TAXONOMY AND EVOLUTION Killer whales are in the order Cetacea which includes all dolphins, porpoises, and whales. They belong to the suborder Odontoceti which includes the toothed whales, dophins and porpoises. They belong to the family Delphinidae or the dolphins, and killer whales are the largest of the group. The genus is Orcinus and species is orca. Killer whales had a reputation for being fierce killing machines which is why the Spanish called them "ballena asesina" or the assassin whale (10). They were often seen attacking other whales, sharks, and dolphins. However in Latin, the name orca means "the shape of a barrel or cask" which is due to their shape (1). Cetaceans roamed the oceans long before recorded history probably up to 5-7 million years ago. It is thought that early dolphins evolved about 55-65 million years ago from now extinct ancient land mammals that ventured back into the sea. One fossil that closely resembles the killer whale is Ambulocetues natans which was found in Pakistan to have legs but also many characteristics of whales (1). Also many fossils from the Pliocene era are thought to be related to the orca because of their teeth. Killer whales are mammals because they control their own body temperature, and it remains constant independent of its environment. They also have small hairs to help in sensory, they have mammary glands in which they use to feed their young. They also breathe through lungs using their blowhole to inhale and exhale. They give a live birth and take care of their young.HABITAT, SOCIAL STRUCTURE AND ACTIVITY CYCLE Killer whales, also called Orcas, live in all of the world's oceans, establishing a particular preference for the cool or coastal temperate climates although they have been spotted off the coasts of Hawaii, Australia, the Galapagos Islands, the Bahamas, and the Gulf of Mexico. They have also been spotted in fresh water rivers such as the Rhine, the Elbe and the Thames River (1). Even though the majority of killer whales favor a more moderate location, there are also those who live within the decidedly colder polar ice regions. There are two separate sub groupings of killer whales when it comes to their mobility: residents and transients. There is also a third sub grouping called offshore whales but they have been little studied. The resident and transients seem to avoid each other at any cost. Resident pods usually consist of 5 up to 50 members while transient pods either travel alone or in groups of 2-7 individuals. Resident pods often travel within specific ranges or direct routes usually from headland to headland along the coast and never more than 500 miles off the coastline. Transient groups ranges are unpredictable and they may spend twice as much time traveling in a circuit that often follows the contours of the shoreline within a 900 mile range (1). Killer whales live and travel in large groups called pods, which are classified as their "extended...
