Chronic wasting disease has impacted Colorado’s deer and elk populations for decades, but new research indicates mountain lion predation on infected deer could help limit the spread of the always-fatal disease.
A Colorado Parks and Wildlife study has shown that adult deer infected with chronic wasting disease are four times more likely to die from mountain lions than uninfected adult deer. Similar studies in Wyoming have shown similar results.
“A lot of evidence points toward the fact that lions at some level pick out infected deer by looking at them as the best opportunity to kill something,” CPW wildlife veterinarian Mike Miller said.
Among the signs of deer infected with chronic wasting disease are loss of awareness and loss of social interaction, meaning the deer are more easily preyed upon.
CPW has been studying the disease’s impact on the deer herd at Table Mesa in collaboration with Boulder Open Space and Mountain Park for several years.
Miller said data from the study also showed mountain lions may help reduce the spread of the disease in the herd by killing infected deer on average several months before the deer die from “wasting,” reducing the time infected deer have to spread the disease to others in the herd.
“For this to be useful from a disease control standpoint, the deer need to die early in the course of the disease,” he said.
The neurological disease is spread among deer and other cervids, including elk and moose, through body fluids such as feces, saliva, blood and urine as well as through direct contact. It also can spread indirectly through environmental contamination of soil, food and water for many years.
There is no known cure for the disease, which is found in 26 states in the continental U.S. and two provinces in Canada. In Colorado, Miller said about half of state’s 55 deer herds and about one-third of elk herds are impacted by chronic wasting disease. The disease was first discovered in captive deer in the 1960s at a Colorado State University research facility on the west side of Fort Collins and in wild deer populations in 1981.
Miller also said in some areas studied that mountain lions kill infected deer four times more than hunters. However, he said hunting remains the top tool used to restrain the spread of the disease.
“Predation plays a complementary role,” Miller said. “But there aren’t enough mountain lions to make a dent in the prevalence of CWD.”
Miller said chronic wasting disease has not shown to be transmissible to mountain lions or other predators. It also is not shown to be transmissible to humans, but experts discourage consuming meat from infected animals.
Now that Colorado voters narrowly passed a bill to reintroduce wolves by the end of 2023, there is a question about whether they will play a role in stemming the spread of the disease.
Last year, CPW confirmed the first wolf pack in the state in seven decades in the far northwestern reaches. Up to six wolves were discovered last year, including three males and one male.
CSU research regarding wolves’ impact on chronic wasting disease said predators that selectively prey on infected animals would be expected to reduce the number of infections but that would be more likely in areas where wolves are well-established.
Miller said with so few wolves currently coming in and out of Colorado, it would be difficult to assess any measurable effect wolves might play in reducing the occurrence or spread of chronic wasting disease.
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