Narwhal (Monodon monoceros) detection by infrared flukeprints from aerial survey imagery

Abstract

Visual and observer aerial surveys are important for monitoring wildlife populations but are subject to visibility biases where animals may go undetected. The use of infrared technology in aerial surveys has the potential to reduce visibility biases, both when recording data and in the retrospective processing of the footage, and thus complements visible wavelength photography. We used infrared video during marine mammal surveys in the high‐Arctic and indirectly detected narwhal (Monodon monoceros) via their thermal flukeprints (i.e., thermo‐stratified water mixing from fluke strokes). This novel indicator persisted for a longer duration than when the animal was at the water's surface, which likely improved the probability of an animal being observed by increasing the duration of its detectability. Using infrared to complement aerial photographic surveys may assist in monitoring whales, especially in remote areas. Our results highlight how infrared technology may be used to develop automatic detection and remote‐monitoring methodology.

Evidence of a narwhal (Monodon monoceros) summer ground in Nares Strait

“…During an expedition to Petermann Fjord in 2015, about 70 hours seismic reflection profiles (210 cubic inch GI airgun and seven hours with a Sparker) were acquired The observations made in Petermann Fjord in 2009, 2012 and 2019, however, suggest that narwhals are regular inhabitants of the fjord. Notably, the observations in Archer Fjord, on the Canadian side, were also recorded in 2019 (Carlyle et al 2021;Florko et al 2021). These two locations are less than 100 km apart, a distance that narwhals can travel in less than two days.…”

Investigating the thermal physiology of Critically Endangered North Atlantic right whales Eubalaena glacialis via aerial infrared thermography

“…Some flukeprints persisted for as long as 2 min and extended as far horizontally as 300 m (Churnside et al 2009). Florko et al (2021) detected thermal flukeprints from narwhals Monodon monoceros when the flukeprints were only 0.3−1.1°C warmer than the surrounding surface water. Our study further supports the use of aerial IRT to detect whales under certain oceanographic and meteorological conditions, even in a lower latitude habitat such as Cape Cod Bay.…”

“…(1) exploring patterns of cranial heat loss and the anatomical structures potentially responsible for these patterns; (2) tracking whales in real-time by observing thermal 'flukeprints', i.e. cooler subsurface water that upwells from depth during a fluke upstroke (Churnside et al 2009, Levy et al 2011, Florko et al 2021; and (3) using post-cranial heat anomalies to diagnose pathology or detect other changes in peripheral blood flow. We consider how the technology can improve our ability to evaluate large whale health, particularly for NARWs in the face of human impacts, while also acknowledging the myriad challenges and limitations related to the use of RPASbased IRT in aquatic environments.…”