TUESDAY, Nov. 2 (HealthDay News) -- Female dolphins are much more successful as mothers if they get help from their female friends or relatives, says a new study.

Researchers analyzed 25 years of field observations of dolphins at Shark Bay in Western Australia and more than a decade of genetic samples taken from the dolphins.

"Surprisingly, the genetic and social effects on reproduction have never been studied together in natural populations," Bill Sherwin, of the School of Biological, Earth and Environmental Sciences at the University of New South Wales in Australia, said in a university news release.

Sherwin said his doctoral student Celine Frere, who led the latest study, "realized that we could do so by using the long-term observations about which females were associated with each other, and putting that together with what we knew about their genetic relationships."

Frere found that a female's success as a mother is increased either by social association with other females who are highly successful mothers, or by having female relatives who are successful mothers.

"Not only that, but the social and genetic effects interact in an intriguing way. Having successful sisters, aunts and mothers around certainly boosts a female's calving success [successful births]. But the benefits of social associates were more important for female pairs who were less genetically related," Sherwin said.

It's not clear why female dolphins need this type of help to be successful mothers, said Frere, who is now at the University of Queensland.

"Dolphins in this population are attacked by sharks, so protection by other females may help reproduction. But the females may need protection against their own species as well, especially when they are younger," she said in the news release.

The study was published Nov. 1 in the journal Proceedings of the National Academy of Sciences.

More information

BlueVoice.org has more about dolphins.