The Killers of California and Oregon

The Killers of California and Oregon
Marine Mammal Research Unit

Thirteen years of photo-identification data of killer whales observed in California and Oregon provide new insights into the distribution and population structure of mammal-eating killer whales in the eastern North Pacific Ocean.

A new catalogue of mammal-eating killer whales (Transients or Bigg’s) found off the coast of California and Oregon has just been published by NOAA. It contains the images and names of 150 individuals compiled from photographs taken over 13 years during whale watch ecotours, dedicated line transect surveys, and opportunistic marine mammal surveys in California and Oregon.

A group of outer coast transient killer whales off Newport, Oregon [photo: NOAA SWFSC].

According to lead author, Joshua McInnes (UBC Marine Mammal Research Unit), “Only 26 of the catalogued 150 individuals known to be alive in 2018 have been seen further north in Washington, British Columbia, and Alaska. The remaining 124 transients have primarily been found near the continental shelf break, or in the deep waters over the Monterey Submarine Canyon.”

Outer coast transient killer whale OCT001 visiting the Salish Sea in 2009 [photo: Josh McInnes, UBC Marine Mammal Research Unit].

The authors suspect these 124 individuals — seen only in California and Oregon — belong to a distinct “outer-coast” assemblage of transients that is separate from individuals in the “west-coast” population known to frequent the near-shore waters of Washington, British Columbia, and Southeast Alaska.

Additional information about this population of killer whales can be obtained from the recently published catalogue available below.

Outer coast transient killer whale OCT030B in pursuit of a Pacific white-sided dolphin in Monterey Bay, California [photo: Selena Rivera].

Josh McInnes is a MSc student at the Marine Mammal Research Unit at the University of British Columbia


Transient Killer Whales of Central and Northern California and Oregon: A Catalog of Photo-Identified Individuals.
McInnes, J.D., C.R. Mathieson, P.J. West-Stap, S.L. Marcos, V.L. Wade, P.A. Olson and A.W. Trites. 2021.
NOAA Technical Memorandum NMFS-SWFSC-644:149 p.
Photo-identification studies of transient killer whales (Orcinus orcas) off western North America have primarily been conducted in the coastal inland waterways of Washington State, British Columbia, and southeastern Alaska. Less is known about transient killer whales along the outer coast and offshore waters of Oregon and central and northern California. We examined 13 years of photo-identification data to identify individuals and obtain a minimum census for this region, and to summarize information that could be useful for evaluating a hypothesis that whales using this area belong to a distinct assemblage. Data contributions came from opportunistic marine mammal surveys, whale watch ecotours, and dedicated line transect surveys. Transient killer whale photographs were obtained from 146 encounters between 2006 – 2018. These included 136 encounters in Monterey Bay, California, 5 encounters off central and northern California, and 5 encounters off Oregon. The number of unique individuals seen during this time totaled 155, of which 150 were considered to be alive (as of 2018). These included 34 adult males, 51 adult females, 24 sub-adults, and 41 juveniles. Through repeated observations of association patterns, a total of 30 matrilineal groups were identified. New whales were identified each year, including previously unidentified adults and new calves. Identification images of the dorsal fins, saddle patches and postocular patches were obtained. Details on sex, maternal ancestry, sighting history, and distribution are provided where known. These cataloged transient killer whales were predominantly encountered off the outer coast near the continental shelf break or in deep pelagic waters overlying the Monterey Submarine Canyon. The vast majority (>83 %) of whales identified in the study area could not be matched to transient killer whales in photo ID catalogs for coastal waters of the Pacific Northwest. These factors are consistent with there being a distinct “outer coast” assemblage within the west coast population of transient killer whales, but more research is needed to investigate this further.
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*Please note the full publication file is very large. It can be found here