December 25, 2008
‘Calculated Reciprocity’ Observed In Orangutans
Scientists have discovered that orangutans can help each other get food by trading tokens, but only if the help is mutual.
It seems orangutans can learn the value of tokens and trade them, helping each other win bananas, according to researchers from the University of St Andrews.
This is the first documented evidence of "calculated reciprocity" in non-human primates. Gorillas and chimpanzees were much less willing to co-operate, researchers said.
In particular, two orangutans - Bim and Dok - who live in Leipzig Zoo, Germany, were especially good at helping each other.
They were initially given several sets of tokens and learned the value of the different types.
The orangutans were able to exchange one type of token for bananas for itself, another type could be used to gain bananas for a partner, and a third had no value.
The female, Dok, was particularly good at swapping tokens to get bananas for Bim, the male. Bim would even occasionally point at the tokens to encourage her.
Interestingly enough, he was less interested in trading tokens that would win bananas for her.
She eventually became less willing to help him out, and Bim responded by trading more and more, until their efforts were more or less equal.
Valerie Dufour, who led the research at the Scottish university, said Bim's move demonstrated a calculation behind the giving.
"If you don't give me enough, then I don't give you either; but if you give me enough, OK, then I buy your co-operation, and I secure it by giving too."
Many animals exchange goods and services with each other; the grooming of primates is an obvious example.
But there has been no experimental evidence before of "calculated reciprocity", where animals adapt their own behavior in response to how another is helping them, researchers said.
"It's not just humans that calculate about giving, and it's not just humans who expect to be given something in return when they are co-operative," said Dr. Dufour. "Orangutans do that too."
The researchers said, however, that other apes like chimpanzees, gorillas and bonobos were less able or willing to play the game.
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