The main Hawaiian Islands (MHI) population of false killer whales was first recognized as a distinct stock in 2008, when the “Hawai‘i stock” was split into both Hawai‘i insular and Hawai‘i pelagic stocks (Carretta et al. 2009). Only a few years after it was first recognized, on December 28, 2012, the MHI insular stock was listed as Endangered under the U.S. Endangered Species Act (ESA), based on evidence of a population decline and a number of threats (Oleson et al. 2010). To help understand and address threats to this population, since 2015 the State of Hawai‘i Department of Land and Natural Resources (DLNR) has obtained grants from NOAA Fisheries under Section 6 of the ESA, and has provided contracts to Cascadia Research Collective (CRC) to collect and analyze data related to this population. Earlier grants (Baird et al. 2019; Baird et al. 2023) have resulted in substantial increases in what is known about this population. This has included identifying areas where individual fishermen are most likely to have encounters with false killer whales, based on the ratio between where tagged whales spend their time and the level of fishing effort in an area (Baird et al. 2021), identification of false killer whale social cluster membership and genetic makeup of clusters (Mahaffy et al. 2023), development of a catalog-based, probabilistic age estimation procedure (Kratofil et al. 2026a) and providing samples for an epigenetic aging study (Martien et al. 2026), documentation of fisheries interactions through injury detection using photographs, and how such interactions vary by age, sex, and social cluster (Harnish et al. 2024), providing data for estimating abundance and trends (Badger et al. 2024, 2025), and examining ecological and social drivers of movement and foraging behavior (Kratofil et al. 2026b, 2026c).
In May 2025 the State of Hawai‘i DLNR Division of Aquatic Resources Protected Species Program provided a one-year contract under NOAA grant NA25NMFX472G0017 to CRC. The goals of the contract to CRC were to collect and synthesize data on the MHI insular population of false killer whales to address life history, demographics, habitat use, and spatial distribution, as well as provide data to NOAA Fisheries Pacific Islands Fisheries Science Center (PIFSC) for continued abundance estimation and population trend analyses. From May 2025 through April 2026, CRC undertook a variety of field work and analytical efforts to address these goals, providing new information on this population, including the first documentation of a false killer whale entanglement in marine debris. This report summarizes the results of these efforts.
Citation:
Baird, R.W., C.J. Cornforth, S.D. Mahaffy, M.A. Kratofil, M.A. Mohler, A.B. Douglas, and A.E. Harnish. 2026. Efforts to Examine Spatial Distribution, Life History, Demographics, and Habitat Use of Endangered Main Hawaiian Islands False Killer Whales in 2025 and Early 2026. Report to the State of Hawai‘i Board of Land and Natural Resources under Contract No. 73039.
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