Not able to migrate, whales wail

Tokyo – Eerie wails, explosive trumpets and ghostly moans. The sounds from the underwater recorders had a story to tell, even without a single intelligible word: the whales had stayed put.

The recordings gathered during the 2018-2019 winter in the freezing cold Arctic waters off Canada proved that a population of bowhead whales had skipped their usual migration south.

Scientists believe this behaviour – never previously detected – could be driven by the effects of climate change and be a potential harbinger of shifting dynamics across the region’s ecosystem.

Ordinarily, the approximately 20 000 bowheads that make up the Bering-Chukchi-Beaufort (BCB) population around Canada have a fairly predictable migration pattern spanning 6 000km.

They spend the winter in part of the Bering Sea, which lies between Russia and Alaska, and head north then east to the Beaufort Sea and Canada’s Amundsen Gulf in the summer, before returning in the autumn.

But in winter 2018-2019, something different happened. Residents in the Canadian region reported seeing bowheads long after they would normally have disappeared south.

A team of scientists decided to comb through hours of audio recorded by underwater devices that are dotted around the region for regular data collection, listening for unusual sounds.

They found them: the distinctive calls of bowhead whales that should have been in their southern winter grounds but had stayed put.

Assisted by a computer programme, they even found recordings of bowheads singing, a behaviour believed to be associated with mating, which has never been recorded in the summer grounds before.

The whale noises appeared in between 0.5 to 3.0% of recording files collected between October to April at four summer spots.

The finding was highly unusual: recordings from some of the same and separate sites in the summer grounds in previous years picked up no whale sounds after October or December, depending on the location.

“The evidence is clear that BCB bowheads overwintered in their summer foraging region in the eastern Beaufort Sea and Amundsen Gulf during the 2018-2019 winter and as far as we know, this is the first time it has been reported,” says the study published yesterday in the Royal Society Open Science journal.

Less clear, however, is why this happened, with the authors positing various theories mostly linked to climate change.

One possible factor could be shifting ice cover, with less ice than usual seen in the summer grounds during the 2018-2019 winter season.