Beware of predatory male American black bears: Attack rates are rising with human population growth

In an article published in the Journal of Wildlife Management, University of Calgary professor emeritus Dr. Stephen Herrero, University of Calgary graduate Andrew Higgins, and colleagues from the Massachusetts Division of Fisheries and Wildlife and Brigham Young University analyzed the circumstances of all recorded deaths inflicted by non-captive black bears in North America between 1900 and 2009. The study found that 63 people were killed in 59 incidents in Canada, Alaska and the lower 48 states. The researchers determined that the majority (88%) of fatal attacks involved a bear exhibiting predatory behaviour, and 92% of the predatory bears were males. The authors suggest male black bears have evolved some different behaviours than females.

"Each year there are millions of interactions between people and black bears with no injuries to people. So while the risk is low, it does exist," said Herrero, an expert in bear behaviour and ecology in the U of C's Faculty of Environmental Design. "Our findings raise some important new insights that can be used to better understand the cause of attacks and how they can be avoided in both the front and backcountry."

In particular, the common belief that surprising a mother bear with cubs is the most dangerous kind of black bear encounter is inaccurate. Instead, lone male black bears hunting people as a potential source of food are a greater cause of deadly maulings and related predatory attempts. The study also found that fatal attacks do not typically involve bears that are familiar with humans, although some fatal attacks did.

"Most fatal black bear attacks were predatory and all fatal attacks were carried out by a single bear," Herrero said. "With training, people can learn to recognize the behaviour of a bear that is considering them as prey and deter an attack by taking aggressive action such as fighting back."

The paper confirms other current perceptions and bear management practices. It found that bears that have previously killed people are more likely to attack again; parties of more than two people are much less likely to be attacked; and human food and garbage tends to attract bears and may increase the likelihood of serious bear attacks.

Examining 110 years of data also allowed the researchers to identify historical and geographic trends of black bear attacks. They found that 86% of fatal attacks occurred since 1960; that fatalities are more common in Canada and Alaska despite lower human populations and less contact between humans and bears than in the lower 48 states; and that human population growth is accompanied by rising fatal bear attacks.

"We didn't demonstrate why population growth is correlated with more bear attacks but we suspect it is because there are more people pursuing recreational and commercial activities in black bear habitat," Herrero said. "Similarly, we don't know exactly why there have been more attacks in Canada and Alaska, but we speculate that it could be because bears in those areas are living in less productive habitat with periodic food stress, which may predispose some bears to consider people as prey."