Scientists initially thought that the newly identified Araguaian river dolphins of Brazil are solitary creatures. However, new evidence suggests that the opposite is true.

Researchers discovered that the aquatic animals, which are also known as botos, can make hundreds of different sounds to communicate with each other.

Talkative Botos

To study the botos, the researchers used underwater cameras and microphones to record the interactions between the marine mammals in a fish market in Brazil. While the creatures are often hard to approach, they are known to visit fish markets because they expect to be fed by the people who go shopping there.

In total. the researchers identified 237 different sounds coming from the river dolphins that converge in the area.

"We found that they do interact socially, and are making more sounds than previously thought," said May Collado, a biologist from the University of Vermont. "Their vocal repertoire is very diverse."

The team has captured 20 hours worth of audio recording from the botos, but they believe that they have not captured the entire vocabulary of the fascinating creatures. They identified however a short two-part calls as the most common sound. It is often heard from baby dolphins approaching their mothers.

The river dolphins also use whistles to communicate with each other, much like the marine bottlenose dolphins. However, these sounds were used less often based on the audio recording gathered during the study.

Forged By The River

The researchers also noticed that the botos made low-frequency calls like baleen whales when communicating over long distances. However, they used high-frequncy calls like marine dolphins when the other botos are within vicinity.

Collado believes that the acoustics of the river dolphins were shaped by their environment.

"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," she stated.

Collard also noted that the Amazon dolphins she studied in 2005 were much quieter. She said that further research is needed to figure out why this population of river dolphins are a lot chattier. The study could aid in understanding how communication between marine mammals evolved.

Araguaian river dolphins are found exclusively in the Amazon, Orinoco, and Tocantins River Basins in South America

The new study appears in the pre-print website PeerJ.