Social associations and habitat selection delineate two subpopulations of west coast transient killer whales (Orcinus orca rectipinnus) in the California Current System
Bibliographic record
Abstract
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, socially and spatially discrete population. We analyzed 2,232 georeferenced encounters of photographed transient killer whales collected between 2005 and 2021 from dedicated research ship surveys, small vessel surveys, and opportunistic sightings, to assess their social and population structure in relation to habitat characteristics. Using social network and geospatial analysis software, we identified two socially and geographically independent subpopulations with cohesive social structures-one that frequents shallow nearshore coastal areas (inner coast subpopulation) and a second that primarily inhabits deeper waters along the continental shelf-break and slope (outer coast subpopulation). The inner coast subpopulation (n = 345 photo-identified whales) most commonly occurred in intracoastal waterways and along the shallow coastal margins of the continental shelf where they fed primarily on pinnipeds and small cetaceans within 5 km of shore. In contrast, the outer coast subpopulation (n = 211 photo-identified whales) occurred within 6.1 km of the continental shelf-break and in far offshore waters (e.g., 120 km offshore) near deep submarine canyons and subsurface sea mounts-where they fed primarily on pelagic pinnipeds, oceanic delphinids, and large cetaceans. Our findings demonstrate that the west coast transient killer whale population, though genetically distinct, is structured into two socially and ecologically distinct subpopulations along the west coast of North America. This division underscores the need for conservation efforts to be tailored to their unique ecological and social characteristics.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.001 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.001 | 0.001 |
| Science and technology studies | 0.001 | 0.000 |
| Scholarly communication | 0.001 | 0.000 |
| Open science | 0.000 | 0.001 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".