US EditionWest Coast Killer Whales Split into Two Distinct Groups
Analysis of 2,200 encounters over 16 years reveals inner and outer coast transient killer whales differ in habitat, prey, and social groups along the West Coast.
- On November 6, 2025 the study in PLOS One used 16 years of data to confirm West Coast transient killer whales split into inner and outer coast subpopulations, with McInnes saying they `eat different things, hunt in different areas`.
- Habitat differences and human activity explain the groups' divergence, linked to inner and outer coast transients occupying nearshore inlets versus continental shelf breaks, with human effects including culling and prey harvesting.
- Field data show stark differences in range and diet: inner coast transients number about 350, forage in groups of about five near six kilometres from shore, while outer coast transients number about 210, hunt in groups of about nine up to 120 kilometres offshore.
- Management authorities should tailor plans to each subpopulation's needs, as McInnes reported `I have seen outer coast transients acting strangely around inner coast animals` and `co-mingling was less than one per cent.` Dr. Trites emphasized distinct lives and the need for tailored conservation.
- Using social network analysis of photographs from 2005–2021, Dr. Trites said, `'We essentially drew friendship maps to see which whales spent time together, and then looked at where they were seen to figure out if they hung out in specific neighborhoods,'` based on over 2,200 encounters over 16 years.
14 Articles
14 Articles
West Coast Mammal-Eating Killer Whales Are Two Distinct Communities That Rarely Mix
New research has confirmed that West Coast transient killer whales who live between British Columbia and California are two distinct subpopulations: inner and outer coast transients.
Eurek Alert
ubc.caWest Coast mammal-eating killer whales are two distinct communities that rarely mix
New research has confirmed that West Coast transient killer whales who live between British Columbia and California are two distinct subpopulations: inner and outer coast transients. Based on 16 years of data from more than 2,200 encounters, the study published in PLOS One challenges previous assumptions about this group of mammal-eating killer whales. “I've been thinking about this possibility for 15 years,” says first author …
West Coast mammal-eating killer whales are two distinct communities that rarely mix, finds study
New research has confirmed that West Coast transient killer whales who live between British Columbia and California are two distinct subpopulations: inner and outer coast transients.
PLOS
National Institutes of Health (NIH)…Social associations and habitat selection delineate two subpopulations of west coast transient killer whales (Orcinus orca rectipinnus) in the California Current System
West coast transient (mammal-eating) killer whales (Orcinus orca rectipinnus) inhabit the California Current off the west coast of North America from southern British Columbia, Canada to southern California, United States. Although genetically distinct from other killer whale populations, observed differences in social associations and habitat use of some individuals suggest that west coast transient killer whales may not constitute a single, so…
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