Understanding the ontogeny of foraging behaviour: insights from combining marine predator bio-logging with satellite-derived oceanography in hidden Markov models.

W James Grecian,Jude V Lane,Théo Michelot,Helen M Wade,Keith C Hamer

doi:10.1098/rsif.2018.0084

Abstract

The development of foraging strategies that enable juveniles to efficiently identify and exploit predictable habitat features is critical for survival and long-term fitness. In the marine environment, meso- and sub-mesoscale features such as oceanographic fronts offer a visible cue to enhanced foraging conditions, but how individuals learn to identify these features is a mystery. In this study, we investigate age-related differences in the fine-scale foraging behaviour of adult (aged ≥ 5 years) and immature (aged 2–4 years) northern gannets Morus bassanus. Using high-resolution GPS-loggers, we reveal that adults have a much narrower foraging distribution than immature birds and much higher individual foraging site fidelity. By conditioning the transition probabilities of a hidden Markov model on satellite-derived measures of frontal activity, we then demonstrate that adults show a stronger response to frontal activity than immature birds, and are more likely to commence foraging behaviour as frontal intensity increases. Together, these results indicate that adult gannets are more proficient foragers than immatures, supporting the hypothesis that foraging specializations are learned during individual exploratory behaviour in early life. Such memory-based individual foraging strategies may also explain the extended period of immaturity observed in gannets and many other long-lived species.

Highlights

The mortality of young animals is typically much higher than that of adults and explaining this difference is fundamental to the study of population age structure, dynamics and persistence [1,2]
We focus on the northern gannet Morus bassanus, a long-lived neritic seabird characterized by over-lapping generations and a long pre-breeding period (5 years) [33]
Adults repeatedly used areas to the northeast and southeast of the breeding colony, while immature birds were much more widely distributed across the North Sea

Summary

Introduction

The mortality of young animals is typically much higher than that of adults and explaining this difference is fundamental to the study of population age structure, dynamics and persistence [1,2]. Young animals may lack the experience to recognize profitable patches [7]. This could lead to the selective disappearance of immatures incapable of developing appropriate foraging skills [8,9] and may explain why many long-lived iteroparous animals delay the age of first breeding until well after they become physiologically mature [10 –12].

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Conclusion