Resourceful mice do not starve: feeding efforts and decision-making process under a restricted unknown food source

Foraging decisions must balance the energy gained, the time investment and the influence of key environmental factors. In our work, we aimed to examine the importance of predation risk cues and experience in the feeding efforts and decision-making process when a novel food resource is presented. To achieve this, free ranging wood mice Apodemus sylvaticus were live-trapped in "Monte de Valdelatas" (Madrid) by setting 80 Sherman traps in 4 plots. Traps were subjected to two food access difficulties three-night consecutive treatments: open plastic bottles and closed bottles, both using corn as bait. To generate predation risk, we set fox faeces in half of the traps in each plot. Also, we considered indirect predator cues as the moon phase. We analyse whether mice had bitten the bottles and the area gnawed of each bottle was measured. We discovered that mice feeding decisions and efforts were driven by food access difficulty, experience and predation risk. The ability of mice to properly balance their energy budget was probed since they bit and performed bigger orifices in the closed bottles, hence, individuals can adapt the feeding effort when a new food source is available. Moreover, experience was determinant in the use of this new resource since recaptured mice gnawed the bottles more successfully and the skill was improved each time an individual was recaptured. Additionally, direct predation risk cues prompt mice to bite the bottles whereas the effect of different moon phases varied among the treatments. This is the first study that provides direct evidence of wild mice formidable efficacy to exploit a new nutrient resource while deepening in crucial environmental factors that shape decision-making procedure.