American Bighorn or Bighorn Sheep

Ovis canadensis

Description

Bighorn sheep have a smooth pelage with an outer coat of brittle huard hairs and short grey, under fur of crimped fleece. The coat of this species in the summer is rich, glossy brown and fades by late winter. Male bighorn sheep (rams) typically weigh 119-27 kg while ewes (females) typically weigh 53-91 kg. Both male and female bighorn sheep have horns. However, the horns of the female bighorn are much smaller and less curved than those of the males.

Habitat

This species is found in the Rocky Mountains from southern Canada to Colorado, a subspecies is found from Nevada and California to west Texas and south into Mexico. Bighorn sheep prefer alpine meadows, grassy mountain slopes and foothill country in proximity to rugged, rocky cliffs and bluffs. Annual snowfall must be less than 60 inches a year because these sheep require drier slopes. Summer ranges of this species habitat are 6,000-8,500 feet above sea level while winter ranges lie 2,500-5,000 feet above sea level.

Feeding Behavior and Diet

This grazing herbivorous species feeds throughout the day, grazing mostly on grasses, sedges and forbs. In the winter months bighorn sheep will also consume browse when food is scarce.

Reproduction

Breeding season for bighorn sheep is called rutting season, which occurs in fall and early winter. The desert subspecies does not rut until July-December. Males do not defend territories but they defend rights to mate with individual females by battling other males. Ewes (females) are seasonally polyestrous, mating with several rams. 1-2 young are born in early spring, 150-180 days after mating. After only a few weeks, young form their own group and only return to their mothers to suckle. Young are weaned after 4-6 months. Female bighorn sheep reach sexual maturity by 10-11 month but do not typically breed until their second year. Males do not typically mate until they are seven years old due to the fierce competition by dominant males.

Months and Times of Activity

Bighorn sheep are diurnal, activity peaking throughout the day. This species migrates seasonally to different elevations; in the summer ranges are 6,000-8,500 feet above sea level while winter ranges lie 2,500-5,000 feet above sea level.

Special Features, Stories, Relationships

• Nematode lungworms (Protostrongylus stilesi and P. rushi) are parasites that infect all bighorn sheep individuals, these parasites most likely co-evolved with these sheep in North America because most sheep do not show any effects from the lungworms.
• Bighorn sheep can zigzag up cliff faces and use ledges of only 2 inches for footholds. They leap from edge to edge and can scramble a mountain slope at 15 miles per hour and can run at 30 miles per hour on flat land.
• The size of ram’s horns are a symbol of rank, a ram with larger, heavier horns are more advantageous when smashing into an opponent at 20 miles per hour. Head butting matches between males can last for 25.5 hours.
• Ram’s horns may weigh up to 14 kg, which is about how much all the bones in a ram’s body weighs.
• Bighorn sheep have double-layered skulls reinforced by struts to protect their brain during battle. Another form of protection is a broad, massive tendon that links the skull and spine, preventing the head from pivoting and recoiling from blows.
• and spine, preventing the head from pivoting and recoiling from blows.
• To read legends featuring this animal go to; www.firstpeople.us/FP-Html-Legends/CoyoteAndMountainSheep-PenDOreille.html
• Children’s book featuring this animal: Rocky Mountain Bighorn Sheep by Dale Toweill

References

Ballenger, L. 1999. "Ovis canadensis" (On-line), Animal Diversity Web. Accessed November 03, 2014 at http://animaldiversity.ummz.umich.edu/accounts/Ovis_canadensis/