The generally greenish-brown vegetation of the tundra consists of shrubs, mosses, herbs and lichens. Coastal tundras have grasses which can become matted. Rocky cliffs are home to algae and some kinds of fungus. In the more severe areas of tundra, the growing season is only two to four months long. That short growth time coupled with a rainfall of only 15 inches a year means that plant growth is minimal. Coastal areas are more temperate and have greater rainfall, which gives them a wider variety of plants.
Polar bears live in the tundra, as do Arctic foxes, wolves, hares and weasels. Many species have white coats in the winter for camouflage. Plant eating animals such as reindeer, musk ox and caribou do well in the tundra because their thick bodies have less heat loss than thinner species. Lemmings provide food to the predators of the tundra and fertilizer to the plants. The manure that accumulates around their burrows helps tundra plants grow.
Mosquitoes and black flies have darker colored bodies to help absorb heat in the tundra. Birds aren't year-round residents. Most, such as geese, migrate into the tundra during the summer and leave when the snow flies. Birds of prey, such as jaegars and snowy owls, stay in the tundra when their food is plentiful but leave when smaller animals hibernate.
Permafrost happens when the ground stays frozen for two or more years. It ranges from less than one foot in depth to several feet. It tends to occur in areas with little snowfall and short dry summers. Permafrost has an active layer at the top, which freezes and thaws every year. Permafrost lies underneath 20 percent of the earth's surface.
