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NATURE SCIENCE UPDATE
Monkey morality: Sharing might not be as nice as it's cracked up to be 

14 January 2004
Michael Hopkin

Have you ever given a friend part of your dessert just so they will stop
bugging you for some? You're not alone - chimpanzees and monkeys share their
food with others to avoid hassle too.

The question of why animals give food to others is a tricky one. Previous
theories suggested that generous animals might benefit from similar kindness
at a later time.

But the no-hassle approach offers a simpler explanation, says Jeffrey
Stevens, who carried out the study at the University of Minnesota. Scrounger
and donor are both acting in their best interests - the beggar gets food and
the other is left in peace.

Stevens placed chimpanzees (/Pan troglodytes/) or squirrel monkeys (/Saimiri
boliviensis/) in a cage and provided them with a meal of fruit. In an
adjoining cage was a hungry member of the same species.

The primates rarely passed food through the cage to their hungry mate next
door. But if the partition was opened - giving the hungry animal the chance
to beg, steal or fight for food - sharing was common (ref. 1).

It is analogous to a parent buying a child a toy just to shut them up, says
Stevens. "It's a selfish way to stop the constant pestering," he says.

Intriguingly, hungry chimps harassed their neighbour more when the food was
cut into small chunks. This could reflect the fact that a beggar is more
likely to get a handout if it doesn't seriously deplete the donor's stash.

This form of 'strategic begging' could help scroungers find success by
setting their sights low, Stevens speculates. "It's like a kid saying: 'Can
I have four cookies? Ok, how about one?'," he says. Likewise, most
street-corner beggars ask passers-by for nothing more than their small
change.

The harassment theory may explain many examples of human 'generosity', says
Stevens. But he remains convinced that we are capable of genuine charity
too. "It's a pretty decent analogy," he says, "but I think there's also a
desire for us to help those who are less fortunate."


References
1. Stevens, J. R. The selfish nature of generosity: harassment and food
sharing in primates. /Proceedings of the Royal Society of London B/,
published online, doi:10.1098/rspb.2003.2625 (2004).


(C) Nature News Service / Macmillan Magazines Ltd 2004