Bears often look cool under pressure, so scientists were surprised to find out that the large predators nearly have a heart attack when drones approach.
The study, published in the journal Current Biology, highlights concerns over the use of drones around bears and other wildlife, given that the devices can make animals' hearts race.
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"Some of the spikes in the heart rate of the bears were far beyond what we expected," co-author Mark Ditmer of the University of Minnesota, St. Paul, said in a press release. "We had one bear increase her heart rate by approximately 400 percent - from 41 beats per minute to 162 beats per minute. Keep in mind this was the strongest response we saw, but it was shocking nonetheless."
Ditmer and his team made the discovery after outfitting four free-roaming bears living in northwestern Minnesota with GPS collars and cardiac biologgers. Every two minutes, the collars sent the researchers an email with each bear's location. The biologgers tracked every heartbeat.
With this setup in place, the researchers ran 18 brief unmanned aerial vehicle (i.e., UAVs or drones) flights in the vicinity of the bears. The flights, which each lasted only about 5 minutes, were comparable to those of drones used to track wildlife movements and for other purposes.
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While the bears looked relatively unfazed during the study, the biologgers revealed that the bears' heartbeats dramatically increased whenever they detected the drones.
"Without the use of the biologger, we would have concluded that bears only occasionally respond to UAVs," Ditmer said.
Fortunately, the bears in the study recovered quickly. The evidence that drones can stress out animals, though, suggests that more investigations of these devices and their possible other impacts on wildlife are needed.
There is no time to waste either, since drones continue to grow in popularity. For example, they are used to discourage poachers and to track down wildlife for ecotourists. As the scientists point out, few rules are in place to guide their usage in many countries.
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Since UAVs do offer many benefits, Ditmer and his colleagues are now working with captive bears to see if they can get used to overhead drone flights over time and, if so, how long that would take.
"UAVs hold tremendous potential for scientific research and as tools for conservation," Ditmer says. "However, until we know which species are tolerant of UAVs, at what distance animals react to the presence of UAVs, and whether or not individuals can habituate to their presence, we need to exercise caution when using them around wildlife."