A research team led by an University of Washington oceanographer has published the largest known set of songs from bowhead whales, the jazz singers of the cetacean tribe.
An analysis of 184 different songs, recorded between 2010 and 2014, finds that bowhead whales swimming in the Arctic Ocean east of Greenland have a surprisingly diverse repertoire of vocalizations.
“If humpback whale song is like classical music, bowheads are jazz,” study lead author Kate Stafford of UW’s Applied Physics Laboratory said in a news release. “The sound is more free form. 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.”
Stafford and her colleagues published their findings in today’s issue of Biology Letters. The research follows up on other underwater recording campaigns that Stafford has conducted throughout the world’s oceans, including a six-month listening session that picked up songs from bowhead whales in 2008-2009.
For the follow-up campaign, researchers placed underwater microphones in Fram Strait, an icy region of the Arctic Ocean between Greenland and Norway’s Svalbard Islands. The area is accessible to ships only in late summer, but the researchers stored up songs from three yearlong cycles.
The whales sang regularly in the region from late fall to early spring, and there was slightly more singing as the years wore on.
The diversity and frequency of vocalizations suggest that the population is healthy. That’s a relief, because bowhead whales had been hunted nearly to extinction, and the whales near Greenland are still considered endangered.
Like their better-known humpback cousins, bowhead whales are thought to use vocalizations to attract mates, and perhaps just to show off. The songs could well serve other purposes as well.
“For marine mammals, acoustics is how they do everything,” Stafford explained. “Humans are mostly visual animals, but marine mammals live in a three-dimensional habitat where sound and acoustic information is how they navigate, how they find food, how they communicate.”
When it comes to bowhead whales, little is known about the details: Do only males sing, or do females carry a tune as well? Do whales share songs? And what’s with the jazz-style improvisation?
“Why are they changing their songs so much?” Stafford said. “In terms of behavioral ecology, it’s this great mystery.”
It may be that song diversity serves as a sign of evolutionary fitness, bumping up the singer’s status for mating or dominance. To help untangle the mystery, researchers are placing radio tags on bowhead whales to get more precise information about all that jazz.
“Bowheads are superlative animals: They can live 200 years, they’ve got the thickest blubber of any whale, the longest baleen, they can break through ice,” Stafford said. “And you think: They’ve evolved to do all these amazing things. I don’t know why they do this remarkable singing, but there must be a reason.”
Stafford’s co-authors for the Biology Letters study, titled “Extreme Diversity in the Songs of Spitsbergen’s Bowhead Whales,” include Christian Lydersen, Kit Kovacs and Øystein Wiig. The research was funded by the Norwegian Polar Institute, the Svalbard Environmental Protection Fund, Svalbard Science Forum, the Fram Centre Incentive Fund and the Norwegian Research Council.