It is now generally accepted that the bowhead whale is the longest lived mammal on the planet, with a lifespan of over 200 years. But that it can sing with "more than one voice" and that it changes its repertoire from year to year is news. This behaviour is unique among baleen whales and is a newly discovered phenomenon that has been investigated by researchers at the University of Copenhagen.
The project comes at a time when the bowhead whale, after many years of absence, has returned to the waters around northwest Greenland, including Disko Bay. It wasn't that many years ago that the bowhead whale was written off as extinct in the waters around Greenland and especially in Disko Bay in northwest Greenland where University of Copenhagen has its Arctic Field Station.
But now the situation has changed and adult bowhead whales, which can grow up to 18 metres long and weigh 100 tons, have returned to the bay. Probably because global warming has opened up the Northwest Passage, making it ice free at certain times of the year for the first time in 125,000 years. This gives bowhead whales from the northern Pacific a chance to reach Disko Bay and mate with the small local population. There is now believed to be around 1200 whales in the waters around Disko Island.
Hydrophones have revealed that the whales have developed very sophisticated songs that are used to attract a mate and thereby ensure the species' survival.
"Whale song is not a new phenomenon. But the special thing about the bowhead whale's song is that they sometimes sing with 'more than one voice'. They produce two different songs or sounds, which are then mixed together. This has not been seen in other baleen whales. It turns out that bowhead whales change their songs from year to year and never repeat songs from previous years. I.e. the whales have a new repertoire each year – presumably as part of the eternal struggle to obtain a mate," said Outi Maria Tervo, a PhD student at the University of Copenhagen and the current scientific leader of the Arctic Station in the town of Qeqertarsuaq (Godhavn) on Disko Island.
"The bowhead whale is in the same weight class as fin whales and blue whales but they produce much more complicated songs, at higher frequencies, between 100 and 2000 hertz – cycles per second. At the same time the question arises whether the changes in their song repertoire are due to bowhead whales being so sophisticated that they change their songs from year to year in order to constantly attract and mate with new partners and thereby spread their genes. The bowhead whale is the only species of 'singing' whale where the gender of the singers has not yet been established," says Outi Maria Tervo, who now has a serious opportunity to study bowhead whales via different types of hydrophones, thanks to donations from, amongst others, the A.P. Møller fund.
Her studies of the love songs of bowhead whales have just been chosen to be presented at large international conference on marine mammals later this year in Canada. At the same time the A.P. Møller fund has chosen to support the project with 1.8 million Danish kroner over a three year period.