for National Geographic News
Humpback whales regularly break into "song" much later in the year than expected, according to a new study. The finding contradicts the idea that the songs are only associated with breeding—and that the species' mating and feeding activities take place in completely separate time periods.
Humpback males were thought to sing mostly during the winter breeding season (October to March, in the Northern Hemisphere), when the up to 40-ton beasts migrate to tropical waters near Hawaii, the West Indies, and elsewhere.
The animals' haunting moans and long complex songs—emitted only by males—are apparently used to woo females and to competitively display to rival males.
But now inadvertent recordings—taken off the coast of Cape Cod, Massachusetts, during May and June—reveal that humpback males also serenade potential lovers throughout spring, as they migrate to polar and other high-latitude feeding grounds.
As a result, humpback calves may sometimes be conceived and born outside of tropical waters, write researchers behind the chance discovery.
"Wall-to-Wall" Chorus
"It was a real surprise to find animals singing wall-to-wall, 24 hours a day through several weeks of spring monitoring," said Phil Clapham, a whale biologist behind the discovery. Clapham works at the Northeast Fisheries Science Center in Woods Hole, Massachusetts.
"Although it's clear that most mating takes place in winter in the tropics, the activity apparently doesn't end there," he said.
Humpback whale (Megaptera novangliae) song has rarely been recorded in high-latitude feeding areas. When it has, most recordings were made during early spring or late autumn.
In contrast, whale singing can be recorded endlessly throughout the species's entire winter breeding season in tropical waters. "Once in a while people had recorded song on feeding grounds," Clapham said. "But most experts thought it was very sporadic."
Clapham and Cornell University whale biologist Chris Clark, based in Ithaca, New York, made the discovery while collecting data for a study on the occurrence of critically endangered North Atlantic right whales (Eubalaena glacialis). Clapham and Clark's results will be published in an upcoming print edition of the science journal Proceedings: Biological Sciences.
Clark deployed self-surfacing recording devices three kilometers (five miles) apart from one another, 150 to 200 meters (500 to 650 feet) deep on the seafloor. (An acoustic signal from a nearby boat would trigger the 1-meter-diameter/3.2-foot-diameter glass orbs to automatically detach from the seafloor and float to the surface for retrieval.)
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