Year-round foraging strategies of far-ranging marine predators: flexibility, consistency and constraint

Recent studies of a wide range of species have revealed that during the breeding season, individual predators may employ consistent and distinctive strategies to locate and capture prey. For instance, during the chick-rearing period each year, individual gannets have marked and consistent differences in their foraging distances, locations, movement patterns at sea and marine habitat associations, all reflecting qualitative differences in the types of food resources that birds exploit when providing food for their chicks (small planktivorous fish such as sandeels, fast mid-water predatory fish such mackerel and herring or material discarded from fishing vessels; Patrick et al. 2015; Wakefield et al. 2015). The constraints on parents with offspring to feed are, however, very different to those operating at other times of year, and it is not known how the foraging strategies of individuals vary across the annual cycle. Yet the degree of within- and between-season flexibility in foraging strategies has important implications both for understanding how such individual specializations are developed and maintained, and for predicting the likely population-level consequences of fisheries and climate related changes to marine ecosystems.

The development of miniaturised electronic logging and tracking devices now enables the detailed study of wide-scale movements of free-ranging wild animals, at costs compatible with obtaining appropriate sample sizes for statistical analysis. In particular, the use of GPS tags and time-depth recorders enables the study of individual movements and behaviour, including diving behaviour, with great precision and at high spatial and temporal resolution, while the use of miniature geolocators allows individuals to be tracked at lower resolution across the entire year. Over the past seven years (since 2010) we have established a study group of >300 breeding adult gannets, each individually colour-ringed for ease of identification, at the world’s largest gannet colony at Bass Rock, SE Scotland. Many of these birds are of known sex and have a known foraging strategy during chick-rearing, identified through analysis of both tracking and physiologically-derived dietary information (Wakefield et al. 2015). Crucially, we are also able to capture and track these birds almost as soon as they return to the colony each spring, providing the exciting prospect of tracking individual birds from pre-laying onwards each year. This project will now take advantage of this near-unique opportunity to examine the variation in individual foraging strategies and specialization across the entire annual cycle.

This research has very strong potential to yield high-impact outputs, building on recent work within this research group (e.g. Wakefield et al 2013). You will work under the supervision of Professor Keith Hamer and Dr Chris Hassall within the wildlife telemetry group in the School of Biology. This project provides a high level of specialist scientific training in capturing, handling and deploying a wide range of trackers and loggers on free-living wild birds, and in analysis and presentation of tracking data using a wide range of advanced geostatistical and related methods. You will also have access to a broad spectrum of training courses and workshops provided by the School of Biology, from numerical modelling and data analysis using R, through to effective use of social media, managing your degree and preparing for your viva (http://www.emeskillstraining.leeds.ac.uk/).