Collaborative Research: Predator facilitation across a variable marine environment.

In the open ocean, unique and poorly understood interactions between apex predators can take place, where one predator influences prey to make them more susceptible to other types of predators. During such “facilitation” interactions between large, predatory pelagic species (dolphins, tunas, swordfish, sharks) attack forage fish from below, driving dense aggregations to the surface where they become available to aerial predators (seabirds).

These interactions are hard to observe, which is problematic because they may be particularly important for numerous seabird species believed to be dependent on facilitated foraging. During this project, we will develop methods to remotely observe these interactions using a novel combination of biologging devices (GPS, cameras, accelerometers, heart rate loggers, and stomach temperature loggers) in concert with new statistical approaches for analyzing animal tracking data.

This will allow the investigators to detect and characterize these interactions more accurately and measure the degree to which facilitation improves foraging efficiency in tropical pelagic seabirds. The project will occur at Palmyra Atoll in partnership with NOAA, the US Fish and Wildlife Service, and The Nature Conservancy in an effort to provide management guidance regarding the importance of predator facilitation and its potential loss on seabird populations world-wide.

Graduate and undergraduate students at the four participating universities will be involved in research and receive valuable hands-on educational and training experiences.

This project will investigate the nature of and importance of open-ocean predator facilitation, a key but overlooked trait-mediated interaction between two predators that target a common prey. To achieve these objectives, the project will develop methods to remotely detect facilitation interactions and evaluate their energetic consequences to foraging seabirds by combining data from a unique suite of biologging devices in analyses using novel statistical modeling techniques.

Specifically, animal-borne cameras will be combined with GPS telemetry deployed on red-footed boobies (Sula sula) to characterize facilitated foraging interactions around Palmyra Atoll in the central Pacific. Cameras will directly observe the presence of facilitation and potentially the taxonomic composition of other predators, while bird-borne GPS data will record movement patterns, location, and frequency of these interactions.

With these data, the investigators will develop Bayesian dynamic parameter movement models that detect facilitation from GPS-observed movement patterns alone, when camera data are not collected. Finally, on a pilot basis to demonstrate feasibility, the models will then be fit to individuals tracked by GPS while carrying biologging equipment that measures energetic expenditure (triaxial accelerometry, heart rate loggers) and gain (stomach temperature loggers) to evaluate the associated energetic impact of facilitation on overall energy balance of foraging seabirds.

These observations will be supplemented with more traditional approaches to demonstrate the technical feasibility of this approach for measuring the impacts of facilitated foraging in free living individuals that forage in the open ocean. Once developed, it will be possible to relate the importance of this ecological interaction to breeding success at the population-level for seabirds that can be similarly observed, making precise observation of foraging behaviors possible from available biologging technologies and statistical modeling approaches.

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.