A UFO would stress out a bear

If you saw a UFO, how would you react? Your heart would probably start to race. And if you were scared enough, you might run away. Bears, it turns out, aren’t so different from us; they react in just this way.

Scientists aren’t actually all that interested in how animals react to aliens, but they are concerned about what happens when animals encounter an unidentified flying object. That’s because drones (or unmanned aerial vehicles) are increasingly used to study and monitor wildlife. But if UAVs stress out or harm animals, then scientists have a problem. That’s one of the reasons that the U.S. National Park Service has banned the public use of UAVs within park boundaries: Someone flew a drone near a herd of big horn sheep, scattering the flock and separating mothers and lambs.

With the growing popularity of drones among the public, there are plenty of videos online showing what happens when an animal encounters one. But few scientific studies have tackled the question. So Mark Ditmer of the University of Minnesota, St. Paul, and colleagues tested the reactions of four black bears in northwestern Minnesota — two moms with cubs, a 1-year-old male and an adult female who had just entered her hibernation den, each of which had been outfitted with a GPS collar and heart monitor. In 18 tests, the researchers flew a small quadcopter 20 meters over a bear and then recorded what happened. They report their findings in the August 31 Current Biology.

The bears definitely took notice of the drone. The animals’ heart rate skyrocketed when the UAV flew overhead, and their stress response was stronger when the quadcopter flew in windy conditions that masked the sound of its approach — apparently bears do not like being surprised. One bear started moving faster after the quadcopter flew by. And the bear that had experienced the greatest increase in heart rate — from 41 beats per minute to 162 — moved nearly 7 kilometers in the next 28 hours, encroaching into a neighboring female’s territory.

All in all, though, the bears weren’t stressed all that much, the researchers concluded. The animals’ heart rates returned to normal within about half an hour of the drone fly-by. But the bears the researchers studied live in a heavily human-altered landscape, they note, so other bears may react differently.

UAVs hold great promise for studying and protecting wildlife, but they also could potentially stress animals, causing harm. Ditmer’s team says that their results reinforce the NPS ban on drones in parks. The study should also make those members of the public who own their own UAVs think twice about where they’re flying their toys — it might be fun to watch an eagle take out a drone or a ram head-butt a UAV, but not all animals will enjoy this as much as the humans behind the controls.