Constantly persecuted and targeted by large scale predator eradication programs sponsored by the federal government, wolves have been pursued with more passion and determination than any other animal in U.S. history. By the time wolves were finally protected by the Endangered Species Act of 1973, they had been exterminated from the lower 48 states, except for a few hundred that inhabited extreme northeastern Minnesota. Second only to humans in their adaption to climate extremes throughout the world, gray wolves were equally at home in the deserts of Israel, the deciduous forests of Virginia and the frozen Arctic of Siberia. Within the continental United States, gray wolves once ranged from coast to coast and from Canada to Mexico. Wolves begin mating when they are 2 to 3 years old, sometimes establishing lifelong mates.
Wolves usually rear their pups in dens for the first six weeks.
Dens are often used year after year, but wolves may also dig new dens or use some other type of shelter, such as a cave. An average of five pups are born in early spring and are cared for by the entire pack. They depend on their mother's milk for the first month, then they are gradually weaned and fed regurgitated meat brought by other pack members. By 7 to 8 months of age, when they are almost fully grown, the pups begin traveling with the adults. Often, after 1 or 2 years of age, a young wolf leaves and tries to find a mate and form its own pack.