Oceanic dolphin in the context of Gestation

The orca (Orcinus orca), or killer whale, is a toothed whale and the largest member of the oceanic dolphin family. The only extant species in the genus Orcinus, it is recognizable by its distinct pigmentation; being mostly black on top, white on the bottom and having recognizable white eye patches. A cosmopolitan species, it inhabits a wide range of marine environments, from Arctic to Antarctic regions to tropical seas, but is more commonly documented in temperate or cooler coastal waters. Scientists have proposed dividing the global population into races, subspecies, or possibly even species.

Orcas are apex predators with a diverse diet. Individual populations often specialize in particular types of prey, including bony fish, sharks, rays, and marine mammals such as seals, dolphins, and whales. They are highly social, with some populations forming stable matrilineal family groups (pods). Their sophisticated hunting techniques and vocal behaviors, often unique to specific groups and passed down from generation to generation, are considered to be manifestations of animal culture. The most studied populations are off the west coast of North America, which include fish-eating "residents", mammal-eating "transients", and offshores.

Porpoises (/ˈpɔːrpəsɪz/) are small dolphin-like cetaceans classified under the family Phocoenidae. Although similar in appearance to dolphins, they are more closely related to narwhals and belugas. There are eight extant species of porpoise, all among the smallest of the toothed whales. Porpoises are distinguished from dolphins by their flattened, spade-shaped teeth distinct from the conical teeth of dolphins, and lack of a pronounced beak, although some dolphins (e.g. Hector's dolphin) also lack a pronounced beak. Porpoises, and other cetaceans, belong to the clade Cetartiodactyla with even-toed ungulates.

Porpoises range in size from the vaquita, at 1.4 metres (4 feet 7 inches) in length and 54 kilograms (119 pounds) in weight, to the Dall's porpoise, at 2.3 m (7 ft 7 in) and 220 kg (490 lb). Several species exhibit sexual dimorphism in that the females are larger than males. They have streamlined bodies and two limbs that are modified into flippers. Porpoises use echolocation as their primary sensory system. Some species are well adapted for diving to great depths. As all cetaceans, they have a layer of fat, or blubber, under the skin to keep them warm in cold water.

Iniidae is a family of river dolphins containing one living genus, Inia, and four extinct genera. The extant genus inhabits the river basins of South America, but the family formerly had a wider presence across the Atlantic Ocean.

Iniidae are highly morphologically different from marine dolphins by way of adaptations suited to their freshwater riverine habitat. They also display a high amount of sexual dimorphism in the form of color and size. Seasonal movement between flooded plains and rivers is common, due to the variation of seasonal rain. There has been little research done on the family, in particular the species aside from the Amazon river dolphin.

The beluga whale (/bəˈluːɡə, bɪ-, bɛˈlʊɡə/; Delphinapterus leucas) is an Arctic and sub-Arctic cetacean. It is one of two living members of the family Monodontidae, along with the narwhal, and the only member of the genus Delphinapterus. It is also known as the white whale, as it is the only cetacean to regularly occur with this colour; the sea canary, due to its high-pitched calls; and the melonhead, though that more commonly refers to the melon-headed whale, which is an oceanic dolphin.

The beluga is adapted to life in the Arctic, with anatomical and physiological characteristics that differentiate it from other cetaceans. Amongst these are its all-white colour and the absence of a dorsal fin, which allows it to swim under ice with ease. It possesses a distinctive protuberance at the front of its head which houses an echolocation organ called the melon, which in this species is large and deformable. The beluga's body size is between that of a dolphin and a true whale, with males growing up to 5.5 m (18 ft) long and weighing up to 1,600 kg (3,530 lb). This whale has a stocky body. Like many cetaceans, a large percentage of its weight is blubber (subcutaneous fat). Its sense of hearing is highly developed and its echolocation allows it to move about and find breathing holes under sheet ice.

Globicephalinae is a subfamily of oceanic dolphins that includes the pilot whales (Globicephala spp.), the pygmy killer whale (Feresa attenuata), the rough-toothed dolphin (Steno bredanensis), the false killer whale (Pseudorca crassidens), the melon-headed whale (Peponocephala electra), Risso's dolphin (Grampus griseus), and the snubfin dolphins (Orcaella spp.).

The false killer whale (Pseudorca crassidens) is a species of oceanic dolphin that is the only extant representative of the genus Pseudorca. It is found in oceans worldwide but mainly in tropical regions. It was first described in 1846 as a species of porpoise based on a skull, which was revised when the first carcasses were observed in 1861. The name "false killer whale" comes from having a skull similar to the orca (Orcinus orca), or killer whale.

The false killer whale reaches a maximum length of 6 m (20 ft), though size can vary around the world. It is highly sociable, known to form pods of up to 50 members, and can also form pods with other dolphin species, such as the common bottlenose dolphin (Tursiops truncatus). It can form close bonds with other species, as well as have sexual interactions with them. But the false killer whale has also been known to eat other dolphins, though it typically eats squid and fish. It is a deep-diver; maximum known depth is 927.5 m (3,043 ft); maximum speed is around 29 km/h (18 mph).

Pilot whales are cetaceans belonging to the genus Globicephala. The two extant species are the long-finned pilot whale (G. melas) and the short-finned pilot whale (G. macrorhynchus). The two are not readily distinguishable at sea, and analysis of the skulls is the best way to distinguish between the species. Between the two species, they range nearly worldwide, with long-finned pilot whales living in colder waters and short-finned pilot whales living in tropical and subtropical waters. Pilot whales are among the largest of the oceanic dolphins, exceeded in size only by the orca. They and other large members of the dolphin family are also known as blackfish.

Pilot whales feed primarily on squid, but will also hunt large demersal fish such as cod and turbot. They are highly social and may remain with their birth pod throughout their lifetime. Short-finned pilot whales are one of the few non-primate mammal species in which females go through menopause, and postreproductive females continue to contribute to their pod. Pilot whales are notorious for stranding themselves on beaches, but the reason behind this is not fully understood. Marine biologists have shed some light on the matter, suggesting that it is due to the mammals inner ear (their principal navigational sonar) being damaged from noise pollution in the ocean, such as from cargo ships or military exercises. The conservation status of short-finned and long-finned pilot whales has been determined to be least concern.

A drift whale is a cetacean mammal that has died at sea and floated into shore. This is in contrast to a beached or stranded whale, which reaches land alive and may die there or regain safety in the ocean. Most cetaceans that die, from natural causes or predators, do not wind up on land; most die far offshore and sink deep to become novel ecological zones known as whale falls. Some species that wash ashore are scientifically dolphins, i.e. members of the family Delphinidae, but for ease of use, this article treats them all as "drift whales". For example, one species notorious for mass strandings is the pilot whale, also known as "blackfish", which is taxonomically a dolphin.

In historical sources, it is not always clear whether a given cetacean washed up alive or dead, but the term "drift whale" focuses on the benefits of its carcass – meat, blubber, fat, and other products – to the people who claimed it. Nowadays, when a dead whale washes up on a beach, often the authorities are required to dispose of it as a potential hazard to human health, so the resource implications go the other way: a drift whale is no longer a benefit to a community, but an expensive disadvantage.

The bottlenose dolphin is a toothed whale in the genus Tursiops. They are common, cosmopolitan members of the family Delphinidae, the family of oceanic dolphins. Molecular studies show the genus contains three species: the common bottlenose dolphin (Tursiops truncatus), the Indo-Pacific bottlenose dolphin (Tursiops aduncus), and Tamanend's bottlenose dolphin (Tursiops erebennus). Others, like the Burrunan dolphin (Tursiops (aduncus) australis), may be alternately considered their own species or be subspecies of T. aduncus. Bottlenose dolphins inhabit warm and temperate seas worldwide, being found everywhere except for the Arctic and Antarctic Circle regions. Their name derives from the Latin tursio (dolphin) and truncatus for the truncated teeth (the type specimen was old and had worn down teeth; this is not a typical characteristic of most members of the species).

Numerous investigations of bottlenose dolphin intelligence have been conducted, examining mimicry, use of artificial language, object categorization, and self-recognition. They can use tools (sponging; using marine sponges to forage for food sources they normally could not access) and transmit cultural knowledge from generation to generation, and their considerable intelligence has driven interaction with humans. Bottlenose dolphins gained popularity from aquarium shows and television programs such as Flipper. They have also been trained by militaries to locate sea mines or detect and mark enemy divers. In some areas, they cooperate with local fishermen by driving fish into their nets and eating the fish that escape. Some encounters with humans are harmful to the dolphins: people hunt them for food, and dolphins are killed inadvertently as a bycatch of tuna fishing and by getting caught in crab traps.

A military marine mammal is a cetacean or pinniped that has been trained for military uses. Examples include bottlenose dolphins, seals, sea lions, and beluga whales. The United States and Soviet militaries have trained and employed oceanic dolphins for various uses. Military marine mammals have been trained to rescue lost naval swimmers, guard navy ships against enemy divers, locate mines for later clearance by divers, and aid in location and recovery of equipment lost on the seabed.

The short-finned pilot whale (Globicephala macrorhynchus) is one of the two species of cetaceans in the genus Globicephala, which it shares with the long-finned pilot whale (G. melas). It is part of the oceanic dolphin family (Delphinidae).

It has a worldwide distribution with a global population of about 700,000, and there may be 3 or 4 distinct populations—two in the Pacific and one in the Atlantic and Indian Oceans. Its range is moving northward due to global warming. In the Pacific, males average 4–6 m (13–20 ft) and females 3–5 m (9.8–16.4 ft). It generally has a stocky build with black to dark gray or brown skin, and can be distinguished from its counterpart by shorter flippers, fewer teeth, and a shorter beak. It is thought to pursue fast-moving squid typically at a depth of 700 m (2,300 ft), but the maximum recorded depth is 1,018 m (3,340 ft).

The melon-headed whale (Peponocephala electra), also known less commonly as the electra dolphin, little killer whale, or many-toothed blackfish, is a toothed whale of the oceanic dolphin family (Delphinidae). The common name is derived from the head shape. Melon-headed whales are widely distributed throughout deep tropical and subtropical waters worldwide, but they are rarely encountered at sea. They are found near shore mostly around oceanic islands, such as Hawaii, French Polynesia, and the Philippines.

The long-finned pilot whale or pothead whale (Globicephala melas) is a large species of oceanic dolphin. It shares the genus Globicephala with the short-finned pilot whale (Globicephala macrorhynchus). Long-finned pilot whales are known as such because of their unusually long pectoral fins.