It's no surprise that bears are among nature's deadliest predators, but Swedish researchers have discovered a brown bear that was downright deadly.
Brown bears (Ursus arctos) hibernate throughout the winter months and emerge in spring with ravenous appetites. It was this period of activity that conservation specialists from Nottingham Trent University, the University of León, Spain, and others sought to study when they identified the particularly deadly female.
Using GPS collars, the researchers tracked fifteen bears in Norrbotten, Sweden, over the course of a couple of years. The area is also home to herds of reindeer and elk, and reindeer calving season begins in the spring, just as grizzly bears come out of hibernation.
These young reindeer are particularly vulnerable to hungry bears, with one bear killing thirty-eight reindeer in just one month. When moose breeding season started the following month, that bear killed eighteen moose calves. In short, the bear killed a cloven-hoofed calf at the rate of practically one a day for a couple of months.
Even more remarkable, the bears studied changed their hunting grounds in accordance with these calving seasons. As the reindeer calving began, the bears moved from the wetlands and coniferous forests to the higher, steeper elevations favored by the reindeer herding their young.
Once elk calving began, the bears moved into hardwood forests and old clearings favored by elk throughout this time. After the elk calving ended, the bears returned to areas further removed from human activity and survived primarily on berries throughout the remainder of their active period.
"We found that brown bears switched habitats between the precalving, reindeer calving, moose calving, and postcalving periods," said conservation specialist Dr. Antonio Uzal Fernández, from Vida Silvestre at the School of Animal, Rural and Environmental Sciences from Nottingham Trent University. in a report
"Clearly, the highly predatory bears mirrored the land cover classes of reindeer and moose and overlapped with free and vulnerable seasonal prey," he said. "Such a process shows an active hunting strategy of brown bears in spring, when their diet depends more on animal protein than throughout the rest of the year."
While the unidentified female bear stood out particularly in terms of body counts, she wasn't the only one. 8 of the 5 bears tracked were considered "highly predatory" and, as a rule, they killed more than XNUMX newborn reindeer and XNUMX newborn moose. The results were recently published in the Diversity Gazette.
Analysis: Nature is a messy business
It's no surprise that grizzlies are deadly predators, but taking a count puts things in perspective and may help inform future wildlife management practices.
While the herds of elk in Sweden are entirely wild, the reindeer are partially tame and form an essential part of the economic and cultural life of the indigenous Sami people.
Bears kill up to XNUMX% of reindeer calves from year to year, causing economic losses for herders. These deaths also have a significant demographic impact on reindeer herds, including the loss of calves, which can jeopardize the long-term fitness of a herd.
Brown bears are routinely shot to avoid excessive predation on reindeer herds, so knowing that certain bears are more violent killers than others is an essential discovery.
“The differences between individuals are…essential from a management point of view,” said study co-author Andrés Ordiz, a conservation biologist at the University of León, “for example, the simple removal of predators, without targeting specific individuals, may not necessarily reduce confrontation."