Killer Whales

Orca 09-13-09

Killer whales (or orcas) are not really whales but are the largest members of the dolphin family, Delphinidae. With their brilliant black and white markings, they are easy to identify and distinguish from other whales. Killer whales exhibit sexual dimorphism, meaning males and females look very different from each other. Adult males in the North Pacific may grow to a length of 27 ft. (8.2 m) and weigh as much as 13,300 lbs. (6,000 kg), while females grow to an average length of 23 ft. (7 m) and weigh about half as much as a large male. Also, a male’s dorsal fin may reach 6 ft. (2 m) in height, while a female’s rarely exceeds 3 ft (1 m).

Photo by Bob Munsey
Photo by Bob Munsey

Killer whales are mostly black on their dorsal surface and white on their ventral surface. They have an elliptical white patch on the lateral side of each eye and large white patches that extend from the ventral surface onto the flanks. There is a usually a gray or white saddle area behind the dorsal fin, and this marking varies from one individual to the next, making it useful for identification.

Killer whales are second only to humans as the most widely-distributed species of mammal. They can be found in all oceans and most seas, but they are most common in coastal, temperate waters. They are apex predators and prey on a variety of vertebrates and invertebrates. They are known to prey upon over 140 species, and they are the only cetaceans that routinely prey upon marine mammals, with documented attacks on 50 different species.

Orcas in Amook PassIn the northeastern Pacific, three distinct ecotypes of killer whales have been identified. Resident killer whales mainly eat fish, while transients concentrate on marine mammals. The third type known as offshores have not been well studied, but it is thought they primarily feed on fish, including sharks. All three types are genetically distinct, suggesting there is little or no breeding between the types, and it is possible they should be considered separate subspecies. There are differences in size, coloration and physical appearance between the three types, as well as differences in hunting strategies. Transients forage in smaller groups than residents, and transients travel silently when hunting, while residents produce a variety of clicks, whistles, and pulsed calls for echolocation.  Killer whale populations in other regions of the world may also specialize in their feeding habits, but more research is needed to be certain. Killer whales often work together to catch fish or marine mammals, and when preying on large animals such as whales, they may attack as a pack, tearing apart the whale from several angles.DSC_0155

Killer whales are very social and usually travel in groups or pods of up to 20 individuals, and members of a pod are linked to each other by maternal descent. Females become sexually mature at 15 years of age on average, and they may give birth at intervals of three to eight years. Killer whales can breed all year, and the gestation period averages 17 months. Whales in a pod often work together to care for the young, and young females will help mothers care for their babies. It has been estimated that males live at least 50 years on average, while females may live 80 years.

Killer whales are highly vocal and use sound for socialization as well as for echolocation.Scientists have learned that call repertoires of resident pods have features that are distinct to that pod, forming group-specific dialects. A second pod may share some of the call repertoire of the first pod, but other sections will be distinct to the second pod.   The amount of similarity of call repertoires between pods reflects the degree of

Photo by Bob Munsey
Photo by Bob Munsey

relatedness between the pods. Killer whales socialize in a number of other ways too, including acrobatic aerial behaviors, such as breaches, spy hops, flipper slaps, tail lobs,and head stands. I’ll discuss more about these various behaviors next week.

Killer whales are always a treat to watch. We only see them a few times a year deep inside Uyak Bay, and it is always exciting. I’ve seen a large group of killer whales herding fish, a small pod trying to catch harbor seals hauled out on an island, and one killer whale with a large octopus in its mouth. Sometimes they want nothing to do with us, and other times, they swim alongside our boat leaping out of the water and diving beneath us. This summer we saw a large bull swimming by himself in water so shallow he couldn’t submerge his tall dorsal fin. He was in an area near a salmon stream, and we assumed he was feeding on salmon.


Have you had any experiences with killer whales? If so, please leave a comment to tell us about it. Also, if you have any questions, don’t hesitate to ask, and for anyone who is a lover of true crime stories, please visit my home page and sign up for my monthly Mystery Newsletter!

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