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.
Can be Confused With
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.
Ecology and Behavior
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.
Feeding and 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.
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.
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