Oceanic Dolphins

Scientific name: Delphinidea

This pilot whale is one of 32 species of oceanic dolphins alive today.
This pilot whale is one of 32 species of oceanic dolphins alive today. Photo © George Karbus / Getty Images.

Oceanic dolphins (Delphinidae) are a group of cetaceans that includes dolphins, pilot whales, and killer whales. There are 32 species of oceanic dolphins alive today, making it the most diverse of all cetacean groups. Oceanic dolphins occur in marine waters and some rivers around the world, but prefer shallow seas and coastal waters. They often remain close to the surface and do not make long, deep dives that are characteristic of other cetaceans.

Oceanic dolphins have a beak-like snout, also called a rostrum, at the front of their head. Their forehead is round and bulging, due to the presence of an internal structure called a melon which helps to focus sound vibrations and enables oceanic dolphins to navigate using echolocation.

Many species of oceanic dolphins are highly social and form large groups (called pods) that travel and forage together. Some groups of oceanic dolphins may include thousands of individuals.

Key Characteristics

  • streamlined body
  • curved dorsal fin
  • distinct color patterns
  • melon structure in forehead used in echolocation

Classification

Oceanic dolphins are classified within the following taxonomic hierarchy:

Animals > Chordates > Vertebrates > Tetrapods > Amniotes > Mammals > Cetaceans > Oceanic dolphins

Oceanic dolphins are divided into the following taxonomic groups:

  • Cephalorhynchus - There are four species of Cephalorhynchus alive today. Members of this group include the Chilean dolphin, Hector's dolphin, Commerson's dolphin, and Haviside's dolphin.
  • Common dolphins (Delphinus) - There are two species of common dolphins alive today, the long-beaked common dolphin and the short-beaked common dolphin.
  • Feresa - There is one species of Feresa alive today, the pygmy killer whale. Pygmy killer whales are rarely-seen cetaceans that travel in pods of between 10 and 30 individuals and feed on cephalopods and fish.
  • Pilot whales (Globicephala) - There are two species of pilot whales alive today, the long-finned pilot whale and the short-finned pilot whale. Pilot whales are highly social cetaceans that form pods of between 10 and 30 or more members.
  • Grampus - There is one species of Grampus alive today, the Rhisso's dolphin. Risso's dolphins inhabit coastal waters in temperate and tropical regions.
  • Lagenodelphis - There is one species of Lagenodelphis alive today, the Fraser's dolphin. Fraser's dolphin have a small dorsal fin and a short beak. They form groups of between 100 and 1000 individuals.
  • Lagenorhynchus - There are six species of Lagenorhynchus alive today. Members of this group include the white-beaked dolphin, Atlantic white-sided dolphin, Pacific white-sided dolphin, hourglass dolphin, Peale's dolphin,and dusky dolphin.
  • Right whale dolphins (Lissodelphis) - There are two species of right whale dolphins alive today, the northern right whale dolphin and the southern right whale dolphin. Right whale dolphins have a slender body, a small fluke, and pointed flippers.
  • Snubfin dolphins (Orcaella) - There are two species of snubfin dolphins alive today, the Irrawady dolphin, and the Australian snubfin dolphin. Irrawaddy dolphins live in the shallow coastal waters of the Indian Ocean, from the Bay of Bengal to the northeastern coast of Australia. Australian snubfin dolphins inhabit shallow waters along the northern coast of Australia.
  • Killer whales (Orcinus) - There is one species of killer whale alive today, the orca. The orca, also known as the blackfish, is among the most widespread of all oceanic dolphins. Orcas form stable groups that undertake complex feeding, hunting, and social behaviors.
  • Peponocephala - There is one species of Peponocephala alive today, the melon-headed whale. The melon-headed whale is among the few types of oceanic dolphins that prefers deep water habitats. Melon-headed whales inhabit tropical marine waters around the world.
  • False killer whales (Pseudorca) - There is one species of false killer whale alive today. The false killer whale inhabit tropical and semi-tropical coastal waters and open ocean habitats around the world.
  • Sotalia - There are two species of Sotalia alive today, the Guiana dolphin and the tucuxi. Formerly classified as a single species, the Guiana dolphin and the tucuxi are freshwater dolphins that inhabit the rivers of the Amazon Basin.
  • Humpback dolphins (Sousa) - There are three species of humpback dolphins alive today. Members of this group include the Chinese white dolphin, the Indian humpback dolphin and the Atlantic humpback dolphin. Humpback dolphins inhabit shallow marine waters along the coast of Africa, India, and Australia.
  • Spotted dolphins (Stenella) - There are five species of spotted dolphins alive today. Members of this group include the pantropical spotted dolphin, Atlantic spotted dolphin, spinner dolphin, Clymene dolphin, and striped dolphin. Spotted dolphins inhabit tropical and temperate marine waters around the world.
  • Rough-toothed dolphins (Steno) - There is one species of rough-toothed dolphin alive today. The rough-toothed dolphin is a large species of oceanic dolphin with a narrow, non-prominent beak and conical head.
  • Bottlenose dolphins (Tursiops) - There are three species of bottlenose dolphins alive today, the common bottlenose dolphin, the Indo-Pacific bottlenose dolphin, and the Burrunan dolphin. Members of this group are among the most common and recognized of all oceanic dolphins.