Northern coniferous forest. Fisher Gray Wolf Moose North American Porcupine Northern Red-Backed Vole Pine Marten Red Squirrel Main Menu

One of the largest concentrations of trees on Earth, the northern, or boreal, forest extends across North America and northern Eurasia. The ecology of this vast landscape of pine, spruce, fir, and larch rarely attains a climax or stable state because of the biome's long winter, short growing season, and frequent natural forest fires.

Some mammal species that inhabit boreal forests also live farther south, but in the north, these species tend to be larger. Their greater size helps them conserve energy, especially in winter, a significant adaptation that outweighs the disadvantage of requiring more food to sustain a larger bulk.

The threat of food shortages dominates the life of most mammals living in the north. The moose and the caribou, for instance, rarely stop foraging in the winter, looking for alternate food sources — aquatic plants in the case of the moose, tundra lichen for the caribou — that are covered by ice and snow. Heavy grazing and digging of forest lichen and new shoots and saplings puts pressure on a forest's ecology. This, coupled with fire damage, sometimes results in serious food shortages and a subsequent decline in the region's moose and caribou populations.

Survival strategies of smaller boreal mammals include hibernation or, as with many rodents, wintertime burrowing under the thick blanket of snow, where mosses, herbs, and shrubs remain available. Predators such as the marten and the mink (Mustela vison) face the winter with pelages of thick underfur and long, stiff guard hairs.

Ready for the first mammal? Check out the Fisher.

>>Map of World Biomes<<