News Release

April 19, 2012

Contact: Sondra Katzen
Public Relations

Note: Images of the Mexican gray wolves at Brookfield Zoo may be downloaded at

Chicago Zoological Society to Embark on First-of-its Kind Study of Mexican Gray Wolves
Study to Aid in Conservation Efforts of Endangered Species

      Brookfield, Ill. —Through a study of Mexican gray wolves, researchers hope to aid in conservation efforts of the endangered species, and determine whether a type of nasal tumor is more prevalent in wolves or domestic dogs. The Chicago Zoological Society, which manages Brookfield Zoo, will embark on a study to determine the occurrence of nasal carcinoma in Mexican gray wolves using CT (CAT) scans. The outcome will provide tools to assist the Species Survival Plan’s (SSP) Mexican Gray Wolf Management Group (MWMG) with the management of the endangered population.

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 (AZA) under its SSP program and the Mexican Technical Advisory Subcommittee for the Conservation of Mexican Wolves.

In the past 12 years, at least 14 cases of nasal carcinoma appeared in Mexican gray wolves at zoological institutions in Mexico and the United States. In comparison, it is estimated that nasal carcinoma affects 1 to 2 percent of domestic dogs.

Preliminary studies suggest that a genetic component is linked to the diagnosis of this disease in both Mexican gray wolves and domestic dogs. Due to the wolves’ low genetic diversity and vulnerability to disease, in 2011 the SSP MWMG identified the investigation of nasal carcinoma in the Mexican gray wolf population as a priority for the species’ management and conservation.

To date, no one has reported on the prevalence of nasal carcinoma in Mexican gray wolves. Veterinary staff for the Chicago Zoological Society want to better understand this condition in the Mexican wolf population and to investigate whether a genetic link plays a role. This could have an immediate impact on conservation efforts of this endangered species in both the United States and Mexico.

To determine prevalence, the study will utilize the following methods at Brookfield Zoo’s Animal Hospital:
  • As part of the Chicago Zoological Society’s preventative medicine program, during this year’s routine examinations, the eight Mexican gray wolves on exhibit at Brookfield Zoo will be screened with the CAT scan on April 18, 19, and 24, 2012.
  • Researchers will conduct CT scans on approximately 150 specimens (heads and skulls) currently stored at the Museum of Southwestern Biology at the University of New Mexico and few specimens archived at The Field Museum in Chicago.
Mexican gray wolves are the rarest and most genetically distinct subspecies of North American gray wolves. The U.S. Fish & Wildlife Services first listed the species 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 57 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.

It is expected that the SSP MWMG will use the information and recommendations generated by this study for future population analysis, breeding plans, and transfer plans. Zoological institutions will use the findings to make informed decisions about the use of CT scans to assist in the early diagnosis of nasal carcinoma and to anticipate potential complications.

“Our study represents the first step in the right direction to provide early diagnosis of affected Mexican gray wolves at all institutions and to protect the survival of this endangered species,” said Dr. Randi Drees, clinical assistant professor in radiology at the University of Wisconsin-Madison’s School of Veterinary Medicine Care and collaborating researcher for the Mexican gray wolf study.
Preliminary study results are expected to be released in November 2012 at the annual meeting of the American Association of Zoo Veterinarians and shared with the Mexican institutions that hold Mexican wolves.

The Chicago Zoological Society inspires 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 Preserve District of Cook County. The Society is known throughout the world for Brookfield Zoo's innovative, naturalistic, multispecies exhibits and for its international role in animal population management and wildlife conservation. For further information, visit

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