Marine biologists have long been fascinated by whale songs, as scientists still don’t understand their function fully. Blue whales, in particular, have a “lonely song” that travels across entire oceans. Recently, scientists at the University of California, San Diego have noticed blue whale songs are changing as this endangered species population rebounds. Specifically, the pitch of blue whale songs is decreasing.
Blue whales are the largest mammals on earth. In fact, the American Cetacean Society states:
On land an animal the size of a blue whale would be crushed by its own weight without the support of large heavy bones. Because its body is supported by water, as a sea animal, the need for heavy bones to support its weight disappeared.
Earlier this fall, a 70 foot blue whale washed up on the Mendocino coast of California when it was struck by a ship, the second blue whale to be beached in just two weeks. Although blue whales are endangered, the species is making a comeback which is affecting the pitch of their song, as well as increasing the occurrence they are injured by ships. There are approximately 3000 to 4000 blue whales in the Northern Hemisphere.
National Geographic News describes the blue whale’s song:
The haunting call of the blue whale is the most intense of any animal alive. These rhythmic pulses and deep moans are so loud they travel across entire oceans, yet the frequency of these calls is often so low that they are totally inaudible to human ears.
In musical terminology, pitch refers to the “perceived fundamental frequency of a sound”. Scientists believe blue whale pitch, or frequency, is changing in response to mating habits. John Hildebrand, professor of oceanography in the Marine Physical Laboratory at Scripps Institution of Oceanography at UC San Diego, describes the changes:
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.
Published in the journal Endangered Species Research, marine biologists have looked for many causes for the blue whale song’s frequency, including climate change; however, they believe it is in response to the population’s numbers rebounding. By examining historical data, scientists have found whale pitch increases when the species is threatened. Science Daily reports:
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).
The fact blue whale song pitch is changing is good news for the species almost hunted to extinction. Males no longer feel pressured to send their mating call around the globe. Scientists expect to see similar song changes amongst other whales worldwide.