Oceanic Orcas: A new population of killer whales in the Northeast Pacific?

Evidence suggests these unknown orcas living in the open ocean may be unlike any other

In the northeastern Pacific, sightings of small numbers of killer whales of unknown ecotype have been sporadically reported during open ocean marine mammal surveys, pelagic birding expeditions, and high seas fishing operations. However, it is unknown whether these oceanic killer whales belong to a mammal-eating ecotype of killer whale, an offshore fish-eating ecotype, or an offshore generalist type. We attempted to determine the ecotype of 49 unknown individuals observed during 9 encounters from 1997-2021 in the deep oceanic waters far from the coastlines of California and Oregon (>65 km) based on their foraging behaviors, prey species consumed, morphologies, and the prevalence of cookiecutter shark bite scars. We hypothesize that these killer whales may represent a distinct oceanic subpopulation of transient killer whales or an undescribed oceanic population that feeds on marine mammals and sea turtles in the oceanic open ocean waters beyond the continental shelf break.

Publication

2024
Evidence for an oceanic population of killer whales (Orcinus orcas) in offshore waters of California and Oregon. McInnes, J. D., A. W. Trites, C. R. Mathieson, M. E. Dahlheim, J. E. Moore, P. A. Olson and K. M. Lester. 2024. Aquatic Mammals 50:90-106. abstract In the northeastern Pacific, sightings of small numbers of killer whales of unknown ecotype have been sporadically reported during open ocean marine mammal surveys, pelagic birding expeditions, and high seas fishing operations. However, it is unknown whether these oceanic killer whales belong to a mammal-eating ecotype of killer whale, an offshore fish-eating ecotype, or an offshore generalist type. We attempted to determine the ecotype of 49 unknown individuals observed during 9 encounters from 1997-2021 in the deep oceanic waters far from the coastlines of California and Oregon (>65 km) based on their foraging behaviors, prey species consumed, morphologies, and the prevalence of cookiecutter shark bite scars. We hypothesize that these killer whales may represent a distinct oceanic subpopulation of transient killer whales or an undescribed oceanic population that feeds on marine mammals and sea turtles in the oceanic open ocean waters beyond the continental shelf break.

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