| Summary: | Infrared thermography (IRT) is a non-invasive, contactless tool for measuring the thermal radiation emitted from an object’s surface. Combined with advancements in remotely piloted aircraft systems (RPAS, commonly “drones”), IRT is being used for detection, counting, and physiological studies of marine mammals. Critically endangered North Atlantic right whales (NARWs, Eubalaena glacialis) were observed in Cape Cod Bay, United States in 2017–2018 with RPAS-based IRT. We discuss four applications of RPAS-based IRT to study the thermal physiology of large whales: 1) exploring patterns of cranial heat loss; 2) tracking subsurface individuals in real-time using thermal “footprints” – cold surface water anomalies resulting from fluke upstrokes; 3) diagnosing pathology or detecting natural changes in superficial blood circulation; and 4) measuring blowhole temperatures as a proxy for internal body temperatures and possibly health of individual whales. IRT of NARW rostra demonstrated that the peri-callosity epithelium radiates more heat than other superficial cranial tissues; we hypothesize that the source of this heat is the underlying corpus cavernosum maxillaris. Thermal footprints were most visible on calm, sunny days, likely due to thermal stratification of the upper water column. A diffuse patch of heat on the caudal dorsum of one NARW may have been indicative of superficial changes in blood flow, potentially associated with pathology or heat dissipation. Finally, we emphasize the need to properly calibrate IRT data before interpreting temperatures of blowholes, although we do believe this technology could be used to approximate near-core body temperatures in the future. RPAS-based IRT presents a new, important opportunity to study and monitor large whales, particularly endangered species like NARWs. Despite the challenges of using aerial IRT in aquatic environments, we believe its applications in marine mammal research will continue to diversify. This project was funded by National Marine Fisheries Service grant, NA14OAR4320158 and the North Pond Foundation.
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