Orcinus orca

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.

• Biogeographic Regions
• arctic ocean arctic ocean
• indian ocean
• atlantic ocean atlantic ocean
• pacific ocean pacific ocean

• Other Geographic Terms
• cosmopolitan cosmopolitan

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.

• Habitat Regions
• temperate temperate
• tropical tropical
• saltwater or marine saltwater or marine

• Aquatic Biomes
• pelagic pelagic
• coastal coastal

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.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• male larger

Reproduction

Killer whales are polygynandrous; both males and females have multiple mates throughout a season or a lifetime.

• Mating System
• polygynandrous (promiscuous) polygynandrous (promiscuous)
• cooperative breeder cooperative breeder

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.

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.

• Key Reproductive Features
• iteroparous iteroparous
• year-round breeding year-round breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• viviparous viviparous

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.

• Parental Investment
• precocial 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.

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.

• Key Behaviors
• natatorial natatorial
• diurnal diurnal
• motile motile
• sedentary sedentary
• territorial territorial
• social social

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.

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.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• echolocation echolocation
• chemical chemical

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 .

• Primary Diet
• carnivore carnivore
  • eats terrestrial vertebrates
  • piscivore piscivore
  • molluscivore molluscivore

• 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.

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.

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.

• Positive Impacts
• food 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.

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.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

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

References

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