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Flying drones at low altitudes may harass belugas
Researchers examined footage to find out why belugas were diving deep into the water of the St. Lawrence Estuary
Jaclyn Aubin and her colleagues were flying drones over pods of beluga whales (Delphinapterus leucas) in the Saguenay Fjord in the St. Lawrence Estuary in Quebec to study their behavior when they began to notice something strange.
Occasionally, the cetaceans would suddenly dive deep into the water en masse, splashing their tails continuously before disappearing under the surface. They wondered if it had something to do with the drones they were using to study the population, which is listed as endangered under Canada’s Species at Risk Act.
“We want to make sure we’re doing a good job by the animals and not disturbing them when we’re trying to study them,” said Aubin, a PhD candidate who studies vocal communication in marine mammals at the University of Windsor.
She and her colleagues decided to take a closer look at the drone footage they’d amassed on a group of belugas in 2018 and 2019 for a study published recently in Marine Mammal Science. They examined the drone altitude, whether it approached from behind or in front of the belugas, drone speed, and whether the approach was the first of the day or occurred later. They also examined wind speed, as the sound could possibly mask that of an approaching drone.
The analysis revealed that sudden dives were relatively rare, only occurring during about 4.3% of the drone flights.
But these dives increased to 14.3% of drone flights when the devices flew less than 23 meters above the surface. “Altitude was a really important factor,” Aubin said.
A literature review showed that this flight threshold was roughly in line with other studies of the effects of drones on cetaceans. Those showed that, on average, the threshold for drone disturbance to whales, dolphins and porpoises was roughly 30 meters above sea level.
The researchers originally believed that smaller groups of belugas may get spooked more easily than when the group was larger. But the opposite was true. Aubin said they believe this may be due to the “many eyes effect” in large groups. “There are more animals out looking for disturbances, and they are more likely to react,” she said.
Finally, they found belugas were more likely to flee for deeper waters when a drone first approached a pod. This shows that operators should take extra caution when first approaching the whales, Aubin said, perhaps by flying the devices a little higher at that time.
When observing large groups, it’s also probably better to keep the drone higher than usual, she added.
“It’s possible to study these animals with drones, but drone pilots have to be cautious and fly the drones with care,” she said.