The world’s largest animal goes from nighttime to daytime crooning before heading south
During the summer feeding season in high latitudes, male blue whales tend to sing at night. But shortly before migrating south to their breeding grounds, the whales switch up the timing and sing during the day, new research suggests.This is not the first time that scientists have observed whales singing at a particular time of day. But the finding appears to be the first instance of changes in these daily singing patterns throughout the yearly feeding and mating cycle, says William Oestreich, a biological oceanographer at Stanford University.
In the North Pacific, blue whales (Balaenoptera musculus) spend summers off North America’s coast gorging on krill before traveling to the tropics to breed in winter. Data collected by an underwater microphone dropped into Monterey Bay in California to record the region’s soundscape for five years allowed Oestreich and his colleagues to eavesdrop on whales that visited the bay. When the team separated daytime and nighttime whale songs, it stumbled upon a surprising pattern: In the summer and early fall, most songs occurred at night, but as winter breeding season approached, singing switched mostly to the daytime.
“This was a very striking signal to observe in such an enormous dataset,” says Oestreich. The instrument has been collecting audio since July 2015, relaying nearly 2 terabytes of data back to shore every month.
