Killer Whales in the Central Tropical Pacific: Occurrence, Resightings, Morphology, and Acoustics

ABSTRACT Compared to their well‐studied coastal temperate counterparts, killer whales ( Orcinus orca ) in tropical‐subtropical and oceanic areas are under‐documented. We used sighting, photo‐identification, and acoustic data of killer whales in the central tropical Pacific (CTP), collected from multiple platforms between 2002 and 2023, to assess their temporal and spatial distribution, group dynamics and behavior, movements, pigmentation and dorsal fin morphology, and vocalizations. Killer whales were rarely encountered but occur year‐round in the CTP, primarily in waters deeper than 1000 m. Photo‐identification of 113 individuals included multi‐year resightings of individuals off the main Hawaiian Islands but found no matches to eastern tropical Pacific catalogs. CTP killer whales share characteristics with other tropical‐subtropical killer whale populations including pigmentation and morphology, small group sizes (range: 1–12, Mdn = 5), and diverse prey choices (e.g., other cetaceans, bony fishes, and sharks). Acoustic recordings, collected during shipboard sightings, were dominated by echolocation clicks and high‐frequency modulated whistles and provide the first detailed characterization of CTP killer whale vocalizations. This is the most expansive study of CTP killer whales to date, and it underscores the importance of continued collaboration between research groups and the local community in order to better understand rarely sighted species.