Wolves live in family groups called packs. Most packs have about 8 members, but some have more than 20. Zoologists believe the members of a pack remain together because they have strong affection for one another. Most maturing wolves leave the pack and become lone wolves. A lone wolf travels alone until it finds a mate. These two may have pups and form their own pack. 
    Habits. Each wolf pack has a social order called a dominance hierarchy. Every member of the pack has a certain rank in the hierarchy. High-ranking members, called dominant wolves, dominate low-ranking members, known as subordinate wolves. A dominant wolf and a subordinate wolf show their rank almost every time they meet. The dominant wolf stands erect, holds its tail aloft, and points its ears up and forward. It may show its teeth and growl. The subordinate wolf crouches, holds its tail between its legs, and turns down its ears. It may also whine. 
   A pack lives within a specific area called a territory. Wolves claim a territory by marking it with their scent. The leader of the pack urinates on rocks, trees, and other objects along the boundaries of the area. Other wolves can then recognize the boundaries. A pack does not allow other wolves to hunt in its territory. If wolves from another pack trespass, they may be attacked and killed. 
   Studies indicate that the size of the territory depends mainly on the availability of prey. If prey is scarce, the territory may cover as much as 800 square miles (2,100 square kilometers). If prey is plentiful, the area may be as small as 30 square miles (78 square kilometers). 
   Young. Wolves mate during the winter. The female carries her young inside her body for about 63 days. She then gives birth to 1 to 11 pups in a sheltered area called a den. The den may be in a cave, a hollow log, an abandoned beaver lodge, or underground. 
   Wolf pups weigh about 1 pound (0.5 kilogram) at birth and are blind, deaf, and helpless. At first, they live on only the mother's milk. When they are about 3 weeks old, they begin to eat meat and to leave the den for short periods. Adult wolves provide the pups with meat. An adult eats much meat after killing an animal. To get some of this meat, the pups lick the mouth of the adult wolf. The adult coughs up the meat, and the pups eat it. 
   Wolf pups leave the den permanently when they are about 2 months old. The pups move to an unsheltered area that is called a rendezvous site, and they remain there during the summer while the adults hunt and bring back food. In the fall, the quickly growing pups and the adults begin to hunt together as a pack. 
   How wolves hunt. When the members of a pack gather to begin a hunt, they greet each other and howl. Their howling may become very loud, and it warns other wolves to stay out of the pack's territory. 
   Wolves roam through their territory until they find prey. They then move in on the prey. They may inch closer to it, perhaps in single file. Then they break into a run, and the chase begins. 
   Wolves hunt and chase many more animals than they can catch. Wolves eat almost any animal they can catch. Many of the animals they hunt, such as caribou and elk, are faster and stronger than wolves. Therefore, wolves must be quick, tireless, and clever to catch their prey. 
   Wolves hunt at any time of the day or night but tend to hunt more in the evening, night, and early morning. If wolves can catch their prey, they attack the rump or sides of the animal. They try to wound the animal and make it bleed until it weakens. Then they grab the victim by the throat or snout. Wolves can usually kill a large animal in only a few minutes. However, the entire hunt may take several hours. The wolves may give up the chase if the animal is strong, such as a healthy moose. They also may abandon the hunt if the animal is exceptionally fast. 
   Sick, injured, or aged animals that lag behind their herds make easy targets for wolves. The wolf helps strengthen the herds of its prey by killing such animals. An old or unhealthy animal can be a burden to its herd. For example, an aged caribou eats food that other caribou need to raise their young. A sick elk may infect other members of the herd. By eliminating such animals, wolves perform an important natural function.