Dolphin in the Baltic Sea talks to itself and may feel alone, scientists claim

A bottlenose dolphin living alone in the Baltic Sea has been documented to produce thousands of sounds, possibly due to loneliness. This dolphin, known locally as Delle, was first spotted in the Svendborgsund Channel near the island of Funen, Denmark, in 2019. Bottlenose dolphins typically thrive in social groups, but no other dolphins have been spotted in the area.

The University of Southern Denmark has deployed underwater recorders to monitor the impact of Delle’s presence on local porpoises. Unexpectedly, 10,833 sounds were recorded over 69 days between December 8, 2022 and February 14, 2023. Dr. Olga Filatova, whale biologist and lead researcher, reported hearing an extensive range of sounds, including whistles and tonal sounds. These sounds are often associated with social interactions between dolphins, but Delle was all alone.

Unpack the recordings

Among the vocalizations recorded were 2,291 whistles and 2,288 burst pulses – clicks often associated with aggression or excitement. Delle also produced three distinctive whistles that resembled “signature whistles,” unique sounds used by dolphins as individual identifiers. These findings, detailed in the journal Bioacoustics on Oct. 31, initially led researchers to speculate that multiple dolphins might be present. Delle’s lonely condition, however, ruled out such assumptions.

Possible explanations for the vocalizations

The sounds may indicate attempts to connect with others or may simply reflect involuntary expressions related to emotions, similar to people laughing while alone. Dr. Filatova suggested that it is unlikely that Delle called other dolphins, as his years in the area would have revealed the absence of companions.

The study highlights a gap in understanding the behavior of solitary dolphins. Thea Taylor, chief executive of the Sussex Dolphin Project, highlighted the potential of these findings to provide insight into the emotions and behavior of dolphins, highlighting that solitary individuals are still under-researched.
Delle’s case underlines the complexity of dolphin communication, with researchers aiming to uncover the motivations behind such vocal patterns in isolated circumstances.