Orcas: Characteristics, Size and Habitat | Sea Life, Islands and Oceania

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ORCAS (KILLER WHALES)

orcas jumping
Orcas (also known as killer whales) are actually a kind of a dolphin. One of the most recognizable marine mammals, with their distinctive black and white bodies, they are the fastest marine mammal and the supreme predator of the sea. The have been timed at 55.5 kilometers per hour (34.5 mph) and have been observing taking on great white sharks, winning decisively, and attacking and feeding on mako sharks, blue whales, gray whales and sperm whales. [Source: Douglas Chadwick, National Geographic, April 2005]

Orcas (Scientific name: Orcinus orca) are arguably the most popular and closely-watched whales in the world. Their name “killer whale” is derived from early descriptions of them as “whale killers” or “killers of whales.” The name orca, which has become fashionable in recent years, is derived from the species scientific name, “ Orcinus orca”. It is not a name some Pacific Northwest Indian tribe gave the whale but rather Latin for “whale from the underworld of the dead.” People that are fond of orcas tend to call them orcas while those that are less fond of them or don’t care call them killer whales.

Orcas are the largest member of the Delphinidae family, or oceanic dolphins. Members of this family include pilot whales, , whose common names contain "whale" instead of "dolphin." The fossil history of orcas dates to the Pliocene Period (5.4 million to 2.4 million years ago), with the oldest fossils being about five million years old. Teeth, partial skulls, jaw bones, and periotic bones (mammal's ear bones) have been found in Japan, Hungary, Italy, and South Africa. [Source: Emily Burnett, Animal Diversity Web (ADW) /=]

Orca Habitat and Where Are Found

Found in every ocean in the world, orcas are the most widely distributed of all whales and dolphins. They can adapt to almost any condition, and occur in both open seas and coastal waters Orcas have been spotted from as far north as the Arctic Ocean near pack ice and are very active around Antarctica. Although Orcas seems to prefer colder waters, they are o strangers to tropical waters. They seem to move to where food sources are most abundant and don’t seem to migrate according to some seasonal, weather or water temperature pattern. [Source: Emily Burnett, Animal Diversity Web (ADW) /=]

range of orcas in dark blue

Orcas live in temperate, tropical and polar saltwater and marine environments. They are found in both coastal areas and in the open sea far from land. They are typically found at depths of 20 to 300 meters (66 to 984 feet) at an average depth of 60 meters (196.85 feet). Orcas visit shallow waters along coastlines and have even been observed beaching themselves in pursuit of seal pups in Argentina. Orcas generally occupy the same home range year round.

Orcas are found in the Arctic Ocean, Indian Ocean, Atlantic Ocean Pacific Ocean and Southern Ocean. They are most abundant in colder waters like Antarctica, Norway, and Alaska. The most well-studied orca populations occur in the eastern North Pacific Ocean along North America are the best studied, Those living around Washington state and British Columbia having been closely monitored for decades. Resident orcas have been seen from California to Russia. Transient orcas occur throughout the eastern North Pacific, and are often seen in coastal waters. Their habitat sometimes overlaps with Resident and Offshore orcas. Offshore orcas have the largest range of any community, and often occur more than nine miles offshore. [Source: NOAA]

Sometimes orcas die when they get trapped in ice. In the early 1920s, 11 members of of a pod 12 whales were trapped by pack ice off eastern Hokkaido in Japan and died According to witnesses the whales made noises and tried to escape but became exhausted and grew quiet. A three-meter-long young whale was rescued.

Orca Populations

Populations of orcas are healthy and stable but counting them is difficult. There are believed to be 30,000 to 80,000 of them worldwide. The populations of some of the prey that orcas feed on is not so stable. In some places the numbers of salmon and seals that they feed on have dramatically declined. It is not clear what effect this has had on orcas. Some evidence suggests that they change prey.

Scientific studies have revealed many different populations with several distinct ecotypes (or forms) of orcas worldwide — some of which may be different species or subspecies. Taken as a whole, the species has the most varied diet of all cetaceans (whales and dolphins), but different populations are usually specialized in their foraging behavior and diet. They often use a coordinated hunting strategy, working as a team like a pack of wolves. [Source: NOAA]

Several different populations and ecotypes of orcas are found throughout the world. NOAA Fisheries estimates population size in our stock assessment reports. It is estimated that there are around 50,000 orcas globally. Approximately 2,500 orcas live in the eastern North Pacific Ocean — home to the most well-studied orca populations. Around 3,000 orcas visit Norway’s fjords each year.

Orcas have no natural predators, although young orcas may be attacked by other orcas or large sharks. They are at the top of the marine food chain. Humans sometimes prey on orcas, but not so much as orcas have few materials that orcas value.

Orca Size and Coloration

Orca size
Orcas are the world’s largest dolphins. They reach lengths of 9.75 meters (32 feet) and weigh Up to 10 tonnes (11 US tons, 10,000 kilograms) . Their average weight is 7.2 tonnes (7200 kilograms, 15,860 pounds). Newborn calves are from two to 2.4 meters long (6.5 to 8 feet) and weigh about 136 kilograms (300 pounds) at birth. The average weight for a male orca is 7.2 tonnes (8 US tons, 7200 kilograms). [Source: Emily Burnett, Animal Diversity Web (ADW) /=]

Males are larger than females. Adult males develop larger pectoral flippers, dorsal fins, tail flukes, and girths than females. The average length for a male adult is eight meters (26 feet), with the maximum length at 9.75 meters (32 feet). The average length in females is seven meters (23 feet) with a maximum length of 8.5 meters (28 feet). The average weight for a male orca is 7.2 tonnes (8 US tons, 7200 kilograms).

Orcas are black on top with white undersides. All orcas have a white patch around each eye and a white or light-colored saddle patch behind their dorsal fin. These markings vary widely between individuals and populations. White coloration extends from the bottom of the chin to just beyond the anus on the bottom. Both sexes have a "saddle spot" — the white or grayish spot behind the dorsal fin on the back. Among calves, the black color is somewhat grey and white on the underside is yellowish until they reach one year old. [Source: Emily Burnett, Animal Diversity Web (ADW) /=]

Iceberg is the name of an all-white, mature male orca that was filmed and photographed in 2010 off the north-east coast of Russia. He is one of the first adult all-white orca bulls discovered in the wild. He was discovered by the Far East Russia Orca Project (FEROP) near the Commander Islands in the Bering Sea in August 2010. He was living in a pod with 12 other orcas, and assumed to be a male and 16 years old based on the size of his two-meter dorsal. FEROP scientists believe he may have been the albino whale spotted off the coast of Alaska in 2000 and 2008. He was still alive as of 2016, when he was again spotted by FEROP with his pod. It is not clear whether Iceberg's pigmentation is the result albinism or leucism. White coloration, more common in the Russian north Pacific than among Antarctic whales, may be a sign of dangerous inbreeding. [Source: Wikipedia]

In July 2021, two white orcas were spotted together by a nature tour off the coast of Rausu on Hokkaido in northern Japan. The white orcas appeared on July 24, according to the Shiretoko Nature Cruise, operator of whale-watching tours based in Rausu. They swam beside each other among a pod of about 20 individuals. The pair is believed to be a male and a female judging from the size and shape of their bodies and dorsal fins. “We are seeing more orcas this year than usual,” said Yuki Hasegawa, captain of the Shiretoko Nature Cruise boat. “Two white individuals seen swimming side by side may be unprecedented in the world.” White orcas have been sighted at only 10 locations in the North Pacific over the past 100 years, according to Hiroshi Oizumi, a professor of marine ecology at Tokai University. Other places include the west coast of Canada and Aleutian Islands in of Alaska.[Source: Masafumi Kamimura, Asahi Shimbun. August 2, 2021]

Orca Characteristics

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Orca anatomy
Orcas have one the largest brains in existence, four times the weight of an adult human brain. Orcas are endothermic (use their metabolism to generate heat and regulate body temperature independent of the temperatures around them) and homoiothermic (warm-blooded, having a constant body temperature, usually higher than the temperature of their surroundings). They need to eat three to four percent of their body weight a day to stay strong.

In males, the erect dorsal fin can reach up to 1.8 meters high; in females and immature males this dorsal fin is only about 0.9 meters high. This fin curves over either to the right or left side.

Their smooth, slick skin and streamlined shape allows them cruise at great speeds through the water. Sometimes water barely breaks over them when they emerge from the water to breath.

Orcas have paddle-shaped flippers, or pectoral fins. The dorsal fins of large males can be over two meters high. Those of females are generally about half that height. Their dorsal fin clears the water every time orcas emerges to breath. The dorsal fins of captive orcas droop over as anyone who has seen “ Free Willy” knows. Stress and poor health are believed to behind the droop.

Orcas rely mostly on hearing and sonar when they hunt. They produce high-frequency sounds using their nasal passages and melon, the fatty lens in their forehead. When used at close range orca can determines whether the animal near them are pregnant, healthy or hungry. The sounds most associated with orcas are series of loud clicks. These help whales navigate and locate prey through echolocation.

Orca Lifespan and Longevity

Orcas live as long as humans and are the longest living of the dolphin family. Mortality rate among observed animals is very low (1 percent a year for males and 3 percent for bulls). Cows live as to be over 80; bulls about 60. One female in Pugent Sound, known as Granny, was estimated to have born in 1911 and was still going at 95 years of age in 2006.

Male orcas typically live for about 30 years, but can live from 50 to 60 years. Females typically live about 50 years, but can live from 80 to 90 years. [Source: NOAA]

Orca mortality rate varies with the age of the animal. Neonatal mortality is very high, in captivity neonatal mortality is between 37 percent and 50 percent. The reason for these high mortality rates is unknown, but predation is not considered a primary threat during this time. After six months, mortality rates steadily decline as orcas learn how to protect and nourish themselves. Mortality rates are said to be the lowest around 12 to 13 years in males and 20 years in females. The average lifespan for a female in the wild is around 63 years, with a maximum of 80 to 90 years. Male life expectancy is a bit shorter, with the average lifespan being around 36 years, with a maximum of 50 to 60 years. [Source: Emily Burnett, Animal Diversity Web (ADW) /=]

Orca Brains

Orcas have one the largest brains in existence, four times larger than adult human brain based on weight. Their brains have similar features as human brains that give them high-functioning abilities like empathy. Orcas also have a high sense of self-awareness, which they use to develop unique hunting tactics. Their brains are wrinkly, which enables them to think and process information quickly.[Source: Emily Swaim, Business Insider, May 31, 2023]

Emily Swaim wrote in Business Insider, Orcas' highly developed insula and cingulate sulcus give them self-awareness, understanding of social relationships, and empathy. These heightened skills come in handy for their hunting tactics. Moreover, "cetaceans like orcas and bottlenose dolphins also have a uniquely elaborated brain area called the paralimbic system," said Lori Marino, founder and president of The Whale Sanctuary Project and a neuroscientist who studies cetacean intelligence. In fact, the paralimbic system has much more intricate folding and detail in orca brains than in humans'.

It's unclear what the advantage may be, but based on their knowledge of other brain areas, scientists think this intricate paralimbic system helps combine information from the parts of the orca's brain that process emotions with those in charge of higher-level thinking. Each pod has its own unique hunting techniques that target its prey's weaknesses. For example, Antarctic seals are different prey entirely from blue whales. A fleeing seal may take refuge on ice floes, but they don't stay safe for long. The orcas can create choppy waves that break up the floes, and the seals slide straight into their waiting mouths. This is made all the more impressive because pods pass down not just their hunting techniques, but also their unique "dialect" of communicative clicks and whistles to offspring across generations.

But it's not just orcas' similarity to humans that makes them so deadly. It's also their differences that make them the sea's apex predator — in particular their brain's ability to detect and process sound. Sound travels four times faster in water than air, and orcas take advantage of that by sending out pulses, clicks, and whistles to scan the area around them like radar — an ability called echolocation.

Most mammals have the same basic brain structure: a wrinkly outside of gray matter, where all the nerve endings pass off messages to each other. Underneath the surface lays the white matter, which acts like cables connecting nerve endings in different parts of the brain. Usually, the larger an animal's brain, the more white matter they need to, hypothetically, keep all the nerve endings connected. But cetaceans, including orcas, don't follow this rule. Instead, they evolved exceptionally wrinkly cortexes with a bunch of extra gray matter folded in on itself.

Orcas have the wrinkliest brains of any animal, even humans, per Orca Nation. The folds on the surface of their brains bring nerve endings closer together, so it takes less time and energy to send messages back and forth. This rapid nerve communication lets orcas register, process, and react to sounds faster than almost any other animal in the ocean. In other words, they think fast and are quick on their feet — er, fins in this case. Between orca's tactical teamwork, their hyper-sensitive echolocation, and overall intelligence, their prey rarely stand a chance.

Orca Food and Hunting Behavior

Orcas are arguably the ocean’s top predator, eating near the top of the food chain. They often use a coordinated hunting strategy and work as a team to catch prey. Although the diet of orcas depends to some extent on what is available where they live, it is primary determined by the culture (i.e., learned hunting tactics) for each ecotype of orca. For example, one ecotype of orcas in the U.S. Pacific Northwest (called Residents) exclusively eats fish, mainly salmon, and another ecotype in the same area (Transients, or Bigg’s killer whales) primarily eats marine mammals and squid. [Source: NOAA]

Orcas feeding habits are frequently assessed through looking at stomach contents. They eat a wide variety of large prey including: sea lions, seals, smaller whales, dolphins, fish, sharks, squid, octopi, sea turtles, sea birds, sea otters, river otters, and other animals. Orcas eat about 45 kilograms (100 pounds) of food a day, but they can eat much more than that. They swallow small prey whole, but tend to tear up larger prey before consumption.[Source: Emily Burnett, Animal Diversity Web (ADW) /=]

Orcas are very successful and highly efficient predators.. Like wolves and lions, they are social hunters who often hunt in packs and use coordinated social behavior, precise cooperation among pod members and communication to hunt prey larger than themselves, such as larger whales. They even hunt great white shark and the largest whales. Transient orcas that preying on gray whale calves off Monterey, the California. drown the babies after separating them from their mothers, often after an agonizing struggle. The calves are rich in fat, but the orcas often remove the tongue before dining on blubber.

Breeding Orcas

adult with juvenile
Orca cows mature at the age of 15 and give birth at very different rates until they are about 40. They average one calf per cow every five years. A female that lived to be over 90 had five or six offspring in her lifetime.

Among resident orcas, mates are chosen from distantly related pods within their communities in order to avoid inbreeding. As far as anyone knows they don’t mate outside their community. This is at least partly for cultural reasons because different communities speak different dialects and have different traditions and customs.

Calves can be 2.2 to 2.4 meters (seven to eight) feet long and weigh nearly 180 kilograms (400 pounds) at birth. They don’t sleep their first month of life. Mothers also stay awake and don’t begin to take short naps until the forth week after birth. See Dolphins.

Orcas Help Explain Why Menopause Exists

Orcas, humans and short-finned pilot whale are the only three species that experience menopause — when females stop reproducing when they get a certain age. For a long time it was thought only human females had menopause. A study published in 2017 in the journal Current Biology suggests that competition between offspring may be the cause among orcas. [Source: Robin McKie, Associated Press, January 15, 2017]

Darren Croft of Exeter University has been studying orcas for years. “Our previous work shows older, post-reproductive females do help their offspring survive but that, on its own, does not explain why they stop reproducing,” said Croft. “Females of many species act as leaders in late life but still breed — elephants for example.”

Croft’s team — working with scientists at York University, Cambridge University, the US Center for Whale Research, and Fisheries and Oceans Canada — suggests the real explanation is more complex. Associated Press reported; Croft’s team have been studying two populations of orcas, which live off the north-west Pacific coast of Canada and the US. The populations included several pods, made up a several family groups. One of these pods — known as J pod, which currently consists of more than 20 individuals — was led by J2, or Granny, the orca matriarch. Granny was thought to be more than 100 years old. She had stopped reproducing when she was 60, it is thought.

Orcas normally start breeding around the age of 15 and then stop between the ages of 30 and 40 — although females often live until they are more than 80. In addition, it has been discovered that older female orcas play a particularly important leadership role in their family group. “They appear to be particularly good at pinpointing places to hunt salmon, the main source of food for the resident killer whales,” said Croft.

male with a the tall dorsal fin, female with a smaller, curved one

This point was backed by Deborah Giles, of the Center for Whale Research, who has been observing Granny and the J2 pod for years. “Granny was the ‘wise elder’ of that orca clan. She had an amazing ability to call the other whales to her by vigorously slapping her tail on the water. Even from miles away the other whales would turn around and come immediately to J2’s side,” she said.

However, it was the study’s observations of middle-aged orca mothers — those approaching menopause — that provided the real insights. It was found that these mother whales suffer much higher costs when competing to reproduce with younger mothers. These older mothers’ offspring were 1.7 times more likely to die than those of younger ones. “This new research shows that old females go through the menopause because they lose out in reproductive competition with their own daughters,” said Croft.

This point was backed by Daniel Franks from the University of York, a co-author of the study. “It’s easy to think that an older female will pass on their genes better by continuing to give birth in late life but our new work shows that if an old female orca reproduces, her late-life offspring suffer from being out-competed by her grandchildren. This, together with her investment in helping her grandchildren, can explain the evolution of menopause.”

Image Source: Wikimedia Commons, NOAA

Text Sources: Animal Diversity Web (ADW) animaldiversity.org; National Oceanic and Atmospheric Administration (NOAA) noaa.gov; Wikipedia, National Geographic, Live Science, BBC, Smithsonian, New York Times, Washington Post, Los Angeles Times, The New Yorker, Reuters, Associated Press, Lonely Planet Guides and various books and other publications.

Last Updated June 2023