Dolphin mums need help from their friends

Dolphin mums are better at raising offspring when they have a little help from their experienced friends.

RAISING HEALTHY CHILDREN CAN depend a lot on having good parenting role models, and it turns out that dolphins aren't much different from humans when it comes to needing moral support.

A study of bottlenose dolphins at Shark Bay, in Western Australia, has revealed that dolphins who hang around with experienced, good mothers, are more likely to be successful mums themselves.

Female bottlenoses usually start to reproduce at about the age of 10, and they invest a great deal in raising their young. "They put a lot of effort into it," says study lead author, Celine Frere, who was at the University of New South Wales at the time of the study, "and it generally takes between three and five years to wean a calf."

The dolphins are also very social. "They live very much like us," Celine says. "Their social relationships are really dynamic but they'll have friends with whom they spend more time than others." And it is this social behaviour that seems to help females raise healthy young.

Good mothering rubs off

Work on other animals, like chimps, has found that females whose mothers, aunts and grandmothers are good at raising offspring tend be good parents themselves. And, by studying data collected on 62 dolphins living in Shark Bay over 25 years, Celine's team found the same thing: there seems to be genes for successful mothering.

But, in a first for studies of wild animals, they also found social effects. Females who chose to hang around with good mothers were more likely to get their calves to the age of weaning. The team also found a that a new mother's success at raising a healthy calf depended more on her female friends than her relatives.

"The interaction between the genetic and social factors is the really exciting finding," says David Lusseau, an expert on animal social interactions at the University of Aberdeen, UK, who was not involved with the study. "Could it be that females coming from families with a poor track record at calving start to look elsewhere for support? It's fascinating."

Head-butting sharks

No one knows for sure how dolphin mothers might help others. But they probably share their experience at raising calves, says Celine - and that might include getting physical with would-be predators where necessary.

"We know dolphins can fight off sharks by head-butting them. It's speculation, but this might be what the other females are doing - getting in a fight if they need to, to protect the calf, and perhaps also keeping new mothers away from habitats where they know sharks live."

The work has been published in the Proceedings of the National Academy of Sciences.

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