T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network


Dolphin (Orca) Orcinus orca

Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Artiodactyla
Infraorder: Cetacea
Family: Delphinidae
Genus: Orcinus
Species: O. orca
Binomial name: Orcinus orca
Synonyms: Orca gladiator
Common names: Orca, Killer whales

Orca (Orcinus orca) is a dolphin which is also known as ‘killer whales’, but they are not true whales. They are the largest member of the dolphin family (Delphinidae). Orcas are found in all oceans of the world, particularly in cooler temperate and polar regions. 
In New Zealand waters there are estimated to be fewer than 200. Because of DNA analysis by New Zealander Ingrid Visser, it is now established that there are probably three resident populations, each made up of several pods in New Zealand waters. One population is off the North Island, another is off the South Island, and a third group that spends its time in both regions. The typical pod size of New Zealand orcas is around two to four individuals.

The male orcas (bulls) are > 8 metres long, weighing up to 5.5 tonnes. The females are smaller, >6 metres in length and up to 3.6 tonnes in weight. The males have a very tall distinctive erect dorsal fin >1.8 metres tall, whereas the dorsal fin of females is much shorter > metres and it is more curved. 
The lifespan of males can be >60 years, whereas for females >80 to 90 years may be attained. 
They feed on fish, marine mammals such as seals and dolphins. They attack baleen whale calves and even adult whales. Killer whales are apex predators, as there is no animal that preys on them. Though they are predators of large marine mammals they have never been recorded attacking humans.

Orcas are totally protected in New Zealand waters under the Marine Mammals Protection Act 1978, which is administered by the Department of Conservation. 

A pod of Orca. The large erect dorsal of a male can be seen top right.

A male (bull) with his large dorsal.


Two female orcas breaching.
 

An illustration showing size comparison to a human.


Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/