VICTORIA — Blue whales are changing their tune, but scientists have no idea why the largest animals in the world are singing in deeper voices.

A study, published in the journal Endangered Species Research, has found male blue whales all over the world have lowered their tone, even though different populations sing different songs.

Blue whales in the northeast Pacific population, including increasing numbers found in the waters off B.C., have lowered their voices by 31 per cent between 1963 and 2008, said Mark McDonald of WhaleAcoustics, which conducted the study with researchers Sarah Melnick and John Hildebrand of the Scripps Institution of Oceanography in California.

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