When should animals share food? Game theory applied to kleptoparasitic populations with food sharing

Animals adopt varied foraging tactics in order to survive. Kleptoparasitism, where animals attempt to steal food already discovered by others, is very common among animal species. In this situation, depending on the ecological conditions, challenged animals might defend, share, or even retreat and leave their food to the challenger. A key determinant of the likely behavior is the nature of the food itself. If food is discovered in divisible clumps, it can be divided between animals in a number of ways. This is the general assumption in one type of game-theoretical model of food stealing, producer–scrounger models. Alternatively, food items may be essentially indivisible, so that sharing is impossible and either the attacker or the defender must retain control of all of the food. This is the assumption of the alternative game-theoretical models of kleptoparasitism. In this paper, using a game-theoretic approach, we relax this assumption of indivisibility and introduce the possibility of limited food sharing behavior between animals in kleptoparasitic populations. Considering the conditions under which food sharing is likely to be common, it is shown that food sharing should occur in a wide range of ecological conditions. In particular, if food availability is limited, the sharing process does not greatly reduce the short-term consumption rate of food and food defense has a high cost and/or a low probability of success, then the use of the food sharing strategy is beneficial. Thus, the assumption of the indivisibility of food items is an important component of previous models.