Killer whales have been observed in all oceans and seas of the world. Although reported from tropical and offshore waters, they occur at higher densities in colder and more productive waters, with the greatest densities found at high latitudes. Along the west coast of North America, killer whales occur along the entire Alaskan coast, in British Columbia and Washington inland waters, and along the outer coasts of Washington, Oregon, and California. Seasonal and year-round occurrence has been noted for killer whales throughout Alaska and in the intracoastal waterways of British Columbia and Washington State, where pods have been labeled as ‘resident,’ ‘transient,’ and ‘offshore’ based on aspects of morphology, ecology, genetics, acoustics and behavior. Through examination of photographs of individuals recognizable by differences in dorsal fin shape and saddle patch patterns, movements of whales between geographical areas have been documented. For example, Alaskan killer whales have been observed in British Columbia, Washington and California. When born, killer whales are 2.1 to 2.4 m long and weigh up to 180 kg; by the time they are adults, males are 9.5 m and weigh at least 8 tons, and females are 7 m long and weigh up to 4 tons.