Friday, 21 December 2018

Whale songs' changing pitch may be response to population, climate changes


Date:  November 28, 2018
Source:  American Geophysical Union
Blue whales around the world are singing a little flat, and scientists may now have more clues as to the reason why.
A new study finds there's a seasonal variation in the whales' pitch correlated with breaking sea ice in the southern Indian Ocean. The new research also extends the mysterious long-term falling pitch to related baleen whales and rules out noise pollution as the cause of the global long-term trend, according to the study's authors.
Blue and fin whales are among the loudest animals in the oceans as well as the largest. Only males sing, humming about as loud as large ships. The whales' loud songs can travel more than 1,000 kilometers (600 miles) underwater, allowing the whales to communicate across vast oceans.
Blue whales have been dropping pitch incrementally over several decades, but the cause has remained a mystery. Now, the new study in AGU's Journal of Geophysical Research: Oceans finds the same mysterious long-term trend of falling pitch in fin whales and Madagascan pygmy blue whales. Pitch, or the perception of how high or low a note sounds, is a result of the frequency of the sound wave, usually measured in hertz.
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