Facts about Orcas (Killer Whales)
Although Orca are sometimes known as Killer Whales, they do in fact belong to the dolphin family. With teeth up to 10 cm in length, Orca are fierce predators who hunt in packs like wolves! Each population of Orca has its own dialect.
|Scientific name:||Orcinus orca|
|Reproduction:||Give birth every 5 yrs|
|Diet:||Baleen and sperm whales, fish, seals, sharks|
|IUCN Conservation status:||Data deficient|
Classification and identification: How to recognise an Orca
Orcas belong to a group called the Cetaceans, which includes all other dolphin species, as well as porpoises and whales. They are also members of the family Delphinidae, ie. the Small Toothed Whales. Delphinids are also sometimes referred to as true dolphins, although the family includes the Orca and Short-Finned Pilot Whale. The word dolphin is adapted from delphis which means ‘fish with a womb’.
Like other toothed whales, Delphinids have a single blowhole situated on the top of their heads. Most have a dorsal fin situated on the centre of their backs. Their flukes are always on the rear margin by a pronounced notch.
Orcas are the largest delphinid. Their bodies are extremely robust. The head is conical and lacks a well defined beak. It has a large dorsal fin which is situated on the middle of their back. In adult males the dorsal fin is erect and spike like reaching a height of 1-1.8m. In females and juveniles, the dorsal fin is falcate. Unlike other delphinids which have sickle-shaped flippers, Orcas have flippers that are large, broad and rounded.
Orcas have distinctive, highly contrasting black and white colouration. They have black backs, sides and flippers with a white underside and white patches on their flanks and prominent oval white patches above and slightly behind their eyes.
Orcas can dive to depths of 30m to hunt. They are capable of swimming very fast. Orcas have been shown to have outstanding memory. Like all cetaceans, Orca rely heavily on sound for orientation, feeding and communication. They produce three types of vocalizations, clicks, whistles and pulsed calls. Clicks are primarily used in echolocation for navigation and finding food. Whistles and pulsed calls are used to communicate with each other. Each population of Orca has its own distinctive set of vocalizations much like human dialects. These vocalizations are passed on culturally amongst individuals to bond the group together.
Habitat and range: Where do Orcas live?
Orcas are the most widespread cetacean. They can occur in all ocean temperatures and depths. Orcas are found in highest densities at high latitudes. Their movements appear to track those of their favoured prey species.
How big are Orcas?
Ocras are the largest of the delphinids. Males are larger than females growing up to 9m and weighing 5,600kg compared to females which grow to 7.9m and weigh 3,800kg.
Life Span: How long do Orcas live?
Male Orcas live from 50 to 60 years whereas females live for 80 to 90 years.
Diet: What do Orcas eat?
Orca eat a large variety of species. Their prey items include schooling fish, baleen whales, sperm whales, otters, turtles, squid, sirenians, sharks, rays and even deer or moose which they catch whilst swimming across channels. Orca hunt in pods of up to 40. When hunting large prey items such as whales they work cooperatively to harass and subdue them. They also work cooperatively when hunting fish to maintain tight balls of fish, taking it in turns to swim through the school and feed. Orcas have also been known to steal food from long lines and scavenge on fishery bycatch.
Predators: What eats Orcas?
Humans are the only known killers of Orcas.
Reproduction: How do Orcas produce their young?
Orca live in matrilinial groups made up of two to four generations of two to nine related individuals. These groups will spend most of their time with a number of other groups to form a pod.
Calving occurs year round, peaking between autumn and spring. Females will calve every five years after a gestation period of 15 to 18 months. Orca calves will begin eating solid food at a very young age but are not fully weaned until almost two years of age. Adolescent female Orca will often help assist the mother in caring for the calves. Reproduction stops when the female reaches 40 years of age.
Conservation status: Are Orcas endangered and if so why?
Orcas are listed as ‘Data Deficient’ by the IUCN.