Blue whales are singing with deeper voices than they used to.
The largest animals on Earth are singing in ever-deeper voices every year.
Scientists first noticed the change eight years ago, when they kept needing to recalibrate the automated song detectors used to track blue whales off the California coast. The detectors are triggered by songs that match a particular waveform. Every year, they had to set them lower.
Since then, they have gathered thousands of blue whale recordings made since the 1960s, spanning populations from the North Atlantic to the South Pacific to the East Indian Ocean. Their analysis, published in Endangered Species Research, shows that the songs’ tonal frequency is falling every year by a few fractions of a hertz.
Noise pollution, ocean warming, or changing whale populations may be the reason, but none of the arguments are truly convincing.