William K Oestreich , Kelly J Benoit-Bird, Briana Abrahms, Tetyana Margolina, John E Joseph, Yanwu Zhang, Carlos Rueda, John P Ryan

The strategies that animals employ to track resources through space and time are central to their ecology and reflect underlying ecosystem phenology. Deep-sea ecosystems represent Earth’s largest habitable space, yet ecosystem phenology and effective animal movement strategies in these systems are unknown. Analyzing seven-plus years of continuous population-level acoustic observations, we find evidence for seasonal, latitudinal migratory movements by sperm whales in the Northeast Pacific. Assessment of size-correlated echolocation click characteristics indicates that all demographic groups undertake seasonal movements in this region. Integration of these population-level empirical results with individual-level movement simulations provides the first evidence of seasonal resource-tracking migration in a deep-sea top predator. While often described as nomadic, we instead find that sperm whales track oceanographic seasonality in a manner similar to many surface ocean predators. Together, these findings elucidate the drivers of this top predator’s long-distance movements and shed light on the shrouded phenology of deep-sea ecosystems.