What 70 Years of Data Says About Where Predators Kill Humans

When 9-year-old Lily Kryzhanivskyy was playing hide-and-seek in the woods near Fruitland, Washington, the last thing she expected was a face-to-face encounter with a deadly predator. But when Lily jumped out to surprise her friends, she was suddenly attacked by a cougar.

Lily punched and kicked the cat for all she was worth, and she survived her serious wounds. The attack made headlines last year because of her toughness and courage, and because such events are rare in North America. Elsewhere, especially in lower-income areas where humans live and work more frequently with predators, such unfortunate news is a lot more common. Just a few months after Lily’s attack, authorities in Champaran, India, shot a tiger that had killed at least nine humans in communities surrounding the Valmiki Tiger Reserve. The Indian government reports that an average of 34 people were killed annually by tigers in that nation between 2015 and 2018, while the United States has seen only nine fatal cougar attacks since 1980.

To study predatory events like these around the world, researchers have created a compilation of large carnivore attacks from the past 70 years. Although the compendium of attacks can’t include every single incident, the detailed data sheds light on where, when and why predatory attacks on humans occur. The results highlight the various reasons big cats, canids and bears tend to attack, and the very different ways humans encounter predators in higher-income nations versus lower-income ones.

The research, published Tuesday in PLOS Biology, delved into records of reported carnivore attacks around the world from 1950 to 2019, mining sources such as scientific papers and news reports. Scientists documented a total of 5,440 attacks from 12 different species of big cats, canids (wolves and coyotes) and bears. Of those attacks, about one in three proved fatal, while the others resulted in human injuries. The study suggests that the number of large carnivore attacks has increased over time, particularly in lower-income countries where humans and predators live in closer proximity, and encounters often occur while residents are engaged in daily livelihood activities like farming or herding. This apparent increase, however, may also be a factor of increased incident reporting in the internet era compared with the study sample’s earlier years.

Big cats like tigers and lions launched the deadliest attacks, with 65 percent proving fatal compared to 49 percent for canids and just 9 percent among the bear attacks. The authors note that this disparity in fatality rate corresponds with two very different types of attacks. While canids and big cats sometimes stalk humans and attack them for food, the bears were more often taken by surprise. Bears were often disturbed when feeding—or a mother may have reacted to protect her cubs. Fatal attacks were also more common in the lower-income countries, primarily because they are home to tigers and lions, which engage in a larger share of such attacks.

Predatory attacks, in which a carnivore tries to kill for food, were most heavily concentrated in India, home to 72 percent of 1,696 total such incidents. Another 14 percent of those attacks occurred in Africa. These high numbers can be largely attributed to the presence of tigers, lions and leopards, and to India’s wolves.

Co-author Vincenzo Penteriani, an ecologist at the National Museum of Natural Sciences in Spain, stresses that humans should keep attacks from these charismatic and sometimes controversial species in perspective. Deadly attacks by scary predators always receive significant media coverage, and this makes them seem far more frequent than they really are. “For example, yearly [pet] dog, bee and snake killings are much more frequent than large carnivore attacks,” says Penteriani.

The numbers back up Penteriani’s calls for perspective. Hornets, wasps and bees kill about 60 humans each year in the U.S. alone, and most years don’t see a single mountain lion or wolf attack fatality. America’s pet dogs are responsible for another three dozen or so annual human deaths. Even lightning strikes kill about 20 individuals in the U.S. each year.

The actual danger large carnivores pose varies by location. In low-income areas, identified by the study for their lower emissions and bigger expanses of agricultural and rural land, villages and farms are often found in carnivore country. As growing populations spread into undeveloped land, humans and carnivores coexist far more often. Some 90 percent of the dangerous encounters in such lower-income areas occurred during the course of daily activities like farming, herding, traveling to school or collecting forest products.

In high-income nations, the authors suggest from their data that most attacks occur when humans choose to pursue recreational opportunities like hiking or camping in carnivore country.

But some protected predator populations are also growing and expanding into urban and suburban areas. For example, research shows that sustainable populations of large carnivores like brown bears, Eurasian lynx and gray wolves are found in one-third of mainland Europe. Many are spreading outside of dedicated protected areas and coming into contact with humans more often. Here, opportunist species like coyotes, bears and wolves can become conditioned to roam near towns in search of easy meals. “Most of the time, food-conditioned behaviors are the consequence of inappropriate human behaviors [like] unintentionally leaving food or trash outside the home, [or] intentionally feeding the predators to take some nice pictures,” says study co-author Giulia Bombieri, a biologist at the MUSE, a science museum in Trento, Italy. “We are starting to see this problem growing in some places in Europe and North America. We may expect more conflicts and even attacks to humans related to this scenario in the future.”

Guillaume Chapron, an ecologist and expert on large carnivore conservation at the Swedish University of Agricultural Sciences not involved with the study, notes that living in proximity to large predators requires an ability to accept that you are sharing the landscape with them and accepting the possible costs. “I’m not sure that in the U.S. or in Western Europe, even where some predators have become popular, if this popularity will stay after an attack happens.”

The dynamics of predator and human interactions are complicated. Depending on local conditions and context, the authors found differences in typical attack circumstances, even by the same species.

For example, in North America wolves are responsible for only 25 human attacks among the 70 years of reports included in the study, and in almost all cases those wolves had been conditioned to seek food associated with humans. In India, on the other hand, at least 300 predatory wolf cases occurred during the same time span. Similarly, while tiger attacks in Russia are usually defensive in nature, predatory attacks by the same big cats are relatively common in the Sundarbans, a Bay of Bengal river delta region in India and Bangladesh. The unusually aggressive local tigers in the swampy mangrove forests collide with a dense population of locals who collect firewood and honey, or who fish from small boats. “In most of the villages of the Sundarbans mangrove area, every family has lost one member because of a tiger attack,” says Penteriani.

Chapron adds that not all carnivores are created equal. The animals are individuals, and, for reasons not entirely understood, some can become more dangerous to humans than the norm. This can create what appears to be a trend of attacks—but isn’t really representative of a larger trend. “There are reports of man-eating lions, and it’s actually one specific individual who has developed a taste and a strategy to kill humans,” Chapron says. “And when you remove that individual, the series of human attacks stops.”

Penteriani and his co-authors hope their study can inform ways to reduce such conflicts. The data shows that odds of an attack can be reduced by following simple guidelines, including avoiding activity at dusk and dawn, and not leaving children unattended or hiking in predator country alone, since the rate of predator success decreases when humans are in groups of two or more.

But just as the nature of the attacks varies by locale, so do the ways and means of deterring them available to local communities. While such advice may be relatively easy to follow for individuals involved in leisure activities, those who regularly risk encountering the animals during work and subsistence activities may not be able to make these choices.

Carnivore confrontations can cause trouble for humans, but they ultimately may be even more dangerous for predator populations. Predators that attack humans are often killed themselves, and publicized attacks can produce fearful reactions that make some individuals view large carnivores far less favorably. Reducing attacks would not only save human lives but could also reduce negative attitudes and boost conservation efforts to ultimately help save the predators’ lives. “For this reason,” Penteriani says, “studies understanding the factors and scenarios triggering large carnivore attacks are crucial.”

Brian Handwerk | READ MORE

Brian Handwerk is a science correspondent based in Amherst, New Hampshire.