Common Dolphin
About
Common dolphins (also referred to as short-beaked common dolphins) are an offshore species but often come close to shore to feed. They are highly social and normally found in groups, travelling at speed and frequently leaping from the water. They feed mainly on fish and will work together to herd their prey into a ball.
Common dolphins are quite slender, they are dark grey above and whiter below. They also have a distinctive hourglass pattern on their sides, including an obvious yellow-cream area starting behind the beak. The dorsal fin is tall and triangular and curves slightly backwards.
Common dolphins can live in aggregations of hundreds or even thousands of dolphins. Common dolphins are often seen in groups numbering several hundred individuals (with subgroups consisting of 20–30 individuals). Occasionally, different groups will come together to form mega-pods which can consist of over 10,000 dolphins.
Quick Facts
Lifespan: Average, 28 years
Habitat: Coastal and offshore waters
Food: Fish and crustaceans
Fun fact: Dolphins sometimes eat jellyfish - Mmm, spicy!
Common dolphins are typically very active at the surface, and jumping and splashing can often be seen and heard at great distances. Breaching (even somersaulting) is frequent, and animals can be observed slapping the water surface with their chins and flippers.
Dolphins are considered one of the world's most intelligent animals, and they have several cognitive abilities that set them apart. Many researchers consider intelligence to be a combination of perception, communication, and problem-solving, and you can see dolphin intelligence in action in the way they communicate and use tools.
Communication is a big part of how dolphins socialize and hunt. They have the ability to echolocate with a series of clicks, allowing them to find other dolphins or similar species and prey, even in the low-light conditions of the ocean. They can do more, too. Did you know that dolphin echolocation allows them to detect surgically implanted metal in swimming humans? The human body is comprised of about 75% water, and once in the water, we provide a prime structure for echolocation. This is how dolphins are able to discern that the metal is denser than human flesh, which is mostly water.
Dolphins also have a complicated method of communicating with each other. From an outside perspective, dolphins may seem to communicate much like humans. However, researchers are still investigating both how dolphins communicate and what information they are able to pass to each other.
Despite lacking hands, dolphins are adept at using tools. For instance, one of their more specialized tricks is to carry a sponge at the end of their beak, also known as a rostrum. This acts like padding, protecting them from sharp rocks as they dig through the seafloor for food.
Behaviour
Several members of a group will often surface together. They are fast swimmers and commonly bow-ride with boats and even large whales such as humpback, fin, grey and blue whales.
Altruistic and epimeletic behaviour (such as females assisting others with birth, and baby-sitting behaviour) have been observed in common dolphins both in captivity and in the wild.
Threats
Human Induced Threats
Human Induced Threats
Like all cetaceans, common dolphins are at risk of entanglement in fishing gear (by-catch) which means they either drown or get taken onto fishing boats. They are also threatened by changes caused by climate change (such as having to find food in new areas), being hit by ships, pollution, oil and gas development and habitat degradation. Some countries, including Japan, also fish dolphins commercially.
Human Induced Threats
Human Induced Threats
Human Induced Threats
In the Eastern Tropical Pacific, the Atlantic and the Indian Oceans, common dolphins’ association with yellowfin tuna brings the species into contact with tuna fisheries and puts them at risk of by-catch, particularly in gillnet or purse seine fisheries. While bycatch is pervasive throughout the species’ range, habitat degradation, contamination, disease, and overfishing are thought to play a bigger role in the documented population declines in the Black Sea and Mediterranean subpopulations.
Predators
Human Induced Threats
Predators
As with other dolphin species, killer whales and large sharks are the most likely natural predators of common dolphins, although they may also be preyed on by false killer whales, or pilot whales in some areas.
Conservation Status
There have been directed hunts for common dolphins in Japan and off the coast of Peru where they are used for bait shark fisheries as well as for human consumption. Globally, common dolphins are designated as Least Concern on the IUCN Red List of Threatened Species, but the Mediterranean subpopulation is listed as Endangered, and the Black Sea subspecies is listed as Vulnerable. These latter two are listed on Appendix II of the Convention on Migratory Species.
