LISTEN TO THE AUDIO VERSION
By Barry R. Noon
Gray wolves, a key component of Colorado’s natural heritage, are noticeably absent from the state’s landscape. Their absence reflects a long history of human persecution and intolerance. For example, many hunter advocacy groups view the re-establishment of a viable wolf population in Colorado as a threat to hunter success and to the abundance of deer, elk and moose (collectively called ungulates).
Unfortunately, the myth that wolves would compromise the health and vitality of ungulate populations in Colorado is as misguided and inaccurate as it is deep-seated.
Hunters have legitimate reasons to be concerned about the future of ungulate populations, but predation by wolves, or other predators, should not be part of their worries. Currently, the greatest threats faced by deer and elk result from the loss and fragmentation of winter range (a consequence of exurban encroachment and oil and gas development), declines in habitat quality arising from climate change (increasing temperatures and drought stress affecting food plants), increased poaching rates (particularly high near areas of oil and gas development), and an increasing prevalence of chronic wasting disease.
CWD is a highly contagious, fatal disease transmitted by both infected animals, diseased carcasses and contaminated environments. No cure or vaccination for the disease is currently in sight. It is unknown if CWD poses a health risk to humans — however, recent studies with macaques (a common animal proxy for humans) suggest the possibility. This is especially troubling for hunters, since there is no way to confirm the presence of the disease in any ungulate absent specific testing.
As of July 2018 in Colorado, at least 31 of 54 deer herds (57%), 16 of 43 (37%) elk herds, and two of nine moose herds (22%) were known to be infected with CWD. Unfortunately, the number of infected herds is increasing over time, as is the number of infected animals within herds. Strategies to control the prevalence and spread of CWD based on increased hunting or culling rates have, to date, been ineffective. One reason is that hunters harvest deer and elk largely at random or avoid infected animals while predators are more likely to target susceptible prey. For example, Colorado Parks and Wildlife researchers have documented that mountain lions preferentially prey on mule deer infected with CWD. Wolves, which detect and assess prey vulnerability more by prey behavior than mountain lions, should show even greater selective predation on diseased animals. However, because of past persecution, the range of wolves does not overlap with the distribution of CWD in Colorado, and a direct test of a positive wolf effect on the prevalence of CWD in deer and elk is not currently possible.
Wolf reintroduction, under the controlled management of CPW, would provide an invaluable opportunity to evaluate the effects of selective predation by wolves on the prevalence of CWD. Based on our understanding of the dynamics of other predator-prey-disease systems studied worldwide, there is little doubt that the absence of large predators increases the risk of disease in many prey species. Returning wolves to Colorado has a high likelihood of decreasing the prevalence of CWD and restoring healthy populations of deer and elk for hunters, and everyone else who takes pride in Colorado’s natural heritage.
Barry R. Noon is emeritus professor, Department of Fish, Wildlife and Conservation Biology, graduate degree program in ecology, Colorado State University.