The tundra is a permanent home to only a few species of animals because of its harsh environment. Birds, caribou, and red deer, for example, spend only the summers there. The Antarctic tundra has the fewest animals of all.

For tundra animals, size is an important factor in preventing heat loss. When an animal's appendages (arms, legs, tails, ears) are small, they lose less heat. The Arctic fox, for example, has small ears, short legs, and a short tail. This means there is less area from which body heat can escape.

Microorganisms

A microorganism is a tiny animal, such as protozoa or bacteria, that cannot be seen with the human eye. Bacteria live in the active layer of the tundra soil and help decompose dead plants and animals.

Invertebrates

Invertebrates are animals that do not have a backbone. Clams, mussels, snails, crabs, and shrimp are invertebrates...