Pack animals, timber wolves usually live in family groups that possess a clear hierarchy of its members. Only the dominant male and female in a pack are allowed to mate, although all members play a role in the care of the young that are produced. Young wolves usually stay with the pack until they achieve sexual maturity and then leave to begin new packs, spreading to new areas in order that there may be sufficient prey to consume. Primarily active at night, timber wolves prefer to feed upon deer, caribou, and other large herbivores that are separated from their group or are in some other way weakened, but will also consume small mammals, carrion, and occasionally vegetation.