The Predator That Deer Fear Most

Dr. Daniel Crawford, the lead investigator—who also happens to be an avid bowhunter—set out to learn if fear of humans prompted deer to change their feeding behavior the same way it did large carnivores.

The test took place on a 30,000-acre ecological research site, where Crawford’s team set up 23 pre-baited sites equipped with trail cameras and audio playback speakers five yards from the corn. They set cameras to record 20-second videos, and audio recordings started playing after 10 seconds. The team loaded speakers with 64 different audio clips of humans, coyotes, wolves, cougars, and dogs, as well as control sounds of innocuous birds. Over the course of the study, the research team collected 823 videos across the 23 sites to analyze how whitetails responded to each sound.

Generally, deer were unphased by bird sounds. They were more alarmed by the sounds of coyotes—some hightailed it out of the feeding area, while others cautiously stuck around. Wolves incited a more prominent flight response, even though these predators haven’t existed in the study area for over a century.

But, the sound of conversational human voices was overwhelmingly the most fear-inducing. Deer were nearly twice as likely to run from human recordings than those of any other predator. Click here to check out a video by the National Deer Association depicting these findings.

Although the numbers might have been more lopsided than expected, the general results weren’t too surprising to the research team.

“Our results are context-dependent for sure,” Crawford told the National Deer Association. “We are in an area where there’s a heavy emphasis on deer harvest, and there are a lot of deer killed every year by people. In hunted places, I expect deer are going to behave like this.”

Deer populations at the Jones Center at Ichauway are intensely managed via annual harvest, so hunting pressure is a factor. The same is true throughout most of the whitetail’s range. Hunter harvest averages around six million whitetails every year.

A 2013 deer mortality study by the Wisconsin Department of Natural Resources and the University of Wisconsin reported human hunting was responsible for more than three times the deer killed than coyotes and wolves combined throughout the study area. In the eastern farmland region of the state, the results were even more extreme, with human hunting clocking in at 53% and coyote predation at only 2%.

Humans are simply the most efficient predators of adult whitetails—and the deer seem to know it. But human pressure doesn’t only cause whitetails to flee an area. It can also reduce feeding time, ultimately impacting health and population numbers, according to the Crawford study:

“Combined with previous, site-specific research linking deer fecundity to predator abundance, this study reveals that fear of humans has the potential to induce a larger effect on ungulate reproduction than has ever been reported. By demonstrating that deer most fear the human ‘super predator,’ our results point to the fear humans induce in large ungulates having population- and community-level impacts comparable to those caused by the fear humans induce in large carnivores.”

A 2016 study found similar results among mesocarnivores such as badgers, foxes, and raccoons. While badgers showed signs of fear at the sound of bears or dogs, they would eventually venture out to feed. But “they would cower in their burrows” for hours when human sounds played and would not emerge until the recordings were completely shut off.

Chatting it up in the woods doesn’t just scare off wildlife. It can literally have impacts that change the population.

So what does this mean for hunters?

Keep your mouth shut in the field. Minimize any human-associated sounds, such as metal clanking, when you’re hunting, too.

The presence of humans in general—not just their sounds—can have these same effects, so be vigilant about staying as concealed and scent-free as possible. Minimize foot traffic in hunting areas, particularly in the weeks surrounding hunting seasons. Stop pulling camera cards every couple days and stomping through feeding areas.

Want to see thriving whitetail populations and kill big bucks? Stop stressing the deer out!

Feature image via Matt Hansen.