Bowhead whales love to sing in dark: study

Bowhead whales - the 'jazz musicians' of the Arctic - prefer to sing many different songs in the darkness of the polar winter, a study has found.

Researchers at the University of Washington in the US have published the largest set of recordings for bowhead whales, to discover that these marine mammals have a surprisingly diverse, constantly shifting vocal repertoire.

The new data suggests bowhead whales may be similar to cowbirds and meadowlarks, birds that learn a diverse, ever-changing repertoire of songs, maybe because novelty offers some advantage.

"Bowhead whales do this behaviour in the winter, during 24-hour darkness of the polar winter, in 95 to 100 per cent sea ice cover. So this is not something that is easy to figure out," said Kate Stafford, an oceanographer at the University of Washington in the US.

"We would never have known about this without new acoustic monitoring technology," said Stafford.

The study, published in the journal Biology Letters, analysed audio recordings gathered year-round east of Greenland.

This population of bowhead whales was hunted almost to extinction in the 1600s and was recently estimated at about 200 animals.

Audio recordings gathered from 2010 to 2014 indicate a healthy population, and include 184 different songs.

"If humpback whale song is like classical music, bowheads are jazz," said Stafford.

"The sound is more freeform. And when we looked through four winters of acoustic data, not only were there never any song types repeated between years, but each season had a new set of songs," said Stafford.

She has recorded whales' sounds throughout the world's oceans as a way to track and study marine mammals.

She first detected bowhead whales singing off the other side of Greenland in 2007.

"We were hoping when we put the hydrophone out that we might hear a few sounds," Stafford said.

"When we heard, it was astonishing: Bowhead whales were singing loudly, 24 hours a day, from November until April. And they were singing many, many different songs," she said.

The new study extends that initial five-month dataset, and confirms that bowhead whales sing in this region regularly from late fall to early spring.

In fact the hydrophones, which are underwater microphones, picked up slightly more singing in the later years of the study.

However, what was most remarkable was the relentless variety in the animals' songs, or distinct musical phrases, researchers said.