Tactical Deception in ravens, Corvus corax

Ravens forage in groups of unrelated individuals at ephemeral food sources such as carcasses. During this crowd- foraging the birds carry off consecutive loads of food and cache it for later consumption at some distance to the feeding site. However, birds may observe each other and raid each others caches. Recent observations and preliminary data derived under controlled conditions in aviaries indicate that cache-making ravens a) attempt to avoid the presence of conspecifics, b) desist from cache-making if watched by conspecifics, and c) immediately retrieve a cache if they discover another individual nearby who may have watched them making their cache. In turn, observer ravens a) pay particular attention to ravens that are about to cache food, b) appear to try to conceal their presence from the caching bird, and c) do not approach the others` cache until the cache-maker has left the area. This indicates that the cachers try to conceal the location of their caches, and observers try to conceal the intention to observe the cachers. Thus, the behaviours of both cachers and raiders are essentially about manipulating the attention of the opponent and hence, may constitute some form of tactical deception. I here purpose to experimentally study the cognitive mechanisms underlying this deception. My studies would be conducted with hand-reared birds in association with Prof. B. Heinrichs aviary complex for ravens at the Univ. of Vermont. It would involve specifically-designed experimental set-ups where I can manipulate visual access between cachers and observers, and where I can control what, relative to cache location, a cacher may allow an observer to see. The results of my discrete series of tests will allow to distinguish whether the deception can be accounted for by associative learning, or by the attribution of mental states to others.