A video of a solitary dolphin swimming in the Baltic Sea has shocked scientists. You can hear mammals making thousands of different sounds. There is a theory among experts that it could talk to itself due to its isolation. Others believe it was an attempt to communicate with other dolphins.
Bottlenose dolphins (Tursiops truncatus) are among the most common dolphins on Earth. These mammals are social animals (live in groups of 10 to 25 individuals) and are generally found in tropical and temperate waters around the world.
In September 2019, a lone dolphin named Delle was found near the Svendborgsund Channel in the south of the Danish island of Funen. This was a very rare event, as the cold waters of the Baltic Sea are not the natural habitat of these mammals and they had never been seen in this area before.
Local scientists decided to place recording devices underwater to investigate the effect of the presence of dolphins on the birds.
“Out of curiosity, I decided to add a recorder that collects real sounds,” said Olga Filatova, a cetacean biologist at the University of Southern Denmark.
Thanks to this, experts discovered the unusual behavior of Delli, which caused a large number of noises. The measurement results are presented in the journal “Bioacoustics”.
More than ten thousand sounds
During the study, which lasted 69 days, the scientists recorded a total of 10,833 sounds, including several sounds commonly associated with communication. These include 2,291 whistles, 2,288 pulses—rapid bursts of clicks sometimes associated with aggression—5,487 low-frequency tonal sounds, and 767 percussive sounds. The recorders also recorded three distinct signals.
– Bottlenose dolphins have so-called distinctive whistles, which are considered unique for each individual, as well as their name, added Filatova.
For experts, the presence of sounds related to communication seemed particularly unusual.
– These sounds are traditionally considered communicative, meaning that at least two dolphins must be “talking” to each other. But Delle was completely alone, – emphasized the author of the study.
Bottlenose dolphin (stock image) Shutterstock
Reasons
It was initially thought that the bottlenose dolphin was trying to “connect” with people who practice water sports. But the sounds were also recorded at night, when the Baltic Sea was deserted. Other scientists believe that dolphins are naturally loud animals, so Delli's behavior was not that surprising.
“Dolphins use sound for basic activities such as hunting and sensing their environment,” said Thea Taylor, manager of the Sussex Dolphin Project, who was not involved in the research.
According to Olga Filatova, due to its isolation, the dolphin could talk to itself or make involuntary sounds caused by certain emotions.
– Just as we sometimes laugh when we read something funny, even if there is no one around to hear it, – added the expert.
The least likely is that the dolphin wanted to contact other people.
– He has already spent three years in this place and probably already knew that there are no more dolphins there, – emphasized Filatova.
For researchers, the most interesting thesis is that emotional signals are involuntary. According to them, analyzing this behavior of dolphins will pave the way for a better understanding of the behavior and emotions of bottlenose dolphins living in the wild.
Main image source: Shutterstock
