London, June 14: A study on migrating humpbacks whales off the east coast of Australia has uncovered strong evidence that males among the species sing to woo females, and not to deter other males.
Joshua Smith and his colleagues at the University of Queensland even think that lone males may use the love songs as an easy way of finding a female. The researchers point out that there have been two theories to explain the role of the humpback song, which is only performed by males. While one is the theory of competition between males, the other points towards serenading of females. Some studies in the wild supported both hypotheses, and suggested that the songs could be serving dual-purpose. Smith says that he and his colleagues wanted to gain a better understanding of the matter, and thus they set up listening and observing stations at Peregian Beach on the east coast of Australia in September and October of 2002, 2003 and 2004.
Using an array of five hydrophones attached to buoys 1.5 kilometres offshore, he says, the research group located and recorded singing whales. He has revealed that the group monitored the whales, migrating northwards from their breeding grounds to feeding sites closer to the equator, by boat and from a hill on the shore. Smith says that he and his colleagues saw 114 singers in all, and 66 of them interacted with other whales. A third of such whales joined a mother and her calf as they swam up the coast, he adds.
"We found singers preferentially joined females with a calf that had no other males accompanying them, escorted these groups for a considerably longer time and spent the greatest proportion of time singing when escorting them compared to all other groups," New Scientist magazine quoted him as saying. Smith admits that it is yet unclear why males escort females that already have a calf, but believes that they might be trying to make a good impression on the female.
He referred to a 2003 study wherein Salvatore Cerchio of the University of Michigan had found that, in one case, the male escort sired the female's next calf. The researcher had also noted that several males that had sired more than one offspring were commonly seen escorting mothers with calves.
Smith said that, if seen in the light of Cerchio's observations, the singing escorts he and his colleagues would appear to be wooing the mothers they escorted. He said what supported the theory was the fact that singing escorts would stop singing when they were approached by another lone male. Had the singing been a way of deterring competition, the singer would have continued to sing, he added.
"We think the song may inadvertently act as a clue to other males of the presence of a female and that lone males that join singers may be prospecting for females," said Smith. A research article on the study has been published in the journal Animal Behaviour.