Narwhals leave infrared 'fluke-prints' in the ocean that can be seen with aerial cameras

A team of researchers was surprised to discover that narwhals can be tracked while swimming in freezing arctic waters by their heat signature.

They spotted traces of the normally elusive whales while doing an aerial survey aimed primarily at other arctic wildlife.

In August 2019, Katie Florko, a PhD student from the Institute of Oceans and Fisheries at the University of British Columbia, and colleagues flew over the ice on Ellesmere Island, Nunavut in a Twin Otter aircraft equipped with infrared camera equipment. The idea was to track walruses, polar bears and seals from the air because they are so difficult to track on the ice. They flew 57 transects over the ice, but kept the cameras rolling over open water. 

It was there that the infrared cameras picked up something else, heat signatures — what the team called 'fluke prints' —of narwhals swimming in the water. Narwhals are a medium-sized whale known for a single protruding tusk. When swimming, they surface for a very brief period of time to breathe. When they do, they change the temperature of the water. That change in temperature remains for five or six seconds, and can be detected by an infrared camera. 

Florko said using infrared technology to detect mammals like narwhals in the water had never been contemplated before, so the case of this study, it was a matter of good timing and a bit of luck. She anticipates in the future, infrared can be used to complement traditional photographic surveys to track the whales.

The other surprise to Florko was that the 28 narwhals her team detected were much further north than expected. She believes they are there because of receding sea ice. 

All of the information gathered will be used to try to survey narwhal populations and to understand how they are surviving in this northern habitat. 

Written and produced by Mark Crawley