Dolphins can use hundreds of different sounds to “talk” to each other. A rare footage obtained by biologists reveals how dolphins have more than 230 noises for communication. This is an important clue in our understanding of how and why dolphins evolved the capacity for communication. The river dolphin species commonly referred to as "botos" were first discovered in 2014. Scientists have been eager to learn more about the mysterious creatures. Botos are notoriously difficult to track down, but researchers found a fish market in a Brazilian town called Mocajuba where the dolphins visit regularly to be fed by locals.
Only 600 to 1,500 are estimated to be in existence in the South American country's Araguaia-Tocantins River system, per a 2014 study published in PLOS One Journal.
The research suggests that the botos’ sounds fall between low-frequency calls by baleen whales for long-distance communication and high-frequency calls from marine dolphins for short distances.
“We found that they do interact socially and are making more sounds than previously thought,” said Laura May Collado, a biologist at the University of Vermont, who worked on the study published in PeerJ.
"It's exciting. Marine dolphins like the bottlenose use signature whistles for contact, and here we have a different sound used by river dolphins for the same purpose. There are a lot of obstacles, like flooded forests and vegetation, in their habitat, so this signal could have evolved to avoid echoes from vegetation and improve the communication range of mothers and their calves," Collado said.
Collado asserted the work could help researchers gain a clearer understanding of how communication evolved in marine mammals. Similar calls have been reported in pilot whales and killer whales, for example, and the similarities and differences between different species could help tease out which signals evolved first, and why.