There's One Predator That Terrifies Bears And Mountain Lions Alike

The wilds of North America can be a hazardous place. It's there that some of the most intimidating predators make their home – black and brown bears that could eviscerate a person with one swipe of a mighty paw, and mountain lions that stalk almost silently on padded feet. Many hikers will gird themselves against the possibility of an attack from one of these feared beasts – but, as two new papers explain, there's an animal out there that even the most formidable predators will try to avoid. Us. In fact, attacks by these animals are so uncommon that, in North America, people are far more likely to be struck by lightning. The research suggests one reason why: bears and mountain lions go to remarkable lengths to stay away from humans whenever they can. "These discoveries change the narrative about human-carnivore conflict," writes Yale University ecologist Oswald Schmitz in a Current Biology dispatch tying together two studies, one on bears and the other on mountain lions. In North America, brown, or grizzly, bears (Ursus arctos) attack, on average, around 11.4 humans per year. Mountain lions (Puma concolor) attack just 4 to 6 people per year, and the rate of black bear (Ursus americanus) attacks is unknown, but just 63 human fatalities due to black bear attacks were documented between 1900 and 2009. By contrast, between the US and Canada, around 580 people are struck by lightning every year. Looking purely at the numbers, lightning strikes outnumber brown bear attacks by roughly 50 to 1 (although, of course, the actual risk depends on other factors such as where you live and how much time you spend in bear-filled woods). So why are these attacks so rare? The answer, according to the two studies, is that these animals don't simply react to humans showing up. Instead, they actively change their behaviors to avoid us. In a study led by wildlife biologist Philip Manlick of the USDA Forest Service, researchers studied black and brown bears feeding along salmon streams in southeast Alaska. Motion-triggered speakers played recordings of either gull calls, off-road vehicles, or human voices whenever a bear approached. Cameras recorded what happened next. The bears were twice as likely to beat a hasty retreat when they heard vehicle sounds compared to the gull sounds. They were almost 10 times more likely to flee from the sound of human voices. This has implications far beyond bear-human interactions. Bears take the salmon they catch into nearby forests, leaving behind decaying remnants that help fertilize the ecosystem. Disrupting that nutrient transport has knock-on effects on other ecosystem processes. The mountain lion paper, led by environmental scientist John Morgan of the University of California, Santa Cruz, told a similar tale. The researchers analyzed 6 years of GPS data collected from 36 tagged wild mountain lions in the Santa Cruz Mountains. They mapped this data against data from the GPS fitness-tracking app Strava, which showed where and when people were hiking, biking, and using trails. The mountain lions didn't just respond to the presence of humans. Rather, they seemed to anticipate where and when human activity was likely to be heavy, and proactively avoided those places at those times. Even when mountain lions lived in areas with lots of human activity, though, they were not more likely to attack. Any higher attack rates in those areas were better explained simply by more frequent encounters between people and mountain lions. Taken together, the two studies suggest that the animals take actions that indicate they perceive humans as a significant threat. Bears abandon their feeding opportunities. Mountain lions plan their movements around predictable human routines. They're already doing a lot of the heavy lifting that prevents dangerous encounters with our own species. For our end of the bargain, the mountain lion study suggests, we can try to avoid forcing them into situations where their avoidance strategies fail. Related: One Super Predator in Africa Instills More Fear Than Lions The popular image of the relationship between humans and carnivorous predators is that the predator is the aggressor, and the human is the helpless prey that stands to lose the most from an encounter. In reality, Schmitz argues, humans have not just the power but the responsibility to do all that we can to keep those animals safe. "By being cognizant of how they shape the landscape of fear experienced by carnivores and their prey species," he writes, "humans can proactively adjust their behavior and spatial use of landscapes in ways that can transform the human-carnivore relationship from one of conflict to one of coexistence and thereby rebalance the attendant cascading effects that human fear effects have on wildlife communities and ecosystems." All three papers appear in Current Biology. You can read the bear paper here, the mountain lion paper here, and Schmitz's dispatch here. This article was fact-checked by Rebecca Dyer and edited by Rebecca Dyer. While we pride ourselves on our process, we are only human. If you spot a mistake, please let us know.