The effect of dominance on food hoarding: A game theoretical model

Many food hoarding animals live in small groups structured by rank. The pre sence of conspecifics in the hoarding area increases the risk of losing sto red supplies. The possibility of stealing from others depends on a forager' s rank in the group. Highly ranked individuals can steal from subordinates and also protect their own caches. Since storing incurs both costs and bene fits, the optimal hoarding investment will differ between individuals of di fferent rank. In a game theoretical model, we investigate how dominant and subordinate individuals should optimize their hoarding effort. Our model im agines animals that are large-scale hoarders in autumn and dependent on sto red supplies for winter survival. Many examples can be found in the bird fa milies Paridae and Corvidae, but the model can be used for any hoarding spe cies that forage in groups. Predictions from the model are as follows: Firs t, subordinates should store more than dominants, but in a predictable envi ronment, this difference will decrease as the environment gets harsher. Und er harsh conditions, dominants should store almost as much as subordinates and, later, spend almost as much time retrieving their own caches as subord inates. Second, if on the other hand, bad winter conditions were not expect ed when storing, dominants should spend more time pilfering caches from sub ordinates. Third, in populations that are highly dependent on stored suppli es, dominants should store relatively more than in populations that are les s dependent on stored supplies. Fourth, harsher environments will favor hoa rding. And finally, if dominant individuals store, it implies that hoarders have a selfish recovery advantage over conspecific pilferers.