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Monday, November 7, 2011
Dolphins team up to get the girl
by ABBIE THOMAS
An alliance of four male dolphins, dubbed The Beatles have shown that when blokes co-operate, they have more sexual success.
The research by a team at Macquarie University is published in the Journal of Animal Ecology.
The study found that male dolphins who form an alliance fathered far more babies than those who worked in smaller groups or alone.
The researchers studied a population of 70 male and 64 female Indo-Pacific bottlenose dolphins living in Port Stephens, New South Wales. They collected skin samples from males and calves and looked for genetic markers which would reveal the paternity of the calves.
They found that 14 different males had sired 32 calves. However, nearly half of the calves - 13 individuals - were sired by a single alliance of four dolphins known as The Beatles.
Three calves were sired by a three-male alliance and five calves were sired by another three-male alliance.
The remaining 11 calves sired by pairs or lone males.
Teaming up works
Males are known to form alliances in a number of species, including lions, chimpanzees, horses and, some would argue, humans.
"But there has not been any evidence to show why an alliance might be preferable," says co-author Dr Jo Wiszniewski.
"This research shows that male dolphins need to cooperate with each other to maximise their reproductive success."
Up to 80 per cent of males form alliances to seek out and reproduce with females during the spring/summer breeding season, says Wiszniewski.
"Males in alliances have better control of the females - we often see the males swimming around the females one on each side, sometimes one at the back. The female can't get away from them," she says.
"They basically herd the female - they try to keep her away from other males. They would swim by her and when she was feeding, they would feed too."
"These kind of herding events can last just from a few hours up to a few weeks at a time," says Wiszniewski.
Pressure to form alliances
Female dolphins only have a calf every two to five years, so in any particular year there are very few females available and ready to mate with.
"That's why there's so much pressure for males to form alliances, to become more competitive," she says.
Previous research from Western Australia also found that male dolphins who form alliances breed more successfully. But in this case, forming cooperative alliances was less surprising, Wiszniewski says, because those dolphins were related.
"If one of those males helps another reproduce, he still gets benefits because his genes still get passed on," she says.
But in Port Stephens, the cooperating dolphins weren't related.
"That's what's so fascinating. By helping another male, they are actually risking the chance that they won't reproduce with a female. So they really need a high level of cooperation and trust so then the male knows that by helping another male, he's also going to get helped."
Wiszniewski points out that one of The Beatles - John - doesn't seem to have fathered any calves.
"We have a feeling he was not a full part of the alliance. He was what we call the odd male out - he wasn't really 'in' with the group."