Bottlenose dolphins who use sponges as tools have shown that social behaviour can shape the genetic makeup of an animal population in the wild.
Some of the dolphins in Shark Bay in Western Australia put conical marine sponges on their beaks when they forage on the sea floor, a non-genetic skill calves apparently learn from their mothers.
Researcher Dr Anna Kopps says sponging dolphins end up with some genetic similarities because the calves also inherit DNA from their mothers.
As well, it is likely that sponging dolphins are descendants of a “sponging Eve”, a female dolphin who first developed the innovation.
“Our research shows that social learning should be considered as a possible factor that shapes the genetic structure of a wild animal population,” says Dr Kopps.
“It is one of the first studies to show this effect – which is called cultural hitchhiking – in animals other than people.”
The study is published today in the journal Proceedings of the Royal Society.
Dr Kopps and her colleagues identified individual dolphins in western Shark Bay about 850 kilometres north of Perth. They observed them from a boat as they foraged for food, travelled around the bay, rested, and played with other dolphins.
Genetic samples were also taken. The dolphins living in shallow waters, where sponges do not grow, mainly fell into a genetic group called Haplotype H.
Those dolphins living in deep waters, where sponges do grow, were predominantly Haplotype E or Haplotype F.
“This striking geographic distribution of a genetic sequence cannot be explained by chance,” says Dr Kopps, who carried out the research while at University of New South Wales and is now at the University of Groningen in the Netherlands.
As well, the DNA results from 22 dolphins that both lived in deep water and used sponges as tools showed they were all Haplotype E.
“For humans we have known for a long time that culture is an important factor in shaping our genetics,” she says.
“Now we have shown for the first time that a socially transmitted behaviour like tool use can also lead to different genetic characteristics within a single animal population, depending on which habitat they live in.”
The team includes UNSW’s Professor Bill Sherwin and researchers from the University of Zurich and Murdoch University.