Bottlenose dolphin residing alone in the Baltic Sea has document producing thousands of vocalisations, potentially as a result of loneliness. Known locally as Delle, this dolphin was first notice in the Svendborgsund channel near Funen Island, Denmark, in 2019.
Bottlenose dolphins typically thrive in social pods, but no other dolphins have seen in the area.
The University of Southern Denmark deploy underwater recorders to monitor the impact of Delle’s presence on local harbour porpoises.
10,833 sounds were record over 69 days between 8th December, 2022, and 14th February 2023.
Dr Olga Filatova, cetacean biologist and lead researcher, report hearing an extensive range of sounds, including whistles and tonal noises.
These sounds are often associate with social interactions among dolphins, yet Delle was entirely alone.
Among the capture vocalisations were 2,291 whistles and 2,288 burst-pulses, clicks often link to aggression or excitement.
Delle also produce three distinctive whistles resembling “signature whistles”, unique sounds use by dolphins as individual identifiers.
These findings, details in the journal Bioacoustics on 31st October 2024, led researchers to initially speculate that multiple dolphins might be present.
But, Delle’s solitary state rule out such assumptions.
The sounds may indicate attempts to connect with others or might simply reflect involuntary expressions linked to emotions, similar to humans laughing while alone.
Dr Olga Filatova suggest it is unlikely that Delle was calling other dolphins, as his years in the area would have reveal the absence of companions.
The study highlights a gap in understanding solitary dolphins’ behaviour.
Thea Taylor, Managing Director of the Sussex Dolphin Project, note the potential for these findings to provide insights into dolphin emotions and behaviour, stressing that solitary individuals remain under-research.
Delle’s case underscores the complexity of dolphin communication, with researchers aiming to uncover the motivations behind such vocal patterns in isolate circumstances.
