Pups are born in the spring in small caves, hollowed out logs, or, most often, underground dens. Dens are dug by both sexes and used again, year after year. The wolf has a gestation period of 62-63 days. Generally there are 5 or 6 pups in a litter, Pups are born blind, deaf and probably unable to smell, weighing about a pound (0.5 kg). At birth the pups have short, dark brown fur which gradually lightens in colour until it turns gray at about three months of age. Neonatal pups are unable to regulate their body temperatures well and depend on the mother for warmth. This is one reason feeding of the mother by the other adult pack members is important to rearing pups successfully. If the mother had to hunt for food she might not be able to spend sufficient time huddled with and nursing the new pups.
For the first week or so, the mother spends most of her time in the den with her babies as they are unable to regulate their body temperature very well and depend on her for warmth. The mother slowly extends her time away from them and almost every pack member becomes involved in the care of the young. If more than one litter is born, all pups which survive are put into one combined litter and are tended and nursed by all mothers. Unmated females or females which lost pups can also nurse pups. When more than one female is in the den at the same time, they are sometimes aggressive to each other but not to the pups. There seems to be some competition among the females for access to pups no matter which female's they are.
During the second week, their eyes open up and activity increases. The pups grow quickly, and at around 3 weeks of age start to explore outside the den. Their baby teeth come in At this time the other pack members, including adult males and yearling, begin to feed pups solid food. The mothers are seldom fed after the pups emerge from the den. By this time, the mother often leaves the pups alone or with another adult or yearling while she hunts for food. Yearlings are somewhat intermediate in that they are fed by adult pack members but also feed pups, presuming there is enough food. (Yearlings are sort of in-between in behavior, stilll being fed by adult wolves, but also taking responsibilty in feeding the pups.) At around 9 weeks of age, the pups are weaned and moved out of the den to the area the pack normally stays in.
All pack members play with and care for pups. The adults also play with each other. Adults and pups play by chasing, jumping over each other, ambushing and wrestling with jaws or forelimbs. Other play behaviours include muzzling, tail wagging, paw raising and licking faces, and of course, running! Play is an important part of establishing rank within the pack.
The period when the young pups emerge from the den and are getting to be highly mobile is to most observers the most exciting time to watch wolves. This is when the wolf's co operative and friendly nature is most strikingly demonstrated. All pack members seem to greatly enjoy playing with and caring for pups. The adults play with each other as well. Adult and pup play is often extremely exuberant with chasing, jumping over each other, ambushing and wrestling with jaws or forelimbs. Other friendly behaviours include muzzling, tail wagging, paw raising and licking faces. Dog owners will recognize these behaviours since they are essentially the same in domestic dogs.
The pup becomes a young wolf, practicing for survival by hunting with the adults (around 3 mos.), losing his baby teeth (at 4 to 6 mos) and finally getting his 42 adult teeth, and quickly enough becoming a yearling; but only about 25% of pups born in the wild make it through their first year, the rest dying because of lack of food, disease (mange, parvovirus among others), accident or attack by bears or humans.
In our captive conditions, the wolves are well provided for so the behaviour we see is basically "boom times". In the wild this is frequently not the case. Roughly only about 25% of pups born in the wild make it through their first year. The adults and yearlings are simply not able to obtain enough food to feed them all or they lose pups to disease or accident.