Killer Whale (Orcinus orca)
The killer whale, also known as an orca, is the largest of member of the dolphin family. Males are larger than females. Male killer whales can reach a maximum length of over 8 metres (24-27 ft.) and can weigh 7 tons!
Killer whales along the coast of British Columbia and Washington State are among the most studied whales in the world. Intensive field research in this region has been undertaken since the mid-1970s. These studies have provided a wealth of knowledge about these whales, yet there’s still much to be learned.
Killer whales are the apex predators of the ocean, above even great white sharks in the food chain. Here in the Pacific Northwest, they serve as ambassadors to one of the richest marine ecosystems on our planet. The biodiversity in the Pacific Northwest is astonishing and includes many other marine mammals: minke whales, grey whales, humpback whales, Dall’s porpoises, harbour porpoises, California sea lions, harbour seals, elephant seals, Steller sea lions and an unbelievable range of marine birds.
Because of their reputation as hunters, killer whales are sometimes called the ballena asesina or “assassin whale” by the Spanish. Over the centuries they were referred to as “whale killers” by sailors who witnessed their attacks on larger cetaceans. Over time this name was flipped to “killer whales.” They’re called this not because they harm humans but because some populations do kill other whales, earning them the title “wolves of the sea.” Orcinus is probably derived from Orcus, an ancient mythological Roman god of the netherworld. Orca literally means “large-bellied jar or cask” in Latin, likely due to the killer whale’s body shape.
Range and habitat
Next to humans, killer whales are the most widely distributed mammal on the planet. They inhabit all oceans of the world but are most numerous in regions with cold-water, nutrient-rich upwellings such as the Pacific Northwest, the Arctic and Antarctica. They’re seen along the shores of Alaska, British Columbia, Washington, Oregon, California, Baja Mexico and along the eastern coast of the US. They’re also sometimes seen in warm water areas such as Australia, the Galapagos Islands, the Bahamas and the Gulf of Mexico. Sightings in tropical waters are possible but infrequent. Although killer whales can be found in open ocean and coastal waters, they primarily inhabit the continental shelf in waters less than 200 metres (660 ft.) deep. In polar areas, their distribution is limited by seasonal pack ice.
Killer whales are the apex predators of the ocean. They’re the largest warm-blooded predator ever known. Adult killer whales eat approximately 3% to 4% of their body weight in food per day. Much like packs of wolves or prides of lions, killer whales often hunt cooperatively for food. Fish, squids, seals, sea lions, walruses, birds, sea turtles, otters, penguins, other cetaceans, polar bears, reptiles, and even a moose have all been found in the stomach contents of killer whales around the world. Each population has its own dietary preferences.
Studies suggest that female killer whales are sexually mature at about 10–14 years. Males usually become sexually mature when they’re about 14–19 years. Studies of some populations show that older males tend to sire more offspring. Breeding can occur in any season. In the North Pacific, mating seems to peak between May and September. Pregnancy is about 18 months— the longest of all cetaceans. A female can have a single calf every 3–5 years, or about five calves in her lifetime.
Calves are usually born tail-first. At birth, calves are up to 2.5 m (7-8 ft.) long and weigh up to 200 kg (440 lb). The mother’s milk is very rich so that the calf can rapidly build up a thick, insulating layer of blubber. The milk fat content fluctuates as the calf develops, ranging from about 48% at the beginning of the nursing period to about 28% in the months that follow. A calf is usually weaned by one year of age but may continue to nurse occasionally for several more months. Despite the mother’s exceptional parental care, mortality in the first year can be as high as 50%.
There are 10 known ecotypes of killer whale around the world, although that may change as we learn more. There are three ecotypes in the North Pacific: resident, Bigg’s (transient) and offshore. There are two types in the North Atlantic and five known ecotypes in the southern hemisphere around Antarctica.
Resident killer whales
Resident killer whales travel in pods made up of several large extended family groups. When several pods travel together these groups can exceed 70 animals. They’re 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 killer whale that resides in the waters surrounding southern Vancouver Island is made up of three groups: J, K and L pods, and is commonly referred to as the southern resident population. These whales traditionally frequented 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). In recent years, they’ve been coming to inside waters less often, no doubt due to the severe decline in chinook salmon.
The southern residents have been extensively studied by field researchers since the mid-1970s and each individual whale has been identified. The saddle patch (the grey marking behind the dorsal fin), is like a fingerprint and allows researchers (and whale watchers!) to identify individuals and keep track of their travels, births and deaths, and family relationships.
The three pods that make up the southern resident population do not interbreed with the northern residents.
Bigg’s (transient) killer whales
Bigg’s killer whales are genetically distinct from residents and travel in small groups, usually up to eight animals. They eat marine mammals, including seals, sea lions, porpoises and dolphins, and other whales. Transients are opportunistic eaters. They don’t vocalize as much as resident killer whales because their prey has very good underwater hearing. They use passive hearing to listen for the sound of prey splashing and breathing. Vigorous displays, such as breaches and playing, are seen less frequently in Bigg’s than in residents. When we do see surface activity with Bigg’s it’s during or immediately following a hunt. Depending on the size of the prey, it can be tossed around like a tennis ball and thrown between individuals using powerful tail slaps. Or it is forced underwater repeatedly until exhausted and drowned.
Bigg’s killer whales roam the west coast of North America from Glacier Bay in Alaska to southern California. The inner coast population of Bigg’s, which we see year-round in the Salish Sea, tends to hug the coastline, foraging in bays, inlets and coves for their next meal. A sub-population known as “outer coast” Bigg’s are sometimes seen further offshore along the continental shelf. They occasionally mix with the inner coast Bigg’s. It’s believed there may be yet another assemblage of Bigg’s that lives further out in the ocean ocean.
Offshore killer whales
Offshore killer whales travel in very large groups, vocalize frequently and appear to eat fish, mainly sharks. Many details about them 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 show many nicks and scarring compared to Bigg’s and resident killer whales, possibly due to their preference for sharks.
Most encounters with offshore killer whales 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 group of offshore killer whales travel into the protected waters of the Pacific Northwest (120+ animals). This was an unexpected treat, as many of us had never seen this distinct group of killer whales in our area before!
Killer whale vocalizations
Resident killer whales vocalize often while going about their various activities. They use echolocation clicks to search for food and and find their way around. The other sounds (more high-pitched) are calls that the whales use to communicate with each other. Killer whales produce a large repertoire of sounds by forcing air through various nasal sacs and cavities that can be rapidly opened and closed. The sounds are then directed toward a fatty melon in the forehead, which functions as an acoustic lens, focusing the sounds into a directional beam as they leave the head.
Resident killer whale sounds — CLICK HERE
Resident, Bigg’s and offshore killer whales have very different vocabularies. Both the sound of the calls and the number of calls vary substantially from population to population. Bigg’s 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. Bigg’s, on the other hand, usually hunt silently, listening and looking for their prey. Bigg’s normally begin to vocalize during or after an attack.