The killer whale, also known as the "orca," is one of the most well-known types of whales. Killer whales are commonly the star attractions at large aquariums and due to these aquariums and movies, may also be known as "Shamu" or "Free Willy."
Despite their somewhat derogatory name and large, sharp teeth, fatal interactions between killer whales and humans in the wild have never been reported. (Read more about fatal interactions with captive orcas).
With their spindle-like shape and beautiful, crisp black and white markings, killer whales are striking and unmistakable.
The maximum length of killer whales is 32 feet in males and 27 feet in females. They can weigh up to 11 tons (22,000 pounds). All killer whales have dorsal fins, but the males is larger than females, sometimes reaching 6 feet tall.
Like many other Odontocetes, killer whales live in organized family groups, called pods, which range in size from 10-50 whales. Individuals are identified and studied using their natural markings, which include a grayish-white "saddle" behind the whale's dorsal fin.
- Kingdom: Animalia
- Phylum: Chordata
- Class: Mammalia
- Order: Cetacea
- Suborder: Odontoceti
- Family: Delphinidae
- Genus: Orcinus
- Species: orca
While killer whales were long considered to be one species, there now appear to be many species, or at least subspecies, of killer whales. These species/subspecies differ genetically and also in appearance.
Habitat and Distribution
According to the Encyclopedia of Marine Mammals, killer whales are "second only to humans as the most widely distributed mammal in the world." Even though they range across temperate areas of the oceans, killer whale populations are more concentrated around Iceland and northern Norway, along the northwestern coast of the U.S. and Canada, in the Antarctic and Canadian Arctic.
Killer whales eat a wide array of prey, including fish, sharks, cephalopods, sea turtles, seabirds (e.g., penguins) and even other marine mammals (e.g., whales, pinnipeds). They have 46-50 cone-shaped teeth that they use to grasp their prey.
Killer Whale "Residents" and "Transients"
The well-studied population of killer whales off the western coast of North America has revealed that there are two separate, isolated populations of killer whales known as "residents" and "transients." Residents prey on fish and move according to the migrations of salmon, and transients prey primarily on marine mammals such as pinnipeds, porpoises, and dolphins, and may even feed on seabirds.
Resident and transient killer whale populations are so different that they don't socialize with each other and their DNA is different. Other populations of killer whales are not as well studied, but scientists think that this food specialization might occur in other areas as well. Scientists are now learning more about a third type of killer whale, called "offshores," which live in the area from British Columbia, Canada to California, don't interact with resident or transient populations, and are not usually seen inshore. Their food preferences are still being studied.
Killer whales are sexually mature when they are 10-18 years old. Mating seems to take place throughout the year. The gestation period is 15-18 months, after which a calf about 6-7 feet long is born. Calves weigh about 400 pounds at birth and will nurse for 1-2 years. Females have calves every 2-5 years. In the wild, it is estimated that 43% of calves die within the first 6 months (Encyclopedia of Marine Mammals, p.672). Females reproduce until they are about 40 years old. Killer whales are estimated to live between 50-90 years, with females generally living longer than males.
Since 1964, when the first killer whale was captured for display in an aquarium in Vancouver, they have been a popular "show animal," a practice that is becoming more controversial. Until the 1970's, killer whales were captured off the western coast of North America, until populations there began to decrease. Subsequently, since the late 1970's, killer whales captured in the wild for aquariums have mostly been taken from Iceland. Today, breeding programs exist in many aquariums and that has lessened the need for wild captures.
Killer whales have also been hunted for human consumption or because of their predation on commercially-valuable fish species. They are also threatened by pollution, with the population off British Columbia and Washington state having extremely high levels of PCBs.
- American Cetacean Society. 2004. Orca (Killer Whale). (Online). American Cetacean Society Fact Sheet. Accessed February 27, 2010.
- Kinze, Carl Christian. 2001. Marine Mammals of the North Atlantic. Princeton University Press.
- Mead, James G. and Joy P. Gould. 2002. Whales and Dolphins In Question. Smithsonian Institution.
- Perrin, William F., Bernd Wursig and J.G.M. Thewissen. 2002. Encyclopedia of Marine Mammals. Academic Press.