Dolphins swimming around a person or a boat is a memorable experience, driven by sensory investigation and social inclination. The act of a dolphin circling a human is a sophisticated form of data collection and evaluation, rather than a simple greeting. Understanding the biology behind this interaction provides a clearer picture of what the dolphin is truly doing when it approaches a human.
Echolocation and Environmental Assessment
The initial action of a dolphin swimming around an unfamiliar object is often an investigative sensory behavior called echolocation, or biosonar. The dolphin produces high-frequency clicking sounds from its nasal passages, focused into a beam by an organ in its forehead called the melon. These clicks travel through the water, bounce off objects, and return to the dolphin’s lower jaw and inner ear as echoes.
By encircling a stationary or slow-moving human, the dolphin gathers a comprehensive, three-dimensional sonic picture of the object from all angles. This process is similar to a medical ultrasound, allowing the dolphin to perceive the external shape, internal density, and composition of the person. Sonar can even detect internal structures like bone, muscle tissue, and scar tissue.
Circling is necessary for complete environmental assessment because the dolphin’s sonar beam has focused directionality. To create a full, detailed image of a person’s size, movement, and physical state, the dolphin must continually adjust its position. This effectively “touches” the human with sound to confirm the object is not a threat or a potential food source. Once this initial investigation is complete, the behavior may transition into a prolonged social motivation.
Social Motivation: Curiosity and Affiliation
Dolphins have complex intelligence, and their tendency to swim around humans often moves beyond sensory scanning into genuine social curiosity. Like humans, dolphins possess distinct personalities. Bolder, more outgoing individuals are more likely to initiate contact with novel objects or species, including people. This desire for social interaction is a significant reason for prolonged encounters in the wild.
In many instances, circling is a form of non-aggressive, exploratory play, especially when dolphins are seen bow-riding or wake-surfing near boats. They are highly social animals that thrive on interaction within their pods. They sometimes extend this affiliative behavior to include humans, which can involve attempting to engage the person in an underwater game, such as passing a piece of seaweed.
There are rare, but documented, accounts of dolphins engaging in protective or “escorting” behavior, where they swim around a human to shield them from perceived threats like sharks. This altruistic tendency is thought to be an extension of their strong social bonds and cooperative nature. The most common social motivation remains a simple desire to interact with another sentient being for social gratification.
Human Response and Interaction Guidelines
When wild dolphins choose to swim around you, the appropriate human response is passive observation and respect for their space. It is recommended to maintain a distance of at least 50 yards from wild marine mammals to avoid disturbing their natural behaviors. If a dolphin initiates contact by approaching closer, remain calm and avoid sudden movements that could startle the animal.
It is necessary to resist the urge to touch or feed the dolphins, even if they come within arm’s reach. Feeding them causes them to lose their natural wariness of people and boats, increasing their risk of injury or death from propellers or entanglement. Touching a dolphin can also transfer harmful bacteria and disrupt the protective layer of their skin.
Pursuing or chasing a wild dolphin is considered harassment, which is illegal under many national laws, such as the Marine Mammal Protection Act in the United States. Your role is to be a calm, non-intrusive presence, allowing the dolphin to control the duration and nature of the interaction. If the dolphin decides to leave, allow it to depart without pursuit.