Reindeer

The reindeer, also known as the caribou in North America, is a deer from the Arctic and Subarctic, including both resident and migratory populations. While overall widespread and numerous, some of its subspecies are rare and one (or two, depending on taxonomy) has already gone extinct.
Reindeer vary considerably in color and size. Both sexes grow antlers, though they are typically larger in males. There are a few populations where females lack antlers completely.
A variety of predators prey heavily on reindeer. Golden Eagles prey on calves and are the most prolific hunter on calving grounds. Wolverine will take newborn calves or birthing cows, as well as (less commonly) infirm adults. Brown Bears and polar bears prey on reindeer of all ages, but like the wolverines they are most likely to attack weaker animals, such as calves and sick deer.
The Gray Wolf is the most effective natural predator of adult reindeer, especially during the winter. As carrion, caribou are fed on by foxes, ravens and hawks.
Blood-sucking insects, such as black flies and mosquitoes, are a plague to reindeer during the summer and can cause enough stress to inhibit feeding and calving behaviors.