Although it is also known as the killer whale, the orca is actually the largest species of
dolphin
They are found throughout all of the world's oceans, and they are thought to be the most
widespread mammal after humans.
Their populations may differ in appearance and behaviour and often specialise on particular
prey.
They commonly hunt marine mammals and it is the world's largest predator of warm-blooded
creatures.
These marine mammals include seals, sea lions, dolphins and sea otters.
They will even kill large whales and also hunts fish sharks, rays, squid, octopuses,
sea turtles and seabirds, such as penguins
Orcas have different hunting techniques depending on their location.
Some like to work together to 'herd' fish, before stunning the prey with strikes from
the tail flukes or join forces to coordinate attacks on large whales.
Some orcas will chase prey such as tuna or dolphins for long periods, to exhaust them.
Some orcas will get seals or seabirds that resting on ice and dislodge them into the
water by rushing to the surface to create a wave.
Orcas in Argentina have even learnt to intentionally strand themselves on beaches to reach seals
and sea lions on the shore.
They are also known to follow fishing fleets to feed on discarded fish, or to take prey
directly from longlines.
They have a marked black and white body which is black on the upperparts, with a light grey
'saddle patch' behind the dorsal fin, and white on the underparts, lower jaw and undersides
of the tail.
Orcas have white lobes that extend up the sides of the body behind the dorsal fin, and
there is a white, oval patch behind each eye.
They have broad, rounded heads and snouts, enlarged foreheads, large, paddle-shaped pectoral
fins and a large dorsal fin.
Males rend to grow larger than females and develop into stockier individuals with larger
fins.
Males also have a tall, erect dorsal fin, which is the largest of any cetacean, which
grows to 1.8 metres in height.
The female orca, has a backward-curving dorsal fin that grows to just 70 to 90 centimetres
in height.
The shape of an orca's dorsal fin and saddle patch are unique to each individual
Males have a head-body length of up to 9.8 m and weigh in at around 9,000 kg.
They reach sexual maturity at around 15 years, but do not become physically mature until
about 21.
Females have a head-body length: up to 8.5 m and weigh in up to 5,500 kg and they reach
sexual maturity in their early teens.
Orcas are a social species, and communicate using a variety of screams, clicks and whistles,
as well as through physical behaviours such as breaching, slapping the flippers or tail,
and 'spyhopping' which is when they bring their head out of the water.
They usually consist of up to 40 or 50 individuals, although larger numbers may gather when several
groups temporarily join together.
Their group structure is complex and consists of a mature female, her adult offspring, and
her daughters' offspring.
Each Orca group shares a unique call repertoire and are known as a pod, while above this are
'clans', which include a number of pods with similar vocal 'dialects'; these pods are probably
distantly related, but may not form a particular social unit.
The orca is found in virtually every marine region, from polar waters to the equator,
and have been known to enter bays, estuaries and rivers, as well as ice areas.