Bighorn Sheep

## Description

Bighorn sheep live in North America and are one of two types of mountain sheep in this country. Their color ranges from light brown to dark brown or grayish, and they have a white rear and a white lining on the backs of their legs. Bighorn sheep take their name from the male's large, curved horns. They are excellent climbers in high, steep, rocky mountain regions. The "bighorn sheep" species has 3 living subspecies: Sierra Nevada bighorn sheep, formerly California bighorn sheep, Rocky Mountain bighorn sheep, and Desert bighorn sheep.

## Distribution

Bighorn sheep live in North America in the western mountainous areas, from southern Canada to Mexico. Their habitat consists of grassy mountain slopes, alpine meadows, and foothill country near rocky, rugged cliffs and bluffs. Bighorn sheep need drier slopes where the snowfall is no more than about sixty inches annually, as they cannot walk in deep snow to feed.

## Behavior

Bighorn sheep are diurnal. They are very social creatures, sometimes forming herds of up to 100, although more common are small groups of 8 to 10. Mature males keep away from young and females in separate flocks for most of the year. Young females remain with their mother's group, which is led by an older ewe. These sheep are very alert and their excellent eyesight enables them to accurately judge distances when jumping and finding footholds. In the autumn, the rams compete for ewes with butting contests, charging at each other faster than 20 miles per hour, their foreheads crashing together with a loud crack that one can hear a mile away. Such battles may go on for as long as 24 hours.

## Diet

The diet of Bighorn sheep varies according to the season. They are herbivorous (folivorous, graminivorous) animals and in summer they eat grasses or sedges. In winter they eat plants that are more woody, like shrubs, and willow. They also seek minerals at natural salt licks.

## Reproduction

The breeding season is from November to December, and the young are born in the spring. Ewes will mate with several rams. After a gestation period of 150-180 days, one, and very occasionally two young are born. After only a week, lambs can follow their mothers confidently over the rocky terrain. Several few weeks after birth, lambs form groups of their own, going to their mothers only to drink milk now and again. By 4 to 6 months they are completely weaned. Females in captivity have been mated at 10 to 11 months, but they usually do not breed in the wild until in their second or third year. Due to fierce competition for females between males, and a hierarchy that is based on age and size (horn size as well), males are usually 7 years old before they mate. If dominant rams are killed, younger males in their group will mate sooner.

## Population

### Threats

Unregulated or illegal hunting is the main threat, as well as competition from livestock, introduced diseases, and ongoing human encroachment where they live. Accidental deaths sometimes occur from falls, fighting, highway traffic, and avalanches. Predators include coyotes, wolves, mountain lions, and bobcats.

### Number

It is thought that at the beginning of the 19th-century Bighorns in North America numbered up to two million, but there are about only 70,000 today, including 15,700 sheep in Canada, 42,700 in the U.S., and 4,500 in Mexico. Overall, Bighorn sheep are currently classified as Least Concern (LC) on the IUCN Red List, and their numbers today remain stable.

### Ecological niche

These sheep are important predators of shrubs and grasses in their native landscapes. Bighorn sheep are also important prey for large predators.

## Fun Facts

The female is called a "ewe" and the male is called a "ram".

Desert bighorn do not need water to drink during winter when green vegetation is present. During summer they drink at waterholes at least once every three days.

The hooves of these sheep have a strong grip when they are walking on rocky surfaces.

In winter, Bighorns move to areas where there is less snow, as they find it hard to walk in the snow.

Desert bighorn sheep use two unusual techniques for cooling their bodies during hot summers: panting and perspiring. Only during rainy seasons do desert bighorn exhibit the usual behavior of their species.

Bighorn sheep have the unique ability to be able to jump 6 meters from ledge to ledge.