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

Abstract

23Foraging decisions must balance the energy gained, the time investment and the 24 influence of key environmental factors. In our work, we aimed to examine the 25 importance of predation risk cues and experience in the feeding efforts and decision-26 making process when a novel food resource is presented. To achieve this, free ranging 27 wood mice Apodemus sylvaticus were live-trapped in "Monte de Valdelatas" (Madrid) 28 by setting 80 Sherman traps in 4 plots. Traps were subjected to two food access 29 difficulties three-night consecutive treatments: open plastic bottles and closed bottles, 30 both using corn as bait. To generate predation risk, we set fox faeces in half of the traps 31 in each plot. Also, we considered indirect predator cues as the moon phase. We analyse 32 whether mice had bitten the bottles and the area gnawed of each bottle was measured. 33 We discovered that mice feeding decisions and efforts were driven by food access 34 difficulty, experience and predation risk. The ability of mice to properly balance their 35 energy budget was probed since they bit and performed bigger orifices in the closed 36 bottles, hence, individuals can adapt the feeding effort when a new food source is 37 available. Moreover, experience was determinant in the use of this new resource since 38 recaptured mice gnawed the bottles more successfully and the skill was improved each 39 time an individual was recaptured. Additionally, direct predation risk cues prompt mice 40 to bite the bottles whereas the effect of different moon phases varied among the 41 treatments. This is the first study that provides direct evidence of wild mice formidable 42 efficacy to exploit a new nutrient resource while deepening in crucial environmental 43 factors that shape decision-making procedure. 44 Keywords 45 Apodemus sylvaticus, food access, energy budget, predation risk, decision making, 46 learning, moonlight 48 Wild animals must cope with unpredictable environmental demands. In this 49 particular setting, choices made by animals when selecting food and regulating intake 50 aim to satisfy their specific levels of nutrient requirements [1, 2, 3]. The variable time 51 and space food availability challenge animals to select the type of food which best 52 meets their nutrient demands and to evaluate if it counterbalances the energetic effort 53 they have to make to obtain it [4]. These changeable environmental conditions have led 54 to the development of a wide array of adaptations to efficiently satisfy the energetic 55 requirements of all life forms [5, 6, 7], making possible for them to exploit and utilize 56 heterogeneous food sources. The mechanisms which underlay feeding choices are rather 57 diverse, being both endogenous and environmental factors involved in the decision 58 process [8, 9, 10, 11, 12]. It is known that animals possess the ability to learn about the 59 characteristics of the items in their diet and that feeding choices are experience 60 dependent [12, 13, 14, 15, 16]. In this manner, experience and learning ...