In the cold waters of Baltica lone dolphin has captured the attention of the scientific community by displaying some intriguing behavior: He seems to talk to himself.
Researchers believe this unusual phenomenon could be a sign of loneliness, raising new questions about the emotional lives of these intelligent marine mammals.
This dolphin, separated from its congeners, emits a series of complex sounds typically associated with communication with other dolphins.
A study published in the International Journal of Animal Sound and its Recording (International Journal of Animal Sound and its Recording) has revealed a unusual acoustic behavior in a solitary bottlenose dolphin residing in the Baltic Sea.
The research, carried out by Olga A. Filatova, an academic at the University of Southern Denmark, and an international team, analyzed the vocalizations of a dolphin that apparently lack recipients, raising questions about the intentionality of its sounds.
Scientists expected that the dolphin would make few sounds when out of reach of other mates; However, the dolphin was found to make a wide variety of sounds, including pops, pulses, and rhythmic tones that did not coincide with echolocation trains, “indicating that they were not associated with feeding activities,” the authors state.
Echolocation is a natural system similar to sonar, used by some animals to orient themselves and locate objects in their environment. According to National Geographicthis process occurs when the animal emits a sound that is reflected by a nearby object and returns as an echo, providing information about the distance and size of the object.
Key findings from this research include three different types of stereotyped whistles and three distinct categories of biphonic sounds, challenging common understandings of intentional communication in bottlenose dolphins.
“These sounds could be emitted unintentionally as emotional signals, fulfill functions other than direct communication, or simply be a byproduct of dolphins’ intrinsic need for social interaction,” the researchers point out.
Observations suggest that, despite its isolation, the dolphin maintained active vocal behaviorproducing sounds that in other circumstances are intended for communication with their peers.
This unexpected acoustic activity could imply that “bottlenose dolphins have a more flexible and diverse capacity for vocal production than previously thought,” according to the authors.
The article also addresses the issue of “first-order intentionality,” which refers to sending signals with a specific objective toward a specific recipient. The researchers suggest that these vocalizations may not be intentional, but rather a manifestation of the emotional or social state of dolphins.
Furthermore, it was observed that a single dolphin could produce several whistles, challenging the idea that each dolphin has a unique whistle, creating a kind of signature.
“The spontaneous production of communicative sounds in the absence of a recipient, known as ‘self-talk’, is also common in humans,” the research mentions.
“Self-talk may simply be a byproduct of our intrinsic need for social interaction, and the same may be true for dolphins and other social animals,” he continues.
The researchers conclude that our limited understanding of receptor-less acoustic signaling, even in humans, indicates that we should be cautious when interpreting communication in other species with complex systems.
The study was carried out in the around the island of Funen, in Denmark, using a self-contained underwater recorder and an FPOD, which allowed sounds to be captured passively for more than 1600 hours. The identification of the solitary dolphin was made based on a photographic catalog from Moray Firth, Scotland, assigning it the number 1022 and the nickname ‘Yoda’.
A passive acoustic monitoring method was used for its development. A self-contained underwater recorder, called SoundTrap ST 500, was placed in the port of Svendborg for two months, from December 8, 2022 to February 14, 2023.
This device operated at a sampling rate of 384 kHz and generated a new file after every 45 minutes of recording. The exact location of the recorder was 10 meters deep and near an area visited by tourists.
Additionally, an FPOD, a device that detects and records trains of echolocation clicks, was used. Both devices were synchronized. To analyze the sounds, PamGuard software was used, which processes spectrogram images to detect tonal sounds. All sounds detected were audited manually to rule out false positives and confirm the presence of dolphin sounds.
The sounds were classified into several categories, such as whistles, pulsed sounds, low-frequency tones, and percussive sounds. Efforts were made to identify the co-occurrence of communicative and echolocation sounds by comparing data from both devices. During the study, 1635 hours of data were collected and approximately 10,833 dolphin sounds were detected in various categories.
