VOICES Voices Icon Ideas and Insight From Explorers


Chicago’s Brookfield Zoo Leads Pioneering Study of Nasal Cancer in Mexican Grey Wolves

Associate Veterinarian Carlos Sanchez & veterinary student Jimmy Johnson prepare a wolf for a CT scan (Chicago Zoological Society)

“Your dog has cancer.” Nothing may be more devastating to a dog owner than those words. Cancer is fairly common in older dogs.  In fact, it is one of the leading causes of natural death in canine companions, period.

What about wild dog species? Are they just as susceptible to these malignancies and does cancer likely impact the conservation programs for wild canids?

Carlos Sanchez, an Associate Veterinarian at the Chicago Zoological Society’s Brookfield Zoo and Randy Drees, a veterinary radiological oncologist at the University of Wisconsin-Madison have teamed up to answer these very questions.

With the help of state of the art diagnostic imaging tools, the veterinarians are spearheading an investigation into the occurrence of nasal tumors in the most endangered wolf in the world—the Mexican grey wolf.  The tumors, which are found in 1-2% of domestic dogs, are also prevalent in grey wolves.

According to Dr. Drees, “Computed tomographic (CT) exams have become the gold standard in diagnosing nasal tumors in companion animals from the diagnostic imaging perspective.”  She indicated that the Brookfield Zoo is particularly poised to lead the study because of their on-site CT scanners–imaging technology not available at all zoo medical facilities.

Mexican grey wolf in CT scanner (Chicago Zoological Society)

Unlike the limited views offered by plain film radiography, the CT scan offers 3-dimensional, cross-sectional views of intricate anatomy like that of the head and rostrum.  “Evaluating the CT exam we can exactly detect the presence or absence of disease, define the extent of disease as well as type [of pathology], and with that usually also the prognosis for the individual animal,” said Dr. Drees.

With as few as 50 of this Mexican subspecies in the wild, it is really important to screen captive individuals that are intended for release into the wild—especially if the disease is genetically linked.

Wolves and other wild dog species are dolichocephalic–long-nosed–and like dolichocephalic dog breeds, these wolves may be particularly susceptible to certain cancers, including nasal tumors.

Mexican grey wolves at the Brookfield Zoo (Chicago Zoological Society)

“To date, no one has reported on the prevalence of nasal carcinoma in Mexican gray wolves,” said Dr. Carlos Sanchez, who is also the veterinary advisor for the Mexican Gray Wolf Species Survival Plan program. “We 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.”

The Mexican grey wolf subspecies, which was extirpated in the US and almost driven to extinction in the wilds of Mexico, has long been a strong candidate for reintroduction programs.  However, the target number of wild animals has not yet been reached following restoration efforts for the wolf. Hence, the health of the captive gene pool remains critical to the conservation effort for the subspecies.

Although determining the presence of the nasal disease may seem straightforward, it is not.  The eight Mexican grey wolves at the zoo are potential candidates for release into the wild and therefore minimal handling of the animals is permitted to reduce potential habituation of the wolves to people.

This past week the wolves were chemically immobilized for fairly lengthy examinations at the Zoo’s hospital.  Because the animals are all part of pack with a strong hierarchical organization, removing any one individual could have been catastrophic for the social dynamic of the group.  To facilitate the cancer screening, Associate Curator of Mammals Joan Daniels worked with the keeper staff to schedule dominant and subordinate animals for scans in a timely and particular sequence to minimize social conflict.   The animals were scanned on the 18th, 19th, and 24th of this month.

For more information on this study, please read my earlier post.


  1. […] more news on Mexican gray wolf conservation at the Brookfield Zoo, please read my earlier posts. Nat Geo Photo […]

  2. Nik
    April 30, 2012, 2:32 pm

    That’s cray-cray!