Orca
The 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. 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.
The International Union for Conservation of Nature lists the orca's conservation status as data deficient as multiple orca types may represent distinct species. Some local populations are threatened or endangered due to prey depletion, habitat loss, pollution, captures for marine parks, and conflicts with fisheries. In late 2005, the southern resident orcas were added to the U.S. Endangered Species list.
Orcas have been revered by indigenous peoples while Western cultures have historically feared them. They have been taken by whalers when stocks of larger species have declined. The orca's image took a positive turn in the 1960s, due to greater public and scientific awareness and their display in captivity. Since then, orcas have been trained to perform in marine parks, a practice that has been criticized as unethical. Orcas rarely pose a threat to humans, and no fatal attack has been recorded in the wild. However, captive orcas have injured or killed their handlers in marine theme parks.
Naming
Orcas are often referred to as "killer whales" because ancient sailors saw them hunt larger whales. Since the 1960s, the term "orca" has increasingly replaced "killer whale" in common usage.Although some sources suggest that Orcinus means 'of the kingdom of the dead', the International Code of Zoological Nomenclature mentions that the name orca originates from the Latin word orca, meaning 'a large-bellied pot.' Orcinus is a derived form created by adding a masculine suffix to it. Ancient Romans originally used orca for these animals, possibly borrowing Ancient Greek ὄρυξ, which was used for various whale species potentially including the narwhal.
They are sometimes referred to as 'blackfish', a term also used for other cetaceans. Historically, 'grampus' was another name for the species, though it is now rarely used. This usage should not be confused with the genus Grampus, which includes only Risso's dolphin.
Taxonomy
Orcinus orca is the only extant species recognized in the genus Orcinus and one of many species originally described by Carl Linnaeus in his landmark 1758 10th edition of Systema Naturae. Conrad Gessner wrote the first scientific description of an orca in his Piscium & aquatilium animantium natura of 1558, part of the larger Historia animalium, based on examination of a dead stranded animal in the Bay of Greifswald that had attracted a great deal of local interest.The orca is one of 35 species in the oceanic dolphin family, which first appeared about 11 million years ago. The orca lineage probably branched off shortly thereafter. Although it has morphological similarities with the false killer whale, the pygmy killer whale, and the pilot whales, a study of cytochrome b gene sequences indicates that its closest extant relatives are the snubfin dolphins of the genus Orcaella. However, a more recent study places the orca as a sister taxon to the Lissodelphininae, a clade that includes Lagenorhynchus and Cephalorhynchus. In contrast, a 2019 phylogenetic study found the orca to be the second most basal member of the Delphinidae, with only the Atlantic white-sided dolphin being more basal.
Types
The three to five types of orcas may be distinct enough to be considered different races, subspecies, or possibly even species. The IUCN reported in 2008, "The taxonomy of this genus is clearly in need of review, and it is likely that O. orca will be split into a number of different species or at least subspecies over the next few years." Although large variation in the ecological distinctiveness of different orca groups complicates simple differentiation into types, research off the west coast of North America has identified fish-eating "residents", mammal-eating "transients", and "offshores". Other populations have not been as well studied, although specialized fish and mammal eating orcas have been distinguished elsewhere. Mammal-eating orcas in different regions were long thought likely to be closely related, but genetic testing has refuted this hypothesis.A 2024 study supported the elevation of Eastern North Pacific resident and transient orcas as distinct species, O. ater and O. rectipinnus respectively. The Society for Marine Mammalogy declined to recognize the two species, citing uncertainty as to whether the types constituted unique species or subspecies. "Pending a more complete global review and revision", the Society provisionally recognized them as subspecies Orcinus orca ater and O. o. rectipinnus, with O. o. orca as the nominate subspecies.
Four types have been documented in the Antarctic, Types A–D. Two dwarf species, named Orcinus nanus and Orcinus glacialis, were described during the 1980s by Soviet researchers, but most cetacean researchers are skeptical about their status. Complete mitochondrial sequencing indicates the two Antarctic groups should be recognized as distinct species, as should the North Pacific transients, leaving the others as subspecies pending additional data. A 2019 study of Type D orcas also found them to be distinct from other populations and possibly even a unique species.
Characteristics
Orcas are the largest extant members of the dolphin family. Males typically range from long and weigh in excess of. Females are smaller, generally ranging from and weighing about. Orcas may attain larger sizes as males have been recorded at and females at. Large males can reach a weight of over, large females can reach a weight of over. Calves at birth weigh about and are about long. The skeleton of the orca is typical for an oceanic dolphin, but more robust. They can also reach speeds of up toWith their distinctive pigmentation, adult orcas are rarely confused with any other species. When seen from a distance, juveniles can be confused with false killer whales or Risso's dolphins. The orca is mostly black but with sharply bordered white areas. The entire lower jaw is white and from here, the colouration stretches across the underside to the genital area; narrowing and expanding some, and extending into lateral flank patches close to the end. The tail fluke is also white on the underside, while the eyes have white oval-shaped patches behind and above them, and a grey or white "saddle patch" exists behind the dorsal fin and across the back. Males and females also have different patterns of black and white skin in their genital areas. In newborns, the white areas are yellow or orange coloured. Antarctic orcas may have pale grey to nearly white backs. Some Antarctic orcas are brown and yellow due to diatoms in the water. Both albino and melanistic orcas have been documented.
Orca pectoral fins are large and rounded, resembling paddles, with those of males significantly larger than those of females. Dorsal fins also exhibit sexual dimorphism, with those of males about high, more than twice the size of the female's, with the male's fin more like an elongated isosceles triangle, whereas the female's is more curved. In the skull, adult males have longer lower jaws than females, as well as larger occipital crests. The snout is blunt and lacks the beak of other species. The orca's teeth are very strong, and its jaws exert a powerful grip; the upper teeth fall into the gaps between the lower teeth when the mouth is closed. The firm middle and back teeth hold prey in place, while the front teeth are inclined slightly forward and outward to protect them from powerful jerking movements.
Orcas have good eyesight above and below the water, excellent hearing, and a good sense of touch. They have exceptionally sophisticated echolocation abilities, detecting the location and characteristics of prey and other objects in the water by emitting clicks and listening for echoes, as do other members of the dolphin family. The mean body temperature of the orca is. Like most marine mammals, orcas have a layer of insulating blubber ranging from thick beneath the skin. The pulse is about 60 heartbeats per minute when the orca is at the surface, dropping to 30 beats/min when submerged.
An individual orca can often be identified from its dorsal fin and saddle patch. Variations such as nicks, scratches, and tears on the dorsal fin and the pattern of white or grey in the saddle patch are unique. Published directories contain identifying photographs and names for hundreds of North Pacific animals. Photographic identification has enabled the local population of orcas to be counted each year rather than estimated, and has enabled great insight into life cycles and social structures.