A wolf which has been driven from the pack or has left of its own accord is called a lone wolf. It avoids contact with packs and rarely howls.
There are many subspecies of wolf including the Arctic wolf, all of which use a variety of howls to communicate to one another.
Wolves are legendary because of their spine-tingling howl, which they use to communicate. A lone wolf howls to attract the attention of his pack, while communal howls may send territorial messages from one pack to another. Some howls are confrontational. Calls may be answered by rival packs. Much like barking domestic dogs, wolves may simply begin howling because a nearby wolf has already begun.