Pitch of Blue Whale Songs Is Declining Around the World, But This Could be a Good Thing


Photo: Wikipedia, CC/GFDL
Frequency of Tones Shifted Down
Scientists from the Scripps Institution of Oceanography at UC San Diego have noticed something very interesting while studying the songs of blue whales: "The basic style of singing is the same, the tones are there, but the animal is shifting the frequency down over time. The more recent it is, the lower the frequency the animal is singing in, and we have found that in every song we have data for," said Hildebrand, a professor of oceanography in the Marine Physical Laboratory at Scripps. Maybe hypothesis have been explored to explain this change. Climate change, maybe? Or the rise in man-made noises in the oceans? But the most plausible explanation so far is actually a positive one.

Photo: Flickr, CC
Easier to Find a Mate
While whale populations are still much lower than they were before humans started commercial whaling (whale fat was widely used before we drilled for petroleum), bans on whaling have helped blue whale populations rebound in recent years. This seems to be the most likely explanation for the pitch change in blue whale songs.

While the function of blue whale songs is not known and scientists have much more to learn, they do know that all singers have been determined to be males and that the high-intensity, or loud, and low-frequency songs propagate long distances across the ocean. Blue whales are widely dispersed during the breeding season and it is likely that songs function to advertise which species is singing and the location of the singing whale.

In the heyday of commercial whaling, as blue whale numbers plummeted, it may have been advantageous for males to sing higher frequency songs, the researchers believe, in order to maximize their transmission distance and their ability to locate potential mates (females) or competitors (other males). [...]

In more recent years, as population sizes have increased, it may now be more advantageous for males to sing songs that are lower in frequency rather than louder.

If this is correct, it could mean that recordings of blue whale songs are a proxy for population density. We could be monitoring the health of the species without having to find them and count them. Maybe this will never be the primary way to assess blue whale population, but it seems to me like it could be a good data point to add to estimates.

Via Scripps Institution of Oceanography
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