Marine mammals are sentinels of the sea. When dolphins and whales show signs of stress or illness, it often signals deeper problems in the ocean ecosystems we all depend on.
But assessing the health of dolphins and whales is notoriously difficult. That’s because they spend most of their lives underwater, move over vast areas, and cannot be examined closely without causing stress or disturbance.
Our new research provides a promising solution to this problem. Published in the Journal of Thermal Biology, it shows how drone-mounted thermal cameras can help monitor dolphins’ vital signs such as skin temperature and breathing patterns.
Monitoring animals without handling them
Scientists have typically relied on hands-on methods to assess the health of wild marine mammals. These include attaching tagging devices or taking measurements during capture and handling.
While these methods can be effective, they are also invasive, expensive, logistically complex, and can alter the animals’ behaviour and physiology. This can induce stress, making results harder to interpret.
To fix this problem, researchers need tools that allow them to monitor dolphins repeatedly and accurately, while minimising disturbance.
One example is drones fitted with thermal cameras.
Thermal cameras detect heat emitted from surfaces, allowing temperature patterns to be measured remotely. When mounted on drones, they can potentially record this information from above, while animals continue to move freely.
In the case of dolphins, they have the potential to measure skin temperature and breathing patterns based on the heat emitted from the animals’ blowholes, body and dorsal fin, without having to get close or touch them.
But until now, no studies have tested how accurate, reliable or practical this approach is in real-world conditions.
Guido J. Parra/CEBEL
Testing drones on dolphins
In our study, we used a drone-mounted thermal camera to measure dolphins’ body surface temperature and breathing rate under controlled conditions designed to reflect how dolphins are monitored in the wild.
The study involved 14 adult common bottlenose dolphins under human care at Dolphin Beach, Sea World on the Gold Coast, Australia. Testing was conducted across different heights, camera angles and environmental conditions to validate drone-based measurements.
We compared measurements obtained from drones with close-range reference data collected at the same time. Body surface temperature was measured using hand-held thermal cameras and breathing rates were calculated from the drone’s visual footage. This allowed us to assess how accurate and reliable the drone measurements were.
This approach required no restraint or tagging. Drone-based measurements were collected without physical handling of the animals.
We found that how the drone was flown substantially affected the accuracy of measurements. For example, flight height influenced how reliably body surface temperature and breathing rate could be estimated.
Measurements collected at lower altitudes, particularly about ten metres directly above the dolphin, consistently produced the most accurate results. At this height, body surface temperatures derived from thermal imagery closely matched close-range reference measurements taken at the same time.
As flight height increased, measurement accuracy declined. However, temperature estimates remained within approximately 1°C of the reference measurements.
Camera angle also influenced the accuracy of measurements. Thermal measurements were most accurate when the camera was positioned directly above the dolphin.
We could estimate breathing rates accurately from thermal imagery. Each breath produced a brief, localised increase in temperature at the blowhole that was clearly visible in the thermal footage.
Charlie White/CEBEL; processing by Andrew P. Colefax
Growing the conservation toolbox
These results show that drone-mounted thermal cameras can reliably measure dolphins’ surface temperature and breathing rate.
This represents a practical advance in how dolphin vital signs can be monitored in the wild. Until now, repeated measurements of temperature and breathing have typically required researchers to be close enough to dolphins to take measurements directly, such as from boats or by capturing and physically handling an animal.
This has limited how often measurements can be taken. Thermal drones offer a way to gather this information routinely, without significantly disturbing dolphins.
This approach has the potential to improve our ability to detect physiological changes and examine how dolphin health may vary over time in the wild. Combined with behavioural observations, drone-based thermal imaging could help explore links between surface temperatures, breathing patterns and environmental conditions.
Our study focused on dolphins under human care. But the same approach could be applied to free-ranging dolphins and other marine mammals for which close-range monitoring of vital signs is difficult.
As coastal ecosystems face growing pressure, tools such as thermal drones that allow researchers to monitor wildlife efficiently, repeatedly and non-invasively will become increasingly important. They provide a practical addition to the conservation toolbox, helping us better understand, and ultimately protect, dolphins and other animals in a changing ocean.
The authors would like to acknowledge the contribution of Dr. Andrew Colefax to this research and the Sea World, Gold Coast team for their support and in-kind contributions.
