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Environment
Chronic wasting disease is crippling deer populations in the Mountain West, around the country and in bordering Canadian provinces. From the Mountain West News Bureau and published in collaboration with High Country News, this four-part special report examines the disease's origins and impact, and a global effort to stop it from spreading.

How Might Wolves In Colorado Affect Chronic Wasting Disease?

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Jacob W. Frank
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NPS
Doug Smith, a Yellowstone National Park senior wildlife biologist, examines the skull of an elk that was killed by a wolf.

Colorado's poised to put the question of wolf reintroduction on the November ballot. One unanswered question is how the predators might affect the spread of chronic wasting disease, if at all.

CWD is a fatal neurodegenerative disease that currently infects deer, elk, moose and reindeer. Critics of wolf reintroduction argue that more predators on the landscape could further spread CWD.

Debbie McKenzie, who studies the disease at the University of Alberta, says wolves and other dog-like animals are generally considered to be resistant to CWD, but that doesn't mean an infected deer's prions—the proteins that spread the disease—die when a wolf preys on it.

"There has been some evidence that although the wolves themselves would not get a prion disease, that some of the infectious prions could end up in their fecal material and it could be a way of moving the disease around," McKenzie said.

She pointed to a study published in 2015 by researchers based in northern Colorado. They studied six coyotes from Utah, feeding them elk brain and analyzing the contents of the resulting feces. As the scientists wrote, the findings show that coyotes can pass infectious prions via their feces for at least three days after eating infected meat, "demonstrating that mammalian scavengers could contribute to the translocation and contamination of CWD in the environment."

On the other hand, proponents of wolf reintroduction say wolves could help limit the spread of CWD by killing off sick animals before they can infect many others. 

A decade ago, Colorado Division of Wildlife researchers found that mountain lions prey selectively on prion-infected mule deer, and they noted other studies indicating that "predators like wolves and coyotes select prey disproportionately if they appear impaired by malnutrition, age or disease."

In a study supporting the pro-wolf line of thinking, published in 2011, researchers from the National Park Service, Colorado Division of Wildlife and Colorado State University wrote in the Journal of Wildlife Diseases, "as CWD distribution and wolf range overlap in the future, wolf predation may suppress disease emergence or limit prevalence."

This story was produced by the Mountain West News Bureau, a collaboration between Wyoming Public Media, Boise State Public Radio in Idaho, KUER in Salt Lake City, KUNR in Nevada, the O’Connor Center for the Rocky Mountain West in Montana, and KRCC and KUNC in Colorado.

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