Wolves travel in groups, and they perform almost all the other activities of their lives in the company of fellow wolves. This is one of the most important facts that modern science have learned about wolves and one of the things that most clearly explain their way of life. The pack is usually a family group. It is made up of animals related to each other by blood. The centre of a pack is a pair of wolves----an adult male and female that have produced young. The other members of the pack are their offspring  : young wolves ranging in age from pups to two- and three-year-olds. Most packs have 6 or 7 members, although some may include as many as 15 wolves. Relationships among creatures that live close together in groups are often very complex, and this is true of the ties that connect the members of a wolf pack. Scientific studies of captive  wolves and wolf packs in the wild have shown that many complex rules of behavior seem to govern the way that the animals relate to each other. When wolf pups are born into a pack, one of the most important things they must learn is the "language" of the group, the method by which pack members keep in touch with each other, sharing information and communicating their feelings. Scientists have discovered that wolves have a very complex system of communication. The most famous wolf sound is, of course, the howl, and it is a very important part of wolf language. When people think about howling, they usually imagine a sad, lonely sound made by a wolf sitting all alone on a hilltop in the moonlight. However, this picture in most human beings' mind is not completely true. Wolves howl at any time, not just at night, and they often howl together, not alone. Group or chorus howling is another means by which the members of a wolf reaffirm  their ties with each other and their closeness as a group. One wolf----often the male leader----will point its nose at the sky, open its mouth, and start to howl. Immediately the other members of the pack rush to stand beside him, shoulder to shoulder, and join their voices to his. Each wolf howls on its own note so that a big chorus of slightly different sounds is produced. Chorus howling often takes place before a wolf pack goes out to hunt. At the end of a successful hunt, the pack may also celebrate with a group howl. While wolves are on the track of prey ,they are usually silent. There are occasions when a wolf will howl by itself. This may happen when an animal is separated from the pack. Pack members seem to recognize each other's voices and will keep responding to the howl of their wandering relative until the group is reunited. Because howling is a sound that carries over a considerable distance, it is very useful in communications among separated members of a pack. Howling is also used when members of different packs have to get in touch with each other to pass on information about their locations and their purposes. How many members do most wolf packs consist of?
3--4 4---5 6---7 10---15