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 1000m. 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.

HAWAIIAN TRANSLATION
ʻAʻole palapala nui ʻia nā naiʻa nui weliweli (Orcinus orca) ma nā wahi kai a me nā wahi kopikala-lalokopikala, inā hoʻohālike ʻia me nā lāhui i kilo nui ʻia ma nā kai kemepale. Ua hoʻohana mākou i ka ʻike ʻana, ka hōʻoia kiʻi, a me ka ʻikepili lohea o nā naiʻa nui weliweli ma ka Pākīpika kopikala waena (CTP), a ua ʻohi ʻia mai nā kahua like ʻole mai ka makahiki 2002 a i ka makahiki 2023, i mea e kālailai aku ai i ko lākou ili pūʻuo ʻana ma ka henua a me ke kaime, i ka hana a me ka lawena o ka pūʻuo, i ka neʻe ʻana, i ke kālaikino o ke kualā a me ke kaukala ʻana, a me ka leo ʻana. Kakaʻikahi ka ʻike ʻana i nā naiʻa nui weliweli, ʻike ʻia naʻe ma ka makahiki ma ka CTP, keu hoʻi ma ke kai i ʻoi aku ka hohonu ma ka 1,000m. Hōʻoia kiʻi ʻia he 113 mea a ʻōkomo ʻia ka ʻike hou ʻia ʻana o nā mea ma nā makahiki i kai o ka paeʻāina Hawaiʻi ʻaʻole naʻe i loaʻa kekahi like ma nā waeʻanona Pākīpika kopikala hikina. Like kekahi mau hiʻohiʻona o nā naiʻa nui weliweli CTP me ko nā pūʻuo naiʻa nui weliweli ma kekahi mau wahi kopikala-lalokopikala, e laʻa hoʻi me ke kaukala ʻana a me ke kālaikino, nā pūʻulu liʻiliʻi (mai ka 1–12, ka ʻawelike=5), a me nā ʻano pio like ʻole, e laʻa me nā māmala kai loa ʻe aʻe, na iʻa iwiiwi, a me nā manō. Helu nui ʻia nā kani ana pīnaʻi a me nā hōkio kani kiʻekiʻe ma nā ʻokileo lohea ma nā wā i ʻike ʻia mai ka moku aku, a ʻo ia mau ʻikepili ka wehewehena mua o ke ʻano kikoʻī o ka leo ʻana o nā naiʻa nui weliweli i loko o ka CTP. ʻO kēia ke kālailaina piha loa o nā naiʻa nui weliweli CTP a hiki i kēia, a he hōʻike i ke koʻikoʻi o ka mālama mau ʻana i ka pilina ma waena o nā pūʻulu noiʻi a me ke kaiāulu i mea e maopopo piha i kēia mau lāhui i ʻike kakaʻikahi ʻia.

Citation:

Hill, M.C., S.D. Mahaffy, J.L.K. McCullough, A. Harmon, and R.W. Baird. 2026. Killer Whales in the Central Tropical Pacific: Occurrence, Resightings, Morphology, and Acoustics. Marine Mammal Science 42: e70197. doi: 10.1111/mms.70197