Fine-scale foraging movements by fish-eating killer whales ( Orcinus orca ) relate to the vertical distributions and escape responses of salmonid prey ( Oncorhynchus spp.)

We sought to quantitatively describe the fine-scale foraging behavior of northern resident killer whales ( ), a population of fish-eating killer whales that feeds almost exclusively on Pacific salmon ( spp.). To reconstruct the underwater movements of these specialist predators, we deployed 34 biologging Dtags on 32 individuals and collected high-resolution, three-dimensional accelerometry and acoustic data. We used the resulting dive paths to compare killer whale foraging behavior to the distributions of different salmonid prey species. Understanding the foraging movements of these threatened predators is important from a conservation standpoint, since prey availability has been identified as a limiting factor in their population dynamics and recovery. Three-dimensional dive tracks indicated that foraging ( = 701) and non-foraging dives ( = 10,618) were kinematically distinct (Wilks' lambda: = 0.321,