The diverse diet of southern Alaska resident killer whales shifts across spatiotemporally distinct foraging hotspots Ecosphere

Top predators influence ecological communities in part through the prey they consume. Prey preferences often shift throughout the year, reflecting both seasonal and geographic patterns of habitat use and the relative abundance of preferred prey species. Killer whales (Orcinus orca) are top predators in the marine ecosystem, and understanding their diet is critical to assess their ecological impacts and role. In this study, we examine the diet of the southern Alaska resident killer whale population across three major foraging hotspots. We leverage two complementary sampling methods—morphological ID and genetic metabarcoding—to reveal strong spatiotemporal patterns in diet from May through September. Chinook, chum, and coho salmon were each important prey resources in different locations and times, with consistent dietary contributions from Pacific halibut, arrowtooth flounder, and sablefish. Our results reveal a diverse, location-specific, and strongly seasonal foraging strategy in this top predator and highlight the increased resolution provided by using ensemble techniques to characterize foraging behavior. Effective conservation and management of this population will depend on broad spatiotemporal sampling to accurately characterize foraging ecology.