West Mojave Plan FEIR/S - Desert Managers Group

investigation. It may not be a significant roost for the six target species.The only identified cliff roosts for spotted bat are within Red Rock Canyon State Park.No roosts of western mastiff bat have been located, but roosts are suspected within Joshua TreeNational Park.Regulatory Status: BLM sensitive (except long-legged myotis), California Species ofSpecial Concern (except long-legged myotis).Threats Affecting Bats: The most serious direct threats to bats are disturbances ofhibernation and maternity roosts and destruction of roosting habitat, primarily old mines andnatural caves. Old buildings and bridges also provide roosts for some species. Loss anddegradation of foraging areas threatens certain species. Potential recreation impacts includeaccess to significant roosts and degradation of foraging habitat for Townsend’s big-eared bat andCalifornia leaf-nosed bat.3.3.5 Other Mammals3.3.5.1 Bighorn SheepLife History: Bighorn sheep were originally distributed from Baja California to Texas inthe south to the Canadian Rockies in the north, with the eastern boundary reaching westernNebraska and the western boundary in California extending from Mount Shasta in the north tothe crest of the central and southern Sierra Nevada to the Transverse Ranges and the east side ofthe Peninsular Ranges in the south. Traditional taxonomy dating back more than half a centurybroke bighorn sheep from the southwestern desert region into four subspecies, one of which, theNelson Bighorn (Ovis canadensis nelsoni), included bighorn from the Transverse Rangesthrough most of the desert mountain ranges of California, including the West Mojave planningarea, and adjacent Nevada and northern Arizona to Utah. Recent research indicates a lack ofsupport for Cowan’s (1940) desert subspecies and instead has found previously unrecognizednorth-south variation of the Nelson Bighorn. The transition between the southern (warm desert)and the northern (cold desert) forms occurs in the middle of the West Mojave planning area, withI-15 east of Barstow representing the approximate boundary. Within the West Mojave planningarea no populations north of I-15 persist that have not been reintroduced or augmented withsheep from south of I-15.Within the West Mojave planning area, 16 bighorn sheep populations are known to haveexisted as defined by mountain range complexes. Five of these 16 areas no longer containpopulations, three have been reintroduced, and two have been augmented with sheep fromanother population. For the past decade, bighorn sheep populations in California have beenviewed in a metapopulation context. Within the West Mojave planning area there are threemetapopulations whose geographic boundaries are now formed by major fenced highways (I-15and I-40) -- the south, central, and north Mojave Desert metapopulations (Torres et al., 1994,1996).Chapter 3 3-170