Killer whale - Orcinus orca

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Killer whales are among the most distinctive, and therefore easily identified, of all cetaceans. The black-and-white color pattern is unmistakable. The lower jaw, undersides of the flukes, and ventral surface from the tip of the lower jaw to the urogenital area is white. White lobes extend up the sides behind the dorsal fin, and there is a white oval patch above and behind each eye. The rest of the body is black, except for a light-gray "saddle patch" behind the dorsal fin. In some populations, the dorsal coloration includes a narrow black cape, below which the dark areas are more nearly charcoal gray.

Their tall, erect dorsal fin is nearly as distinctive as their color pattern, reaching 0.9 m in females and 1.8 m in males. Adult males tend to have dorsal fins that are triangular or that may even cant forward to varying degrees. Killer whales have blunt snouts with short, poorly-defined beaks. The flippers are large and oval, and grow to lengths of up to 2 m in bulls.

There are 10-12 large, recurved teeth in each half of both jaws, which are oval in cross section. In older animals, they are often worn and damaged by abscesses. Adult females are up to 8.5 m and 7,500 kg; adult males up to 9.8 m and nearly 10,000 kg. Newborn killer whales are 2.1-2.4 m in length and about 180 kg in weight.

Killer whales are easily recognizable. The great size of the dorsal fin (especially of adult males) and unique black and white color pattern are diagnostic. At a distance, groups without adult males can be confused with Risso’s dolphins and false killer whales.

This is probably the most cosmopolitan of all cetaceans. Killer whales can literally be seen in any marine region, and they have even been known to ascend rivers. Killer whales are found in all oceans and seas, from the ice edges to the equator, in both hemispheres; however, they appear to be more common in nearshore, cool temperate to subpolar waters.

Killer whales are generalists when it comes to habitat. Studies in the eastern North Pacific, from Washington State to Alaska, have distinguished two types of killer whales, referred to as residents and transients. Although distinguished by ecological differences, there are also differences in coloration and external morphology. mDNA restriction patterns provide evidence that these groups are genetically distinct. A third designation, “offshore” is also recognized on the Pacific Coast of the U.S. and Canada. In Washington and British Columbia, at least, residents are primarily fish eaters and transients eat mostly marine mammals. Some studies in other parts of the world suggest that this pattern may be universal.

Pods of resident killer whales in British Columbia and Washington represent one of the most stable societies known among non-human mammals; individuals stay in their natal pod throughout life. Differences in dialects among sympatric groups appear to help maintain pod discreteness. Most pods contain 1-55 whales and resident pods tend to be larger than those of transients. In the Pacific Northwest, calving occurs year-round, with a peak from October to March. Similarly, in the northeast Atlantic, it occurs from late fall to mid-winter. Migration, where it occurs, is probably related to the movements of prey.

Killer whales have a broad diet. Though best known for their habits of preying on warm-blooded animals (killer whales are known to have attacked marine mammals of all groups, from sea otters to blue whales, except river dolphins and manatees), killer whales often eat various species of fish and cephalopods. Killer whales also occasionally eat seabirds and marine turtles. It is thought that different pods of killer whales specialize in different types of prey. They feed by seizing prey.

Killer whales have been documented cooperatively herding schools of herring, driving them into tight balls and stunning them with slaps with their flukes. They exhibit a wide range of predation strategies when hunting larger prey, including drowning their prey, ramming them, throwing them into the air with mouth, beak, or flukes, and intentionally stranding or breaking through ice from below. When killer whales attack large prey, such as other whales, they rip parts of their kill off the carcass and eat them. They often leave large portions of their prey uneaten in this case.

Known prey species include:

Mammals: Alces alces, Lagenorhynchus obliquidens, Baleanoptera acuterostrata, Eschtrichtius robustus, Lagenorhynchus obscurus, Enhydra lutris, Physeter macrocephalus, Baleanoptera edeni, Mirounga leonina, Phoca vitulina, Phocoenoides dalli, Eumetopias jubatus, Megaptera novaeanglia, Phocoena phocoena, Pontoporia blainvillei, Zalophus californianus, Eumetopias jubatus, Monodon monoceros, Odobenus rosmarus, Delphinapterus leucas, Lobodon carcinophagus, Otaria flavescens, Lagenorhynchus obliquidens, Hyperoodon ampullatus

Fish: Clupea harengus, Oncorhynchus sp., Oncorhynchus kisutch, Oncorhynchus tshawytscha, Clupea pallusii, Hippoglossus stenolepis, Isurus oxyrinchus, Carcharodon carcharias, Myliobatus sp., Reinhardtius hippoglossoides, Anoplopoma fimbria, Atheresthes stomias, Thunnus sp., Xiphias gladius, Bathymaster signatus, Hyperoglyphe porosa, Salmo sp., Scomber scombrus, Gadus morhua, Pollachius virens

Birds: Eudyptes sp., Spheniscus demersus, Tachyeres leucocephalus, Somateria molissima, Alle alle, Fulmaris glacialis

Invertebrates: Loligo sanpaulensis, Loligo plei, Lycoteuthis lorigera, Octopoteuthis sp., Moroteuthis robsoni, Gonatus antarcticus, Histioteuthis spp., Ornithoteuthis antillarum, Ommastrephes bartramii, Cranchiidae, Ocythoe tuberculata

Reptiles: Dermochelys coriacea

Main threats include:

• Pollution

• Habitat degradation

• Ship strikes

The IUCN lists the killer whale as “lower risk/conservation dependent”, in that programs are in place regionally that address conservation concerns. The killer whale is not considered threatened or endangered by the United States government, but the Eastern North Pacific Southern Resident stock (estimated at 82 individuals) was listed as “depleted” under the Marine Mammal Protection Act in early 2003. In addition, the resident stock in British Columbia is listed as threatened by the Canadian Government.

Killer whales have at one time or another been targets of both commercial and subsistence whalers, although never on a large scale. They have also been persecuted because of real or perceived interference with fisheries and threats to humans. Entanglements in fishing nets, vessel collisions, and live-captures for oceanaria have also contributed to their problems. Recently, the effects of high levels of environmental contaminants have become of concern, especially for Pacific Northwest animals. Although not considered to be highly abundant anywhere, killer whale populations in many areas appear to be healthy.

• iOBIS
• World Register of Marine Species (WoRMS)
• Encyclopedia of Life
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• Integrated Taxonomic Information System (ITIS)
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Baird, R.W. 2000. The killer whale foraging specializations and group hunting. pp. 127-153 in J. Mann, R.C. Connor, P.L. Tyack and H. Whitehead, eds. Cetacean societies field studies of dolphins and whales. University of Chicago Press.

Baird, R.W. 2001. Status of killer whales, Orcinus orca, in Canada. Canadian Field-Naturalist 115:676-701.

Dahlheim, M.E. and J.E. Heyning. 1999. Killer whale Orcinus orca (Linneaus, 1758). pp. 281-322 in S.H. Ridgway and R. Harrison, eds. Handbook of marine mammals, Vol. 6: The second book of dolphins and the porpoises. Academic Press.

Ford, J.K.B. 2002. Killer whale Orcinus orca. pp. 669-676 in W.F. Perrin, B. Würsig and J.G.M. Thewissen, eds. Encyclopedia of marine mammals. Academic Press.

Ford, J.K.B., G.M. Ellis and K.C. Balcomb. 1994. Killer Whales. University of British Columbia Press.

Ford, J.K.B. and G.M. Ellis. 1999. Transients mammal-hunting killer whales. University of British Columbia Press.

Matkin, C.O. and E.L. Saulitis. 1994. Killer whale (Orcinus orca) biology and management in Alaska. Marine Mammal Commission Report.

Simila, T., J.C. Holst and I. Christenen. 1996. Occurance and diet of killer whales in northern Norway seasonal patterns relative to the distribution and abundance of Norwegian spring-spawning herring. Canadian Journal of Fisheries and Aquatic Science 53 769-779.

Waring, G.T., J.M. Quintal and C.P. Fairfield. 2002. U.S. Atlantic and Gulf of Mexico Marine Mammal Stock Assessments – 2002. U.S. Department of Commerce, NOAA technical memorandum, NMFS-NE-169.