Among-individual differences in foraging modulate resource exploitation under perceived predation risk

Jana A. Eccard,Melanie Dammhahn,Thilo Liesenjohann

doi:10.1007/s00442-020-04773-y

Jana A. Eccard, Melanie Dammhahn + Show 1 more

Open Access

https://doi.org/10.1007/s00442-020-04773-y

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Abstract

Foraging is risky and involves balancing the benefits of resource acquisition with costs of predation. Optimal foraging theory predicts where, when and how long to forage in a given spatiotemporal distribution of risks and resources. However, significant variation in foraging behaviour and resource exploitation remain unexplained. Using single foragers in artificial landscapes of perceived risks and resources with diminishing returns, we aimed to test whether foraging behaviour and resource exploitation are adjusted to risk level, vary with risk during different components of foraging, and (co)vary among individuals. We quantified foraging behaviour and resource exploitation for 21 common voles (Microtus arvalis). By manipulating ground cover, we created simple landscapes of two food patches varying in perceived risk during feeding in a patch and/or while travelling between patches. Foraging of individuals was variable and adjusted to risk level and type. High risk during feeding reduced feeding duration and food consumption more strongly than risk while travelling. Risk during travelling modified the risk effects of feeding for changes between patches and resulting evenness of resource exploitation. Across risk conditions individuals differed consistently in when and how long they exploited resources and exposed themselves to risk. These among-individual differences in foraging behaviour were associated with consistent patterns of resource exploitation. Thus, different strategies in foraging-under-risk ultimately lead to unequal payoffs and might affect lower trophic levels in food webs. Inter-individual differences in foraging behaviour, i.e. foraging personalities, are an integral part of foraging behaviour and need to be fully integrated into optimal foraging theory.

Highlights

A fundamental problem governing animal behaviour is to balance the benefits of foraging with the costs of becoming food for others (Krebs and Davies 1978)
We aimed to test (1) whether foraging of rodents in artificial landscapes of uniform risks and resources is adjusted to perceived risk level and type, (2) whether aspects of foraging behaviour and remaining resource landscapes vary with perceived risk during different components of foraging, (3) whether individuals differ consistently in aspects of foraging under perceived predation risk, and (4) whether these potential among-individual differences in foraging behaviour are associated with individual patterns of landscape-wide resource exploitation
Supporting the classical patch use model (Brown 1988), risk during feeding was a strong predictor of foraging behaviour and of remaining resource landscapes

Summary

Introduction

A fundamental problem governing animal behaviour is to balance the benefits of foraging with the costs of becoming food for others (Krebs and Davies 1978). One singular erroneous assessment of predation risk, i.e. the likelihood of falling prey to a predator’s attack, may have fatal consequences for individual fitness. Natural selection has favoured adaptations of activity, foraging, space use, and sociality to minimise predation risk (Caro 2005). Predators can affect the fitness of their prey either directly by killing it, or indirectly by scaring it. The changes in prey morphology, physiology, life-history and behaviour in reaction to the mere presence of a predator are collectively referred to as non-consumptive, non-lethal, or indirect predation effects (Lima 1998).

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