Ecologists are interested in learning how to predict changes, determining the consequences of these changes, and projecting what will happen if humans interrupt some of these processes. A large variety of animals live in or use forests. These animals range in size from microscopic mites to large mammals such as bears. Animals which inhabit forests may make their homes in burrows, caves, tree cavities, nests, or other shelters. As you can see, the animal community of a forest is diverse and complex.
Some birds build nests or peck out cavities in trees.
Rodents may collect straw and other insulating material to make their dens warmer. Many also store seeds and other foods for winter. Beavers harvest trees and build dams in order to create the type of environment they need for survival. Many activities of animals help spread the seeds of forest plant species. This eventually has an impact on the species composition of a forest.