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Orcinus orcakiller whale(Also: orca)

By Emily Burnett

Geographic Range

Orcinus orca is found living in all oceans of the world. They have been spotted from as far north as the Artic Ocean near pack ice to as far south as the Antarctic Ocean. Although Orcinus orca seems to prefer colder waters, they have also been observed in tropical waters. There seems to be no or very little migration due to weather and water temperature, but killer whales will move to other areas when food becomes scarce. (Estes, et al., 2006; Ford, et al., 2000; Heintzelman, 1981; Mann, et al., 2000)

Habitat

Killer whales live in aquatic marine habitats. They are found in all oceans of the world. Normally prefering depths of 20 to 60 m, killer whales also visit shallow waters along coastlines or dive to 300 m in search of food. Killer whales generally occupy the same home range year round. (Estes, et al., 2006; Heintzelman, 1981; Mann, et al., 2000; Norris, 2002; Slijper, 1979)

  • Range depth
    20 to 300 m
    65.62 to 984.25 ft
  • Average depth
    60 m
    196.85 ft

Physical Description

Killer whales have streamlined, black and white bodies. They are black on the dorsal surface, white extends from the bottom of the chin to just beyond the anus on the ventral surface. There is also a white spot above the eye. In both sexes there is a "saddle spot" which is a grey spot behind the dorsal fin on the back. In calves, their black is somewhat grey up to a year old. Also, the white on the calf's underside has a yellow tint to it until they reach 1 year old. The average length for a male adult is 8 m, with the maximum length at 9.75 m. The average length in females is 7 m with a maximum length of 8.5 m. Newborn calves are from 2 to 2.4 m long and weigh about 136 kg at birth. The average weight for a male killer whale is 7200 kg. Female average body size and weight is slightly smaller than that of males. In males, the erect dorsal fin can reach up to 1.8 m high; in females and immature males this dorsal fin is only about 0.9 m high. This fin curves over either to the right or left side. (Estes, et al., 2006; Heintzelman, 1981; Mann, et al., 2000; Watson, 1981)

  • Sexual Dimorphism
  • male larger
  • Average mass
    7200 kg
    15859.03 lb
  • Average mass
    3.9875e+06 g
    140528.63 oz
    AnAge
  • Range length
    9.75 (high) m
    31.99 (high) ft

Reproduction

Killer whales are polygynandrous; both males and females have multiple mates throughout a season or a lifetime. (Mann, et al., 2000; Payne, 1995; Robeck, et al., 2004)

While killer whales are difficult to study in the wild some of their reproductive habits have been recorded and studied in captive whales. Killer whales can reproduce whenever females enter estrus, which can occur mutiple times a year. However, most breeding happens in the summer, and killer whales are typically born in the fall. Females reach sexual maturity between 6 and 10 years of age. Males reach sexual maturity between 10 and 13 years old. Female killer whales begin to mate between 14 and 15 years of age. The youngest female whale on record to give birth was 11 years old. Females have a calf every 6 to 10 years and they stop breeding around the age of 40. The result is 4 to 6 offspring over a 25 year span. (Estes, et al., 2006; Mann, et al., 2000; Robeck, et al., 2004; Watson, 1981)

Gestation takes about 14 months, although a gestation length in captivity was recorded at 539 days. Killer whales have a single calf at a time, twins have only been recorded once. Newborn calves nurse for about a year before weaning. Some studies show that almost half of all newborn calves die before their first birthday. (Estes, et al., 2006; Mann, et al., 2000; Robeck, et al., 2004; Watson, 1981)

  • Breeding interval
    Females breed every 3 to 10 years.
  • Breeding season
    Breeding can occur at any time of the year, most often in the summer.
  • Range number of offspring
    1 (low)
  • Average number of offspring
    1
  • Average number of offspring
    1
    AnAge
  • Range gestation period
    12 to 18 months
  • Range weaning age
    12 to 24 months
  • Range age at sexual or reproductive maturity (female)
    6 to 10 years
  • Range age at sexual or reproductive maturity (male)
    10 to 13 years

Killer whale females invest a lot of energy in raising their offspring. They carry the calf for almost a year and a half, then give birth and nurse for another 12 months. During that time, mothers teach their calves to hunt and include their offspring in the social network of their pods. Because these animals are not monogamous, it is assumed that the fathers exhibit no parental involvement after mating. When a killer whale calf is born into a pod, it relies on its mother for nutrition and support. Calves remain in their natal pod after independence. (Estes, et al., 1998; Mann, et al., 2000; Robeck, et al., 2004; Slijper, 1979)

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female
  • post-independence association with parents
  • extended period of juvenile learning

Lifespan/Longevity

Killer whale mortality rate varies with the age of the animal. Neonatal mortality is very high, in captivity neonatal mortality is between 37% and 50%. The reason for these high mortality rates is unknown, but predation is not considered a primary threat during this time. After six months, mortality rates steadily decline as killer whales learn how to protect and nourish themselves. Mortality rates are said to be the lowest around 12 to 13 years in males and 20 years in females. The average lifespan for a female in the wild is around 63 years, with a maximum of 80 to 90 years. Male life expectancy is a bit shorter, with the average lifespan being around 36 years, with a maximum of 50 to 60 years. (de Magalhaes, et al., 2005; Mann, et al., 2000)

  • Range lifespan
    Status: wild
    90 (females) 60 (males) (high) years
  • Typical lifespan
    Status: wild
    63 (females) 36 (males) (high) years

Behavior

Killer whales are highly social and social structure is complex. They travel in pods which can contain several to as many as 50 individuals. There has even been reports of hundreds of individuals in one pod, but this was a temporary association between a group of smaller pods. Individuals in pods are generally multiple generations of related individuals and made up of about 20% mature males, 20% calves, and 60% females and immature males. Killer whales have limited dispersal from the maternal pod and young whales are always part of their mother's pod. Individuals in pods swim within 100 meters of each other and coordinate their activities. They may share prey and rarely leave the pod for more than a few hours. Killer whales teach pod members through apprenticeship. Skill in hunting and parenting are among the skills taught to younger whales. (Mann, et al., 2000; Matthews, 1978)

Home Range

Home range size is unknown, but some studies have shown that killer whales live with their pods together in their home range for many years. While home range size is unknown, they have been documented to swim up to 160 km a day. (Mann, et al., 2000; Matthews, 1978)

Communication and Perception

There are 3 categories of vocalizations used by killer whales: whistles, discrete calls, and clicks. Vocalizations are used both for communication and navigation. They use discrete calls and whistles when communicating within and among pods. Each pod has their a discrete dialect that sounds slightly different from that of other pods. This dialect has been shown to stay the same in a pod for up to six generations. Clicks seem to be used only for echolocation. Killer whales do have good vision, but in dark water their vision is not helpful in catching prey or navigating. As in other toothed whales, killer whales use sonar to perceive their aquatic environment.

The whale's ears are very small openings behind the eyes, which have no outer flap. The killer whale hears the whistles and clicks through an auditory bulla (earbone complex) in its lower jaw. The sound waves enter through the jaw where they then enter into the earbone complex. In this auditory bulla, there are bones that are like the bones found in the human ear. They waves travel trough these bones, then enter into the brain via an auditory nerve. (Bower, 2000; Deeke, et al., 2005; Estes, et al., 2006; Mann, et al., 2000; Miller, 2006; Norris, 2002)

Food Habits

Killer whales are exceptionally successful predators. Orcinus orca diet is difficult to study and is most frequently assessed through looking at stomach contents. They eat a wide variety of large prey including: seals, sea lions, smaller whales and dolphins, fish, sharks, squid, octopi, sea turtles, sea birds, sea otters, river otters, and other animals. Killer whales eat on average 45 kg of food a day, but they can eat much more than that. They swallow small prey whole, but tend to tear up larger prey before consumption. Killer whales are social hunters, as are wolves and lions. They often hunt in packs and use coordinated social behavior and communication to hunt prey larger than themselves, such as larger whales. (Heintzelman, 1981; Mann, et al., 2000; Watson, 1981)

  • Animal Foods
  • birds
  • mammals
  • reptiles
  • fish
  • mollusks
  • aquatic crustaceans

Predation

Killer whales have no natural predators, although young killer whales may be attacked by other killer whales or large sharks. They are at the top of the marine food chain. Humans sometimes prey on killer whales, but not in great numbers. (Mann, et al., 2000; Matthews, 1978)

Ecosystem Roles

Killer whales are top predators in most marine ecosystems and impact the populations of common prey, such as seals and sea lions in breeding areas. Killer whales are host to some endoparasites and ectoparasites. They are host to killer whale lice (Cyamus orcini), trematodes (Fasciola skiranini), cestodes (Trigonocotyle spasskyi), and nematodes (Anasakis simplex).

A disease that affects killer whales and is often studied is toxoplasmosis (Toxoplasma gondii). While this parasite is often benign, it can have serious and fatal effects. (Chadwick, 2001; Murata, et al., 2004; Estes, et al., 1998; Heyning and Dahlheim, 1988; Mann, et al., 2000)

Commensal/Parasitic Species
  • killer whale lice (Cyamus orcini)
  • trematodes (Fasciola skirabini)
  • cestodes (Trigonocotyle fasciola)
  • nematodes (Anasakis simplex)

Economic Importance for Humans: Positive

Killer whales are hunted and used for a number of things. In various parts of the world, they are used for oil and meat. Meat is sold for human consumption or used for fertilizer or bait. (de Magalhaes, et al., 2005; Estes, et al., 2006; Heyning and Dahlheim, 1988; Mann, et al., 2000)

  • Positive Impacts
  • food
  • body parts are source of valuable material

Economic Importance for Humans: Negative

There are no known adverse effects of Orcinus orca on humans.

Conservation Status

According to the IUCN red list there is insufficient data about killer whale populations to assess their status. The data on the endangered species act list states that killer whales are endangered. They are on Appendix II of the CITES site, which means they are not threatened by extinction, but conservation efforts must be employed to help keep them from moving closer to extinction. Killer whales have not been as directly impacted by human exploitation as other whale species. They are occasionally hunted but management of harvests seems to have been effective. (Mann, et al., 2000)

Other Comments

The fossil history of killer whales dates to the Pliocene epoch, about 5 million years ago. The fossil history is not rich, but some finds link Orcinus orca to its early ancestors. Teeth, partial skulls, jaw bones, and periotic bones (found in a mammal's ear) have been found and identified in many countries of the world, including: Japan, Hungary, Italy, and South Africa. (Heyning and Dahlheim, 1988)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Emily Burnett (author), Radford University, Karen Powers (editor, instructor), Radford University.

Glossary

Arctic Ocean

the body of water between Europe, Asia, and North America which occurs mostly north of the Arctic circle.

Atlantic Ocean

the body of water between Africa, Europe, the southern ocean (above 60 degrees south latitude), and the western hemisphere. It is the second largest ocean in the world after the Pacific Ocean.

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

cooperative breeder

helpers provide assistance in raising young that are not their own

cosmopolitan

having a worldwide distribution. Found on all continents (except maybe Antarctica) and in all biogeographic provinces; or in all the major oceans (Atlantic, Indian, and Pacific.

diurnal
  1. active during the day, 2. lasting for one day.
echolocation

The process by which an animal locates itself with respect to other animals and objects by emitting sound waves and sensing the pattern of the reflected sound waves.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

food

A substance that provides both nutrients and energy to a living thing.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

molluscivore

eats mollusks, members of Phylum Mollusca

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

piscivore

an animal that mainly eats fish

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

young precocial

young are relatively well-developed when born

References

Bower, B. 2000. Culture of the Sea. Science News, Vol. 158, Iss.18: 284-286.

Chadwick, D. 2001. Evolution of Whales. National Geographic, Vol. 200 Issue 5: 64-78.

Deeke, V., J. Ford, P. Slater. 2005. The Vocal Behaviour of Mammal-Eating Killer Whales: Communicating with costly calls. Animal Behaviour, 69/2: 385-405.

Estes, J., M. Tinker, T. Williams, D. Doak. 1998. Killer Whale Predation on Sea Otters Linking Oceanic and Nearshore Ecosystems. Science, New Series, Vol. 282 No. 5388: 473-476.

Estes, J., D. Demaster, D. Doak, T. Williams, R. Brownell, Jr.. 2006. Whales, Whaling, and Ocean Ecosystems. Berkely and Los Angeles, California; London, England: University of California Press.

Ford, J., G. Ellis, K. Balcomb. 2000. Killer Whales. University of Washington Press, unknown: 104.

Heintzelman, D. 1981. A World Guide to Whales, Dolphins, and Porpoises. Tulsa, Oklahoma 74101: Winchester Press.

Heyning, J., M. Dahlheim. 1988. Orcinus orca. Mammalian Species, 304: 1-9.

Mann, J., R. Connor, P. Tyack, H. Whitehead. 2000. Cetacean Societies: Field Studies of Dolphins and Whales. Chicago, Illinois: The University of Chicago Press, Chicago 60637; The University of Chicago Press, Ltd., London.

Matthews, L. 1978. The Natural History of the Whale. Great Britan and New York: Columbia University Press; Weidenfeld and Nicolson.

Miller, P. 2006. Diversity in Soundpressure Levels and Estimated Active Space of Resident Killer Whale Vocalizations. Journal of Comparative physiology, 192: 449-459.

Murata, K., K. Mizuta, K. Imazu, F. Terasawa, M. Taki, T. Endoh. 2004. The Prevalence of Toxoplasma gondii Antibodies in Wild and Captive Cetaceans from Japan.. The Journal of Parasitology, 90: 896-898.

Norris, S. 2002. Creatures of Culture? Making the Case for Cultural Systems in Whales; and Dolphins. Bioscience, vol. 52, no. 1: 9-14.

Payne, R. 1995. Among Whales. New York, New York 10020: Charles Scribner's Sons.

Robeck, T., K. Steinman, S. Gearhart, J. Reidarson, S. Monfort. 2004. Reproductive Physiology and Development of Artificial Insemination Technology in Killer Whales. Biology of Reproduction, Vol. 71 no. 2: 650-660.

Slijper, E. 1979. Whales. Ithaca, New York: Hutchinson and Co. ; Cornell University Press.

Watson, L. 1981. Whales of the World. New York, New York: Elsevier-Dutton Publishing Company.

de Magalhaes, J., J. Costa, O. Toussaint. 2005. "HAGR: Human Ageing Genomic Resources" (On-line). Accessed December 01, 2008 at http://genomics.senescence.info/species/entry.php?species=Orcinus_orca.

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