The deep, vibrating chants of fin whales are love ballads sung by males to woo whale señoritas, a new study finds. The researchers think that these sleek and speedy whales beckon females from hundreds of kilometers away to lure them to food-rich breeding grounds.
Unlike other whale species such as humpbacks or gray whales, fin whales carry on a loner's life. Marine biologists always wondered how these mammals found mates. Using underwater microphones, they recorded fin whale sounds from afar, but the whales themselves were never seen. Although researchers suspected that the animals used their calls to stay in touch over long distances, the exact purpose of the sounds remained mysterious.
To track the whales behind the song, marine biologist Donald Croll of the University of California, Santa Cruz, and his colleagues rigged their research vessel with a 120-meter-long wire that they towed through waters in the Gulf of California, off the Mexican coast. Afixed to the wire were 16 underwater microphones. When they recorded a fin whale singing, the researchers approached and waited for the animal to surface; when it did, they snagged a patch of its skin with a small arrow and later used genetic analysis to determine the animal's sex. The group also collected skin from silent whales they saw. To their surprise, Croll's team found that not a single vocalist was female, although both males and females were present in the surveyed area. The researchers theorize that the males use their vocals to tell females where to find breeding grounds rich in krill, the shrimplike crustaceans serving as their main food source.
The theory makes good sense to whale biologist Phil Clapham from the Northeast Fisheries Science Center in Woods Hole, Massachusetts. He also believes that it underscores calls from marine biologists to explore how sonar produced by military and commercial ships could garble low-frequency signals sent by sea mammals.