• Desert, grasses and shrub mosaic, shrublands
• Important habitat requirements are topography (escape terrain), visibility, water, and forage quality and quantity
• Terrain typically rough, rocky and broken by canyons and washes
• Depends on steep slopes for lambing and to escape predators
• Uses cliff overhangs to rest from the hot desert sun and dry environment
• Desert bighorn sheep avoid low visibility areas with dense vegetation
• Distribution of waterholes influences pattern of home range for some desert bighorn subspecies

• Adult Body Weight: Male (ram) - 150-200 lbs., Female (ewe) - 100 -125 lbs.
• Adult Body Length: 50 -62"
• Adult Shoulder Height: 32 - 40"
• Horns: Male horns become a full curl by 7-8 years of age and spread of up to 33 inches (up to 30 lbs.) Female horns are smaller than the rams and never exceed half a curl.

• Both sexes have horns that grow throughout their lives. Male horns are massive, curling and diverging. Female horns are smaller, thin and curved.
• Horns consist of a bony core with a permanent sheath of keratin. Sheaths grow from the base
• Mountain bighorns have by far the biggest horns. Longest horn length recorded measured 52 inches with a basal circumference of 18 inches (Horn tips are often broken, splintered or broomed)
• Clark (1940) reports a weight of 44 lbs (upper skull and horn) for a Canadian Rocky ram
• Growth rings (annuli) are formed in the fall and are associated with hormone and diet changes. First visible annulus is 2.5 years. Fourth year is the first heavy, dark ring.

• Smooth outer coat of brittle guard hairs and short, gray, crimped fleece underfur
• Fur is a pale brown, paler in appearance than other bighorn sheep
• The summer coat is a rich, glossy brown but can fade by late winter
• Female fur is often lighter than the males
• Whitish patch on rump
• Molting usually occurs in June and July. Molting progresses from posterior region with chest the last to shed.

• Compact and muscular body
• Climbing, cloven hooves providing amazing jumping ability
• Acute eyesight

• Largely determined by availability of food and water (rain dependent)
• Predominantly diurnal but also may be active on moonlit nights
• Alternate between feeding and rest-rumination bouts
• Feeding bouts generally occur at dusk and dawn
• Some areas used repeatedly as bedding sites by groups
• Can move over level ground at 30 mph and up mountain slopes at 15 mph

• Matrilineal (based on female associations)
• Gregarious and faithful to natal home range. "Home range groups" or "ewe groups" tend to be related females and lambs
• Young learn from older sheep their home range, escape terrain, water sources and lambing habitat. Familiarity with range is an advantage in evading predators.
• Rams are not as tied to a specific group - they tend to range, moving between "ewe groups"
• Linear dominance orders among ewes
• Rams with larger horns and body size dominate both males and females

• Playing between lambs is highest during spring when food is available and lambs are young
• Threat jumps, clashes, and mounting are the most frequent social patterns used by lambs associated as play

• “Clashing” of rams’ horns during rutting season to determine / maintain rank

• Male horn size is a symbol of rank. Head-to-head combat between rams may occur during mating season.

• During the rut, bighorn rams will snort loudly. The lambs bleat, and the ewes respond with a guttural "ba."
• Adult males utter a growl or gutteral

• Scent mark spread by rubbing eye glands on trees and rocks

• Natural predators include: mountain lions, wolves, bobcats, coyotes and golden eagles
• Mule deer are the primary competitor for resources
• Known to become alarmed and startled by a flock birds or other sudden animal movements
• Unnatural competitors include: cattle, horses, domestic goats and humans
• Urbanization and human disturbance (habitat fragmentation, recreation use, development)
• Disease caused by domestic livestock

• Desert bighorn sheep are opportunistic herbivores and ruminants. Turner (1973) documented 43 species of plants in diet.
• Diet consists of shrubs, forbs, cacti, grasses (favorites include: acacia or catclaw, encelia, sweetbush, and krameria).
• Low terrain and washes provide high quality forage (productive soils) and water during summer months and reproductive season
• Sheep are ruminants with a 4 chambered stomach that can digest most of the cellulose in vegetation with the aid of bacteria and protozoans.
• Forage quality influences daily and seasonal patterns. When forage digestibility is low, bighorn spends most of its time ruminating. (Chewing cud).
• Daily food intake of captive bighorn sheep is estimated at 3 lbs (1.5 kg) plant material.
• Desert bighorn sheep will be found 3-5 kilometers from water sources during the summer months. Can go without drinking for 5 to 15 days
• Efficient digestive system is able to utilize dry, abrasive forage

• Estrus cycle averages 28 days and female is receptive for 48 hours.
• Females are estimated to produce lambs between the ages of 2 to 16.
• Males have been documented as breeding successfully as young as 6 months of age. (Turner & Hansen, 1980. Larger rams would control this in the wild.
• Rams routinely check estrus status of ewes by flehmen (urine-testing), and they can stimulate females to urinate by licking the vulva.
• Rut (term designating the breeding period)occurs in late summer and fall.
• Male will begin courtship when a female is in estrous with a series of contact patterns (twist, nose, kick, chest push).
• Females courtship is exhibited by the rubbing their body and horns on the male.
• Dominant males gain priority over females but subordinate males still attempt to mount estrous females.
• A ewe in estrous will often be pursued by numerous rams
• Mating and lambing seasons of desert species are extended because of unpredictability of rain and forage availability.

• Birth rates and lamb survival vary with the quality of food supply available
• Rates vary significantly among ewe groups in the desert region from 8 lambs: 100 ewes to 100 lambs: 100 ewes
• Breeding and parturition periods of desert bighorns more lengthy than northern species. (May be due to unpredictable food supply)
• Twinning is rare in all bighorn sheep
• As the ewes age, there is a decrease in their fertility

• Ewes select an isolated, sheltered site with unobstructed view to give birth.
• Lambing season (greatest # of lamb births)is generally between February - August.
• Usually single young are born, but twins have been recorded
• Neonates are precocial and often called “followers”.
• After a few weeks of not being seen, the mother rejoins the herd and put the lamb in a community nursery with other lambs.

• Body weight in newborns is 8-10 lbs.
• Body length at birth: 420 mm (16.5 inches)
• Young lambs are a grayish coloration with soft hooves and a black-brown tail.

• Body weight is 41-50 kg (90 - 110 lbs.) (females) to 52-59 kg (115 - 130 lbs.)(males).
• Body length is 690 mm (27 in.) (females) to 915 mm (36 in.) (males).
• Yearling ram horn is much like adult ewe horn but thicker at the base and blue-gray.
• Female horns are 125-178 mm long, thin and sharp-pointed.

• Body weight is 45.8 kg (101 lbs.)(females) to 69.4 kg (153 lbs.) (males).
• Body length is 851 mm (33.5 in.) (females) to 991 mm (39 in.)(males).

• Body weight is 55.6 kg (122.5 lbs.) (females) to 64.9 kg (153 lbs.) (males).
• Body length is 965 mm (38 in.) (females) to 977 mm (39in.)(males).

• Body weight is 57.2 kg (126 lbs.) (females) to 78.5 kg (173 lbs.)(males).
• Body length is 876 mm (34.5 in.) (females) to 1010mm (39.75 in.)(males).
• Ram adults have a large knob on the back of their head, often calloused and without hair while younger rams often have no knob.
• Permanent dentition is in place after four years of age.

• 1971 study of Desert Bighorn mortality in Arizona and southeastern Nevada: Poaching 41%, road kills 20%, natural accidents 15%, drownings 12%, fence mortalities 12%.
• Precipitous 52% decline in 1988-89 in Arizona due to livestock viral disease and nutritional stress
• Other documented threats in Arizona: automobile collisions, coyote/mountain lion predation

• Common disease problems: chronic sinusitis, pneumonia, psoroptic scapies
• Multiple pathogens (contagious ecthyma virus, blue tongue, Pasteurella, and parainfluenza-3 virus) have been found in declining populations.
• Improperly fitted radio collars have caused injury to osseous and dermal tissues decreasing fitness
• Peninsular bighorn sheep and other southern California bighorn populations have shown higher levels of pathogen exposure than other species of bighorn sheep.
• Diseases introduced by domestic livestock - They devastated bighorn populations in the mid and late 1900's.

• IUCN status of Ovis canadensis(all subspecies): Low Risk / conservation dependent
• Ovis canadensis cremnobates - IUCN status: Endangered (Listed as "rare" in 1971 by the California Fish and Game Commission. Listed as "endangered" in 1998 by USFWS) The Latest population estimate (excluding lambs) 334. (Rubin, 1998)
• Ovis canadensis mexicana - IUCN status: Vulnerable
• Ovis canadensis nelsoni - IUCN status: Low Risk
• Ovis canadensis weemsi - IUCN status: Critically Endangered
• Bighorn sheep subspecies in North America were estimated at 1.5 - 2 million during pre-columbian periods (Seton, 1929)
• By 1960, the population of bighorn sheep in North America dropped to 15,000 - 18,200 (Buchner, 1960)
• Major declines occurred from 1850's to early 1900's due to hunting (Buchner, 1960)
• In 1960 the total desert bighorn sheep population was estimated at 7,065 - 8,475
• In 1993 the overall desert bighorn sheep population increased to 18,965 - 19,040
• The California desert bighorn sheep subspecies were estimated in 1960 at 2,150 - 2,450, 1993 at 4,300 - 4,325
• The endangered Peninsular bighorn sheep, a population of desert bighorn sheep was estimated in 1993 at 400 - 425 in California, and 780 - 1,170 in Baja California, Mexico
• March 18, 1998, the United States Peninsular Ranges population of desert bighorn sheep was federally listed United States Fish and Wildlife Service as an endangered species
• Census from Shackleton, 1997: O.c. cremnobates <2,500, O.c. mexicana >2,000?, O.c. nelsoni 15,000? O.c. weemsi 500?
  (Low Risk northern species: O.c. californiana 8,900 O.c. canadensis 36,700)

• U.S. began preserving large parcels of wildlands as early as 1872 with the establishment of Yellowstone. Animals in National Parks are protected
• Since 1976
• A genetic ID program has been initiated in Jaspar National Park to deter trophy poaching.
• Management consists of establishing hunting quotas, regulating harvests, habitat improvement, annual censuses, translocation of animals and promoting research
• State wildlife agencies have reintroduced bighorns into many native ranges as well as into areas where the animals did not naturally occur
• Many non-governmental conservation organizations are involved in protecting bighorns. The Zoological Society of San Diego has had a Conservation Program for the Peninsular Bighorn since 2000.

• Populations of Sonora and Baja (cremnobates, nelsoni, mexicana, and weemsi) have been greatly reduced due to widespread illegal hunting of trophy males.
• Unpredictable epizootics (rapidly spreading disease affecting a large number of animals throughout a wide range)
• Human disturbance. (Desert bighorn are highly intolerant of human activity)
• Competition from domestic sheep, goats, feral burros for forage, water, space
• Populations have a predominance of old indiviuals and insufficient lamb recruitment (relationship between production and survival)
• Habitat loss, degradation, and fragmentation by urban and commercial development
• Mountain lion, wolf predation coinciding with low population numbers
• Failure of populations to disperse into contiguous, suitable habitat (caution / fear)
• Loss of genetic variation is always a danger when dealing with small populations.
• Invasive plant species (e.g. tamarisk) compete with native plants bighorns feed on.
• Introduced Barbary sheep could take over bighorn habitat.
• Fire suppression has created taller, denser vegetation. Reduced visibility makes the bighorn more vulnerable.
• Drought - Limiting water & forage. Global warming may prove to be a problem for the desert bighorns

• Require large enclosures with native vegetation, water source and a variety of habitat types and topographic relief.
• Enclosure fencing at least 10 feet high and at least 2 feet underground for predator control
• Males and females should be separated in nonbreeding season.
• Two captive populations of Peninsular bighorns: 1. The Bighorn Institute, formed in 1982 to investigate bighorn population decline. They established a captive breeding program in 1985. (more than 75 animals released to wild). 2. The Living Desert Museum is maintains a small group of bighorns for educational purposes.
• The San Diego Wild Animal Park currently has two species of desert bighorn sheep O.c. mexicana and O.c. nelsoni at the Condor Ridge exhibit.
• In 1932 a Mexican sheep was brought to the San Diego Zoo after being hand raised by a Mexican family. It joined a group of Rocky mountain sheep that had been donated by the Canadian Department of Parks.

USFWS Recovery Plan -- For bighorn sheep in the peninsular ranges of California
Bighorn Institute
Coachella Valley Multiple Habitat Species Conservation Plan
Oregon's Big Horn Sheep and Rocky Mountain Goat Management Plan (PDF)
United States Geological Survey

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