Dolphin gangs bully females into mating: Scientists
The bottlenose dolphin is sometimes thought of as a carefree creature, happiest when cavorting in the ocean.
When it comes to courtship, however, a study says that males are wedded to an unsentimental code – you scratch my flipper and I’ll scratch yours.
The dolphins in Shark Bay, Western Australia, have been studied for 40 years and zoologists say that they exhibit the most complex system of alliances between individuals and groups seen in any animal other than humans.
Each male dolphin forms a lifelong pact with one or two males; they will co-operate to boost their chances of procreating. When they find a female who is ready to mate they will surround her and usher her away from other dolphins. This ‘‘herding’’ seems intended to impress and intimidate.
There are acrobatic displays, in which the males leap and somersault around the female in unison. If she tries to make a break for it they are quite likely to bite and charge at her. The stakes are high: a female gives birth to one calf about every five years. A gang of males may have to fend off other suitors for a month before one of them has the chance to copulate.
Known as ‘‘first-order alliances’’, the male pairs and trios will work together to try to ‘‘steal’’ females from other males. But they do not necessarily operate alone: they can call for back-up.
Each pair or trio is nested in a broader system of allegiances where up to 14 males band together to form a tribe.
This larger group is known as a second-order alliance and two will sometimes team up to form a thirdorder alliance. At every level the main purpose is the same: to attack other alliances for access to females and to defend against such raids.
This complexity sets the dolphins apart. Male primates, including chimpanzees, are known to form gangs to attack rival camps. However, dolphins are the only creatures, other than humans, where one group has solicited a second to confront a third.