Spatiotemporal Variation in Marine Mammal Antipredator Behaviors Resulting From a Predation Pinch Point

Predator-prey relationships are fundamental aspects of ecological systems that determine the behavior and distribution of animals across time and space. Variation in predation risk can be used to explore when and why individuals perform antipredator behaviors. In marine environments, it is difficult to observe predation and antipredator behaviors. Fortunately, biologgers have long been used to study the distribution and dive behaviors of northern elephant seals (Mirounga angustirostris) on their twice-yearly foraging trips. Here, we analyzed the horizontal and vertical movements of 353 adult female seals across 17 years to investigate how they move through a "predation pinch point"-an area where predators and prey co-occur due to habitat features. Specifically, we explored the diel timing of departure from and arrival to the colony and spatial concentrations in benthic diving (diving close to/along the seafloor). Benthic diving and temporal concentrations in movement to and from the colony may serve antipredator functions, such as minimizing detection and ambush by predators. We found that only the timing of departure from and not arrival to the colony showed any significant temporal pattern. Seals tended to depart during the late afternoon or at night but arrived throughout the day. Spatially, there were consistent patterns of benthic dives during the first and final parts of their trips as seals crossed the continental shelf. By combining dive, location, bathymetry, and predator data, we were able to identify how seals modified behaviors that likely help them avoid predators. These findings illustrate how animals respond to varying levels of predation risk and can be used to develop more precise dynamic landscapes of fear.