Mexican Gray Wolves (images)

U.S. Fish and Wildlife Service

Mexican gray wolf pups in southeastern Arizona. The U.S. Fish and Wildlife Service proposes to add the subspecies of Mexican gray wolves to the federal endangered species list.

Luis Sinco / Los Angeles Times

A female Mexican gray wolf runs around in a holding pen at the Sevilleta National Wildlife Refuge in New Mexico in 2009. This animal is distinguished by burn scars to its ears, which were sustained when a wildfire nearly overran its pen at another holding site.