Risk of predation makes foragers less choosy about their food

PLoS One. 2017 Nov 9;12(11):e0187167. doi: 10.1371/journal.pone.0187167. eCollection 2017.

Abstract

Animals foraging in the wild have to balance speed of decision making and accuracy of assessment of a food item's quality. If resource quality is important for maximizing fitness, then the duration of decision making may be in conflict with other crucial and time consuming tasks, such as anti-predator behaviours or competition monitoring. Individuals facing the risk of predation and/or competition should adjust the duration of decision making and, as a consequence, their level of choosiness for resources. When exposed to predation, the forager could either maintain its level of choosiness for food items but accept a reduction in the amount of food items consumed or it could reduce its level of choosiness and accept all prey items encountered. Under competition risk, individuals are expected to reduce their level of choosiness as slow decision making exposes individuals to a higher risk of opportunity costs. To test these predictions, the level of choosiness of a seed-eating carabid beetle, Harpalus affinis, was examined under 4 different experimental conditions of risk: i) predation risk; ii) intraspecific competition; iii) interspecific competition; and, iv) control. All the risks were simulated using chemical cues from individual conspecifics or beetles of different species that are predatory or granivorous. Our results show that when foraging under the risk of predation, H. affinis individuals significantly reduce their level of choosiness for seeds. Reductions in level of choosiness for food items might serve as a sensible strategy to reduce both the total duration of a foraging task and the cognitive load of the food quality assessment. No significant differences were observed when individuals were exposed to competition cues. Competition, (i.e opportunity cost) may not be perceived as risk high enough to induce changes in the level of choosiness. Our results suggest that considering the amount of items consumed, alone, would be a misleading metric when assessing individual response to a risk of predation. Foraging studies should therefore also take in account the decision making process.

MeSH terms

  • Animals
  • Choice Behavior*
  • Food Preferences*
  • Food*
  • Kaplan-Meier Estimate
  • Movement
  • Predatory Behavior / physiology*
  • Risk
  • Seeds

Grants and funding

This work was supported by the Joint Programming Initiative on Agriculture, Food Security and Climate Change, European Research Area Network in the Coordinated-Integrated Pest Management in Europe Strategic Research Agenda (FACCE ERA-NET C-IPM) project BioAWARE (AFB Projet 00000877, https://www.faccejpi.com) and the PEERLESS (ANR-12-Agro-0006) and AGROBIOSE (ANR-13-Agro-0001) grants from the French Agence Nationale de la Recherche (http://www.agence-nationale-recherche.fr/en/) to DB and SP. The PhD of Alice Charalabidis was co-funded by the Institute Nationale de la Recherche Agronomique (INRA) and the Region of Burgundy Franche-Comté. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.