Ravens can imagine being spied upon by a hidden competitor, showing a capacity for abstraction once thought to be exclusively human, according to a study released Tuesday.
In a clever set of experiments, scientists showed that the famously intelligent birds take extra care to hide food if they suspect their movements are being monitored by another raven, even when the second bird is not really there.
The findings, published in the journal Nature Communications, suggest that ravens - without recourse to direct observation - are able to understand what might be going on in the mind of another individual.
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"This shows that traits that we consider ‘uniquely human' may be found in animals too," said lead author Thomas Bugnyar, a professor at the University of Vienna and a leading expert on social cognition in animals.
Over a six-month period scientists studied 10 ravens that had been raised in captivity.
The birds were placed in adjoining rooms divided by a window, that was initially left uncovered so one raven could watch while the other was given food to hide.
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Researchers then covered the window, but left a peephole in it that the birds were taught they could see and be seen through.
Once this basic training was in place, the scientists played a recording of raven sounds while a bird was in the process of storing its food.
Only when the peephole was open, however, did the raven take extra care to hide its goodies. If the peephole remained closed, the bird - even when raven noises were audible - somehow concluded that it could not be spied upon.
Previous research, mainly with chimpanzees, has shown that non-human animals can understand what others are seeing.
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But it was assumed that they did so by monitoring an individual's head or eye movements, what scientists call "gaze cues."
"It was still an open question whether any non-human animal can attribute the concept of ‘seeing' without relying on behavioural cues," the study noted.
Even without those cues, however, the ravens showed that they understood they were perhaps being watched, and changed their behaviour accordingly.
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"This strongly suggests that ravens make generalisations based on their experience, and do not merely interpret and respond to behavioural cues from other birds," said Bugnyar.
Scientists determined that the caching bird thought it was being observed when it hurried to hide its food, or when it later - once the coast was clear - returned to improve the food's hiding place.
Young ravens are known to form and break alliances, demonstrating "social flexibility." As adults, they typically defend territory and live in long-term monogamous relationships.