In the waters of the Baltic Sea, a solitary dolphin, nicknamed Delle by locals, is intriguing scientists with its unusual behavior. This dolphin appears to be talking to itself, raising questions about its isolation and social needs.
A Dolphin Out of Its Habitat
Bottlenose dolphins (Tursiops truncatus) are known for their sociable nature and typically live in groups. However, in September 2019, a solitary individual was spotted in the Svendborgsund channel, south of the island of Funen in Denmark. This location, outside the species’ usual range, has remained Delle’s territory for several years. No other dolphins have been observed nearby.
To study its impact on local porpoises, researchers installed underwater recorders in the area. What they discovered was a surprising level of acoustic activity. The team, led by Olga Filatova, a cetacean biologist at the University of Southern Denmark, was not expecting such an extensive range of vocalizations from a single individual. Their findings were recently published in the journal Bioacoustics.
An Unexpected Aquatic Symphony
Between December 2022 and February 2023, the recorders captured an impressive total of 10,833 distinct sounds over a 69-day period. These vocalizations included 2,291 whistles, 2,288 burst pulses (rapid click sequences often linked to aggressive interactions), 5,487 low-frequency tonal sounds, and 767 percussive sounds.
Fascinatingly, Delle produced at least three signature whistles, which are typically unique to each dolphin and comparable to a « name. » This discovery astonished researchers, as these signals are usually associated with communication among peers, yet Delle was alone.
Ms. Filatova did not expect to hear vocalizations or other communication-related sounds. “If we didn’t know about its solitude, we might have thought there was a group of dolphins interacting with each other,” she said. This behavior raises questions about Delle’s motivations, particularly whether these vocalizations indicate loneliness or an attempt at social interaction.
Hypotheses on an Enigmatic Behavior
Why is Delle so vocal despite the absence of other dolphins? Several theories have emerged. It may simply be « talking » to itself, a behavior comparable to humans laughing or muttering when alone. These sounds might also be an unintentional expression of emotions. Another hypothesis suggests that Delle is desperately trying to attract potential companions to the area.
However, this explanation seems unlikely. After three years in this isolated region, it’s improbable that Delle is still hoping to find other dolphins. For Thea Taylor, director of the Sussex Dolphin Project, the idea that vocalizations could reflect unintentional emotional expressions opens new perspectives on understanding dolphin behavior and emotions.
This study represents a significant breakthrough, as scientists rarely focus on the sounds produced by solitary dolphins, often dismissing them as atypical or marginal cases. However, analyzing these behaviors can provide valuable insights into the cognitive and emotional capacities of these animals. As Taylor emphasizes, “We still have much to learn about why dolphins produce different sounds and what they mean.”
Meanwhile, Bolivian river dolphins holding an anaconda in their beaks continue to puzzle scientists.
Source: dailygeekshow
