Offshore killer whales
Offshore killer whales are the least understood of the killer whale assemblages in the north eastern Pacific. They are thought to be more closely related to resident killer whales than transients due to appearance, vocalization and genetics.
It is thought that these killer whales feed on large ocean fishes such as sharks and halibut. Most offshore killer whales bear large numbers of nicks and scars, perhaps inflicted by large sharks. Also lending weight to this theory is the extensive tooth wear observed in stranded offshore killer whales, possibly caused by the sandpaper-like skin of sharks.
Photo: Jackie Hildering www.themarinedetective.ca
Offshores often travel in large groups and are very vocal.
As their name indicates, most encounters with offshore killer whales occur well away from the coast. They are usually found on the continental shelf particularly near Haida Gwaii and 15 or more kilometers off the west coast of Vancouver Island. However, some groups have been sighted in inshore waters (Johnstone Strait and Strait of Georgia). They have been encountered as far south as Los Angeles and as north as the northern Gulf of Alaska.
Offshore killer whales are listed as Special Concern under the Species at Risk Act (SARA) in Canada; however in 2008 COSEWIC (Committee on the Status of Endangered Wildlife in Canada) recommended the listing be changed to Threatened. While population estimates are still imprecise, 288 individual offshore killer whales have been identified so far and a few 'new' individuals have been seen in recent encounters.
Photo: Rachael Griffin aquagreenmarine.org
The extensive wear seen on the teeth of offshore killer whales may be caused by preying on sharks.
Offshore killer whales are very vocal and use echolocation frequently, much like resident killer whales. See Communication to listen to offshore killer whales.
Offshore killer whales are typically encountered in groups of 30 – 70 or more. Very little is known about their social structure.