Killer whale (Orca)
(Photos)

Class: Mammalia
Order: Cetacea
Family: Delphinidae
Genus species: Orcinus orca

Killer whales are found in all oceans, but are never abundant. Sightings in the northwest Atlantic have been reported from the ice edge south to the Caribbean. They seem to prefer coastal areas and can sometimes be seen in bays. Movements in the northwest Atlantic are poorly understood but probably correspond with that of their prey.
 

Individual whales can be recognized by the greyish "saddle patch" behind the dorsal fin. Researchers have been studying the population dynamics of killer whale pods. They can identify individuals by taking pictures of the whales' dorsal fins, noting differences in shape, relative size, scars, and deformities. On the west coast of Canada, a catalogue of such photos has allowed scientists to follow and study groups of killer whales for years.  

Killer whales may live for up to 35 years. At the end of a year-long pregnancy, a 3 m calf weighing 400 lbs. is born, and is nursed for one year. Males reach maturity at a length of 6 m, and females at 5 m. Males are generally larger than females, and can be up to 10 m long and weigh 8 tons. Females do not exceed 8.5 m in length. Males have a tall, straight dorsal fin, while that of the female is smaller and hooked.  

The basic social unit appears to be an extended family consisting mainly of related females, with about 20 percent males. Such groups remain together for life and travel as a cohesive unit. Vocalizations consist of a wide variety of whistles, and there is evidence that different groups are recognizable by their unique dialects. Killer whales live in groups called pods. A pod may have less than 5 to about 30 individuals: a mix of males, females, and calves of varying ages. Sometimes several smaller pods join together to form larger herds of 50 or more whales.

Killer whales feed on fish, squid, seabirds, and other marine mammals. They are known to hunt cooperatively, in a manner reminiscent of wolves on land. Smaller prey can be swallowed whole, while larger animals such as other whales must be torn apart. Each day they eat about 4% of their body weight. Killer whales are among the fastest swimming marine mammals. They can swim as fast as 48 kph (30 mph), but they usually cruise at much slowerspeeds, about 3-10 kph (2-6 mph).

Killer whales are a popular topic of many legends, and are prime attractions in some marine parks. Although great ferocity is often attributed to them, there is little evidence that they pose a threat to man, any more than other large, wild animals.