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Unmanned aerial vehicles, or drones, are fast becoming a popular tool for studying marine mammals such as whales, dolphins, and dugongs. But little is known about how these vehicles are affecting their study subjects.
New research suggests drones can stress bottlenose dolphins and cause them to change their behavior. Ticiana Fettermann, a marine biologist at the Auckland University of Technology in New Zealand and lead author of the study, says drones should be flown at least 25 meters above the ocean’s surface as a precaution against disturbing dolphins.
“When drones are not used safely, appropriately, and responsibly, they can put marine mammals at risk,” Fettermann says. “These findings provide invaluable guidance for the regulation of recreational and commercial use of drones around wildlife.”
In an experiment on resident dolphins near New Zealand’s Great Barrier Island, Fettermann and her colleagues studied how the dolphins behaved with no drone present and when a drone was flying 10, 25, and 40 meters above the water. The scientists were watching for stress responses, such as when the pod changed directions or when an individual slapped the water with its tail or chin.
When the drone flew 10 meters above the surface, the dolphins changed direction twice as often as when there was no drone in the sky. They also slapped their tails four and a half times more often. When researchers flew the drone at 25 and 40 meters, however, the scientists saw no difference in behavior.
Fettermann says that even short-term stress responses can have serious implications for the dolphin population. Crucial behaviors such as feeding, breeding, resting, and navigation may be altered, affecting survival and reproductive success.
Intriguingly, other marine mammal species seem to react differently, or not at all, to the presence of a drone. Previous studies on humpbacks and blue whales show no evidence of disturbance by drones flying as low as five meters above the water.
“We found absolutely no impact, no change in behavior, when the whales were approached from the tail end,” says Diane Gendron, a research scientist at Mexico’s Centro Interdisciplinario de Ciencias Marinas, Instituto Politécnico Nacional, who worked on the blue whale study.
These differences between species may come down to their physiologies and how long they tend to spend at the surface, says Gendron.
Fettermann and her colleagues say more work is needed to understand these species-specific effects. Ambient noise levels, the type of drone, and the animal’s auditory range and behavioral state during the drone flight are all important factors to consider when assessing the potential for disturbance.
Despite these knowledge gaps, drone technology offers a low-cost, minimally invasive alternative to sampling techniques such as tagging and biopsy, Fettermann says. Drones “can potentially complement and enhance many ongoing conservation programs,” as well as gather high-resolution spatial and biological data.
Drones will continue to be an essential tool for those studying marine mammal behavior, agrees Gendron. “With drones, you can see interactions between individuals,” she says. “When something special is happening, the drone is a necessity.”