Overview
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. They range in color from light brown to grayish or dark, chocolate brown, with a white rump and lining on the backs of all four legs.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. 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. Bighorns from the Rocky Mountains are relatively large, with males that occasionally exceed 230 kg (500 lb) and females that exceed 90 kg (200 lb). In contrast, Sierra Nevada bighorn males weigh up to only 90 kg (200 lb) and females to 60 kg (140 lb). Males' horns can weigh up to 14 kg (30 lb), as much as the rest of the bones in the male's body.
Taxonomy
- Kingdom
- Animalia
- Phylum
- Chordata
- Class
- Mammal
- Order
- Artiodactyla
- Family
- Bovidae
- Genus
- Ovis
- Species
- Bighorn sheep, canadensis
- Subspecies
- Rocky Mountain bighorn sheep, Desert bighorn sheep, Mexican bighorn sheep, Peninsular bighorn sheep, Weems' bighorn sheep, California bighorn sheep
Habitat
Bighorn sheep generally inhabit alpine meadows, grassy mountain slopes, and foothill country near rugged, rocky cliffs and bluffs. Since bighorn sheep cannot move though deep snow, they prefer drier slopes, where the annual snowfall is less than about 150 cm (60 in) per year. A bighorn's winter range usually lies at lower elevations than its summer range.
Diet
Bighorn sheep graze on grasses and browse shrubs, particularly in fall and winter, and seek minerals at natural salt licks. Females tend to forage and walk, possibly to avoid predators and protect lambs, while males tend to eat and then rest and ruminate, which lends to more effective digestion and greater increase in body size.
Behavior
Bighorn sheep live in large herds, and do not typically follow a single leader ram, unlike the mouflon, the ancestor of the domestic sheep, which has a strict dominance hierarchy. Prior to the mating season or rut, the rams attempt to establish a dominance hierarchy to determine access to ewes for mating. During the prerut period, most of the characteristic horn clashing occurs between rams, although this behavior may occur to a limited extent throughout the year. Bighorn sheep exhibit agonistic behavior: two competitors walk away from each other and then turn to face each other before jumping and lunging into headbutts. Rams' horns can frequently exhibit damage from repeated clashes. Females exhibit a stable, nonlinear hierarchy that correlates with age. Females may fight for high social status when they are integrated into the hierarchy at one to two years of age.
Hunting
Hunting bighorn sheep is a highly regulated activity that supports conservation efforts, with tag systems ensuring sustainable populations and funding habitat restoration through programs like the Pittman-Robertson Act, which has channeled billions into wildlife recovery across North America. Focus on spot-and-stalk methods in rugged, mountainous terrain, where hunters must glass from a distance to locate rams in alpine meadows or steep slopes, then carefully approach for a clean shot; always prioritize wind direction and terrain cover to avoid spooking the herd. Use a reliable rifle in calibers like .270 Winchester, .30-06 Springfield, or .300 Winchester Magnum for ethical one-shot kills, aiming for the vital area just behind the shoulder with precise shot placement to minimize suffering and ensure quick harvests. The best timing is during the fall rut from late October to December in the northern hemisphere, when rams are more active and visible, increasing opportunities for trophy-sized animals. Trophy criteria emphasize horn curl and mass, with record-book entries through Boone & Crockett or Pope & Young requiring minimum scores based on fair-chase ethics—look for rams with horns exceeding 15 inches in base circumference and full curls. Legal hunting occurs in specific regions of western United States states like Montana, Wyoming, Colorado, and Nevada, as well as western Canada provinces such as British Columbia and Alberta, and limited areas in northern Mexico, all requiring drawn tags or permits to maintain population health and prevent overhunting, demonstrating the effectiveness of regulated harvest in conserving this species.
Conservation Status
Bighorn sheep are classified as Least Concern by the IUCN, but some subspecies are endangered due to threats like diseases from domestic sheep, habitat fragmentation, and overhunting, which have caused population declines in certain regions.