Romeo dolphins find weeds and a stick do the trick

Men might say it with flowers, but amorous male dolphins prefer to woo a mate with a nice bunch of weeds.

A three-year study of Amazon river dolphins in Brazil has found that males often carry objects such as clumps of weed or sticks in their mouths as they swim, and that the behaviour is almost certainly a kind of sexual display.



While the behaviour had been reported before, it had been assumed to be playful and to have no function.

However, research on 6,026 groups of dolphins has shown that the carriers are usually adult males and that they behave in this way more often when adult females are around.



Of the groups, 221 included at least one individual that was carrying weed, a stick or a lump of clay. The evidence points to these items being used as part of a sexual display to impress females and persuade them to mate.

The research, led by Tony Martin, of the British Antarctic Survey in Cambridge, and Vera da Silva, of the National Institute of Amazonian Research in Amazonas, Brazil, will be presented this week at the Society for Marine Mammology conference in Cape Town, South Africa.