Mathematically modelling the effects of boldness on foraging success in pelagic seabirds

Many animal populations include a diversity of personalities, and these personalities are often linked to foraging strategy. However, it is not always clear why populations should evolve to have this diversity. Optimal foraging theory typically seeks out a single optimal strategy for individuals in a population. So why do we see a variety of strategies existing in a single population? We aim to provide insight by modelling the particular case of pelagic seabirds that forage on patchy prey. Seabirds have partial knowledge of their environment: they do not know where the next patch will emerge, but they may have some understanding of which locations are more likely to lead to patch emergence. Many optimal foraging studies assume complete knowledge (e.g. Marginal Value Theorem) or no knowledge (e.g. Lévy Flight Hypothesis). Here, we construct new modelling approaches that incorporate partial knowledge. To assess the optimality of personality types, we construct an ordinary differential equation model, incorporating the foraging strategies favoured by different birds along the bold-shy personality continuum. We show that being shy (resp. bold) is optimal when living in a population of bold (resp. shy) birds. This observation gives a plausible mechanism behind the emergence of diverse personalities. By extending our model using individual-based modelling techniques, we further explore the effects of memory use and environmental heterogeneity on the foraging success of different personalities. We show that memory use in foraging decisions, particularly movement towards known foraging sites, is beneficial, but an over-reliance on this strategy is detrimental. We also show that poor environmental conditions force bolder individuals to adopt a shyer foraging strategy, and will likely result in a narrowing of the diversity of personalities in seabird populations.