New research tracked wild bears' heart rates when they notice airborne drones around, finding they get significantly more agitated.

According to Live Science, authors of a study published in the journal Current Biology learned bears' hearts would beat up to four times faster than usual if they sensed a drone nearby. Also classified as unmanned aerial vehicles (UAVs), drones are proving to have a wide array of uses, including wildlife observation.

In that respect, the usage of such UAVs could save scientists a great deal of time as well as long, difficult or sometimes dangerous treks.

"Some of the spikes in the heart rate of the bears were far beyond what we expected," study lead 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."

The researchers acknowledged their results are based on limited data because they only tested the heart rates of four bears with 18 flybys with the UAVs, Live Science reported. They monitored heart rates with cardiac biologgers and tracked their movements with GPS collars.

The researchers also pointed out that their conclusions would have been impossible without the heart monitors, because the bears appeared calm and collected while their hearts were racing.

"The magnitude of some of the heart-rate spikes were shocking," Ditmer told Live Science.

"By no means are we advocating against the use of UAVs, especially for research or conservation," he said. "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, especially at close distances."