What do they look like?
Orcinus orca is a toothed cetacean and it is the largest member of the dolphin family.
Orcas have a distinctive black and white colouring making them easily recognisable. They have a black body with a grey patch (or saddle) behind the dorsal fin and a white eye-patch just above and behind each eye. Their lower jaws, underbellies and the underside of their tails are white. This black and white colouring works like camouflage in the water making it harder for their prey to see them.
Orcas have tall dorsal fins and, therefore, they can be easily spotted when they are swimming close to the surface.
There is considerable variation between different ecotypes. For example, Type D Orcas have a more rounded head, a smaller eye patch, relatively small teeth and a narrower dorsal fin than other ecotypes.
Where are they found?
Orcas are the most cosmopolitan of all cetaceans and, after humans, are the most widely ranging mammal species on the planet. They are found throughout the world’s oceans, from tropical to polar waters, though they are most common in cool, high latitude waters where there is a high level of marine productivity.
What is their habitat?
Depending on the population, Orcas can be found from the surf zone to the open sea. Neither water temperature nor depth seems to have an impact on their range. Some ecotypes, for example Transient Orcas which feed on mammals, tend to roam over larger areas looking for their prey; whereas other ecotypes, such as Resident Orcas (which feed on fish), have smaller home ranges.
When are they active?
Orcas are not strictly diurnal or nocturnal. Instead they follow the activity of their prey and, in some cases, this may involve actively foraging at night. In fact foraging, socialising and travelling can all take place at any time of the day or night. Orcas rest when they are tired rather than following a specific daily routine.
How do they mate?
Female Orcas become sexually mature between 6 and 10 years of age, and usually start mating when they are about 14 years old. Males reach sexual maturity between 10 and 13 years old. Females come into oestrus several times a year and mating can take place at any time, although it is more common in the summer. Pregnancy lasts between 15 and 18 months and most calves are born in the autumn. Females have a calf every 6 to 10 years and stop breeding when they are about 40 years old.
What do they eat?
Orcinus orca eats a variety of prey including fish, seals, sea lions, dolphins, porpoises, whales, sharks, rays, penguins, octopuses and squids. Different Orca pods specialise in eating different types of prey. For example, in the North Pacific different communities of Bigg’s (or Transient) Orcas specialise in different prey (from harbour seals to minke whales to grey whale calves). Orcas hunt in packs, working together to catch their prey. They use a variety of hunting tactics. Type B (large) Orcas, for example, work together to create waves to wash seals off ice floes.
About their offspring
Female Orcas give birth to a single calf, which they nurse for at least 12 months.
Adults teach the calves the skills they need to hunt and to interact with other Orcas. They show them the best feeding and breeding grounds and migration routes. Knowledge is passed down from one generation to the next and this Orca culture can vary greatly between different populations. Orcas stay with their mothers even when they reach adulthood.
Communication and the senses
Orcas communicate using a variety of vocalisations including whistles, discrete calls and clicks. Vocalisations are used to communicate and to navigate. Each pod has its own accent or dialect that sounds different to that of other pods. Orcinus orca produces variable and stereotyped whistles to communicate with their pod members and the different ecotypes have differing whistle repertoires.
Clicks are used for echolocation because, although Orcas have good eyesight, they rely on echolocation to navigate and hunt in dark waters. Echolocation helps them to identify the exact location of their prey. Orcas have very sensitive hearing. They hear whistles and clicks through an ear-bone complex in their lower jaw.
Are there any subspecies?
A number of different ecotypes of Orca have been described. They differ in size, appearance, genetics, prey preferences, hunting techniques, dialects, behaviour and social groups. Although the areas where different ecotypes live may overlap, they are genetically distinct and do not appear to interbreed or interact with other ecotypes.
In the Northern Hemisphere, the ecotypes that are currently recognised are: Resident Orcas, Bigg’s (or Transient) Orcas, Offshore Orcas, North Atlantic Type 1 and North Atlantic Type 2. In the Southern Hemisphere Type A, Type B (large), Type B (small), Type C and Type D (or Sub-Antarctic) are recognised.
Other specific populations of Orcinus orca need to be studied further to determine whether they are separate ecotypes. For example, the small group around New Zealand and the Orcas in the Strait of Gibraltar.
Are there any similar species?
Orcas, which are also known as Killer Whales, belong to the family of oceanic dolphins. Other members of this family include the False Killer Whale (Pseudorca crassidens) and the Pygmy Killer Whale (Feresa attenuata). These two species got their names because they share some physical characteristics with Orcinus orca. For example the False Killer Whale’s skull is similar to that of the Orca. However, they do not really look like Orcas and would not be easily mistaken for them, particularly as they do not have the distinctive black and white colouring which makes the Orca so easy to recognise.
Male and female differentiation
Males can weigh up to 10,000 kg and can measure up to 9.8 m; whilst females weigh up to 7,500 kg and are up to 8.5 m long. However, some ecotypes are considerably smaller, for example Type C males are only 6 m long.
In males the dorsal fin tends to be tall and triangular. It can reach more than 1.8 m in height. The female’s dorsal fin is shorter (0.9 m – 1.2 m) and curves backwards.
Do they have predators?
Adult Orcas do not have any predators apart from humans (although, in fact, very few are killed directly by humans each year). Young Orcinus orca may be attacked by other Orcas or large sharks.
How long do they live for?
Average lifespan in the wild for males: 36 (maximum 60) years. Average lifespan in the wild for females: 63 (maximum 90) years.
What is the global population?
There are estimated to be a minimum of 50,000 Orcas in the world, but some of the different ecotypes have very low numbers and are considered endangered.
How do they behave?
Orcas are highly social and they have complex social structures. They live in pods of up to 50 individuals, though this varies according to ecotype. Transients, for example, tend to live in smaller groups than Residents. The eldest female Orca (or matriarch) leads the pod and decides when and where they will feed. A pod is made up of a mixture of males, females and calves of varying ages. They swim together, share their prey and rarely leave the pod for more than a few hours at a time.
Orcas demonstrate a variety of different behaviours including breaching, porpoising and spy-hopping. They rarely show aggression to one another and are known to take care of old and sick individuals in their pod.
Are they endangered?
Orcas are threatened by:
- Accidentally getting caught in fishing nets.
- Toxic waste and pollution that accumulates in their bodies.
- Oil spills.
- Boat traffic which can lead to collisions.
- Underwater noise pollution.
- Hunting (in Greenland, Japan, Indonesia and some Caribbean islands), and also being killed by fishermen who see them as competitors for fish.
- Live capture for the captivity industry (this has decreased in recent years, but still takes place in Russia).
- Prey depletion.
- Disturbance (for example, by whale-watching tourism).
- Climate change.
Certain populations of Orcas are considered endangered. For example, the Southern Resident population (which inhabits the inland waters of Washington State and southern British Columbia) is listed as endangered under the US Endangered Species Act and Canada’s Species at Risk Act.
Evaluated by the IUCN Red List of Threatened Species Vulnerable (2016).
Did you know?
- Orcas are the most widely distributed of all cetaceans. They are found in every single ocean.
- Orcas sleep with one half of their brain at a time meaning that they do not lose consciousness and are able to surface to breathe.
- Orcas are also known as “killer whales” a name given to them by ancient sailors who saw Orcas killing other whales and called them “whale killer”, a term which then got flipped to become “killer whale”.
- Some people call Orcas “Blackfish”.
- Some Orcas intentionally beach themselves to capture sea lions which are on land.
- Orcas have the second heaviest brain of any animal on the planet (after the sperm whale).
- “Granny” was the oldest known Orca. Some researchers estimated her to have been 105 years old when she died. She belonged to the Southern Resident population in the northeast Pacific.
- Orcas are 1 of only 3 species known to experience menopause (along with short-finned pilot whales and humans).