Desert bighorn sheep (Ovis canadensis nelsoni) is a subspecies of bighorn sheep (Ovis canadensis) that is native to the deserts of the United States' intermountain west and southwestern regions, as well as northwestern Mexico.

The trinomial of this species commemorates the American naturalist Edward William Nelson (1855–1934). The characteristics and behavior of desert bighorn sheep generally follow those of other bighorn sheep, except for adaptation to the lack of water in the desert. They can go for extended periods of time without drinking water.

The desert bighorn sheep is also the mascot of the Universidad Autónoma de Baja California.

Distribution
The range of desert bighorn sheep includes habitats in the Mojave Desert, Colorado Desert, and Sonoran Desert. Anza-Borrego Desert State Park, Joshua Tree National Park, Death Valley National Park, Kofa National Wildlife Refuge, Cabeza Prieta National Wildlife Refuge, and Mojave National Preserve all offer protected habitat for this animal.

Populations of the desert bighorn sheep declined drastically with European colonization of the American Southwest beginning in the 16th century. These declines were followed by a period of population stabilization ascribed to conservation measures. As of 2004, desert bighorn sheep numbers remained extremely low, although the overall population trend had increased since 1960.

Characteristics
Desert bighorn sheep are stocky, heavy-bodied sheep, similar in size to mule deer. Weights of mature rams range from 115 to 280 pounds (52 to 127 kg), while ewes are somewhat smaller. Due to their unique concave elastic hooves, bighorn are able to climb the steep, rocky terrain of the desert mountains with speed and agility. They rely on their keen eyesight to detect potential predators, such as mountain lions, coyotes, and bobcats, and they use their climbing ability to escape.

Both genders develop horns soon after birth, with horn growth continuing more or less throughout life. Older rams have curling horns measuring over three feet long with more than one foot of circumference at the base. The ewes' horns are much smaller and lighter and do not tend to curl. After eight years of growth, the horns of an adult ram may weigh more than 30 pounds. Annual growth rings indicate the animal's age. The rams may rub their own horns to improve their field of view. Both rams and ewes use their horns as tools to break open cactus, which they consume, and for fighting.

Desert bighorn sheep typically live for 10–20 years. The typical diet of a desert bighorn sheep is mainly grasses. When grasses are unavailable, they turn to other food sources, such as sedges, forbs, or cacti.

Desert adaptations
The desert bighorn has become well adapted to living in the desert heat and cold and, unlike most mammals, their body temperature can safely fluctuate several degrees. During the heat of the day, they often rest in the shade of trees and caves.

Southern desert bighorn sheep are adapted to a desert mountain environment with little or no permanent water. Some may go without visiting water for weeks or months, sustaining their body moisture from food and from rainwater collected in temporary rock pools. They may have the ability to lose up to 30% of their body weight and still survive. After drinking water, they quickly recover from their dehydrated condition. Wildlife ecologists are just beginning to study the importance of this adaptive strategy, which has allowed small bands of desert bighorns to survive in areas too dry for many of their predators.

Social life
Rams battling with their horns
Desert bighorn sheep are social, forming herds of eight to 10 individuals; sometimes herds of 100 are observed.

Rams battle to determine the dominant animal, which then gains possession of the ewes. Facing each other, rams charge head-on from distances of 20 ft or more, crashing their massive horns together with tremendous impact, until one or the other ceases.

Bighorn sheep live in separate ram and ewe bands most of the year. They gather during the breeding season (usually July–October), but breeding may occur anytime in the desert due to suitable climatic conditions. Gestation lasts 150–180 days, and the lambs are usually born in late winter.

Source
Wikipedia