Yellowstone wolves avoid hunting bison as a means of self-preservation
It has been a long time since most humans have had to think about hunting animals for food – at least out of necessity, and given that you’re reading this on the internet that probably applies to you. Because of this, it’s easy to forget the dangers of hunting certain types of game. It’s also likely you’ve never been faced with a decision of which game to hunt for, unless you count standing amongst all the packaged meats at your local grocery store. So the phenomenon known as “prey switching” has likely never been a factor in many of our lives.
Prey switching has been observed amongst predacious species for a long time. It’s the tactic of changing the pursuit of one prey species for another, and can occur for a variety of reasons. One of those reasons is that a prey species may become less plentiful, so the predator switches to another, more abundant prey. For this reason alone, prey switching is ecologically important, as it helps stabilize wildlife populations.
But there are certain circumstances where a predator would rather hunt a scarce species than go after one that is abundant.
Utah State University researchers Aimee Tallian and Dan MacNulty observed this exact circumstance play out amongst the wolves in Yellowstone National Park. The researchers found that Yellowstone wolves seldom hunt bison and instead pursue elk, even though the later is much more scarce.
“Prey switching has been observed in natural systems, where prey are small and generally helpless when attacked by a predator,” says Tallian. This, however, is not the case in Yellowstone.
The researchers discovered the “data [revealed] wolves maintained a strong preference against bison, even when bison were twice as abundant as elk.” The reason for this: bison are incredibly dangerous game. An adult bull bison can weigh almost a ton.
“Hunting is hazardous business for wolves,” explains MacNulty. The researchers have observed wolves being kicked, gored, and stomped to death in the pursuit of large bison and other prey. “Wolves minimize the risk of injury by focusing on more vulnerable prey, which are generally rare.”
The study also revealed that wolves became increasingly resistant to hunting bison as the bison population increased. This is likely due to the fact that hunting bison becomes easier when the herd is smaller and wolves are able to target the more vulnerable and less dangerous calves.
Rather than hunting live bison, most wolves stuck to scavenging on bison carrion, which became more frequent as bison populations increased. Tallian believes an increase in bison carrion consumption also helps stabilize elk population dynamics, saying, “The ability of wolves and other predators to shift between hunting and scavenging is an under-appreciated behavior that may play an important role in the dynamics of ecological communities with dangerous prey.”
Observations like the ones made in this study help us better understand the hunting behaviors and strategies of these predators, as well as how they impact the ecosystem as a whole.
Source: Utah State University
Image: Daniel Stahler, NPS