Pups have blue eyes at birth and weigh about one pound. Their eyes open when they are about two weeks old, and a week later begin to walk and explore the area around the den. Pups romp and playfight with each other from a very young age. Scientists think that even these early encounters establish hierarchies that will help determine which members of the litter will grow up to be pack leaders. Wolf pups grow rapidly, reaching 20 pounds at two months and full size in a year.
All adults share parental responsibilities for the pups.
They feed the pups by regurgitating food for them from the time the pups are about four weeks old until they learn to hunt with the pack. A wolf pup is the same size as an adult by the time he or she is about a year old, and is able to mate by about two years of age. Pups remain with their parents for at least the first year of their of their lives, while they learn to hunt. During their second year of life, when the parents are raising a new set of pups, young wolves can remain with the pack, or spend periods of time on their own. Frequently, they return in autumn to spend their second winter with the pack.