The ontogeny of caching in ravens, Corvus corax

Ravens scavenging on carcasses devote much of their time to carrying off loads of food for temporary storage in caches. Ways of reducing conspecific pilfering of these caches include camouflaging caches with debris and positioning caches at a distance from and/or out of sight of potential competitors. We examined the acquisition and improvement of these caching skills in young captive ravens. We identified a hierarchy of elements in the caching behaviour, ranging from simply pressing the caching items towards solid structures to the appropriate covering of them with surrounding material. The development of these elements was closely linked with the birds' acquisition of Piagetian Stages of object permanence. Furthermore, we distinguished between the young ravens' initial caching of edible and inedible items. We tracked the individuals' temporal development of placing their caches at a distance from and out of sight of conspecifics and their social interactions over caches. Behaviours aimed at preventing pilfering were associated with competitive interactions and were manifested only with edible items. We conclude that the skills for camouflaging caches are primarily affected by maturation of representational capacities for hidden (i.e. not visible) items, whereas the skills for the positioning of caches are strongly affected by experience gained through social interactions.