DOLPHINS can use hundreds of different sounds to “talk” to each other, experts have found.
Rare footage obtained by biologists reveals how “genius” dolphins have more than 230 noises for communication – and there may still be more that remain a secret.
Paulo Castro An Araguaian river dolphin swimming in the Araguaia River near a fish market in the Brazilian town of Mocajuba
Brazil’s elusive Araguiana river dolphin has always been considered a “solitary” species.
But biologists have managed to obtain around 20 hours of recordings of the creatures, which are also known as botos.
It turns out that they communicate regularly, and have a wide range of sounds that they can use.
“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.
Getty – Contributor Botos have a very distinctive grey-to-pink body
Getty – Contributor Biologists think the botos make more than 237 different sounds for communication
She added: “Their vocal repertoire is very diverse.”
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.
The clear water in the area allowed biologists to film the dolphins, and record the noises they make.
Scientists identified as many as 237 different types of sounds – and say there may be others that weren’t captured by the recordings.
The most common sounds were short two-part calls, which were made by baby dolphins approaching their mothers.
Laura called the findings “exciting”, and said:”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.”
Araguaian river dolphins – the key factsHere’s what you need to know…
The Araguaian river dolphin is a river dolphin native to Brazil
They’re also known botos, and are difficult to find – and therefore hard to study
Most of the dolphins are grey to pink in colour, and grow as long as 8.5 feet
These dolphins don’t have fins, and instead have a dorsal “ridge”
Botos were first distinguised as a separate species in January 2014, although some scientists disagree over how distinct they are from Amazon river dolphins generally
Experts believe there are as few as 600 (up to 1,500) botos in the wild
Biologists have warned that their habitat is under threat from agriculture, ranching and industrial activities
Dams used for creating hydroelectric power also negatively effect the ecology of their home
The river dolphins also made longer calls and whistles, but these were rarer.
Biologists were unable to identify what some of the sounds were being used for too, but one theory is that whistles are used to “maintain distance” from other botos.
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.
This, Laura believes, may be down to the local environment.
“There are a lot of obstacles like flooded forests and vegetation in their habitat,” Laura explained.
“So this signal could have evolved to avoid echoes from vegetation, and improve the communication range of mothers and their calves.”
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