London, October 30 : A team of Canadian and British researchers has found that sperm whales sing duets to cement the bonds between individuals within a social group.
Researchers from Dalhousie University in Halifax, Nova Scotia, Canada, and the University of St Andrews in the UK followed a group of nine sperm whales in the Pacific Ocean near the Galapagos Islands, and seven in the Caribbean.
The team used a series of underwater hydrophones to record the whales' characteristic clicking sounds.
They said that on 15 of the 19 occasions, when the position of each whale could be identified, the animals were close enough to see one another, suggesting that the song was not being used to locate another whale.
The researchers further observed that the whales appeared to be synchronising their calls, and that more often than not, each animal would respond to another whale's song within 2 seconds.
The researchers said that the whales also tended to copy the phrases that their partners were using, with the same timing of pauses between their clicks, resulting in duets in which the clicks of the two singers were in unison.
"There's a real rhythm to the sounds they are producing. They tend to copy the last coda used by the duet partner, until both converge on one choice that dominates their repertoire," New Scientist magazine quoted Luke Rendell from the University of St Andrews, a member of the research team, as saying.
Rendell believes that sperm whales use duets to cement the bonds between individuals in the same way as gelada monkeys and some tropical wrens do.
An article describing the study has been published in the journal Animal Behaviour.