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Mexican Gray Wolf "Ernesta" at Brookfield Zoo
With only 58 Mexican gray wolves living in the wild in New Mexico and Arizona, a 4½-year-old female Mexican gray wolf is leaving Brookfield Zoo, which is managed by the Chicago Zoological Society, to prepare to enter the wild. The release to the wild would help bolster the population of this endangered species.

On October 27, the wolf, Ernesta, will relocate to the U.S. Fish & Wildlife Service’s (USFWS) Sevilleta Wolf Management Facility at the Sevilleta National Wildlife Refuge near Socorro, NM. Once Ernesta arrives at this facility, she will choose a mate to be paired with for potential release. They will receive survival skills conditioning through a prerelease “boot camp” to prepare them for life in the wild.

“Just a few decades ago, the Association of Zoos and Aquariums’ Mexican Gray Wolf Species Survival Plan was put in place to save the wolves from absolute extinction,” said Joan Daniels Tantillo, associate curator of mammals for the Chicago Zoological Society. “Ernesta’s potential transfer into the wild is an important step to help foster genetic diversity within the re-introduced population to allow this species to survive.

The purpose of the prerelease conditioning is to make sure wolves are good candidates for release into the wild. Wolf biologists with the USFWS wildlife refuge will observe Ernesta as they slowly transition her to feedings that mimic the typical wolf food patterns found in the wild. She will transition to eating native prey (road-killed deer and elk) and experience conditions that imitate their natural eating patterns in which prey kills happen only every several days. She will also be subjected to conditioned taste aversion to avoid eating beef so that if released she does not cross paths with cows and ranchers.

While Ernesta may have skills to learn at boot camp, her natural wolf behaviors have been encouraged since her first day at Brookfield Zoo and will help ensure a safe and healthy transition for her potential release to the wild. Regenstein Wolf Woods, the wolf exhibit at the zoo, includes design implementations to cultivate these behaviors, such as:
  • Wolves socialize only with each other. Keepers do not interact directly with wolves.
  • Wolves receive native prey species such as elk hide, bison meat, and whole prey items.
  • Climbing logs, a pool, heated rocks, and loose dirt encourage natural behaviors like playing, lounging, and digging.
  • Dens and tunnels are the size, shape, slope, and length of those in the wild, and there is space for the wolves to dig their own dens.
  • Buildings blend in with the natural surroundings so that the wolves don’t associate manmade structures with shelter or food.
“We are committed to the highest level of animal care, and Regenstein Wolf Woods ensures that wolves participating in the release program will be successful in their transition into the wild,” Daniels said.

Accompanying Ernesta to the Sevilleta Wolf Management Facility will be two potential mate choices from the Endangered Wolf Center in Eureka, MO, where Ernesta was born in April 2008 before coming to Brookfield Zoo in 2010 with her litter mates (three brothers and four sisters). Her pack will remain at Brookfield Zoo after she leaves. The flight to New Mexico is sponsored by LightHawk, a volunteer pilot organization that sponsors flights of animals partaking in release programs. LightHawk also participates in other conservation-related monitoring in North America to provide aerial views of the land and assist in environmental protection.

Mexican gray wolves are part of a breeding program that is managed by the U.S. Fish & Wildlife Service in coordination with the Association of Zoos and Aquariums under its Species Survival Plan and the Mexican Technical Advisory Subcommittee for the Conservation of Mexican Wolves. Mexican gray wolves are the rarest and most genetically distinct subspecies of the North American gray wolves. The U.S. Fish & Wildlife Service first listed the species as endangered on the Endangered Species List in 1976. There are 283 Mexican wolves living in 52 institutions across the United States. The 2011 census recorded a minimum count of 58 individuals in the wild in New Mexico and Arizona, and in October 2011, five wolves were released for the first time in the northern Mexican state of Sonora.