Open ocean ecosystems represent the vast majority of Earth’s habitable space and host its largest animal communities. Animals inhabiting these ecosystems tend to aggregate in dynamic, ephemeral hotspots of social and predator-prey interactions. These aggregations are not only central to the lives of oceanic animals, but they also play a major role in global carbon cycling and drive patterns of interactions between animals and humans. The physical movement of these fluid ecosystems plays a role in driving these aggregations, but many pelagic organisms are not simply passive drifters subject to ocean currents. A growing body of research is revealing the significant role of active behavior in the social aggregation of oceanic animals. This project aims to understand how ocean physics and animal social behaviors interact to drive predator-prey aggregations in the pelagic ocean. This study focuses on endangered blue whales and their obligate krill prey, and will provide critical information not only to understand how these animals survive and thrive in the ocean, but also to help manage the dynamic ecosystems they inhabit. The results of this project will be communicated to resource managers to inform management of the several existing and proposed U.S. West Coast National Marine Sanctuaries which these species inhabit. This project will also provide research and educational opportunities in partnership with local ocean science internship programs focused on breaking down barriers to participation in the ocean sciences.<br/><br/>Biological patchiness and dynamism across a wide range of spatial and temporal scales are defining characteristics of pelagic ecosystems. The physical processes driving this biological patchiness across trophic levels are increasingly well-understood. Yet behavioral processes also interact with these physical drivers to play a central role in the ephemeral aggregation of predators and prey in the pelagic. This project will make use of recent high-resolution and persistent in situ observations of pelagic prey (krill) behavior, predator (blue whale) behavior, and physical oceanographic dynamics, integrated with in silico experimentation via biophysical and evolutionary simulations. In combination, these observations and simulations will help to unveil the role of social behavior in the biophysical formation of pelagic predator-prey aggregations. The outcomes of this work will influence both broad-scale understanding of how physics and behavior interact to drive patterns of life in Earth’s largest habitable space, as well as local-scale management of the ecosystems these specific predators and prey inhabit.<br/><br/>This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.