for National Geographic News
Humpback whales, known for their haunting songs and arduous migrations, are the ocean's great wanderers.
The whales undertake the world's longest mammalian migration, but their motivations are poorly understood.
Scientists have assumed that the animals are driven by a mix of reproductive needs and a desire for warm water, which saves energy and thus helps calves grow larger.
Now, data from whales wintering off the Pacific coast of Central America is backing up assumptions that the marine mammals go on the move mostly in search of warmer waters (see photos of humpback whales).
What's more, the study suggests that cold-water patterns are forcing southern humpback whales into the breeding grounds of their northern cousins for the first time, raising the possibility of genetic mingling.
"We have shown that, at the basin scale, humpback whales are choosing their wintering areas based on warm water temperatures," said Kristin Rasmussen, a study co-author and researcher at Cascadia Research Collective.
"While this had always been the assumption, it had never before been quantified globally."
Changing patterns of sea-surface temperatures could lead different whale populations to mix and mingle, potentially altering the whales' gene pool and even leading to changes in a given population's song patterns.
(Related news: "Humpback Whale Calls Are Love Songs, Biologist Suggests" [September 15, 2006].)
Humpback whales are divided into Northern and Southern Hemisphere populations.
Both groups of whales feed in one place and breed in another, sometimes crossing thousands of ocean miles in between.
SOURCES AND RELATED WEB SITES