June 17th, 2015
Their flippers may forever prevent them from starting card-playing leagues, but bottlenose dolphins do form social clubs much like ours, a study from Georgetown University suggests. There is one major difference between dolphin and human social groups that should give us some pause; the dolphins appear to be nicer.
Janet Mann, professor of biology and psychology at Georgetown, and her team have tracked dolphins in Shark Bay, Western Australia, for 22 years. The researchers found that some dolphins used sponges to hunt fish, and that the sponge-wielding dolphins banded together more often, forming tight social groups, or ‘cliques’. The study, published in the journal Nature Communications, suggests that dolphins are capable of creating culture, the sophisticated relationships thought to be exclusive to humans. ‘Dolphins can identify and prefer others based on a socially learned trait,’ said Mann. ‘Humans use cultural traits to frame their social interactions and relationships. Our study suggests that dolphins might do the same.’
Shark Bay is an incredibly compact and controlled place to study dolphins. Think of it as the Galapagos Islands for dolphins. There’s little migration in and out of the area and the dolphins are not shy around humans. Some dolphins of Shark Bay learned to hunt sand perch using a marine sponge, held in their snouts. Scouring the ocean floor with the sponge prods the well-camouflaged sand perch into moving, so the fish can be captured more easily by the hunting dolphins. Altogether, Mann and her colleagues found 55 dolphins that used the sponge for hunting, out of 105 dolphins in the entire study group.
Using the sponge was a convenient way to study social behaviour, because hunting with sponges is a solitary behavior. ‘Affiliation between spongers would not be based on foraging, but on identifying other individuals as spongers,’ the scientists wrote. Indeed, the study found that most sponge-using dolphins not only hunted together, but formed social alliances and occupied the same areas. They did not associate as much with non-sponge-using dolphins and non-sponger dolphins did not form alliances quite as strong as the sponge-users. However, unlike some human social groups, the sponge-using ‘cliques’ did not reject non-sponging dolphins. Mann said, ‘Although humans think of (cliques) in a pejorative way, they are thinking of cliques which are excluding others outside said clique. We have no evidence this is the case with dolphins.’
One of the traits that scientists and philosophers alike assumed made us uniquely human was culture. While many in academic circles have not agreed on a common definition of ‘culture’, most agree that components of culture include adopting traits that are learned socially. The social interactions discovered among Shark Bay’s dolphins showed this cultural ability, forming associations based on hunting with sponges, for the first time. While other animals such as Killer Whales and parakeets, for example, can make calls that are specific to a social group, they have not shown the tool use and social interactions seen only in humans and now, in dolphins.
Source: Mann, J., Stanton, M., Patterson, E., Bienenstock, E., & Singh, L. (2012). Social networks reveal cultural behaviour in tool-using using dolphins Nature Communications, 3 DOI: 10.1038/ncomms1983
Photo: Wllly Volk