Dolphin in the Baltic Sea Was Recorded Talking To Himself. Scientists Unravel the Disheartening Truth Behind It

Between the islands of Funen and Tåsinge in Denmark, the greenish waters of the Baltic Sea are undulating and popping restlessly. The Svendborgsund channel, which is usually occupied by rasping seagulls, clicking porpoises, and swirling pikes, is nowadays rumbling with some mysterious sounds. Puzzled by the strange whistles and moans echoing from the water, researchers lowered some underwater microphones into the water. They made a heartbreaking discovery. Slinking in these waters, a male dolphin is engaged in self-talk, apparently because he is lonely. According to a study published in the journal Bioacoustics, the locals nicknamed the world’s saddest dolphin “Delle.”

What surprised researchers the most in this episode was that this area lies outside the typical range of bottlenose dolphins. But Delle appeared to hang out regularly during daylight, near the waterfront. Locals identified him by his distinctive notches on the dorsal fin. Some snapped pictures and videos of the dolphin and posted them on social media. Before being named Delle, the dolphin was named “Yoda,” according to the photo identification catalog of Moray Firth, Scotland.

Previously, Simon Allen, a biologist not involved in this study, shared with BBC that bottlenose dolphins are highly social animals that live in pods. “Bottlenose dolphins are highly social animals, and this sociality can be expressed in very physical ways.” So when a dolphin gets separated from its pod and becomes isolated, it takes an emotional toll which they usually express through aggression or in this case, sound-making. Delle is not the only dolphin who has expressed his loneliness. Take the case of Japan’s aggressive bottlenose dolphin who is attacking humans because he is lonely and desirous of touch.

When researchers sent the recording devices underwater to investigate the behavior of solitary Delle, they were beyond surprised to receive so many sounds. "I thought we might pick up a few distant whistles or something along those lines. I certainly didn't anticipate recording thousands of different sounds," lead author Olga Filatova, a cetacean biologist at the University of Southern Denmark, told Live Science.

Over a 69-day period between Dec. 8, 2022, and Feb. 1,4 2023, the recording devices detected 10,833 sounds, including 2,291 whistles, 2,288 burst-pulses, 5,487 low-frequency tonal sounds, and 767 percussive sounds. Burst pulses are rapid click trains that dolphins make, sometimes while expelling bubbles and expressing aggression. Filatova explained that these sounds are "traditionally considered communicative, meaning there should be at least two dolphins 'talking' to each other. But Delle was completely alone.” There weren’t either paddleboarders or other humans nearby either.

Keeping all these points in mind, the unusual behavior of this dolphin has unlocked a new mystery for researchers. If he is not making these sounds for communication, then what could be the purpose? One possibility is that the sound could have been triggered by a certain emotion "much like how we sometimes laugh when we read something funny, even if no one else is around to hear," said Filatova. Another hypothesis is that the dolphin is making these sounds to attract or call other dolphins nearby. However, this is very unlikely given that Delle has been prowling this portion of the water for nearly three years.  

Considering other theories, researchers noted in the study that these sounds could just be Delle’s way of expressing his intrinsic need for social interaction. However, as for now, no conclusion can be marked as certain. “The fact that we cannot fully understand the functions of acoustic signaling in the absence of recipients even in our own species suggests that we should be particularly cautious in drawing conclusions about other species with complex communicative systems,” researchers wrote. Or maybe, the sad, lonely dolphin is just doing a loving self-talk, just like we humans do.