Desert bighorn sheep

Ovis canadensis nelsoni

Desert bighorn sheep (Ovis canadensis nelsoni) is a subspecies of bighorn sheep (Ovis canadensis) that is native to the deserts of the USA's 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.
The rare and shy desert bighorn in all of his majesty We were at Anza-Borrego State Park in the California desert, and hoping to see this very rare and shy animal. The signs all say that they see you long before you can see them - and that they generally avoid humans. I had been there several times but never seen any desert bighorns - but this time we surprised a few on an early morning hike in Borrego Palm Canyon Trail and they luckily did not seem so shy, and lingered for a few photos - amazing! Anza-borrego SP,California,Desert bighorn sheep,Geotagged,Ovis canadensis nelsoni,San Diego County,Summer,United States

Appearance

Desert bighorn sheep are stocky, heavy-bodied sheep, similar in size to mule deer. Weights of mature rams range from 115 to 280 pounds , 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 Bighorn Close-up Another view of the Desert Bighorns we saw - this one almost seemed like he was posing. Anza-borrego SP,California,Desert bighorn sheep,Geotagged,Ovis canadensis nelsoni,San Diego County,Summer,United States

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.
Two prime male Desert Bighorn Sheep Although we had great view of a number of Desert Bighorn Sheep, because it was not in the mating season, the males got along just fine with each other - so no chance for the iconic butting head battles that the males engage in when fighting for control of a group of females. Anza-borrego SP,California,Desert bighorn sheep,Geotagged,Ovis canadensis nelsoni,San Diego County,Summer,United States

Status

The number of desert bighorn sheep in North America in pristine times is unknown, but most likely was in the tens of thousands. In 1929, E.T. Seton estimated the pre-Columbian numbers of all subspecies of bighorn sheep in North America at 1.5-2.0 million. By 1960, however, the overall bighorn population in the United States, including desert bighorns, had dwindled to 15,000-18,200. Buechner documented major declines from the 1850s to the early 20th century. These declines were attributed to excessive hunting; competition and diseases from domestic livestock, particularly domestic sheep; usurpation of watering areas and critical range by human activities; and human-induced habitat changes.

In 1939, after intense lobbying by Frederick Russell Burnham and the Arizona Boy Scouts, President Franklin D. Roosevelt signed a proclamation to establish two desert areas in southwestern Arizona to help preserve the desert bighorn sheep: Cabeza Prieta National Wildlife Refuge and the Kofa National Wildlife Refuge. In 1941, the San Andres National Wildlife Refuge in New Mexico was added.

Desert bighorn sheep populations have trended upward since the 1960s when their population was estimated at 6,700-8,100. The upward trend was caused by conservation measures, including habitat preservation. 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 US desert bighorn sheep population at 15,980. The 1993 estimate of the population is 18,965-19,040. The results of the state-by-state survey are shown to the right.

In southern California, by 1998, only 280 individuals of the peninsular bighorn sheep population remained, and that population was added to the list of the United States' most imperiled species. Populations in three southern counties had suffered greatly from disease, development, and predation. As of 2008, about 800 peninsular bighorns are believed to populate the desert backcountry from the US-Mexico border to the San Jacinto Mountains, with known populations in Anza-Borrego Desert State Park. These gains, combined with Bush Administration policies, prompted the US Fish and Wildlife Service to propose a reduction in protected sheep habitat by more than 50%, from 844,897 to 384,410 acres .

Behavior

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 , 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.

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Status: Unknown
EX EW CR EN VU NT LC
Taxonomy
KingdomAnimalia
DivisionChordata
ClassMammalia
OrderArtiodactyla
FamilyBovidae
GenusOvis
SpeciesO. canadensis nelsoni