Ovis canadensis

Description

The bighorn weighs 115 to 280 pounds (with an average of 198 pounds), and is 5 to 6½ feet long. Rams are larger than ewes.

The summer coat is dark brown, but the color fades somewhat in the winter. Both sexes have a white belly, rump patch, muzzle, and eye patch; the backs of the legs are also white.

Rams have massive horns that curve around the back of the head past the neck. Ewes also have horns, but they are much smaller and only slightly curved. The horns are divided into concentric rings, with each ring representing one year's growth.

Distribution and Habitat

Bighorn are found throughout the Rocky Mountains from southern Canada to the Mexico border. It inhabits alpine meadows, grassy mountain slopes, and foothill country, in proximity to rugged, rocky cliffs and bluffs. It requires drier slopes where annual snowfall is less than about sixty inches a year, and the vegetation must be sparse enough to allow for an unobstructed view. In lives at an elevation of 2,500 to 5,000 feet in the winter; at 6,000 to 8,500 feet in the summer.

Diet

Bighorn feed primarily on sedges and grasses, along with new aspen and spruce buds. In the autumn and winter, herbs, fungi, lichens and berries are also eaten. Most feeding is done during the day.

Social Behavior

In the summer, sexes segregate into flocks of about a dozen individuals (groups of ewes with young are usually larger than ram groups). In the winter, these focks assemble into mixed herds of up to 100 animals.

There is vigorous rivalry between rams. This rivalry often escalates to full force head-to-head combat, during which the two animals charge at each other at full speed and literally butt heads. This combat can last a full day or more, after which both sides generally lose interest in the conflict and go their separate ways. Despite some popular depictions, bighorn do not strike each other with their horns, as their horns are not actually strong enough to withstand such an impact. The forehead bones, however, are very strong and specially adapted for taking such punishment, so rams literally "butt heads" during combat.

Reproduction

Breeding season runs from July through December, with most activity taking place in the fall and early winter. Females are promiscuous, so there is no real competition among rams for ewes.

Gestation takes 6½ months. The ewe gives birth in seclusion, and the lamb is able to follow its mother soon after birth. It is weaned at about 5 months.

Although rams reach sexual maturity at 4 years, most do not actually breed for the first time until about 6 or 7 years of age. Ewes reach sexual maturity at 2½ years, and usually give birth in their third year. Average lifespan is 10 years in the wild.

Other Information

Not surprisingly, bighorn can zigzag up and down cliff faces easily. They can get a foothold on ledges as narrow as two inches, and can leap a span of up to 20 feet. Bighorn can move over level ground at 30 mph, and up mountain slopes at 15 mph, and swim freely.

Scientific Classification

phylum Chordata
subphylum Vertebrata
class Mammalia
order Artiodactyla
family Bovidae
subfamily Caprinae
genus & species Ovis canadensis

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