Scientists studying bottlenose dolphins that use sponges as tools to protect their sensitive beaks has shown that social behavior can shape the genetic makeup of an animal population in the wild.
The study has been carried out on dolphins in Shark Bay in Western Australia. With many of these bottlenose dolphins, the mammals put conical marine sponges on their rostrums (beaks) when they forage on the sea floor. This is a non-genetic skill that calves apparently learn from their mother.
However, a team of researchers have found that sponging dolphins end up with some genetic similarities because the calves also inherit DNA from their mothers. It is also likely that sponging dolphins are descendants of a female dolphin that first developed the innovation.
Bottlenose dolphins live in groups typically of 10–30 members, called pods, but group size varies from single individuals up to more than 1,000. Their diets consist mainly of forage fish. Dolphins often work as a team to harvest fish schools, but they also hunt individually. Bottlenose dolphins also use sound for communication, including squeaks and whistles emitted from the blowhole and sounds emitted through body language, such as leaping from the water and slapping their tails on the water surface.
This is based on genetic samples taken and analysed for mitochondrial DNA type from the dolphins. The study was for samples that are only inherited from the mother. It was found that the dolphins that lived in shallow waters, where sponges do not grow, mainly fell into a genetic group called Haplotype H; whereas, the dolphins living in deep waters, where sponges do grow, were predominantly Haplotype E or Haplotype F.
With humans scientists have known for a long time that culture is an important factor in shaping our genetics. It now seems that the same is true with dolphins.
The findings have been described in the journal Proceedings of the Royal Society B. The paper is titled “Cultural transmission of tool use combined with habitat specializations leads to fine-scale genetic structure in bottlenose dolphins.”