bighorn sheep populations in Mexico, including the Weems subspecies, from all other bighorn sheep, thereby producing a significant gap in the range of bighorn sheep. In addition, the Peninsular bighorn sheep occur in an area that has marked climatic and vegetational differences as compared to most other areas occupied by bighorn sheep. The majority of the range of the Peninsular bighorn sheep is classified as Colorado Desert, a subarea of the Sonoran Desert. This area experiences significantly different climatic variation (e.g., timing and/or intensity of rainfall) than the Mojave or other Sonoran deserts and contains a somewhat different flora. Though rainfall is greater in the higher mountains (e.g., San Jacintos), rainfall averages less than 5 in (13 cm) and snow is almost unknown in most of this area. It is important to note that the Peninsular bighorn sheep do not typically occur above 4,000 ft (1,200 m) in the higher mountains. This is unusual because bighorn sheep typically occupy higher elevation habitat that contains sparse vegetative cover. The low amount of rainfall, high evapotranspiration rate, and temperature regime in the majority of the Peninsular bighorn sheep's range is notably different from other North American deserts. The species' ability to exist under these conditions suggests unique behavioral and/or physiological adaptations.
Bighorn sheep are found along the Peninsular Mountain Ranges from the San Jacinto Mountains of southern California south into the Volcan Tres Virgenes Mountains near Santa Rosalia, Baja California, Mexico, a total distance of approximately 500 mi (800 km).
The Peninsular bighorn sheep in the United States declined from an estimated 1,171 individuals in 1971 to about 450-600 individuals in 1991. 1997 population estimates indicate continued decline, and Peninsular bighorn sheep in the United States now number approximately 280. The population of Peninsular bighorn sheep in the United States is currently divided among approximately eight ewe groups.
The range of this big horn sheep extends from the northern San Jacinto Mountains to the international border between the United States and Mexico. The range of Peninsular bighorn sheep in Mexico extends southward into the Volcan Tres Virgenes Mountains, located just north of Santa Rosalia, Baja California, Mexico.
The continuing decline of the Peninsular bighorn sheep is attributed to a combination of factors, including: (1) the effects of disease; (2) low recruitment; (3) habitat loss, degradation, and fragmentation; (4) and, more recently, high rates of predation coinciding with low population numbers, although the population had remained stable over the past seven years. The population in the United States has declined from an estimated 1,171 individuals in 1971 to approximately 280 in 1997.
Although data were not available to plot specific population trends for all portions of the Peninsular bighorn sheep range (such as that in Mexico), there is a marked difference in recent and historic population estimates. Based on these estimates, there appears to have been a decline in the number of Peninsular bighorn sheep in Baja California, Mexico. It is not surprising that Peninsular bighorn sheep have declined in Baja California, Mexico, given the presence of the same factors identified for the decline in the United States (e.g., introduced pathogens). Although there is no empirical evidence that active epizootics are occurring at this time, the same diseases that have been implicated in the mortality of Peninsular bighorn sheep in the Santa Rosa Mountains have been detected in Peninsular bighorn sheep within Anza Borrego State Park, and Baja California, Mexico. However, recent information provided by the Mexican government, regarding bighorn sheep found on the peninsula of Baja California, Mexico, supports the position that the Mexican population is not likely to be in danger of extirpation within the foreseeable future.
Urban development and associated increases in human activities in bighorn sheep habitat were reported to be the leading cause of extinction of an entire bighorn sheep population (ewes, rams, and lambs) in Tucson, Arizona. In the River Mountains, Nevada, nine of 17 marked desert bighorn sheep ewes altered their normal watering patterns; seven of these ewes abandoned the site. Because ewes are more restricted in their movements and display a relatively high degree of fidelity to water sources, such abrupt changes in watering patterns are probably the result of extrinsic disturbances.
Abandonment of preferred habitat is anticipated to be detrimental to the long-term survival of Peninsular bighorn sheep. Abandonment of a lambing area in the Peninsular Ranges has been reported, and it has been attributed to human activities. The construction of a flood control project took place in Magnesia Canyon within the City of Rancho Mirage in 1982. This construction took place below a lambing area that was occupied by the northern Santa Rosa Mountains ewe group. During the construction of the flood control project, the northern Santa Rosa Mountains ewe group relocated their lambing area from Bradly Peak (above Magnesia Canyon, and in direct line of site to the flood control project area) to Ramon Peak. The distance between these two lambing areas is estimated at about 1.5 miles. Ramon Peak is situated away from areas occupied by humans, and human activities were correspondingly absent compared to Magnesia Canyon during construction. This relocation corresponded to the shift in habitat use and abandonment of some areas affected by the noise and view of humans during construction, causing a marked difference in behavior when ewes with lambs used a watering area located 660-1650 ft (200-500 m) from the construction area. The ewe group re-occupied the Bradly Peak lambing area the following year after construction and human activities subsided. Approved and future projects such as Shadowrock Golf Course and Mountain Falls Golf Course, respectively, may result in the abandonment of the main remaining lambing area in the San Jacinto Mountains.
The Coachella Valley Association of Governments anticipates that by 2010 the human population there will increase from 227,000 to over 497,000, not including 165,000-200,000 seasonal residents. Increased human populations and associated commercial and residential development will likely continue to increase destruction of habitat and disrupt sheep behavioral patterns.
Shadowrock Golf Course and Altamira represent examples of locally approved projects that could have significant adverse effects on the Peninsular bighorn sheep. The City of Palm Springs approved the Shadowrock project which would eliminate important canyon bottom habitat and compromise or curtail sheep movement corridors. In addition, a settlement agreement between the developer of Shadowrock and the California Department of Fish and Game allows the project to proceed with only minor changes from the original design. Similarly, the City of Palm Springs has processed the Andreas Cove project proposal under a Negative Declaration, rather than the more rigorous Environmental Impact Report analysis. Moreover, the General Plans for most of the cities in the Coachella Valley inadequately address potentially significant development threats to the long-term conservation of Peninsular bighorn sheep.
Several studies have shown that bighorn sheep respond to human presence (as well as roads and housing developments) by altering behavior patterns to avoid contact. This behavioral response may preclude or disrupt sheep use of essential water sources, mineral licks, feeding areas, or breeding sites. Proposed country club/residential developments that have been approved or proposed within or immediately adjacent to Peninsular bighorn sheep habitat will substantially increase human activity. Unrestricted use of hiking and mountain bike trails in sensitive areas could further disrupt bighorn behavior and negatively affect this species. A reversal in behavior has been noted by the immediate return of Peninsular bighorn sheep to areas that were recently closed off to hikers in the Santa Rosa Mountains.
Some species of ornamental plants, associated with urban developments, have been attributed to causes of mortality in bighorn sheep. Between 1991 and 1996, five Peninsular bighorn sheep in the northern Santa Rosa Mountains ewe group died from ingesting ornamental, toxic plants such as oleander and laurel cherry. A toxic, ornamental night-shade plant may have caused the death of a young ram (a necropsy revealed an unknown species of nightshade) in Palm Springs in 1970 . Due to the absence of comprehensive studies of the toxicity of ornamental plants to bighorn sheep, only the two plant species mentioned above are known to be poisonous to the Peninsular bighorn sheep. It is expected that more species of ornamental plants are toxic to this species.
Collisions with vehicles also are a source of Peninsular bighorn sheep mortality. Bighorn sheep are being killed as a result of automobile collisions on Highway 74 in areas where blind curves exist in known sheep movement areas. The Thunderbird Estates and golf course is located across Highway 111 from Peninsular bighorn sheep habitat in Rancho Mirage.
Individuals from the northern Santa Rosa Mountains ewe group cross over Highway 111, or use a flood control channel that is under Highway 111, to access forage and water at this golf course. Dominant ewes will lead five to seven other ewes and rams to the golf course across Highway 111 which has led to collisions with automobiles. Nine Peninsular bighorn sheep in the Santa Rosa Mountains were hit and killed by automobiles between 1991 and 1996, and in combination with other urban-related factors, accounted for the majority of mortalities.
Disease is a major factor responsible for the precipitous decline of Peninsular bighorn sheep in the northern Santa Rosa Mountains and appears to significantly contribute to population declines elsewhere throughout its range. There is a higher level of exposure to viral and bacterial pathogens in the Peninsular bighorn sheep population than in other California bighorn sheep populations. Past higher exposure to pathogens suggests that disease may have been a major contributing factor in this distinct population segment's decline.
Bighorn sheep are susceptible to a variety of bacterial, fungal, and viral infections. Lambs and older sheep may be most susceptible to disease. Numerous endoparasites and ectoparasites are known to occur in this species. The relationship between disease, its transmission, and factors such as stress, density, competition, water availability, and disturbance are not well understood. Disease manifestation probably occurs during stressful periods such as high or low population levels, reproductive activity, low nutrient availability, and climatic extremes.
Disease is responsible for high lamb mortality rates in Peninsular bighorn sheep. In the northern Santa Rosa Mountains, excessive lamb mortality has occurred since 1977 due to pneumonia. Bacterial pneumonia is usually a sign of weakness caused by another agent such as a virus, parasite, or environmental stress that lowers an animal's resistance to disease. Serological evidence suggests that a combination of viruses may be contributing initiating factors for the development of pneumonia in the Santa Rosa Mountains ewe group. Vaccination has been used with limited success in captive and wild sheep.
Domestic and feral cattle can act as disease reservoirs. Several viruses discovered in sick bighorn sheep lambs were non-native and thought to be introduced by domestic livestock. However, the potential role of livestock in disease transmission is not well understood. Staff of the Anza-Borrego Desert State Park completed a project to remove 119 feral cattle from the Park in 1990. Six types of viruses were detected in these cattle. Blood samples taken from cattle grazing in allotments adjacent to Peninsular bighorn sheep habitat within the Park have contained several viruses. Peninsular bighorn sheep in Mexico have also tested positive to exposure to viral and bacterial diseases.
Other livestock may transmit diseases as well. Domestic sheep harbor bacteria and viruses that can kill bighorn sheep, and close contact results in transmission to and the subsequent death of most or all of the exposed animals. Domestic sheep associated with commercial operations have been observed in the San Jacinto River along the northern edge of the San Jacinto Mountains. In addition, small numbers of domestic sheep are raised by private individuals living along the northern edge of the San Jacinto Mountains.
Cattle or domestic sheep do not have to occupy Peninsular bighorn sheep habitat for disease transmission to occur. Overlap in habitat use by Peninsular bighorn sheep, southern mule deer, and the biting midge may provide a pathway for disease transmission from deer populations associated with livestock to bighorn sheep. This pathway may involve either movement of an infected individual or the progression of an epizootic through the general deer population to Peninsular bighorn sheep where the two species overlap.
The northern Santa Rosa Mountains ewe group has been exposed to several unnatural conditions leading to relatively high levels of mortality: Excessive exposure to high levels of fecal material increasing the chance for the spread of disease; excessive use of an unnaturally moist environment suitable for harboring infectious disease and parasites; unusually high levels of adult mortality associated with predation; exposure to non-native and potentially toxic plants; short-term lamb abandonment leading to increased risk of lamb predation; and loss of ewe group "memory" of other available water and forage areas in their historic home range. Urbanization is the leading known cause of death to Peninsular bighorn sheep occupying the northern Santa Rosa Mountains. During their investigation in the northern Santa Rosa Mountains, urbanization accounted for 34.2% of all recorded adult mortalities. Mortalities directly caused by urbanization were associated with ingestion of toxic, non-native plants, automobile collisions, and fences. Indirect causes of death associated with urbanization included parasite infestations and altered habitat use.
Exposure to high concentrations of feces can lead to unnaturally high levels of exposure to disease and parasites, and may contribute to Peninsular bighorn sheep population declines. Development in and adjacent to the Santa Rosa Mountains has established irrigated grass lawns, golf courses, and ponded waters providing environmentally suitable conditions for the strongyle parasite to successfully complete its life cycle, and increase its presence in a naturally arid environment. Sheep can be exposed to the strongyle parasite from the feces of an infected individual. Strongyle parasites have been reported in the northern Santa Rosa Mountains ewe group. Animals exhibiting symptoms from the infection of a strongyle parasite are less active, forage less, tend to stay unusually close to water sources, become weak, are extremely emaciated, and exhibit anemia. Mortality from infection of the strongyle parasite may be experienced in sheep, particularly under situations that create additional stress.
Strongyle parasites are common in domestic ruminant, horse, and pig hosts, and require moist environments for the survival of its larval stages outside of the host. The strongyle parasite life cycle cannot be completed in arid environments, and strongyle infestations are generally rare in desert regions. However, between 1991 and 1996, more than 85% of the Peninsular bighorn sheep sampled in the Santa Rosa Mountains ewe group were infected with the strongyle parasite. Ewes, rams, and lambs are susceptible to infection with the strongyle parasite. Clinical signs of strongyle parasites in the Peninsular bighorn sheep have been reported only from the Santa Rosa Mountains ewe groups. Strongyle parasites have not been detected in the San Jacinto Mountains ewe groups, and are considered rare or absent in other ewe groups.
Peninsular bighorn sheep exhibiting physiological stress related to an infestation of the strongyle parasite are at greater risk of predation, and less likely to successfully reproduce. Presently, there is no local or regional program to inoculate Peninsular bighorn sheep against non-native, introduced diseases, viruses, and parasites.
The reduction of disease outbreaks centers, in large part, on reducing factors that stress Peninsular bighorn sheep. Stress predisposes animals to disease. One of the major factors that stress bighorn sheep is human encroachment into their habitat. The decline of the Peninsular bighorn sheep is markedly steeper where the population borders the developing areas of the Coachella Valley. The decline in the population adjacent to urban areas in the Coachella Valley has been 35% greater than that occurring in Anza Borrego Desert State Park. Disease has been documented as an important factor in the decline of the population in the northern Santa Rosa Mountains. Although the pathogens responsible for the diseases in the Santa Rosa Mountains have also been detected in Anza Borrego Desert State Park, the population in Anza Borrego Desert State Park has declined at a slower rate (57% versus 92%).
Increased risk of predation has also been attributed to unnatural environments found at the urban interface. Higher numbers of adult Peninsular bighorn sheep mortalities are caused by mountain lions closer to the urban environment as compared to wild lands. Domestic dogs often occur along the urban-wild lands interface, and are also capable of injuring and killing lambs, ewes, and young or unhealthy rams. Encroaching development not only increases the abundance of domestic dogs along the urban-wild lands interface, but also creates unnatural landscape characteristics such as hedge rows, dense patches of tall vegetation, and other unnatural cover suitable for predators to hide and ambush potential prey. Residents of Thunderbird Cove have complained that the presence of Peninsular bighorn sheep feeding on lawns attracts mountain lions, which some of the residents have observed.
Predation, as a mortality factor, decreases in significance as the size of a population increases. In addition, major predation problems have occurred with populations occupying restricted home ranges or fenced areas. Compared to the northern Santa Rosa Mountains ewe group, ewe groups to the south, the majority of which do not occupy restricted home ranges, have experienced high rates of natural predation compared to urban-related mortalities. Ewe group sizes in these areas are larger than the northern Santa Rosa Mountains and San Jacinto Mountains ewe groups, and can likely tolerate such predation levels.
Coyote, bobcat, mountain lion, gray fox, golden eagle, and free-roaming domestic dogs prey upon bighorn sheep. Predation generally has an insignificant effect except on small populations. Mountain lion predation of Peninsular bighorn sheep appears to have increased in the northern Santa Rosa Mountains and sheep encounters with domestic dogs are likely to increase with more urban development.
Recurrent drought, disturbance at watering sites, urban and agricultural water withdrawals, and domestic livestock use decrease the amount of water available for Peninsular bighorn sheep. In particular, small ewe groups are affected. Peninsular bighorn sheep, similar to other bighorn sheep, exhibit a seasonal pattern of distribution based on forage and water availability. Water is available via tenajas (natural catchment basins adjacent to streams), springs, and guzzlers.
During late summer and early winter (July to November), when water requirements and breeding activities are at a peak, the sheep tend to concentrate near water sources, particularly as tenajas and springs dry up. During this time, the sheep depend on reliable water and food sources. Bighorn sheep require a quantity of water approximately equal to 4% of their body weight (1 gal [4 l]) per day during the summer months and a dependable water supply is needed at about 2 mi (3 km) intervals. When water is not available in sufficient quantities (especially during hot, dry weather) the mortality rate for older sheep, lambs, and sick or injured animals is likely to increase.
Peninsular bighorn sheep have been extirpated from several historic locations, including the Fish Creek Mountains (Imperial County) and the Sawtooth Range (San Diego County) because of habitat loss (especially canyon bottoms), degradation, and fragmentation associated with the proliferation of residential and commercial development, roads and highways, water projects, and vehicular and pedestrian recreational uses.
Peninsular bighorn sheep are susceptible to fragmentation due to the distribution of habitat (narrow band at low elevation), use of habitat (e.g., occupying low elevations), and population structure. Restricted to elevations below the distribution of chap-arral habitat 3,500 ft (1,000 m), encroaching urban development and human related disturbance have the dual effect of restricting remaining animals to a smaller area and severing connections between ewe groups.
The Peninsular bighorn sheep distinct population segment, like other bighorn sheep populations, is composed of ewe groups that inhabit traditional areas (cluster of canyons) and rams that move among these groups exchanging genetic material. Maintenance of genetic diversity allows small ewe groups to persist. The inability of rams and occasional ewes to move between groups erodes the genetic fitness of isolated groups. Urban and commercial development may ultimately fragment the metapopulation into isolated groups too small to maintain long-term viability, as apparently was the case in the extirpation of one ewe group in the United States.
The Peninsular bighorn sheep apparently is currently functioning as a metapopulation (interaction between separate groups). However, the potential loss of dispersal corridors and habitat fragmentation by residential and commercial development and roads and highways may isolate certain groups. Isolation increases the chances for inbreeding depression by preventing rams from moving among ewe groups and eliminating exploratory and colonizing movements by ewe groups into new or former habitat. Inbreeding and the resultant loss of genetic variability can result in reduced adaptiveness, viability, and fecundity, and may result in local extirpations. Small, isolated groups are also subject to extirpation by naturally occurring events such as fire. Although inbreeding has not been demonstrated in the Peninsular bighorn sheep, the number of sheep occupying many areas is critically low. The minimum size at which an isolated group can be expected to maintain itself without the deleterious effects of inbreeding is not known. Researchers have suggested that a minimum effective population size of 50 is necessary to avoid short-term inbreeding depression, and 500 to maintain genetic variability for long-term adaptation.
Conservation and Recovery
The habitat still remaining for the Peninsular bighorn sheep in the United States is managed by the California Department of Parks and Recreation (46%), Bureau of Land Management (27%), private landowners (24%), Bureau of Indian Affairs (1%), U.S. Forest Service (1%), and other State agencies (1%).
Information received from the Mexican Government indicates the population in Baja California is not likely to be in danger of extirpation within the foreseeable future because there are significantly more animals there than occur in the United States. There are estimated to be between 780-1,170 adult Peninsular bighorn sheep in Baja California, Mexico, north of Bahia San Luis Gonzaga. In addition to the higher population numbers, the Mexican Government has initiated a conservation program for bighorn sheep that should improve the status of these animals. Based on information received from the Mexican Government, components of the conservation program include the involvement of the local people in the establishment of conservation and management units that allow some use of the bighorn sheep while promoting its conservation and recovery. Approximately 485,306 acres (196,400 hectares) have been included in this program for Peninsular bighorn sheep.
About 20 Peninsular bighorn sheep are held in captivity at the Bighorn Institute in Palm Desert, California. The Bighorn Institute, a private, nonprofit organization, was established in 1982 to initiate a research program for the Peninsular bighorn sheep. The Living Desert, an educational and zoo facility also located in Palm Desert, California, maintains a group of 10-12 Peninsular bighorn sheep at its facility.
The Peninsular bighorn sheep receives some benefit from the presence of the endangered species least Bell's vireo and southwestern willow fly-catcher in its range. However, this benefit is limited due to the specialized habitats (riparian woodland) utilized by these birds. Similarly, the Clean Water Act provides limited protection to small portions of the Peninsular bighorn sheep's range through the U.S. Army Corps of Engineers' regulation of the discharge of dredged and fill material into certain waters and wetlands of the United States.
The California Fish and Game Code provides for management and maintenance of bighorn sheep. The policy of the State is to encourage the preservation, restoration, utilization, and management of California's bighorn sheep. The California Department of Fish and Game supports the concept of separating livestock from bighorn sheep (to create buffers to decrease the potential for disease transmission) through purchase and elimination of livestock allotments. However, it has not been a policy of the California Department of Fish and Game to revoke current State livestock permits, nor does the State have authority to regulate grazing practices on Federal lands.
Since the Peninsular bighorn sheep was listed by the State of California in 1971, the California Department of Fish and Game has: (1) prepared management plans for the Santa Rosa Mountains and for the McCain Valley area of eastern San Diego County; (2) acquired 30,000 acres (12,000 hectares) of land in the Santa Rosa Mountains; (3) initiated demographic, distributional, and disease research; and (4) established three ecological reserves that protect important watering sites. These actions are important to Peninsular bighorn sheep conservation, but, are not sufficient to stem the long-term population decline.
The Bureau of Land Management and the Forest Service manage lands that contain habitat for Peninsular bighorn sheep. The Bureau of Land Management has management plans that include management activities for the Peninsular bighorn sheep. The San Bernardino National Forest Plan also addresses the Peninsular bighorn sheep. Both agencies administer grazing allotments on portions of their land. The Bureau of Indian Affairs, Bureau of Reclamation, and the Department of Defense also conduct activities within or adjacent to the range of this distinct population segment.
The majority of sheep range is owned by State and Federal agencies and managed for multiple human uses, especially recreational pursuits. Four of eight ewe groups in the U.S. largely occur in the Anza Borrego State Park, renowned as a premier hiking and camping destination. The remaining four ewe groups largely occur within Bureau of Land Management's Santa Rosa Mountains National Scenic Area, which is intended to expand recreational opportunities through acquiring private lands for public use and enjoyment. Coachella Valley commercial interests are aggressively promoting and developing outdoor recreational industries that capitalize on the scenic beauty of the Santa Rosa and San Jacinto mountains. These industries and activities include jeep nature tours, mountain biking, hiking, horseback riding, dog walking, camping, sight-seeing, and other ecotourist forms of recreation in bighorn sheep habitat that often use bighorn sheep images as advertising themes, corporate and civic logos, etc. During the more temperate months of October through April, the Coachella Valley attracts millions of tourists and seasonal residents from across the Country and around the world. The timing of maximum human use levels corresponds with particularly sensitive periods in bighorn sheep life history, including the lambing season, rut, and the late summer water stress period. An increase in human activity, even when harm is not intended, would disrupt bighorn sheep behavior and could cause abandonment of essential environments (e.g., lambing areas or watering holes).
The Bighorn Institute and Living Desert Museum maintain captive populations of Peninsular bighorn sheep for scientific and educational purposes. This use is thought to have no negative impact on free-ranging bighorn.
U.S. Fish and Wildlife Service
Carlsbad Fish and Wildlife Office
2730 Loker Avenue West,
Carlsbad, California 92008
Telephone: (760) 431-9440
Fax: (760) 431-9624
U. S. Fish and Wildlife Service
Regional Office, Division of Endangered Species
Eastside Federal Building
911 N. E. 11th Ave.
Portland, Oregon 97232-4181
Telephone: (503) 231-6121
U. S. Fish and Wildlife Service. 18 March 1998. "Endangered Status for the Peninsular Ranges Population Segment of the Desert Bighorn Sheep in Southern California." Federal Register 63 (52): 13134-13150