World’s Loneliest Dolphin Talks to Himself in Baltic Sea

Five years ago a bottlenose dolphin strayed far from his usual habitat and ended up in the chilly waters off the Danish coast. He hung around, the locals named him Delle, and marine biologists at the University of Southern Denmark began studying the 17-year-old loner.

Specifically, the scientists listened to Delle. They submerged a microphone in the area where Delle had been for several months, but they kept their expectations low. “We expected that he would produce few, if any, communicative sounds in the absence of potential recipients,” the researchers write in the journal Acoustics.

But Delle did produce communicative sounds, even in the absence of conspecifics (members of the same species). “We found the dolphin to be highly vocal, emitting burst-pulse and tonal sounds in rhythmic bouts,” the team writes.

Over 69 days, the researchers recorded 10,833 sounds: whistles, burst-pulses (clicks associated with aggression), low-frequency tonal sounds, and hundreds of percussive sounds. “Bottlenose dolphins have what are known as signature whistles, believed to be unique to each individual, much like a name,” lead author and cetacean biologist Olga Filatova tells LiveScience. “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.”

Who is he talking to and why? The researchers don’t know, but they suspect Delle is making involuntary sounds that could be triggered by a feeling, maybe even an emotion. “Much like how we sometimes laugh when we read something funny, even if no one else is around to hear,” Filatova says.

The researchers conclude that Delle’s vocalizations into the void could “simply be a byproduct of dolphins’ intrinsic need for social interaction.” They hope they can learn about cetacean communication from studying loners like Delle. We hope that if Delle is feeling an emotion, it isn’t loneliness.

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