Blue whales’ songs are hauntingly deep, filled with extraterrestrial vibratos, and utterly mysterious. Despite many attempts to interpret them, scientists still don’t know what the world’s largest animals are saying.
Now, the mystery only thickens. For decades, blue whales have been singing with increasingly deeper voices, reports a new study. In some cases, the pitch of their songs has dropped by more than 30 percent. Frustrated researchers cannot yet explain why.
“It’s a worldwide phenomenon,” said Mark McDonald, an ocean acoustician and independent researcher in Bellvue, Colo. “All blue whales are shifting their frequencies downward. They are all going in the same direction, and we really don’t understand it.”
“Maybe by putting this data out there,” he added, “someone will have a eureka moment and see something that really explains this.”
McDonald first suspected something was going on about eight years ago, when he started setting up underwater detectors to study blue whales across the Pacific Ocean.
To get the devices to work, he and colleagues noticed that they had to shift the detector frequencies downward every year. At the time, they didn’t know if something was amiss with the detectors or with the whales.
For the new study, McDonald and colleagues collected acoustical data on blue whales from as far back the 1950s. Some recordings came from underwater microphones put in place by whale researchers or the military. More recently, researchers have developed new technologies to monitor whale sounds over large distances and time-spans.