I’ve lost track of how many times I’ve been told that mountain lions target male mule deer (“bucks”) and, to a lesser extent, male elk (“bulls”). I remember one exchange in which a ranch hand in Colorado told me that if I walked out into the nearby sagebrush, I’d stumble upon buck carcasses just about everywhere—gory evidence that mountain lions indeed target mature male deer.
This was a sensitive topic. This man, like many of his coworkers, guided deer and elk hunters in the fall season as part of his revenue stream. People hired him specifically to find big bucks and bulls, and his success ensured more clientele and more money in the future. Mountain lions were competition, plain and simple as far as he was concerned, and needed to be “controlled.”
The idea that mountain lions target male deer and elk is an ideology so pervasive, even if poorly tested, that it contributes to the current management strategies for large carnivores today. As Americans (and Canadians too), we think reducing predators just might help us reach that elusive goal of increasing the deer and elk populations that we hunt ourselves (though most research shows that predator control does little to nothing to aid mule deer and elk populations long-term).
As a scientist charged with studying mountain lion prey selection, I was especially taken with this ideology—because it can so easily be tested. Thanks to GPS collars and the legs that carry us, we record nearly everything mountain lions eat in our studies. We just needed to ask the question.
In our latest scientific paper, published in the scientific journal Wildlife Research, my colleagues—Jennifer Feltner, of Panthera’s Puma Program and the University of Montana, and Dr. Howard Quigley of Panthera—and I pulled together data from two study areas in the Rocky Mountains, USA. We were interested in how many bucks and bulls mountain lions killed—but more importantly, whether mountain lions sought them out, passing up other prey to preferentially “target” bulls and bucks.
We documented 339 deer and elk killed by mountain lions in our Colorado study site—only six were bulls and 23, bucks. We documented 578 deer and elk killed by mountain lions at our Wyoming study site, also called Panthera’s Teton Cougar Project, 38 of which were bulls and 28, bucks. In terms of numbers, the influence of mountain lions on bulls and bucks was tiny—they were just 8.5% of the total deer and elk killed by mountain lions in Colorado, and 11.4% of the total deer and elk killed by lions in Wyoming.
The results of our preference analyses were more interesting. Overall in both Colorado and Wyoming, mountain lions went out of their way and targeted the youngest elk and deer, rather than the adult male animals hunters prize. This should be a great relief to hunters. In fact, mountain lions purposefully avoided adult elk in both areas, which are large and dangerous for mountain lions that are only a fraction an elk’s size. Mountain lions, however, did show a very slight preference for bucks as well, which they primarily hunted during the rut when bucks were stressed, moved alone and were highly distracted with courting females. This result was also in part because there were so few bucks on the landscape as compared to other deer, so even a small number of bucks killed showed up as preferential feeding in our analyses.
Neither mountain lions nor human hunters in our study systems—or the combination of the two—decreased bulls or bucks to levels that hurt local populations. This is a testament to sound management in both areas, and also highlights the fact that killing mountain lions over competition for bulls and bucks is not justified. We should instead focus management, media attention, and conservation science on disentangling the complex ecology driving local declines of mule deer and elk in the west; many drivers of their declines are caused by humans and can be addressed.
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