According to NPR, bears have similar reactions to the sight of a mysterious flying object as humans. Researchers from the Cell Press journal Current Biology fitted wild, free-roaming American black bears in northwestern Minnesota with GPS collars and cardiac biologgers. With these tools, the researchers were able to monitor both the location and the heart rates of these bears.

Then, the researchers programmed an unmanned aerial vehicle (UAV) to fly to the bear’s most recent location. Although American black bears rarely run away when a UAV comes near, the new study reveals that despite their calm demeanor, their heart rates soar, a sign of acute stress.

Mark Ditmer of the University of Minnesota, St. Paul says “Some of the spikes in the heart rate of the bears were far beyond what we expected. 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 says, “Without the use of the biologger, we would have concluded that bears only occasionally respond to UAVs.”

The result of this study is that it will now be important to consider the stress caused by UAV flights on wildlife when deciding how best to monitor them. UAVs are becoming increasingly popular for a variety of purposes in wildlife study, such as discouraging poachers and tracking down wildlife for ecotourists.

Now, Ditmer and his colleagues are studying the behavior of captive bears to determine whether or not the animals can become desensitized to overhead UAV flights over time.