Author: Gary Skiba
When a population of gray wolves is established in Colorado, how will they impact deer and elk numbers? The short answer is that the precise effects aren’t really known, because predator/prey systems are complicated and many factors other than predation affect prey, including weather, disease, human hunting, and other predators.
The Yellowstone northern range elk herd is the most intensively studied elk/wolf system in the world (there is no similar body of research on mule deer populations). Dozens of researchers have worked to understand the dynamics of the elk population and the effects of wolf predation. While much has been learned, there are many unanswered questions, and researchers have noted the difficulty of separating out and understanding the impact of wolf predation alone. Here are a few conclusions and quotes from studies on the impact of wolves on that elk herd:
- Scientific consensus about the role of wolves in driving the dynamics of the northern herd has yet to emerge, despite 20 years of research by numerous federal, state, and academic investigators.
- The challenge of inferring causation helps explain why the debate about the influence of wolves on northern Yellowstone elk dynamics is unsettled and why it will remain so for the foreseeable future.
- Wolf reintroduction was neither a controlled nor replicated experiment.
- Because wolves tend to concentrate on calves and older elk, their overall impact on herd size appears to be much less than that of hunter harvests of antlerless elk.
- Large hunter harvests of females in the presence of wolf predation can result in a marked decline in elk abundance
- The basic biology of wolves suggests that they have a modest influence on elk dynamics.
- Grizzly bears, black bears, cougars and coyotes all hunt elk in Yellowstone making the effects of wolves alone difficult to tease out, and human hunting outside the Park affects the elk population in the Park.
- In addition to hunting (human and non-human), elk populations are affected by disease, winter severity, vegetation condition, and other environmental factors.
Given the lack of strong scientific information on the exact potential effects of wolf predation on Colorado’s elk population, what DO we know? Here are some important points:
- Elk make up about 80% of the diet of Yellowstone wolves; it’s likely that their diet would be similar in Colorado
- About half of the elk taken by wolves are calves.
- Wolf-killed elk cows are on average much older than hunter-killed elk cows (13.9 vs. 6.5 years old), younger cows influence future population growth more than older cows.
And then there are the common sense considerations:
- Wolves and their prey evolved together for a long time; it makes no sense that they would “eliminate” or “decimate” prey populations
- There were a lot more wolves and their prey when Europeans got to North America
- Elk populations in Montana, Idaho, and Wyoming have actually increased (a modest 1-3% in ID and WY, and by 26% in MT). Elk numbers in many management units in all 3 states are over the desired population level.
Wolves and their prey can and do survive and thrive together. With active management, there is no reason to believe that elk populations and hunter opportunity will be reduced in Colorado due to wolf predation.