Here's the graphic from the article showing what happened when the flew the drone over the bear. The gray bars are the 5-minute overflights:In those five-minute windows, one bear's heart rate climbed all the way from 41 beats per minute to 162, while the rest of the bears saw beats-per-minute jumps as low as 30 and as high as 80. Still, each bear had the spike in common, along with a resulting drop to a normal heartrate shortly afterward. This came despite a seeming lack of visible response, with the exception of one bear that appeared to react. The bears in the study included two mama bears and their respective cubs; a lone male bear; and a female bear on the verge of hibernation.