A solitary bottlenose dolphin has been roaming the Baltic Sea since 2019. The only one of his kind in the Baltic Sea, he has been completely alone for the last five years. Without any pals to keep him company, he seems to have been muttering to himself.
The dolphin, known as Delle, has captured the hearts of locals and the curiosity of marine biologists. Bottlenose dolphins are inherently sociable and usually inhabit warm and temperate waters. They are a rare sight in Denmark, which makes Delle so interesting to researchers. He has been solo since he was first spotted in the Svendborgsund Channel. Despite its chilly waters, he seems keen to stay in the region. Distinctive markings on his dorsal fin show that before his unusual migration, Delle was one of a well-researched pod of dolphins off the coast of Scotland.
Using underwater recording devices, a team from the University of Southern Denmark listened to Delle’s various noises for three months. They expected to hear him making some noises but assumed he would be relatively quiet since he was by himself. That could not have been further from the truth. To the researchers’ surprise, he made 10,833 different sounds.
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Mysterious chatter
“I thought we might pick up a few distant whistles or something along those lines,” Olga Filatova, lead author of the study, told Live Science. “I certainly didn’t anticipate recording thousands of different sounds. If we hadn’t known that Delle was alone, we might have concluded that a group of at least three dolphins was engaged in various social interactions.”
The complex vocals are usually associated with dolphin-to-dolphin communication. This suggests he is having an ongoing conversation with himself. Researchers detected everything from the whistles and high-pitched clicks normally heard during echolocation and social interactions to deeper noises usually linked with territorial behavior. He even made “signature whistles” — noises that dolphins make to identify themselves. They’re a bit like a nametag.
Why he is making the noises is a mystery. Initially, researchers thought he might be attempting to communicate with nearby humans. But he was also making them at night when no one was around. Researchers now think he could be trying to distract himself from loneliness like humans often do when they are alone. He could also be making involuntary noises like when we laugh aloud, reading or seeing something funny.
It is an intriguing window into the behavior and psychology of another species. Though the researchers are speculating on what the noises might mean, they admit we must be “cautious in drawing conclusions about other species with complex communicative systems.” We still don’t fully understand why humans talk to themselves, let alone why Delle the dolphin is doing so.
