London, March 28 : German scientists have shown that just like primates, birds can also cooperate with each other to win a food reward by performing tasks that are difficult for them to do on their own.
Amanda Seed, a researcher at the Max Planck Institute for Evolutionary Anthropology in Leipzig, says that her team has tested co-operation between pairs of rooks in a study.
During the study, the researchers placed a 60 centimetre-long tray laden with food just out of the reach of two rooks placed inside a box.
The food was visible to the birds through a slit, but they would have to use a string thread through eyeholes at the back of the tray to drag it through the slit towards them.
The tray could move only when each bird pulled one end of the sting simultaneously.
At first, the researchers had to force the rooks to team up. But, with very limited training, all eight birds they studied mastered the act of co-operation, a specialisation previously thought unique to primates.
The researchers, however, observed that the birds came unstuck when the depth of their understanding of cooperation was tested.
In another experiment, one rook was presented with an out-of-reach tray, and the other was placed in an adjoining room. The second rook had to scrabble through a hatch before getting into a position where it could pull on the string.
The researchers observed that the first rook almost invariably pulled its own end of string instead of waiting for its partner to arrive.
Similar studies have revealed in the past that chimpanzees wait for their partner before acting.
From these observations, Seed deduces that rooks may fail to fully grasp the benefits of cooperation because individuals rarely compete.
She says that in polygamous chimp society, an individual interacts with others chimps, and thus has to quickly learn about cooperation as a "commodity" on the "biological market".
The researcher says that rooks, on the other hand, form monogamous relationships, seldom interact with other individuals, and thus never learn the true value of cooperation.
"It may be that the sort of cooperation we see in humans (and chimps) could only evolve in response to a very particular combination of pressures that lead to an awareness of when cooperation is worthwhile," New Scientist quoted her as saying.
A report describing Seed's study has been published in the journal Proceedings of the Royal Society.