Dolphins are often perceived as creatures of the open ocean, but they do swim close to shore. This behavior is not universal across all species. Specific populations, known as coastal ecotypes, routinely inhabit the shallow, nearshore waters of bays, estuaries, and inlets. Understanding which dolphins use these habitats and why helps explain sightings from the beach or a boat.
Coastal Dolphin Species
Not all of the world’s dolphin species venture into the nearshore environment; this behavior is restricted to specific, geographically adapted populations. The most recognized example is the common Bottlenose Dolphin, Tursiops truncatus, which exists in two distinct forms: coastal and offshore ecotypes. Coastal Bottlenose Dolphins are adapted to life in shallower, warmer, and often more turbid waters, living within a few miles of the shore.
These coastal dolphins are generally smaller and less robust than their offshore counterparts, which inhabit the deeper, cooler waters beyond the continental shelf. Recent genetic studies suggest the coastal form in the Western North Atlantic may even be a separate species, Tursiops erebennus. Other coastal species, such as the Indo-Pacific Bottlenose Dolphin and the Guiana Dolphin, also preferentially use sheltered bays and estuaries.
Motivations for Shallow Water Use
The primary driver for coastal dolphins to utilize nearshore habitats is reliable access to food sources, which are often concentrated in these productive environments. The narrow confines and shallow depths of estuaries and mud flats allow for specialized, cooperative hunting techniques not possible in the open ocean. One remarkable feeding method is “strand feeding,” where dolphins herd fish onto a sloping mud bank or beach, temporarily lunging out of the water to snatch the prey.
This strand feeding behavior is a learned tradition, passed down from mother to calf. Another localized technique is “mud ring feeding,” where a dolphin uses its tail to stir up a circular plume of mud that corrals fish until they are easily picked off. Shallow coastal areas also offer protection from larger, offshore predators, such as certain species of sharks, which are less likely to venture into confined bays and inlets.
Coastal populations also utilize these sheltered environments as preferred nursery areas for their young. Estuaries and lagoons provide warmer water temperatures and an abundance of prey, which is beneficial for developing calves. The physical protection afforded by the shallow, restricted waterways allows the pod to form a defensive barrier around the vulnerable young, ensuring their safety as they learn complex social and hunting behaviors.
Environmental Factors Affecting Proximity
The presence of dolphins close to shore is influenced by external environmental conditions, particularly the ebb and flow of water. Tidal cycles play a significant role in dolphin movement, as the rising tide grants easier access to shallow feeding grounds and marsh creeks. Conversely, specific behaviors like strand feeding are timed around low tide, when exposed mud banks create a natural trap for fish.
The time of day also affects the likelihood of a sighting, often correlating with increased feeding activity. Dolphins are frequently seen closer to the coast during the early morning and late afternoon or early evening. These times often coincide with calmer water conditions, making it easier for the dolphins to hunt. Seasonal changes also alter their distribution, with some coastal populations exhibiting peak abundance in summer due to shifts in water temperature and prey availability.
Responsible Viewing Guidelines
Observing dolphins requires adherence to guidelines designed to protect the animals and minimize human impact. Whether watching from the shore or from a boat, maintaining a safe and respectful distance is necessary. Federal guidelines recommend staying at least 50 yards away from dolphins to prevent disturbance to their natural behaviors.
Approaching, chasing, or attempting to encircle the animals is prohibited, as this can cause stress and disrupt their foraging or resting patterns. It is illegal and harmful to feed wild dolphins, as this causes them to lose their natural fear of humans and associate boats with food. If a dolphin approaches a watercraft, the engine should be placed in neutral, and the vessel should move away slowly only after the animal has passed. If an injured, entangled, or stranded dolphin is observed, immediately contact local marine mammal stranding networks rather than attempting to intervene personally.