SCIENCE DAILY : BLUE WHALES SWITCH NIGHT SINGING TO DAY
Excerpt: By focusing on the whale song wavelengths in the hydrophone data, the researchers noticed a distinct change over several months. Through the summers, the whale arias grew louder and were sung mostly at nighttime. Over the five years of data, the whale chorus was loudest around October and November, and singing happened more at nighttime. Following each annual peak in song activity, as the whales began to depart for warmer waters, singing because more of a daytime activity.
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This is a very exciting discovery about our world's largest living creatures.