Dall sheep

The Dall sheep or Dall's sheep is a subspecies of Thinhorn sheep. They usually eat grass and other plants. They live in northwestern North America, in Canada and Alaska.
Appearance.
These sheep are about 1.5 m high and can weigh up to 110 kg. The female sheep have small horns but the male sheep have larger horns that twist more as they get older. The horns are tan in color. The wool of Dall's sheep is almost pure white.
The sheep's horns grow fastest in warm weather and slowest in cold weather. This puts rings in the horns called annuli. The number of rings shows how old the sheep is.
The other kind of thinhorn sheep, the stone sheep, can breed with Dall sheep. These thinhorn sheep are sometimes called Fannin's sheep.
Most Dall sheep live to be about 12 years old, but some ewes live to be 16 or even 19.
Home.
There are about 100,000 Dall sheep in the world. They live in Alaska in the Kenai Peninsula and Brooks Range. They live in Canada's Yukon and Northwest Territories in the Mackenzie Mountains, Kluane and Saint Elia ranges.
Behavior.
Like other thinhorn sheep, Dall sheep live in mountains. Because they do not have long legs or large feet, they cannot move easily in snow. Instead, they live in places where the wind blows the snow away before it gets too deep. They climb onto rocks to escape animals that want to eat them. They follow the same paths from summer places to winter places for generations.
Dall sheep live in herds. Most of the time, the rams live together in a bachelor herd, and the ewes and young sheep live together in other herds. Male sheep leave the female herds when they are two or three years old.
The sheep mate in November. Although younger rams can mate, it is mostly the older rams who actually do.
Before an ewe gives birth, she climbs into a rocky place that humans call a "lambing cliff." She gives birth there. She and her lamb stay there for a few days before coming back down. This makes it harder for predators to find and eat the new lamb. The lamb can eat grass by October.
Predators.
Golden eagles, wolves, grizzly bears, and wolverines eat thinhorn sheep.
History.
Thinhorn sheep and snow sheep became two separate species around the time the last ice age ended, 10,000 to 18,000 years ago. After that, the thinhorn sheep moved east and spread out. The Dall sheep and stone sheep became separate subspecies some time after that.