A new study suggests that a lone dolphin of the Delphinus species in the Baltic Sea may have begun speaking to itself due to loneliness and lack of companionship. The male dolphin, named "Delle" by the locals, spends time in the Svendborgsund channel in Denmark, far outside the species' usual territory.
Delphinus dolphins are highly social animals known for cooperating in various behaviors such as hunting and mating. Their complex communication methods show they thrive in groups.
These dolphins are also known to call one another using "signature whistles," similar to personal names, which help them identify who is calling.
Finding a solitary example of such a social species living alone in the channel puzzled scientists.
A study conducted this year suggested that Delle's presence might be connected to the displacement of marine mammals in the Baltic Sea. Scientists intended to investigate Delle's behavior further to understand how it might affect other marine life in the channel.
In the latest study, underwater recording devices were used to capture the sounds made by Delle.
The devices recorded a range of different sounds, including whistles, low-frequency tonal sounds, and percussive bursts of sound, made by the lone dolphin.
Researchers tried to determine whether Delle's calls were "targeted," meaning whether they were intended to provoke specific responses from other members of the species.
Animals use targeted signals to alter the mental state of others, such as alarm calls to warn of predators. It is known that intelligent, social animals, including monkeys and Delphinus dolphins, produce such signals.
The researchers found that Delle's calls were not targeted because there was no one else in the channel to respond to the signal.
They noted that the lone dolphin was surprisingly talkative, producing sounds typically used for maintaining communication with other dolphins and coordinating actions.
The researchers said, "If we didn't know the dolphin was alone, we might have concluded that the recordings came from a group of three different dolphins. It's highly unusual for the dolphin to make these sounds in a place where there are no others of its species."
Scientists speculated that Delle's sounds could be "emotional signals" or sounds unrelated to communication.
The researchers concluded that this form of "self-talk" might have emerged from an internal need for social interaction. However, they admitted that they do not have a "clear explanation" for this phenomenon.
