Dolphins 'impress with weeds'
Thursday, 06 Dec 2007 10:37
Dolphins carry weeds to impress the opposite sex, research suggests
Male dolphins use objects they find in rivers to impress the opposite sex, new research suggests.
Scientists watching river dolphins in the Brazilian Amazon found that the males carried objects including weeds.
Tony Martin of the British Antarctic Survey in Cambridge and Vera da Silva of the National Institute of Amazonian Research in Amazonas, Brazil, believe the practice is a sexual display.
They observed 6,026 dolphins over three years in a flooded rainforest reserve.
Although the groups included females only the males were seen carrying weeds and aggression was higher in the object-carrying groups.
These factors point to the practice being a form of sexual display and not play, Dr Martin told the New Scientist.
"It's so unusual that many of my colleagues were sceptical when I first suggested the idea, but now I think the evidence is overwhelming," he said.
The theory has been backed up by genetic research which revealed that some of the most frequent object-carriers are among the most successful fathers.
Dr Martin said the fact that object-carrying has been reported in isolated populations is remarkable as it means the behaviour is either ancestral or has evolved independently.
Other research has suggested bottlenose dolphins in Shark Bay, Western Australia, have learnt to break off a piece of marine sponge to carry over their snouts to protect them.
"I'm now convinced this behaviour is social learning – and from that point of view, you can call it a culture," said one of the researchers in this project, Michael Krutzen of the University of Zurich.