Description and Fascinating Facts
The orca, also known as the killer whale, is actually a dolphin. It is the largest of the dolphin family (Family Delphinidae: 32 species, including the dolphins, pygmy killer whales (Feresa attenuata) and false killer whales (Pseudorca crassiddens). Orcas reach a maximum length of over 9 m (30 ft) and can weigh 7,257 kg (16,000 lbs).
Killer whales along the coast of British Columbia and Washington are among the most studied whales in the world. Intensive field research in this region has been undertaken for 43+ years. These studies have provided increased knowledge about these whales, yet there still is much to be learned.
Killer whales are the ultimate (apex) predators of the world’s oceans, above even great white sharks. Here in the Pacific Northwest, they serve as ambassadors of one of the richest marine ecosystems on our planet. However, the bio-diversity in the Pacific Northwest is astonishing and includes many other marine mammals: minke whales, gray whales, humpback whales, Dall’s porpoise, harbour porpoise, California sea lions, harbor seals, elephant seals, Steller sea lions, and an unbelievable range of marine birds.
Because of their fierce reputation, orcas are sometimes called the ballena asesina or “assassin whale” by the Spanish. They were referred to as “whale killers” by sailors who witnessed their attacks on larger cetaceans, and over time this name was changed to “killer whales.” They are called this not because they harm humans but because they do sometimes kill other whales, hunting them in packs thereby earning the title “wolves of the sea”. Orcinus is probably derived from Orcus, an ancient mythological Roman god of the netherworld – a reference to the ferocious reputation of this animal. Orca literally means “the shape of a barrel or cask” in Latin, likely due to the killer whale’s body shape. Orcas are usually seen travelling in pods of between 3–45 individuals, usually including at least one large male.
World Range and Habitat
Next to humans, orcas are the most widely distributed mammal. Orcas inhabit all oceans of the world but are most numerous in the Arctic, the Antarctic and areas in nutrient-rich cold-water upwellings such as the Pacific Northwest. They have been sighted along the shores of Washington, Oregon, California, Baja California, and along the eastern coast of the United States. In addition to cold water areas, orca also have been seen in warm water areas such as Hawaii, Australia, the Galapagos Islands, the Bahamas, and the Gulf of Mexico. Such sightings are infrequent, but they do demonstrate the orcas ability to venture into tropical waters. Even more surprising, orcas have been seen in fresh water rivers around the world such as the Rhine, the Thames, and the Elbe. One orca was reported to have even travelled some 177 km (110 miles) up the Columbia River in search of fish. Although orca can be found in both the open ocean and coastal waters, they primarily inhabit the continental shelf in waters less than 200 m (660 ft) deep. In cold water areas, their distribution is limited by seasonal pack ice.
Active and opportunistic, orca are the apex predators in the ocean. In fact, they are the largest warm-blooded predator ever known. Fishes, squids, seals, sea lions, walruses, birds, sea turtles, otters, penguins, cetaceans (both mysticete and odontocete), polar bears, reptiles, and even a moose have all been found in the stomach contents of orcas. The diets of orcas vary from one region to another. In the Antarctic, orcas eat about 67% fishes, 27% marine mammals and 6% squid. In the Bering Sea near Alaska, they eat about 65% fishes, 20% squids and 15% marine mammals. The diets of resident and transient orcas differ as well. Resident pods eat a wide variety of fishes and rarely seek out marine mammals. Transient groups primarily eat marine mammals and occasionally eat fishes. Adult orcas eat approximately 3% to 4% of their body weight in food per day; fully weaned calves can eat up to approximately 10% of their body weight during growth periods. Much like packs of wolves or prides of lions, orcas often hunt cooperatively in pods for food. They work together to herd prey into a small area before attacking. When hunting a large whale, a pod of orcas may attack from several angles.
Studies of orcas in marine zoological facilities suggest that females become sexually mature when they reach 4.6–4.9 metres long (16 ft), at about 10–14 years. Males usually become sexually mature when they reach about 5.5–6 m (20 ft), at about 14–19 years. Breeding may occur in any season, but it is most common in the summer. In the North Atlantic, mating seems to peak in October and November; in the western North Pacific, mating seems to be at its highest between May and June, and mating seems to be at its highest between May to September around the Pacific Northwest region (southern resident killer whale community). The gestation period of an orca is about 17 months – the longest known of all cetaceans. A female may bear a calf every 3–5 years totalling approximately 4–6 offspring in her lifetime, although a decade may pass before some have another successful birth.
Calves are born in the water. The majority of deliveries seen by humans have been tail-first births, although a headfirst birth has been observed. Size estimates of captive-born orcas suggest that calves average 2.6 m (8.6 ft) in length and weigh between 136–181 kg (400 lbs). Calves nurse below water, close to the surface. The mother glides in a horizontal position with her tail arched, and the calf swims on its side with its mouth on the right or left mammary gland. The mother’s milk is very rich so that the calf rapidly develops a thick, insulating layer of blubber. The milk fat content fluctuates as the calf develops, ranging from about 48% milk fat at the beginning of the nursing period and gradually decreasing to approximately 28% in the months that follow. A calf may nurse for 12 months or more. A calf may essentially be weaned at one year of age but may continue to nurse occasionally for several more months.
Warnings and Comments
No attack on a human by an orca has ever been recorded (in the wild). Orcas are not yet regarded as an endangered species. In 1946, 14 countries formed the International Whaling Commission (IWC) by signing the International Whaling Convention. The IWC set regulations of whaling to protect the future of whale stocks as a resource to humans. Currently the IWC has no jurisdiction over dolphins such as orcas. However, now that the harvest of most large whales has stopped, the IWC has expressed an interest in playing a role in managing smaller cetaceans as well.
There are three known ecotypes in the North Pacific: Resident, Bigg’s (Transient) and Offshore. There are two types in the North Atlantic: Type 1 and Type 2 Eastern North Atlantic. There are in the Southern hemisphere at least five known ecotypes.
Resident Killer Whales
Resident orca travel in pods made up of several large extended family groups. When several pods travel together these groups can exceed 80 animals. They are extremely vocal compared to Bigg’s (transient) killer whales. Their diet consists primarily of Chinook salmon, though it can include up to 32 different species of fish. Residents use echolocation to locate their prey; they produce short bursts of clicks that reflect on the environment around them and produce a picture of their surroundings. They can even tell the difference between species of salmon!
Resident killer whales on the BC coast are divided into two groups: the NORTHERN community and the SOUTHERN community. The population of orca that resides in the waters surrounding southern Vancouver Island is made up of three pods: J, K and L pods, and is commonly referred to as the Southern Resident population. These whales frequent the inshore waters of the Pacific Northwest in the summer months, feasting on returning Chinook salmon populations that are running from the Pacific Ocean to the Fraser River to spawn (April-October).
The Southern Residents have been studied for the past 35 years and each individual orca has been identified. The saddle patch (the white marking behind the dorsal fin), acts like a fingerprint and allows researchers (and whale watchers!) to keep track of their information, including ID numbers (and nicknames), ages, and family relationships.
The three pods that make up the Southern Resident population mate amongst each other and do not interbreed with the Northern Residents.
Northern Resident Killer Whale sounds: ‘click’ on speaker
Southern Resident Killer Whales sounds: ‘click’ on graph
Bigg’s (Transient) Killer Whales
Transient orca are genetically distinct from residents and travel in small groups, usually up to eight animals, vocalize infrequently and eat marine mammals, including seals, porpoise and other whales. Transients are opportunistic eaters. They do not vocalize as much as resident killer whales because many of their prey have effective underwater hearing. A more successful hunting strategy used by transients is to quietly stalk their prey using surprise to their advantage with fast animals such as porpoise. Vigorous displays, such as breaches and playing, are seen less frequently in transients than in residents, for fear of their prey being alerted to their impending approach. The occasions when transients do show a lot of surface activity are usually during the act of subduing or killing their prey. Depending on the size of the animal being killed, it can be tossed around like a tennis ball, thrown between individuals using powerful tail slaps, or forced underwater repeatedly until exhausted and drowned.
Transients can be seen all along the western coast of North America, from Glacier Bay in Alaska to the southern California coast. They tend to hug the coastline, examining each cove for unsuspecting prey that will make their next meal. They are sometimes seen far from shore, although the extent of their range in the open ocean is unknown. Transients can be seen year-round.
Offshore Killer Whales
Offshore orca travel in very large groups, use frequent vocalizations and a great deal of echolocation. It is thought that these killer whales feed on schooling fish, however nothing has been confirmed and the possibility that off-shore orca also hunt marine mammals cannot be ruled out. Many details about offshore orca are still unknown, as they were only discovered in the early 1990s. They tend to spend most of their time far from the coastline in very open and exposed waters. These whales have a large proportion of nicks and scarring, relative to transient and resident killer whales, and one hypothesis is that sharks could be an item on their menu. One pod of California transient orca are known to hunt large sharks regularly with an apparent taste for the shark’s liver.
Most encounters with offshore orca have taken place near Haida Gwaii (formerly Queen Charlotte Islands) and 15 or more kilometres off the west coast of Vancouver Island. However in 2003/2004, we had a very large community of offshore orca travel into the protected waters of the Pacific Northwest (120+ animals). This was a very unexpected pleasure, as many of us had never seen such a strong presence of this distinct group of orca in our area before.
Orcas vocalize regularly while going about their various activities. The clicks that you hear are the sounds orca use to echolocate (search) for food and other underwater objects. The other sounds (more high pitched) are calls that the whales use to communicate with each other. The killer whale produces its large repertoire of sounds by forcing air through various nasal sacs and cavities that can be rapidly opened and closed. The sounds are then apparently reflected toward a fatty melon in the forehead, which seems to function as an acoustic lens, focusing the sounds into a directional beam as they leave the head.
You can learn more about – and hear samples of – echolocation and vocalizations above, simply by clicking on the speakers.
Resident, Bigg’s, and offshore orca have very different vocabularies. Both the sound of the calls and the number of calls vary substantially from population to population. Transient orcas vocalize significantly less than residents because they normally don’t use sound while foraging for food. Residents will send out calls to other residents and use sound clicks to locate their prey. Transients, on the other hand, usually hunt silently, listening and looking for their prey. It is speculated that the reason for this is that the dolphins, porpoises, seals, and sea lions that constitute the transients’ primary prey could recognize transient calls and thereby rob the transients of the advantage of surprise. Transients normally begin to vocalize during or after an attack.