Bighorn sheep can be found in several areas of Yellowstone National Park. Although widely distributed across the Rocky Mountains, bighorn sheep (Ovis canadensis) persist chiefly in small, fragmented populations that are vulnerable to sudden declines as a result of disease, habitat loss, and disruption of their migratory routes from roads and other human activities. About 10 to 13 interbreeding bands of bighorn sheep occupy steep terrain in the upper Yellowstone River drainage, including habitat that extends more than 20 miles north of the park. The last count in 2014 found 421 bighorn sheep in the northern Yellowstone area, with 197 counted inside the park. Mount Everts receives the most concentrated use by bighorn sheep year-round. The Rocky Mountain bighorn sheep which are found in greater Yellowstone, differ from other currently recognized subspecies in the United States: Desert bighorn sheep, Dall sheep found in Alaska and northwestern Canada, and Stone’s sheep, which are a subspecies of Dall sheep.
Female (ewes) and young bighorn sheep near Yellowstone River Picnic Area
Younger bighorn ram, his horns don’t yet make a full spiral
Adult males (rams) weigh 174–319 pounds, including horns that can weigh 40 pounds. The horns of an adult ram can make up 8–12% of his total body weight. Rams can live to be 9-12 years old. Adult females (ewes) weigh up to 130 pounds and have an average life span of 10–14 years. Mating season begins in November. Ewes give birth to one or two lambs born in May or June. Bighorn sheep feed primarily on grasses in spring and summer and forage on shrubby plants in fall and winter.
Three bighorn rams eating grasses
Here are some facts about the horns of bighorn sheep:
- Unlike deer/elk antlers that are shed annually, bighorn sheep keep their horns for their entire life.
- Both rams and ewes have horns, but ewe horns are substantially shorter.
- Horn growth is greatest during the summer and early in life. Female horns grow very little after 4–5 years, likely due to reproductive costs.
- The horn size of bighorn sheep rams can influence dominance and rank, which affects social relationships within herds.
- Older ram horns may be “broomed” or broken at the tip, which can take off 1–2 years of growth.
- Ram skulls have two layers of bone above the brain that function as a shock absorber, an adaptation for the collision of head-on fighting that is used to establish dominance between rams of equal horn size, especially during mating.
Ram bighorn sheep in winter in the area of Soda Butte Creek/Lamar River Junction
Places to view bighorn sheep in Yellowstone:
- Summer: slopes of Mount Washburn and along Dunraven Pass
- Year-round: Gardiner Canyon between Mammoth and the North Entrance, Leaving Tower Junction on the Northeast Entrance road- the area around the bridge over the Yellowstone River; both sides of the NE Entrance road between the Yellowstone River bridge until the terrain opens up past the Yellowstone River Picnic entrance; Along NE Entrance road- the area where Soda Butte Creek meets Lamar River
- Also: On cliffs along the Yellowstone River opposite Calcite Springs; above the Soda Butte Creek near Pebble Creek; Barronette Peak; and in backcountry of eastern Absarokas
Two bighorn ewes near the Yellowstone River Picnic Area
A group of bighorn sheep in winter: 2 rams (lower), 2 ewes (higher) & 1 young sheep
A herd of bighorn sheep ewes near Yellowstone River Picnic Area
Bighorn sheep heading back to high country after getting a drink at Soda Butte Creek
