Some common adaptations of resident animals in the arctic and alpine tundra:
- short and stocky arms and legs.
- thick, insulating cover of feathers or fur.
- color changing feathers or fur: brown in summer, and white in winter.
- thick fat layer gained quickly during spring in order to have continual energy and warmth during winter months.
- many tundra animals have adapted especially to prevent their bodily fluids from freezing solid.
- resident animals like the ptarmigan and the ground squirrel use solar heating to stay warm and save energy. Both animals stay out in the sun to warm up and during the summer when the weather is warm, seek shade to cool off.
Not only do animals have to keep warm, but insects needed to develop ways to prevent freezing of their bodily fluids. Like tundra animals, insects also use the sun to keep warm. Insects are also dark in color and hairy for the same reason animals are. Being small also makes it easier for tundra insects to keep warm. However, it also makes them more prone to freezing. This is why insects of the tundra have built up antifreeze agents in their bodies to prevent their cells from freezing. Some insects even dehydrate so that there will be less body fluid to freeze. Some insects and animals, along with solar heating, use supercooling to prevent fluids from freezing. Supercooling allows the animals or insects body fluids to cool below freezing without becoming solid. Very little of the supercooled animals and insects' bodies freeze anyway, because they clean their bodies of ice producing nuclei.
Animals and insects are obviously well adapted to the tundra's climate. Their diets must also be adaptable. If their diets were not adaptable, many of the tundra's animals and insects would starve in the winter because of the lack of certain types of food. An example of this type of adaptation is the diet of the brown bear. In the spring, since food is still scarce, bears may dig up roots or even eat seaweed found along water sides. In the summer the brown bear's diet is more complete. They will hunt for salmon and eat berries.
Since the tundra is the youngest biome, some tundra plants, insects, and animals, can also be found in other biomes. For example, brown bears and caribou can also be found in the taiga biome.