Dolphins that cooperate with artisanal fishermen in Laguna, Brazil sound different than their independent counterparts, new study finds.
But while the humans are united, the dolphin community is divided. Only some of the population cooperate with fishers in this manner.
Scientists discovered that the ones that work with people form their own cohesive social network, separate from the other dolphins in the area. “The cooperative fishery appears to have influenced the structuring of this bottlenose dolphin population into social communities,” explain Bianca Romeu and her colleagues at Brazil’s Universidade Federal de Santa Catarina in a new paper this month in the journal Ethology. Their latest work reveals the depth of this rift: the cooperative dolphins don’t just behave differently, they communicate differently, too.
Other cetacean communities with explicit social structures have shown similar communicational differences. Specific sounds help killer and sperm whales navigate the complex social relationships of their matrilineal societies, for example. But it’s unclear why the dolphins that hunt with the artisanal fishers have this distinct dolphin accent. “Our attempts to infer causes of the acoustic distinction and function of these social sounds remain speculative at the moment,” the authors say.
Given the overall importance of language to intelligent, social animals, one can’t help but wonder if this slight divergence is the beginning of something much bigger. Killer whale species, which hunt different prey, are distinguished in part by acoustic differences.
Perhaps with evolutionary hindsight— of thousands of years from now—our descendants will point to shift in dialect as the first essential step that led the cooperative dolphins down a divergent evolutionary path.