It's tempting to use drones to observe wildlife instead of aircraft or hidden cameras, especially since some animals aren't visibly annoyed by the presence of these robotic viewers. However, that calm exterior might be hiding serious stress underneath. University of Minnesota researchers have learned that the heart rate of a black bear can jump dramatically when a drone is overhead, even if there's no outward signs of trouble. One bear's heart rate quadrupled from a placid 41 beats per minute to 162. While the bears' heart rates fell soon after the UAVs flew away, it's possible that they're simply familiar enough with human-operated machines to relax -- isolated bears might not be quite so placid.