(This is an edited version of a news release issued jointly by the Endangered Wolf Center, the Chicago Zoological Society, the U.S. Fish and Wildlife Service, and the Arizona Game and Fish Department. It contains information about the cross-fosters that was previously reported on the Endangered Wolf Center website and in the Center’s Summer 2016 Magazine.)

Albuquerque, New Mexico — In their native habitat of the southwestern United States, Mexican wolves are on the rise due to dedicated and collaborative efforts to cross-foster captive-born wolves into the wild by several agencies and organizations, including the Endangered Wolf Center in Eureka, Missouri; the Arizona Game and Fish Department; the Chicago Zoological Society; and the U.S. Fish and Wildlife Service (USFWS).

The institutions this week announced evidence that cross-fostered pups are surviving in the wild.

On April 23, the Endangered Wolf Center flew two just-born critically endangered Mexican wolf pups to New Mexico to be cross-fostered by a wild pack. This historic collaborative effort between the Endangered Wolf Center staff and the USFWS represented the first time pups born in captivity were “adopted out” in this way. Two of those pups from a litter of six — m1461 and f1462 — made the long journey from St. Louis to New Mexico and were placed into the New Mexico based Sheepherder’s Baseball Park Pack.

A few days later, five Mexican wolf pups were born at Brookfield Zoo in Illinois and two of their pups — m1471 and f1472 — were placed in the den of the Arizona-based Elk Horn Pack of wild wolves.


These two Mexican wolf pups born in May 2016 at the Endangered Wolf Center were placed into the litter of the Arizona-based Panther Creek Pack. In October 2016,biologists detected evidence that at least one of the pups has survived.

In May, another litter of four Mexican wolf pups were born at the Endangered Wolf Center, and two of the pups — f1480 and f1481 — were placed in the den of the Arizona-based Panther Creek Pack.

All three wild dens were documented with five pups, and the addition of the captive born pups increased the total litter size of all three packs to seven each.

The goal of the Mexican Wolf Recovery Program is to reintroduce the species to its native habitat, and biologists have developed this novel way of helping this effort. Cross-fostering is a technique where wolf puppies from one litter are placed with another litter. The wolf mother will adopt the additions as her own. Placing pups from captivity into a wild litter not only helps increase the population size in the wild but also helps increase genetic diversity. It is also a wonderful way to have wild parents (with an established territory and experience) raise and teach the pups how to survive.

Extreme terrain and logistics make it very challenging, and timing has to be just right. Wild and captive litters have to be born within a few days of one another, and the transfer from captivity to the wild has to occur before the pups are 10 days old. This means the wild den location needs to be known, a flight needs to be scheduled, perfect weather conditions need to exist and many other logistics need to be coordinated. All of these factors make the success of the efforts all the more remarkable.

On Sept. 18, 2016, the Mexican wolf Interagency Field Team (IFT) captured a male pup associated with the Elk Horn Pack. Genetic analysis done by the Laboratory for Ecological, Evolutionary and Conservation Genetics at the University of Idaho recently confirmed that the pup is m1471 (one of the cross-fostered pups). During the capture and handling, biologists gave the wolf a brief exam, administered vaccines, and fitted him with a radio collar, which will allow the IFT to track him and learn important information about the animal’s behavior, survival and dispersal, and will provide potential new pack formation in the future.

The ITF includes wildlife biologists from the Arizona Game and Fish Department, USFWS, U.S. Forest Service, White Mountain Apache Tribe and USDA Wildlife Services,

In October, IFT biologists also confirmed via trail camera photos that the Panther Creek Pack had a minimum of six pups. This indicates at least one cross-fostered pup — f1480 or f1481 — in that pack has survived.

IFT continues efforts to monitor and confirm pup survival in the Sheepherder’s Baseball Park Pack.

“It’s a long way from St. Louis to the recovery area, and the time-sensitive nature of fostering adds an extra layer of intensity. But seeing the pups safely into the wild — and learning now that they are not only surviving but thriving — makes the entire journey all the more remarkable,” said Regina Mossotti, Director of Animal Care and Conservation at the Endangered Wolf Center. “The Mexican wolf is vital to keeping the ecosystem healthy. I’m amazed that so many institutions could partner together to overcome all of the logistical challenges.”

“We are thrilled to hear that one of the pups was located and is doing well with his foster pack,” said Bill Zeigler, Senior Vice President of Animal Programs for the Chicago Zoological Society. “The success of the program is a true testament to the collaboration with our partners.”

“The support and partnership we have with the Brookfield Zoo and the Endangered Wolf Center is tremendous,” said Benjamin Tuggle, the U.S. Fish and Wildlife Service’s Southwest Regional Director. “Survival of these pups increases the chances of improving the genetic health of the wild population.”

Another Mexican gray wolf with a link to the Endangered Wolf Center and the Brookfield Zoo also has been confirmed in the wild. In 2014, female wolf F1126, known as Ernesta — who was born at the Endangered Wolf Center in 2008, and then moved to Brookfield Zoo in 2010 — was released to the wild with a mate. Shortly after release the two got separated, possibly as a result of an encounter with an already existing pack. Alone, she gave birth in the wild to six pups. To help the survival of her puppies, two of them were cross-fostered into the Dark Canyon Pack. This wild-to-wild litter foster paved the way for the captive-to-wild foster. One of these puppies (now 2 years old), was recently identified as Ernesta’s son and appears to be paired with a female leading into the 2017 breeding season. (Following a re-release of Ernesta with a new mate and her four other pups, her body was found in early 2015. The cause of death for Ernesta is undetermined due to the condition of her remains, although illegal mortality is suspected.)

The Mexican Gray Wolf Recovery Program is a multi-agency collaboration between the USFWS, the Association of Zoos and Aquariums, the Arizona Game and Fish Department, the White Mountain Apache Tribe, the USDA Forest Service, and the USDA Animal and Plant Health Inspection Service—Wildlife Services, several counties, as well as private organizations.

Mexican wolves are the most rare and most genetically distinct subspecies of North American gray wolves. The current population of the species in the captive breeding program is 243 individuals in 54 institutions. As of December 2015, a minimum of 97 Mexican gray wolves were living in the wild in the United States. This reintroduced population is now a naturally functioning wolf population.

About the Chicago Zoological Society

brookfieldThe mission of the Chicago Zoological Society is to inspire conservation leadership by connecting people with wildlife and nature. The Chicago Zoological Society is a private nonprofit organization that operates Brookfield Zoo on land owned by the Forest Preserves of Cook County. The Society is known throughout the world for its international role in animal population management and wildlife conservation. Its Center for the Science of Animal Care and Welfare is at the forefront of animal care that strives to discover and implement innovative approaches to zoo animal management. Brookfield Zoo is the first zoo in the world to be awarded the Humane Certified™ certification mark for the care and welfare of its animals, meeting American Humane Association’s rigorous certification standards. Open every day of the year, the zoo is located off First Avenue between the Stevenson (I-55) and Eisenhower (I-290) expressways and is also accessible via the Tri-State Tollway (I-294), Metra commuter line, CTA, and PACE bus service. For further information, visit CZS.org.

About the Endangered Wolf Center

The Endangered Wolf Center in St. Louis, Mo., is the premier wolf conservation, education, reproduction, and research center in the United States. Its mission is to preserve and protect Mexican wolves, red wolves and other wild canid species, with purpose and passion, through carefully managed breeding, reintroduction and inspiring education programs. The Center was founded in 1971 by Marlin Perkins and his wife Carol. Perkins is best known as the longtime host of television’s “Mutual of Omaha’s Wild Kingdom.” The Endangered Wolf Center is an Association of Zoos and Aquariums (AZA) certified facility. It has been the birth site of about 200 Mexican wolves, and every Mexican wolf in the wild can trace its lineage back to the Center. For more information, visit www.endangeredwolfcenter.org and follow the Center on Facebook and Twitter.

For more information on the Mexican Wolf Reintroduction Program, please visit: http://www.fws.gov/southwest/es/mexicanwolf or www.azgfd.gov/wolf.