Bighorn Sheep

Description:

is a species of sheep in North America[4] named for its large horns. These horns can weigh up to 30 pounds (14 kg), while the sheep themselves weigh up to 300 pounds (140 kg).[5] Recent genetic testing indicates that there are three distinct subspecies of Ovis canadensis, one of which is endangered: Ovis canadensis sierrae. Sheep originally crossed to North America over the Bering land bridge from Siberia: the population in North America peaked in the millions, and the bighorn sheep entered into the mythology of Native Americans. However, by 1900 the population had crashed to several thousand. Conservation efforts (in part by the Boy Scouts) have restored the population. Bighorn sheep are named for the large, curved horns borne by the rams (males). Ewes (females) also have horns, but they are shorter with less curvature.[14] They range in color from light brown to grayish or dark, chocolate brown, with a white rump and lining on the back of all four legs. Males typically weigh 127–316 pounds (58–143 kg), are 36–41 inches (91–100 cm) tall at the shoulder, and 69–79 inches (180–200 cm) long from the nose to the tail. Females are typically 75–188 pounds (34–85 kg), 30–36 inches (76–91 cm) tall and 54–67 inches (140–170 cm) long.[15] Male bighorn sheep have large horn cores, enlarged cornual and frontal sinuses and internal bony septa. These adaptations serve to protect the brain by absorbing the impact of clashes.[16] Bighorn sheep have preorbital glands on the anterior corner of each eye, inguinal glands in the groin and pedal glands on each foot. Secretions from these glands may support dominance behaviors.[16] Bighorns from the Rocky Mountains are relatively large, with males that occasionally exceed 500 lb (230 kg) and females that exceed 200 lb (90 kg). In contrast, Sierra Nevada Bighorn males weigh up to only 200 lb (90 kg) and females to 140 lb (60 kg). Males' horns can weigh up to 30 lb (14 kg), as much as the rest of the bones in the male's body.[17]

Habitat:

The Rocky Mountains and Sierra Nevada Bighorn occupy the cooler mountainous regions of Canada and the United States. In contrast, the desert bighorn sheep subspecies are indigenous to the hot desert ecosystems of the Southwestern United States. Bighorn sheep generally inhabit alpine meadows, grassy mountain slopes and foothill country near rugged, rocky cliffs and bluffs.[17] Since bighorn sheep cannot move though deep snow, they prefer drier slopes where the annual snowfall is less than about sixty inches a year.[17] A bighorn's winter range usually lies 2,500-5,000 feet in elevation, while its summer range is tends to be 6,000-8,500 feet.[18] Bighorn sheep are highly susceptible to certain diseases carried by domestic sheep such as scabies and pneumonia; additional mortality occurs as a result of accidents involving rock fall or falling off cliffs (a hazard of living in steep, rugged terrain). Bighorns are well adapted to climbing steep terrain where they seek cover from predators. Predation primarily occurs with lambs which are hunted by coyotes, bobcats, lynxes and golden eagles. Bighorn sheep of all ages are threatened by bears, wolves and especially cougars, which are perhaps best equipped with the agility to predate in uneven, rocky habitats.[14][19][20] They are considered good indicators of land health because the species is sensitive to many human-induced environmental problems. In addition to their aesthetic value, bighorn sheep are considered desirable game animals by hunters. Bighorn sheep graze on grasses and browse shrubs, particularly in fall and winter, and seek minerals at natural salt licks.[19] Females tend to forage and walk, possibly to avoid predators and protect lambs,[21] while males tend to eat and then rest and ruminate which lends to more effective digestion and greater increase in body size.[21]