- Researchers assessing the utility of small, multi-rotor unmanned aerial vehicles (UAVs) to survey and study humpback whales found that video data collected from a UAV improved upon data recorded by an expert observer from a research vessel, a standard technique.
- The observer mischaracterized certain behaviors, primarily socializing and nurturing, as other activities, such as traveling or resting, that the aerial viewpoint of the UAV captured clearly, even when the animals were below the surface.
- The whales did not show changes in behavior when the UAV approached or remained present at 30 meters above them.
- Their results suggest that small UAVs add value to cetacean behavioral research as a non-invasive research tool that can capture information that is otherwise difficult to detect from the angle and distance of a ship or shore observer.
A New Zealand-based research team assessing the utility of small, multi-rotor unmanned aerial vehicles (UAVs) to survey and study humpback whales determined that video data collected from a UAV improved upon data recorded by an expert observer from a research vessel, the standard behavioral technique. The team found the UAV captured some social activities not detected by the observer, with no observable effect on whales’ behavior.
They published their methods and test results last month, including clear descriptions of the selected UAV setup, UAV deployment from research vessels, and the data collected on the whales’ behavior using UAV-derived video compared to synchronized observations by a trained expert aboard the vessel.
Researchers have successfully used video camera-equipped unmanned aerial vehicles (UAVs, or drones) to count and identify cetacean species, as well as to photo-identify and estimate sizes of individual whales and dolphins. UAVs offer a safe, lower-cost alternative to manned flights and so have become increasingly popular in cetacean research.
Although small multi‐rotor UAVs offer only limited flight time (15-30 minutes per flight), research teams can launch them repeatedly from boats on the water and so can also track the animals’ position over time. The aerial viewpoint the UAVs offer enables scientists to collect behavior data, even when the animals are underwater.
Nevertheless, the researchers write in their paper, quantitative assessments of disturbance to animals and associated guidelines for responsible use of UAVs around cetaceans remain unpublished, a sentiment echoed by others.
For this study, the research team studied 33 groups of humpback whales over 19 days in Vava’u, Kingdom of Tonga. They surveyed the population and compared behavioral data collected using the standard method of an experienced observer recording the animals’ activities from a research boat to data taken (analyzed) from UAV-derived video footage.
They launched the UAV equipped with a GoPro camera from the research ship and flew the aircraft at 30 meters (98 feet) during its entire flight. They compared whale diving and movement behaviors when the UAV was present above the group versus when it was absent to assess any effects of the device on the whales’ behavior. They observed no changes in the whales’ behavior when the UAV first appeared above them, and the whales’ dive, respiration, and movement behaviors were the same whether the UAV was present or absent.
Nevertheless, lead researcher Lorenzo Fiori told Mongabay, he would recommend that researchers interested in incorporating UAVs into their research test for potential responses of their species of interest in the early stages of the survey design.
“Different species can react in different ways to the UAV presence,” he said. “This is extremely important as we aim to document the natural behaviour of whales and dolphins, ideally in absence of any other stimuli that can bias the observation.”
For each encounter with a whale group, an experienced observer on board the research vessel collected initial data on the number and respective sizes of whales observed (calves were whales that were half as large as adults), environmental variables such as weather, and the state of wind, tides, and the sea at the beginning of each encounter.
Every two minutes, the vessel observer also recorded movement and social behaviors of the group. Movements included number of dives, time of each dive (in seconds), breathing, and any changes in swim direction of 90 degrees or more with respect to the whales’ original heading direction.
To subsequently compare the information recorded from the UAV, the researchers synchronized the observations made by the expert observer from the vessel with simultaneous aerial video recording. After each flight, they analyzed the video clips, collected at 2.7 K resolution, and categorized behavior every two minutes to match the ship observer, who also confirmed the observations.
Useful tools for behavioral research
Although the postflight data processing effort can be time-consuming and cost-intensive, the authors write in their paper, “the opportunity to use close aerial video records of behavior significantly improves the quality and accuracy of data for cetacean behavioral studies.”
Having a permanent record of the flight offers teams the chance to reexamine and share video recordings with other experts to improve their confidence in the accuracy of their behavioral categorizations.
The researchers’ analysis of the aerial video footage showed that the boat-based observer frequently mischaracterized certain behaviors, primarily socializing and nurturing, as other activities, such as traveling or resting.
With their eyes roughly 2.5 meters (8 feet) above the water and their boat maintaining a respectful distance from the whales (in this case the legally required 300 meters (990 feet), even expert observers can’t pick out events occurring below the surface, such as the approach of another whale or contact between two submerged whales.
The UAV’s “birds-eye” viewpoint and capacity to hover just 30 meters above the whales provided better views of the whales, even when the animals were below the surface, and thus more accurate categorizations of their behavior.
The authors write that they expect new techniques, such as analysis of UAV-assisted video data, to make major advances in cetacean behavioral research and substantially change our understanding of the behavioral ecology of marine mammals.
“We have already conducted tests on bottlenose dolphins and dusky dolphins,” Fiori said. “Other researchers are focusing on other species too (e.g., gray whales). This methodology can be virtually extended to all cetacean behavioural studies.”
Citation
Fiori, L., Martinez, E., Bader, M. K. F., Orams, M. B., & Bollard, B. Insights into the use of an unmanned aerial vehicle (UAV) to investigate the behavior of humpback whales (Megaptera novaeangliae) in Vava’u, Kingdom of Tonga. Marine Mammal Science.
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