Five Mexican gray wolf puppies ventured out of their den at the Brookfield Zoo in Illinois. The almost four weeks old pups are from different packs, but came together at the zoo as part of their cross-fostering program. Three of the pups, all males were born at Brookfield Zoo in April. The other two, a male and female pup, we born to the San Mateo wild wolf pack in New Mexico. Mexican gray wolves are the rarest subspecies of gray wolves in North America. About 4,000 wolves once lived in what’s known as their historic range, from central and northern Mexico and southwestern United States.