West Mojave Plan FEIR/S - Desert Managers Group

Basic to the biology of bighorn sheep is their agility on steep rocky terrain, an adaptationused to escape predators. Preferred habitat of bighorn is primarily on or near mountainousterrain above the desert floor.Radio telemetry studies of bighorn sheep in various southwestern deserts, including theMojave Desert of California, have found considerable movement of these sheep betweenmountain ranges. This is especially true of males, but also of ewes. Within individual mountainranges, populations often are small. Levels of inbreeding could be high in such populations, butintermountain movements provide a genetic connection with a larger metapopulation, and thiswill counteract potential inbreeding problems.Surface water is another element of desert bighorn habitat considered to be important topopulation health. Male and female bighorn sheep inhabiting desert ecosystems can survivewithout consuming surface water, and males appear to drink infrequently in many situations ;however, there are no known large populations of bighorn sheep in the desert region that lackaccess to surface water.Population Status in the Planning Area: The majority of bighorn sheep herds arelocated on military bases, especially China Lake NAWS and Twentynine Palms MCAGCC.Additional populations are found in the Rodman and Ord Mountains (occasionally ranging westonto Sidewinder and Stoddard ridges), Newberry Mountains, and on the north slope of the SanBernardino Mountains. Much of the habitat is within designated Wilderness.Regulatory Status. BLM Sensitive.Threats Affecting the Bighorn Sheep: Potential threats to bighorn include loss ordisturbance of springs and waterholes, incremental loss of habitat, contact with domestic sheepthat can introduce disease, and blockage of linkages by roads, canals, or fences. Significantmountain lion predation in the San Bernardino Mountains is a threat. Vehicle intrusion intooccupied habitat, especially lambing areas, can be a minor threat.Rural development with fencing threatens corridors; one corridor formerly extendedthrough the city of Twentynine Palms. The bighorn traveling between the Pinto Mountains andthe Bullion Mountains on Twentynine Palms MCAGCC now travel through the SheepholeMountains (BLM, 2002). The dispersal corridor between the San Bernardino Mountains and theGranite Mountains is threatened by rural development in western Lucerne Valley. Miningoperations have not been shown to significantly impact bighorn numbers in the San BernardinoMountains, although the mines result in a loss of habitat, block access to water sources andpasture, and bring new disturbances into the permanent range. New cyanide heap leachingmines have the potential to harm bighorn if open water containing cyanide is present onoperations within bighorn habitat.Chapter 3 3-171