Blue Whales Singing at Ever-Lower Frequency
McDonald and his associates first discovered the change in the whales’ song eight years ago. In order to capture the changing sound of the whales over the years, scientists had to keep recalibrating the detectors to recognize the lower frequency. McDonald, along with Sarah Melnick and John Hildebrand of Scripps Institution of Oceanography, has gathered blue whale recordings made since the 1960s, from whale populations all over the world. Their work “shows that the songs’ tonal frequency is falling every year by a few fractions of a hertz,” Keim writes.
“It’s a fascinating finding,” John Calombokidis, a blue whale expert at the Cascadia Research Collective, told Wired. “It’s even more remarkable, given that the songs themselves differ in different oceans. There seem to be these distinct populations, yet they’re all showing this common shift.”
A change in population may be another explanation. Blue whales were hunted to near extinction at the first half of the 1900s, and they’ve been recorded only since hunting stopped. “Maybe songs were higher-pitched when recording started, because the whales had to sing extra-loud in order to reach their scattered brethren,” Keim writes. “Now that there are more, they can lower their voices and their pitch.”
But even in areas where the whale population hasn’t grown significantly, the songs are still getting deeper. “The population of blue whales off the U.S. west coast hasn’t shown a dramatic upwards trend in numbers, but its pitch is declining,” Calombokidis told Wired.
“What is staggering is that all the males have switched to the new song which was brought over by a few ambassadors from the west coast,” Michael Noad, a marine scientist, told Reuters.
Humpback whale songs are quite varied and complex. The patterns are distinct to where the whale lives, and the songs are usually between seven and 15 minutes long, “and contain several themes like verses in human songs,” ABC News reports. Male humpback whales sing their songs to attract females during the mating season.
“The theory is the novelty of the new song is what made it popular,” Noad said. “Female whales hear the same song over and over again and get bored and disinterested in the males, so the males alter their songs slightly to stand out in the crowd.”
Like their country cousins, white-crowned sparrows in the city have also had to make changes to their song in order to be heard. In 2009, ABC Science reported that researchers David Luther and Luis Baptista looked at white-crown sparrows in the San Francisco area from the late 1960s to 1998. They found that as urban noise increased, so did the frequency of the birds’ song. “In response to high levels of low-frequency ambient noise, urban birds have songs with higher frequencies,” the researchers wrote.