Mystery of bowhead whale song

Connecting the dots between bowhead whale songs and the songs of songbirds is a stretch, but there is one area in which they are linked.

Oceanographer Kate Stafford of the University of Washington’s Applied Physics Laboratory, is researching the sounds of bowhead whales in Fram Strait off the coast of Greenland.

The research project started in the winter of 2008-09.

“The Fram Strait population was at one time the largest in the world but (because of commercial whaling) is now critically endangered, thought to number in the 10s of animals,” Stafford said.

Two hydrophones were placed on moorings used by the Norwegian Polar Institute and the Alfred Wegener Institute of Germany.

As so often in research, what one might expect is often different from the result.

“We thought we’d get a few grunts, but we heard nearly constant singing throughout the winter.”

All male humpback whales on tropical breeding grounds sing the same song in one group or region although the song changes from one year to the next.

“Bowhead males, we assume they are males, rather than sing one song by all, sing at least 60 songs within the same year. The next year they have a new (repertoire) of completely different songs.

“That’s unprecedented in the whale population. That diversity is closer to songbirds than other whale species,” Stafford said.

Stafford was excited after discovering, along with researcher Sue Moore of NOAA, the relative immensity of the song list.

“It was just astounding. I went over them again and again because it’s pretty fun to listen to them. This was a beautiful chorus underwater,” she said.

The acoustic repertoire included simple calls, call sequences and complex songs.

Based on the song diversity, loudness and period over which the songs were recorded, western Fram Strait appears to be a wintering ground and potentially a mating area, as well.

“Humans are constrained by what we can see visually, and most whales spend almost all of their time underwater. What we might call a group or a single whale might not be true. They can make contact long distances underwater; a group might be more spread out than we can see, similar to elephants when they migrate.

“Bowhead sounds, depending on oceanographic conditions such as temperature, rough surface and the depth of the whale, can travel more than 31 miles. Sound travels farther underwater than through air,” Stafford said.

Mystery-solving is made difficult by the bowhead whales swimming in 24-hour darkness and under a nearly 100 percent ice cover during the study periods.

“One question that we’re trying to answer is: Does an individual sing all the songs or does a group share songs?” she said.

“We suspect a constant rotation of animals with their own songs or the songs of their year. Now so far as we know, each whale doesn’t sing 60 songs. They probably overlap. It’s still a complete mystery,” Stafford said.

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Columnist Sharon Wootton can be reached at 360-468-3964 or www.songandword.com.