Blue whales, the largest animals on earth, are singing with deeper voices every year, but scientists are unsure of the reason.

Whale Acoustics is a company that specializes in recording the songs of blue whales off the coast of California. According to their President, Mark McDonald, they have many recordings of blue whales, but each year they have had to recalibrate their song detectors to lower frequencies. Possible reasons include noise pollution at sea, new mating strategies, and changing population dynamics, but none of these theories is convincing.

McDonald, along with John Hildebrand and Sarah Melnick of the Scripps Institution of Oceanography, have collected and analyzed thousands of recordings of blue whales from the 1960s onwards, from populations around the globe, and have found the tonal frequency of the songs has reduced by fractions of a Hertz every year. Read the rest of this entry »