Whale hunts in the name of "scientific research" will resume in 2015, Japan's Prime Minister Shinzo Abe announced Monday at a press conference - a declaration that is in direct opposition to a ruling from the UN's International Court of Justice (ICJ) earlier this year. (Photo : Reuters)

A new study suggests that humpback whales are increasingly singing songs outside their traditional breeding grounds.

Humpback whales sing songs, comprising of complex sounds, during breeding season. But a team of researchers involved in a new study has found that the whale species also indulges in singing while feeding on prey.

Humpback whales need to multitask and maintain a balance between the need to feed continuously and exhibiting mating behaviors like song displays. "They need to feed. They need to breed. So essentially, they multi-task," study co-author Ari S. Friedlaender, research scientist at Duke University, said in a statement. "This suggests the widely held behavioral dichotomy of breeding-versus-feeding for this species is too simplistic."

For their study, the research team attached multi sensor tags to 10 humpback whales with suction cups, so as to record their underwater movements and vocalizations as they continued their foraging activities.

They noticed that all ten tags recorded sounds of background songs, and in two cases, they heard whales singing continuously with a level of organization and structure approaching a typical breeding-ground mating display. The songs lasted for at least an hour in some cases and in one particular case, the sensor indicated the whale singing in foraging grounds and at times when it was diving into deep waters.

Humpback whales are also known to sing during migration. It is not clearly understood as to why the whales sing other than during their breeding season. But researchers noticed that whale songs sung in breeding grounds are different in duration, phrase type and theme structure from those songs heard at other locations.

"That fact that we heard mating displays being sung in late-season foraging grounds off the coast of Antarctica suggests humpback whale behavior may be more closely tied to the time of year than to physical locations. This may signify an ability to engage in breeding activities outside their traditional warm-water breeding grounds," said Douglas P. Nowacek, Repass-Rogers University Associate Professor of Conservation Technology at Duke's Nicholas School.

Earlier studies have shown that global warming has delayed the migratory process of humpback whales. Western Antarctic Peninsula is one of the best feeding grounds for humpback whales, where they feed on small crustaceans like krill. These whales move from Antarctica to warmer breeding grounds during late autumn, as the winter draws in and covers with sea ice.

But increase in global temperatures has delayed the arrival of winter sea ice cover. Hence, humpback whales are staying there for longer periods into austral autumn to feed on krill instead of moving to traditional breeding grounds. "Mating may now be taking place at higher latitudes," Nowacek said. "This merits further study."

The findings of the study, "Humpback Whale Song and Foraging Behavior on an Antarctic Feeding Ground," are published in the journal PLoS ONE.