The Desert Bighorn Sheep (Ovis canadensis nelsoni) is a subspecies of Bighorn Sheep that occurs in the desert Southwest regions of the United States and in the northern regions of Mexico.

Populations of the Desert Bighorn Sheep declined drastically with European colonization of the American Southwest beginning in the 1500s. As of 2004, Desert Bighorn Sheep numbers are extremely low, although the overall population trend has increased since 1960.

These declines were followed by a period of population stabilization that was ascribed to conservation measures. The decline of Desert Bighorn Sheep probably mirrored the pattern of decline of the overall bighorn population. Desert Bighorn Sheep population trends have been upward since the 1960s when their population was estimated at 6,700-8,100. In 1980 Desert Bighorn Sheep populations were estimated at 8,415-9,040. A state-by-state survey was conducted a few years later and estimated the overall U.S. Desert Bighorn Sheep population at 15,980. The 1993 estimate of the population is 18,965-19,040.

Source: http://en.wikipedia.org/wiki/Desert_Bighorn_Sheep

Caprinae Specialist Group (1996). Ovis canadensis ssp. nelsoni. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006.

Nevada Department of Wildlife Report: 2004-2005 Big Game Status

USGS Report: Our Living Resources - Desert Bighorn Sheep by Henry E. McCutchen of the National Biological Service (adapted public domain text)

Photograph courtesy of the U.S. Geological Survey