Drones have changed the way scientists study whales and dolphins. Previously restricted to boat decks and viewing platforms, we could only glimpse the backs of animals as they surfaced. Getting an aerial view of whales and dolphins has already taught us a lot about their physiology and their behaviours.
The use of drones in marine research, however, has a downside.
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My doctoral research focuses on the behavior of belugas in the St. Lawrence Estuary. I have hundreds of hours under my belt as a drone pilot, flying over these amazing endangered animals. For my doctoral research at the University of Windsor, I use images of belugas taken by drones to better understand their behaviors and social structure, including differences between males and females.
While conducting my research with drones, I quickly noticed that these seemed to disturb the belugas. Other colleagues have observed that it happens that most animals that are under a drone suddenly dive, with a lot of splashing. These reactions seemed to be particularly common when the drone was flying at low altitude, about 20 meters above water.
We were concerned that this disruption would affect our ability to study whales and, even worse, impact these mammals.
We undertook a study of our observations, the results of which were published in the journal Marine Mammal Science. We examined whether a series of drone piloting variables impacted the likelihood of beluga whales reacting to the drone.
We predicted that the reactions to the drone would increase at low altitude, when the drone speed is high (which increases the noise of the rotors), when the drone approaches the whales head on, when the wind speed is low (which which makes the noise more audible) and during the first flight of the day.
We also looked at observed whale variables and predicted that drone disturbance would increase when whales are in small groups, when calves are present, and when they are resting.
We found that sudden dives are relatively rare, occurring in only about 4% of sightings. However, their frequency seems to increase when the drone flies at low altitude. Sudden dives are especially common when the drone is below 23 meters above sea level. This observation is logical, the drone being much more visible when it flies directly above our heads than when it is 100 meters above sea level.
We also found that sudden dives appear more frequent when drones fly over large groups. We did not expect this, as previous studies on dolphins had indicated that the small groups were more easily disturbed.
However, a recent study on the impact of drones on bottlenose dolphins revealed the same trend of increasing disturbance with group size. The authors suggested this was due to the ‘many eyes’ effect, with larger groups being more vigilant because there are more animals on the lookout for threats.
We have also found that sudden dives often occur when the drone first approaches whales. This suggests that whales are more frightened by the first passage of a drone.
We also conducted a literature review on the impacts of drone altitude on other species of whales and dolphins. We found that disturbances caused by drones rarely occurred when this one was flying above 30 meters in altitude.
Interestingly, the disturbing effects of drones were reported more when the authors included detailed descriptions of how these were assessed and measuredwhich suggests that these disturbances can go unnoticed when scientists do not dwell on them.
We have also observed that most studies on the impact of drones on whales and dolphins have used small drones (less than five kilograms), which are much more discreet than the large models of drones over 10 kilograms whose it is often used in modern research programs.
Our findings led us to make seven recommendations for future drone studies of whales and dolphins:
Observation of belugas by drone should be done at an altitude of at least 25 meters.
Scientists who use drones to study whales and dolphins should weigh the environmental benefits of low-level flights against the disruptions they can cause.
Pilots should be especially careful when their drone is flying over a large group.
Pilots should be especially careful when approaching a group for the first time.
Pilots using large drones (over 10 kilograms) should be very mindful of the disturbance they may cause and should report the effects of large drones on whales and dolphins.
Future drone studies should clearly indicate the disruptive behaviors observed.
As a precaution, drone pilots should avoid sudden accelerations, do not approach animals head-on, and be especially careful in light winds.
By limiting the disruption caused by research on whales and dolphins, we can help protect these amazing animals.