Thinhorn sheep

The thinhorn sheep (Ovis dalli) is a hoofed animal in the family Bovidae. They live in northwestern North America.

There are about 115,000 thinhorn sheep alive.  There are two subspecies of thinhorn sheep, the Dall sheep (Ovis dalli dalli) and stone sheep (Ovis dalli stonei).  Most thinhorn sheep are Dall sheep.

Most of the stone sheep live in British Columbia.

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 wool of the stone sheep is almost all black. Stone sheep's horns do not flare out as much and are lighter in color.

Behavior

These sheep live in mountains.  In the summer, they come to grassy places to eat twigs, sage, buds, leaves and grass.  These places are 1200 to 1500 meters above sea level.  In the winter, they stay on the south sides of the mountains, where it is warmer.  These places are about 1500 to 2200 meters above sea level.  Although they do well in the cold, thinhorn sheep do not move easily through deep snow.  They have short legs and small feet, so they cannot walk through snow or on top of it.  Instead, they try to live in forests where the snow is not deep or near cliffs.  They can climb the cliffs to get away from animals that want to eat them.  They follow the same routes from summer places to winter places for generations.

Thinhorn 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 about two years old.

The sheep mate in November.  Although younger rams can mate, it is mostly the older rams who actually do.  Rams only fight each other if their horns are almost the same size.  Otherwise, rams with smaller horns give way to rams with larger horns. Thinhorn rams do not fight each other as much as bighorn rams do.

The ewes give birth when the Spring plants are growing.  The ewe climbs up into a rock place and gives birth.  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.

Predators

Golden eagles, wolves, bears, and wolverines eat thinhorn sheep.  It is easiest for predators to catch sheep in bad winters, when the snow is deep and the spring comes later.  The sheep are hungry and cannot run away quickly.

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.

References

Category:Caprids
Category:Mammals of North America