American Bighorn Sheep

American bighorn sheep
(Ovis canadensis)

A stocky sheep with very large horns living in the mountains of North America. The males stage impressive fights each year, and have extra-thick skulls to prevent brain damage during clashes.

Subspecies
Seven races, sometimes the southernmost race is cited as a subspecies, O.c. nelsoni.

Life span
On average, 9 years, but up to 24.American bighorn sheep

Statistics
168-186cm long, standing 94-110cm at the shoulder and weighing 57-140kg (females slightly smaller, weighing 56-80kg).

Physical Description
A stocky sheep with a short, crimped coat. In the summer they are a rich brown with large white patches on the buttocks, but they fade to grey in the winter. The males have very large, curved horns weighing up to 14kg, whilst the females’ are much smaller and less curved. The skull is double-layered to absorb the impact of fighting blows, and there is a strong tendon running from the skull down the neck to help protect the neck during twisting movements.

Distribution
From South-western Canada to Western USA and North Mexico.

Habitat
Alpine to dry desert.

Diet
Grass and some other vegetation.

Behaviour
Males and females live in separate herd, usually forming small groups of 8-10 individuals, but sometimes congregating into much larger herds. Female lambs tend to stay in their mothers’ herd whilst males leave. They range over quite large areas, and move from sheltered valleys in the winter onto the upland areas during the summer. They are very agile on rocky surfaces and narrow ledges and are good swimmers.

Reproduction
Mating takes place in the late autumn and early winter. Males fight over receptive females, running and clashing horns at up to 20 miles per hour. Such battles can go on all day, with an average of 5 clashes per hour. Gestation lasts 150-180 days, after which 1-4 young are born. The lambs are capable of following their mother almost immediately. After a few weeks they start to form creches, being nursed only occasionally by their mothers. Weaning is at 4-6 months. Females generally have their first lambs when 2-3 years old, whilst males cannot usually gain enough dominance to mate until at least 7, although they reach sexual maturity much earlier than that.

Conservation status
Listed as ‘Lower risk – Conservation Dependent’.

Voice
Bleating and snorting, although generally quieter than many sheep.

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