Types of Orcas in the Pacific Northwest

There appear to be three distinct populations of orcas found in the waters of the Pacific Northwest. In the early stages of Orca Survey, researchers encountered killer whales in pods containing 10 to 25 or more whales that had movement patterns that were fairly predictable during the summer months and these killer whales were observed feeding on salmon. These were named the resident killer whales. Occasionally groups of 2 to 5 individuals were encountered whose patterns of occurrence and movements were erratic. These killer whales were observed feeding on the seals, sea lions and porpoises found in the Greater Puget Sound waters. These killer whales were called transients killer whales. On August 26, 1990 another group of killer whales were discovered that did not match the ID catalogues of either the residents or the transients. It is believed that these whales form a distinct race and they are called the offshore killer whales

The ranges of residents, transients, and offshores overlap, but they have never been seen to mix. It is now believed that transients and residents are so different in their behavior, social organization, and ecology that scientists are speculating that they are separate subspecies on the evolutionary path towards becoming distinct species. Presently, little is known about the offshores so it is unknown yet how they fit into the overall picture although there is speculation that they may be related to the residents.

The preliminary DNA evidence suggests that Northern residents derived from one matriline of offshores and Southern residents derived from a different matriline of offshores.

The three populations of orcas can be distinguished physically by close observation of the dorsal fin and saddle patch. The dorsal fin and saddle patch of an orca are its fingerprints and individuals within each population can be distinguished by these two unique features.

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