Orcas (Orcinus orca), also known as killer whales, belong to the Order Cetacea, a group of marine mammals that includes whales and dolphins. Orcas are closer relations to dolphins than to whales. The name 'killer whale' is for this reason slightly misleading and may in fact be the result of an error in translation. 18th-century Spanish sailors used to refer to orcas as 'asesina-ballenas' which probably should have been translated as 'whale killers' (orcas are known to form pods and hunt some species of whales) instead of 'killer whales'.
Orcas have a distinct color pattern—black back and sides, with white patches on the belly and behind their eye. Males are larger than females and can reach up to 31ft (9.5m) in length. Females reach lengths of up to 28ft (8.5m). In males, the dorsal fin can be as much as twice the size of that seen in females. Additionally, the dorsal fin in females is more curved. Both sexes have a large, rounded pectoral fins.
Orcas are social predators and hunt in groups known as pods. They feed on fish, squid, birds, seals and whales. Orcas also use the pods to give structure to their breeding behavior. Each pod contains one breeding male and several breeding females as well as a number of younger individuals of both sexes. Pod size can vary between about four and forty individuals. Larger pods tend to be more stable.
Throughout most areas of their range, orcas breed in spring and summer. Their gestation period lasts about 12 months and young are born when they are about 2m in length.
Orcas are most common in cooler waters such as the Arctic and Antarctic but are also found in the Atlantic, Pacific, and Indian Oceans.
- Kingdom: Animalia
- Phylum Chordata
- Class: Mammalia
- Order: Cetacea
- Family: Delphinidae
- Genus: Orcinus
- Species: Orcinus orca
Burnie D, Wilson DE. 2001. Animal. London: Dorling Kindersley. 624 p.
Sessine S. 2000. Orcinus orca, Animal Diversity Web. June 14, 2007.