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Surveying Killer Whale Abundance and Distribution
In the Gulf of Alaska and Aleutian Islands

Three Killer Whale Ecotypes

Photographs below illustrate how the three recognized Northeast Pacific killer whale ecotypes can be distinguished based on examination of morphological differences in the dorsal fin and adjacent saddle patch region.

photo of group of resident-type killer whales; see caption

Resident-type (fish-eating). The dorsal fin is often more falcate and there is greater saddle patch variation. In particular, a black cup, finger, swirl or open area may intrude into the top of the white saddle patch. Photo by Nancy Black.

photo of transient type killer whale; see caption for more info

Transient-type (mammal-eating). The dorsal fin is often more triangular with a broad base and the saddle patch is large and uniform (without black intrusions, although sometimes with a “feathering” pattern along the front edge of the saddle). Photo by Janice Waite.

photo of offshore type killer whale; see photo for more info

Offshore-type. The dorsal fin is often rounded at the tip with multiple nicks in the fin. The saddle patch can also have black intrusions like resident-type whales. Photo by John Durban.

Three forms of killer whales, termed “resident,” “transient,” and “offshore” have been described in the coastal waters of the Northeast Pacific Ocean. These terms were originally designated by killer whale researchers to describe the whales’ patterns of occurrence, particularly in British Columbia and Washington. “Residents” were generally in inland waters all summer, whereas “transients” only appeared occasionally, and “offshore” whales were seen only in outer coast waters.

As studies have increased over larger geographical and temporal scales, it has become apparent that these terms do not fully depict the ranging patterns of these three ecotypes. However, recent research continues to confirm that the three terms do refer to very distinct types of killer whales that can be distinguished based on genetics, acoustics, and morphology. Research also shows the terms apply to distinct types of feeding ecology. Resident killer whales are known to be primarily fish-eaters, in contrast to transients that feed primarily on marine mammals. Relatively few feeding observations have been made for the offshore type, but initial data suggest they also eat fish.

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