If one of the alpha pair dies, the beta wolf will take its place. Within the pack, only the alpha pair will mate, usually around 2 years of age. Wolf litters average around six pups. However, only about half of the litter survives, making the pups the most important priority of the pack. Wolves are able to survive anywhere there is adequate food and human tolerance.
Wolves usually feed on elk, deer, and moose.
However, in 1997 the Crystal Creek pack was responsible for the death of a bison. Wolves usually rest during the day and hunt in the early morning or in the evening. While in Yellowstone, it isn't likely to see a pack of wolves, but you may hear them. The howl of the wolf can be frightening, but it is their main use of communication. Wolves also yip, squeal, growl, chirp, and bark to express themselves.