- Also called:
- orca
killer whale
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What is a killer whale?
The killer whale, or Orcinus orca, is the largest member of the dolphin family Delphinidae. Killer whales are easily identifiable due to their size and distinct coloring, which includes a jet-black top and a pure white bottom, along with a white patch behind each eye. They also possess a variable "saddle patch" located just behind their dorsal fin.
Killer whales are distributed across all oceans, from polar ice caps to the Equator. They live in small groups called pods, which typically contain fewer than 40 individuals. Known for their intelligence, killer whales are among the few nonhuman animals capable of recognizing themselves in a mirror.
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Why are killer whales considered mammals?
Killer whales are classified as mammals due to several key characteristics. Like all mammals, killer whales nourish their young with milk produced by mammary glands. They also share unique mammalian traits such as hair (though only present during the fetal stage in many whales), a lower jaw hinged directly to the skull, three tiny bones that transmit sound waves in the middle ear, and a muscular diaphragm separating the heart and lungs from the abdominal cavity.
Additionally, killer whales are warm-blooded, maintain a constant internal body temperature, breathe air with lungs, and possess a four-chambered heart. These traits, along with the characteristic of bearing live young (viviparous), firmly place killer whales within the mammalian class.
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Where do killer whales live in the ocean?
Killer whales, or orcas, are distributed patchily throughout all the world's oceans, from polar ice caps to the Equator, in areas with many large prey animals such as tuna, salmon, and seals. They can be found along the Alaskan coast, in British Columbia and Washington waterways, and off the coast of Baja California in the North Pacific. In the North Atlantic, killer whales live in waters off of Newfoundland and Labrador to Iceland, Norway, and the British Isles. They can be seen off the coasts of Argentina, South Africa, New Zealand, and the Galapagos Islands in the Southern Hemisphere.
Killer whales are apex predators, meaning they have no natural predators and sit at the top of the food chain in their oceanic habitats. They are known for hunting in groups called pods, using diverse and effective hunting techniques to capture prey ranging from fish and seals to other whales. They may be evolving into separate species, with some preferring to remain near shore and others offshore.
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What do killer whales eat?
Killer whales, also known as orcas, are apex predators with a varied diet that depends on their location and hunting habits. They are toothed whales that actively hunt for their food.
Resident pods primarily eat fish, especially salmon, while transient pods consume other cetaceans, seabirds, and seals. They also eat squid, sea lions, penguins, whales, and porpoises. Killer whales have been observed disabling their prey before eating it and can tear apart larger animals that cannot be swallowed whole. They have strong jaws and teeth for grabbing and tearing their prey.
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How do killer whales communicate with each other?
Killer whales, or orcas, use a variety of vocalizations to communicate, including clicks, whistles, grunts, moans, squeaks, and pulsed calls. These sounds help them navigate, share information, find food and other whales, and compete for resources.
Toothed whales, including killer whales, produce high-pitched clicking sounds, typically ranging from 5 to 150 kHz, by blowing air through vibrating tissue in their nasal passages. The clicking sound travels through a fatty organ called the melon, located on the whaleâs forehead, and then out into the water. When these sound waves strike an object, they bounce back to the whale, and the vibrational energy is conveyed to the whaleâs inner ear via a structure called the acoustic window in the lower jaw.
Killer whales also use echolocation for feeding and communication. They can vary the frequency of the sound to gain information about the size of a target. High-frequency sound waves reflect better from small targets than low-frequency sound waves.
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How do killer whales care for their young?
Killer whales, like all cetaceans, exhibit social behavior, with the basic unit being a mother and her calf. Gestation lasts about a year, after which mothers give birth to a single calf tail first. Calves are relatively large at birth, and they nurse for about six months with milk that has a high fat content. These close-knit groups, called pods, often consist of related individuals that travel and feed together. Older females within the pod may share food with the rest of the group, which may increase the pod's overall success. Cetaceans also exhibit epimeletic behavior, where healthy animals care for those that are temporarily incapacitated.
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killer whale, (Orcinus orca), largest member of the dolphin family (Delphinidae). The killer whale is easy to identify by its size and its striking coloration: jet black on top and pure white below with a white patch behind each eye, another extending up each flank, and a variable âsaddle patchâ just behind the dorsal fin. Despite the fact that this cetacean is a powerful carnivore, there is no record of its having killed humans in the wild. Dozens of killer whales have been kept in captivity and trained as performers, a practice that in the 21st century was increasingly viewed as unethical.
Natural history
The largest males attain a length of more than 10 metres (32.8 feet) and a weight of about 9,800 kg (about 10 metric tons or 11 short [U.S.] tons), whereas females reach about 8.5 metres (27.8 feet) and weigh significantly less than males. Males also have proportionally larger appendages, with flippers up to 2 metres (6.6 feet) longâapproximately 20 percent of the body lengthâand almost 1 metre (3.3 feet) wide. Flipper length among females is 11â13 percent of body length. The dorsal fin of older males is very tall (up to 1.8 metres [5.9 feet]) and straight; females and young males have a dorsal fin that is about half that size and distinctly sickle-shaped (falcate). The skull is a metre or more in length and holds the largest brain of all the dolphins, averaging 5.6 kg (12.3 pounds). The muscles that close the mouth are enormous, and within the jaws is a set of more than 40 interlocking curved teeth. Most of the teeth are large, measuring about 10 cm (4 inches) long and 4 cm (1.6 inches) wide.
The killer whale has a patchy distribution in all oceans, from the polar ice caps to the Equator, where large prey such as tuna, salmon, and seals are abundant. Other food sources are squids, sea lions, penguins, whales, and porpoises. In the North Pacific several populations live along the Alaskan coast, in the intracoastal waterways of British Columbia and Washington, and off the coast of Baja California. In the North Atlantic they can be found from the waters off Newfoundland and Labrador to Iceland, Norway, and the British Isles. In the Southern Hemisphere killer whales can be seen off the coasts of Argentina, South Africa, New Zealand, and the Galapagos Islands.
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Killer whales live in small groups, usually called pods, that number fewer than 40 individuals each. Resident pods and transient pods have been differentiated within the populations of British Columbia and Washington. Sound production and diet differ between them, with resident pods (that is, those that inhabit Puget Sound and nearby coastal waters) eating fish (primarily salmon) and transients (that is, those that range over larger areas of coastal waters) eating other cetaceans, seabirds, and seals. Echolocation is used by killer whales in feeding and communication.
Known to be highly intelligent, killer whales are among the few nonhuman animals to be able to recognize themselves in a mirror. Killer whales are also one of the small number of speciesâalong with human beings (Homo sapiens), short-finned pilot whales (Globicephala macrorhynchus), false killer whales (Pseudorca crassidens), belugas (Delphinapterus leucas), and narwhals (Monodon monoceros)âthat experience menopause (that is, the stoppage of ovulation prior to the end of their natural lives). The circumstances under which menopause evolved in killer whales are a matter of debate, but it may have emerged in response to increases in the mortality of offspring from older generations during times when mothers and their daughters bred simultaneously. Some scientists argue that younger females in the pod tend to focus on the success of their own offspring and may be more competitive for food resources than older females (see competition). Killer whale pods are extended families that have matriarchal hierarchies (see also dominance hierarchy). The older females, tending to focus on the success of the overall pod, may be more willing to share food with the rest of the pod, thereby reducing the amount of food that could be given to their own offspring.
Evolution
The evolutionary record of the genus Orcinus is scanty. The earliest fossil identified as a killer whale is O. citonensis from the Pliocene Epoch (5.3 million to 2.6 million years ago) in Italy. This small mammal was about 4 metres long (13.1 feet) and had 14 teethâmore like a typical dolphin. This implies that the ancestors of the present-day killer whale diverged from other cetaceans during the Miocene Epoch (23 million to 5.3 million years ago); most dolphin evolution took place near the beginning of this epoch.
Although the taxonomy of the killer whale is clear at the genus level and at the family level (Delphinidae), relationships between killer whales and other toothed whales (suborder Odontoceti) are ambiguous. The false killer whale (Pseudorca crassidens), pygmy killer whale (Feresa attenuata), Rissoâs dolphin (Grampus griseus), and pilot whales (Globicephala species) have been thought to be relatives of the killer whale. Killer whales are sometimes assigned to one or another subfamily of the Delphinidae: Orcininae (killer whales and kin) or Globicephalinae (pilot whales and kin). More than 20 species names have been applied to the killer whale, but a consensus now recognizes only O. orca. Killer whales were formerly referred to as grampuses, but that term is now a synonym for Rissoâs dolphin.
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Evidence suggests that O. orca is in the process of diverging into two species in the North Atlantic. Based on genetic analysis and studies of body size and tooth wear, scientists contend that two separate populations with distinct feeding habits and morphological characteristics have arisen. One population, characterized by relatively small individuals with a maximum length of 6.6 metres (21.7 feet) and significant tooth wear, preys on fish, seals, and other animals. In contrast, the other population, characterized by larger individuals that can grow to a length of 8.5 metres (27.9 feet) and possess relatively little tooth wear, is thought to feed solely on whales and other dolphins.
There is evidence that killer whale speciation may also be occurring in the North Pacific, where as many as three genetically divergent groups exist with significantly different dispersal patterns, calls, social structure, and diets. These groups are called âresidentsâ (fish-eating populations primarily located in the Sea of Okhotsk and the western part of the Bering Sea), âtransientsâ (mammal-eating populations inhabiting the Gulf of Alaska, the eastern Aleutian Islands, and the eastern Bering Sea), and âoffshoresâ (killer whales located along the west coast of North America between the Queen Charlotte Islands and California).