After several weeks at the den, pups are moved to their first ground nest or homesite. Movement to new homesites becomes more frequent as the pups mature. Pups grow rapidly and approach adult size by autumn or early winter. Sexual maturity usually is attained at 2 years. In large packs, however, it is doubtful that many wolves breed at that age.
Some wolves leave their packs to become lone wolves.
Loners may start their own packs if a mate and a vacant area can be found. The major prey of wolves are large hoofed mammals, including deer, moose, elk, caribou, bison, musk-oxen, and mountain sheep. Beaver is eaten when available. In summer a variety of smaller foods, such as small rodents and berries, supplement the diet. Animals killed are usually young, old, or otherwise weaker members of their populations because they are easiest to capture.