The animal population of the tundra is always changing due to immigration and emigration.
Birds such as ravens, falcons and loons migrate.
Animals that stay in the tundra must deal with the long winters. Several have a layer of fat for insulation. Most of them raise their young in the summer and hibernate during the winter.
A polar bear cub. (http://animals.timduru.org/dirlist/bear/Cute-PolarBear-Cub-SittingOnSnow.jpg)
Tundra animals include: lemmings, caribou, arctic foxes, wolves, and polar bears.(The tundra biome, par. 5)
An arctic fox. (Rosing)
Fish in the tundra include: cod, salmon and trout.
Animals in the alpine tundra must also be well adapted to the environment and they include: mountain goats, sheep and elk. (The tundra biome, par. 8)
Adaptation is the ability of an organism to survive in a particular environment due to changes in form of behavior.