Killer Whale (Orca) Fact File
The killer whale also known as the orca is not actually a whale, in fact they are the world’s largest species of dolphin. They enjoy the widest distribution of any dolphin species being found along the coastline of every continent along with in the open ocean.
Groups of orcas (known as pods) will include up to 40 members which communicate using a range of vocalizations. These groups work together to hunt for marine mammals, fish and penguins with a range of unique skills used to hunt.
They are easily noticeable due to the black and white skin which covers the body. A triangular fin is present on top of the body with a pair of large flippers and a strong tail fluke used to push them through the water.
Orcas face a number of threats in the water including pollution, overfishing and capture for the aquarium trade.
Learn more about these marvellous mammals by reading on below.
The orca is a large black and white species of whale. Their body is stocky and powerfully built to assist them when hunting. The underside is white with a stripe up the side halfway along the body. In many individuals a grey patch is present behind the flipper like a saddle.
Their black and white coloration is an adaptation which helps them to camouflage in the water both from above and below. This works by breaking up their shape making them harder to spot.
A small number of all white orcas have been discovered off the coast of Russia. The first found in 2010 was named Iceberg by scientists. Some scientists have suggested that this could be evidence of inbreeding in the population.
A white patch is present around the eye. The coloration and shape of this is variable between subspecies.
At the end of the body the tail spreads out on either side in two side flukes. The tail is incredibly muscly and helps to push them through the water.
A large paddle shaped flipper is present on either side of the body just behind the head. This flipper evolved from the arms of land mammals and contains extended finger like bones.
Protruding from the back is a triangular shaped, tall dorsal fin. Males have a taller fin than females. The shape of each fin varies between individuals and can be used to tell them apart.
Inside the mouth are a number of teeth which are up to 10cm (4in) long. These help them to grab and hold their slippery prey.
The body shape is cylindrical and tapers at either end giving them a hydrodynamic shape to help them move through the water.
An orca will reach a length of up to 9m (30ft) and a weight of up to 10 tonnes (10 tons).
Orcas are carnivores and feed on a range of fish, marine mammals, turtles, birds, sharks and whales. Over 140 species of prey have been recorded as part of their diet.
These animals have a short tongue which is incredibly sensitive with taste buds to help determine whether prey is edible.
Prey is found using echolocation. They send out a click and this is the reflected back helping them to locate prey.
Groups of orcas will work together to hunt their prey. When they find a mammal such as seals on ice they will swim together to try and drive waves created by them over the ice pushing the seal in the water and towards a waiting member of the pod. They may also push animals up against the shore so they can feed on them.
Some populations of orcas have been reported to be specialists which feed solely on one type of prey.
Reports exist of orcas feeding on land mammals such as deer and moose which enter the water.
Humpback whales have been found with tooth rakes from orca attacks which occurred when they were young and small enough for a killer whale to try and attack.
Orcas enjoy a wide range in the world’s ocean being found in almost any aquatic habitat though larger numbers are concentrated in cold-water areas with high marine productivity. They are also recorded from a range of semi-enclosed areas.
Orcas are an aquatic species which spend their entire life in the water. Here they can be found in almost all habitat types from the tropics to polar areas.
Populations congregate in areas with high marine productivity.
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Mating can occur year round but peaks during spring and summer.
Orcas are considered polygamous with both males and females mating with multiple females.
A single calf is born tail first after a 15 to 18 month gestation period. While a single calf is almost always born twins have been recorded on rare occasions.
At birth the dorsal fin and tail fluke are flexible. They harden over the first few days. Their white patches are colored cream, yellowish or tan at birth and turn white over the first year.
Calves feed on milk from the mother which they suckle for 5 to 10 seconds at a time several times each hour. Suckling may occur for up to 2 years. This takes place while underwater. They can swim as soon as they are born.
Sexual maturity appears to be correlated to size. Females reach this between 7 and 16 years old or at lengths of 4.6 to 5.5m (15 to 18ft) long. Males reach this at 13 years old or 5.5m (18ft) long. In captivity they have been recorded to breed at younger ages.
They are one of the only other animals which exhibit menopause. Females do not reproduce after reaching an age between 38 and 46 years old.
Females may produce a calf once every three to ten years.
Orcas breathe using the blowhole. This is a circular hole just behind the head which is closed while swimming. It opens to allow air in when they come to the surface.
When swimming they will reach speeds of up to 56km/h (35mph). These high speeds are only reached for short periods before cruising at a slow period. They will ride waves or wakes to reach higher speeds easier.
These highly social animals will live in groups (known as pods) with up to 40 members. These pods includes grandmothers, mothers and their daughters. Hunting techniques are passed down through the generations by these groups.
A number of pods may join together to make a group known as a superpod.
Each pod has a hierarchy with females being dominant.
When the pod travels the young will be in the center with the females while the males are at the edges.
To communicate with one another the orcas with produce a range of whistles, clicks and other calls. They also communicate through body movements including leaping and fin slapping at the surface.
Three ecotypes of orca are recognized These are the residents, transients and offshores. These have different coloration, morphology, behavior and vocalizations. These populations tend not to mix or interbreed even though some have overlapping ranges.
Instead of sleeping like most males dolphins, including orcas, will place one half of their brain in a sleep state at a time.
Predators and Threats
Killer whales have been hunted by humans for a variety of reasons. These include for food and population control along with capture for the captive trade.
Populations are subject to killing as a result of fisherman seeing them as competition. They may also be affected by fisheries which remove their food source. Incidental mortality also occurs from entanglement in fishing lines. Reduction in prey is a larger issue for resident populations which rely on a single food source.
Melting sea ice in the arctic has allowed them to access larger amounts of marine mammals which used to use the sea ice for protection.
Populations have been affected through the accumulation of contaminants within the water. As an apex predator they consume additional poisons within their food. Another threat is oil spills which both affect the whales directly and reduce prey availability.
High levels of tourism in their range affect them through disruption and boat noise which will disrupt echolocation which interrupts their foraging attempts.
Due to the ongoing taxonomic arguments over the status of the orca the IUCN is yet to determine their conservation status and decide if the population is in decline. An estimate of the population is 50,000 individuals.
Despite the name killer whale causing humans to fear orcas no attacks have been recorded in the wild. Unfortunately some attacks have occurred in captive populations.
Recorded causes of mortality for orcas include injuries from prey, stranding while aiming to capture prey and stingray spine injuries while attacking a stingray.
While called a whale the orca is actually the world’s largest species of dolphin.
Outside of humans the orca is believed to be the world’s most widely distributed mammal.
Orcas are believed to be one of the world’s smartest animals rivaling humans and other apes such as chimpanzees.
The name killer whale is believed to have originally been coined as “whale killer” by a fisherman who saw them working together to take down a larger whale.
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