Two Mexican gray wolves nuzzle each other in the Sedgwick County Zoo. With a family structure that more closely resembles ours than many primate societies, most wolf packs are led by a breeding pair—an alpha male and female, both of which care for pups and fight to defend their family.

(Text adapted from and photograph shot on assignment for, but not published in, "Return of the Gray Wolf," May 1998, National Geographic magazine)