From New Scientist via ArtJournal:
Sperm whales may take as much pleasure in singing well-timed duets as humans do.
New underwater recordings have shown that the whales carefully coordinate their song to match the calls of their singing partner. The animals appear to enjoy singing to each other, possibly to strengthen relationships among females within the group.
Till now biologists had assumed that the sounds with which whales communicate are mainly intended to scout out other members of their group. But humpback males are thought to woo females with solo love songs, and male killer whales whistle to each other, perhaps to help social bonding.
To investigate whether sperm whale song is also social, a team 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. They recorded the whales' characteristic clicking sounds using a series of underwater hydrophones.
Listen to the whales' songs here and here
The team found that on 15 of the 19 occasions when they could identify the position of each whale, the animals were close enough to see one another. This suggests that the song was not simply being used to locate another whale.
More detailed analysis of the recordings showed that the whales seemed to be synchronising their calls. More often than not, each animal would respond to another whale’s song within 2 seconds, for example. They also tended to copy the phrases that their partners were using – with the same timing of pauses between their clicks. The result was a duet in which the clicks of the two singers were in unison.
"There's a real rhythm to the sounds they are producing," says Luke Rendell from the University of St Andrews, who worked on the project. "They tend to copy the last coda used by the duet partner, until both converge on one choice that dominates their repertoire."
Rendell compares this to the behaviour of gelada monkeys and some tropical wrens, which sing tightly coordinated duets in a similar way. With the monkeys the duets appear to help cement the bonds between individuals within a social group.
Rendell believes it would make sense if sperm whale duets served the same purpose. The whales are also highly social creatures that stay in tight-knit groups for 10 or more years, and mothers typically rely on other adults to look after their young.
Whales are also known to possess the brain cells that allow us to process emotions, suggesting that they too may experience emotions such as love.