Officials with the Mexican wolf recovery program say they're finding evidence of success in cross-fostering.
The Arizona Game and Fish Department, Chicago Zoological Society, Endangered Wolf Center and U.S. Fish and Wildlife Service are working to reintroduce the Mexican wolf to its native habitat in Arizona and New Mexico.
In April, five Mexican wolf pups were born at Brookfield Zoo in Illinois.
Two pups were placed in the den of the Arizona-based Elk Horn Pack of wild wolves with the intention that the pack's adults would raise the two with its own litter.