Research press release


Nature Communications

Zoology: Ravens know when they are being spied on



今回、Thomas Bugnyarたちの研究グループは、競争相手の姿が見えない条件下に置かれたワタリガラス個体の食物貯蔵行動を観察することで、この可能性を無視することができた。今回の研究では、完全に壁に囲まれ、小さなのぞき穴だけがついた実験場にワタリガラス個体を入れ、のぞき穴の反対側で別のワタリガラスが発する音の録音を再生して、このワタリガラス個体が他者に見られている可能性をシミュレートした。


Ravens are able to infer what a competitor might be able to see, even when they are unable to see the other raven themselves, finds a study in Nature Communications. This provides support to the notion that members of the crow family possess a so-called ‘Theory of Mind’ - the ability to predict the mental state of other individuals - which was once thought to be confined only to humans and non-human primates.

Previous studies testing whether birds might possess a basic Theory of Mind found that scrub-jays are able to infer that they are being watched by competitor birds who might steal their stores of hidden food. However, these studies have been unable to discount the possibility that focal individuals might be following gaze cues from competitor birds, for example by following their line of sight to the food.

Thomas Bugnyar and colleagues discount this possibility by observing individual ravens' food-hiding behaviour when they are unable to see a competitor. By placing an individual raven in a study area that is completely enclosed except for a small peephole, they simulate the possibility that the individual is being observed by playing the recorded sound of another raven on the other side of the peephole.

When the sound is played, the individual raven hides its food in a way that is consistent with the possibility of it being observed by a competitor through the peephole, and it does the same when provided with full visual access to a live bird. This strongly suggests that ravens make generalizations based on their experience, and do not merely interpret and respond to behavioural cues from other birds.

doi: 10.1038/ncomms10506

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