Wildlife Drones May Stress Animals Out, Study Says

Drones, says conservation biologist Mark Ditmer, can revolutionize the way wildlife is studied. They're pretty affordable, can access remote, difficult terrain, and get close to animals that are easily spooked by humans. Researchers are increasingly turning to them to monitor populations, collect data and deter poachers, but for the most part, no one has stopped to ask what the animals might think of them. Anecdotal evidence suggests that elephantshabituate to drones pretty quickly, and earlier this year research showed that they rarely affect bird behavior.

Just because animals don't appear to be bothered, though, doesn't mean they aren't. In a study published today in Current Biology, Ditmer and a team of researchers from the University of Minnesota found that some animals that seem calm in the presence of drones actually get very stressed out in ways that we can't easily see.

After fitting a group of black bears with GPS collars and heart rate monitors, Ditmer and his team programmed a small quadcopter drone to circle the animals and hover over them for a few minutes. These flights were made over four different bears, including one in a den getting ready to hibernate, several times over the course of a few weeks.

During 18 flights, the researchers only saw changes in the bears' behavior twice, when two bears reacted to the drone by hurrying off to another area. The heart monitors, though, showed that all the bears' heart rates spiked sharply during the flights (by as much as 300 percent in one case), a sure sign of stress.

The bears' behavior and physiology were telling two different stories, Ditmer says, and if it weren't for the heart monitors, his team would have wrongly concluded that bears only respond to drones occasionally. What's more, the bears that Ditmer studies live on the fringes of farmland and frequently encounter cars and farm equipment. The team thinks that other animals less accustomed to man-made noise likely get even more stressed out by drones and recover slower.

Stressing wildlife out not only affects scientists' data, but can also be disastrous for the animals. Last year, a low-flying drone in Zion National Park sent a herd of big horn sheep into a panic and separated lambs from their mothers. Ditmer's team also points out that stressed animals fleeing from a drone could run into roadways or encroach into other animals' territory and be injured or killed.

The study's results make it clear that there's a knowledge gap that needs to be closed before any revolution in animal monitoring can happen, and that biologists need to proceed with caution until they know which animals will or won't tolerate drones and how they'll react.