ARI SHAPIRO, HOST:
The world's largest animal, it turns out, has good table manners. Ana Sirovic of Texas A&M University has been studying blue whales for 20 years.
ANA SIROVIC: We have found that they tend to be quite polite and not sing while they're eating.
(SOUNDBITE OF BLUE WHALE SONG)
SHAPIRO: This is the song of a blue whale sped up five times to make it easier for humans to hear.
TONYA MOSLEY, HOST:
And some news out today tells us when blue whales off the coast of California switch from eating to singing. Normally, the giant creatures fill their huge mouths with tiny krill during the day and sing at night. Now, after analyzing five years of underwater recordings, scientists have observed a flip-flop.
WILLIAM OESTREICH: When these animals started migrating south along the California coast, the time of day that they were producing their song switched to the daytime.
SHAPIRO: That's William Oestreich of Stanford's Hopkins Marine Station in Pacific Grove, Calif. He's lead author of a paper out today in the journal Current Biology.
MOSLEY: Blue whales can swim a thousand miles or more. They eat krill in the north, then head to breeding grounds off the coast of Mexico and Central America.
OESTREICH: The timing of that switch from intensive feeding to southward migration is actually a really critical decision in the survival of these animals. So they're relying on all of the food and energy that they obtained during this short feeding season to fuel their migration, their reproduction, their rearing of young.
MOSLEY: Learning about this night to day song-switching could help scientists understand how and when whales decide to leave their feeding grounds, which Oestreich says is key to understanding their survival amid climate change.
OESTREICH: It gives us the opportunity to learn a little bit about how flexible or adaptable these animals really are because they're inhabiting an ecosystem that's changing rapidly.
(SOUNDBITE OF BLUE WHALE SONG)
SIROVIC: It's actually been challenging sometimes to see those patterns because they're often quite subtle.
SHAPIRO: Ana Sirovic was not part of the research team, but she says there are lots of good reasons scientists want to understand blue whales.
SIROVIC: In addition to being the largest animal that has ever lived, they're also, as we're learning, an important link in the carbon cycle on the planet because they eat a lot of food. And they help sequester carbon in a way and take it out of the environment. So even if you care just about climate change, they are one component of that piece.
MOSLEY: By the way, she says there's another mystery attached to the whale song. Whales all over the world have their own tones. And no matter where they sing, in each year over the past decade, the pitch of whale song has dropped, and no one can fathom why.
(SOUNDBITE OF BLUE WHALE SONG) Transcript provided by NPR, Copyright NPR.