Bighorn sheep in the Peninsular Ranges have been protected under California State law since 1971. The population declined from approximately 1,100 animals in the 1970s, to about 400 in 2000. This decline was attributed to habitat loss and modification, human disturbance, fragmentation due to roads, rail and tram construction, livestock grazing, disease, poaching, and fire suppression. Low sheep numbers were further impacted due to mountain lion predation which is typically not a concern in a healthy population of bighorn sheep. In March of 1998, the U.S. Fish and Wildlife Service (USFWS) listed this population segment (metapopulation) as an endangered species and a recovery plan was drafted in 2000. The Recovery Plan for Bighorn Sheep in the Peninsular Ranges, California (PDF) listed several criteria that must be met before delisting occurs: (1) a minimum of 25 ewes must be present in each of 9 recovery regions (Recovery Region Map (PDF) during 12 consecutive years without continued population augmentation; (2) the range-wide population must average 750 individuals with a stable to increasing population trend over 12 consecutive years; (3) regulatory mechanisms and land management commitments have been established that provide for long-term protection of sheep and all essential habitat. Furthermore, connectivity among all portions of habitat must be established to allow sheep to move freely throughout the Peninsular Ranges.
Since 1992 DFG has implemented population assessment and recovery program designed to determine and track population status, distribution, habitat use, recruitment and survival rates, and mortality factors of desert bighorn sheep in the Peninsular Ranges. The current population monitoring effort estimates population size for each subpopulation and also produces a range-wide total on a biennial basis. Since 2000, the range-wide sheep population estimate has increased from approximately 400 individuals to 955 in 2010. Despite recent increases in population size, the Peninsular Ranges bighorn sheep population remains extremely vulnerable to demographic and environmental stochasticity, habitat loss and fragmentation, disease, predation, and human disturbance. Continued implementation of this program remains crucial to the development and refinement of management and recovery strategies and achieving established recovery objectives.
Desert bighorn sheep are typically smaller and more slender than bighorn sheep found in northern habitats. An adult bighorn sheep stands at 30 to 39 inches tall at the shoulders. The average weight of adult rams is about 160 lbs and 105 lbs for adult ewes. The horns of desert bighorn sheep are similar in size to those of their northern counterparts; therefore desert bighorn sheep have horns disproportionately large relative to their body size. They also have a shorter, sleeker coat than northern bighorn sheep. The coat can vary from a light sandy color to a brown or slate color, with white on the rump, the stomach area, the muzzle, and on the back of the legs. The newborn lamb has a mouse-gray color, which turns lighter after several months.