December 20, 2012
Study Says Whale Songs Are For Hunting Too, Not Just Mating
Brett Smith for redOrbit.com - Your Universe Online
Humpback whales have always been known to sing to their potential mates, but new research shows that the marine mammals don´t need to be “in the mood” to belt out their favorite tunes.
According to a report in the open-access journal PLOS ONE, the whales also sing while on the hunt for food, making certain whale songs are the most ominous sounds krill will ever hear.
In addition to finding different songs-related behaviors, the researchers found whales breeding outside of their traditional warm-water locations.
"They need to feed. They need to breed. So essentially, they multi-task," said study co-author Ari S. Friedlaender, an environmental scientist at Duke University. "This suggests the widely held behavioral dichotomy of breeding-versus-feeding for this species is too simplistic."
The distinction between the whale´s monolithic seasonal behaviors — including breeding, migration and foraging — that occur in different regions of the world first alerted the scientists to the possibility that humpback songs don´t correlate solely to breeding activities.
"We were surprised to find such structured song in the Antarctic feeding ground,” said co-author Alison Stimpert of the Naval Postgraduate School. “The tag data are also exciting because this is the first time that we can see that the singers aren't sitting off by themselves like they do on the breeding grounds — they're right in the midst of the feeding action, choosing to sing instead."
The research team tracked 10 humpback whales across the coastal waters near the Western Antarctic Peninsula in the spring of 2010. The whales prefer the peninsula's bays and fjords as late-season feeding grounds before they migrate to warmer calving grounds thousands of miles away.
Using non-invasive computer tags, the researchers recorded the whales´ movements and vocalizations as they foraged for food. All of the tags detected the sounds of background songs, and two of the tags recorded intense and continuous whale singing that resembled a typical mating display. Breeding ground songs were found to be quite different in style and duration from those heard during other seasons and at different locations.
Many of these solo aquatic concertos lasted almost an hour and one of the sensors showed that the whale, or a close companion, was diving and lunging for food while it sang.
"The 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 co-author Douglas Nowacek, Associate Professor of Conservation Technology at Duke.
The researchers noted that climate change forces have affected the ecosystem around the Western Antarctic Peninsula in recent years. The result has been that water stays open and ice-free later in the foraging season. They speculate that the whales have been remaining there longer instead of heading off to their warmer breeding grounds.
"Mating may now be taking place at higher latitudes," Nowacek said. "This merits further study."