WHEN it comes to grooming, female baboons seem to have a lot in common with
commodity traders.
Most primatologists believe that baboons groom each other to cement long-term
strategic allegiances that will give the animals a competitive edge. But Peter
Henzi of the University of Natal in South Africa, and Louise Barrett of
Liverpool University believe they have a better explanation. They say baboons
exchange grooming for more immediate favours within a 鈥渂iological market鈥�. Such
commodities are controlled by individual animals, and can usually only be got by
trading.
鈥淧eople make an awful lot of assumptions about grooming, and now that鈥檚 being
questioned. That鈥檚 very valuable,鈥� says Joan Silk of the University of
California in Los Angeles.
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Henzi and Barrett reasoned that grooming, which keeps animals healthy by
removing ticks, is an ideal baboon commodity. Female baboons also like to hold
the young of other baboons, so baby holding might also be a commodity.
When the two researchers monitored both activities in baboons living in South
Africa, the patterns fitted those of a market-place. For instance, females were
more likely to get their hands on another鈥檚 infant if she groomed the mother
first.
The supply of infants also affected the cost of handling one. When two or
more infants were in a troop of baboons, handling an infant 鈥渃ost鈥� significantly
less in terms of time spent grooming the mother than when there was only one
infant available.
One reason baboon researchers may have overlooked commodity trading before,
says Henzi, is that social hierarchies distort the market forces鈥攁
lower-ranking female has to groom her superior for longer to hold her baby.
What鈥檚 more, groomings are also traded for return groomings, which is difficult
to distinguish from reciprocal grooming associated with bonding.
Barrett also argues that, unlike great apes, baboons do not have the mental
skills needed to form long-term allegiances. 鈥淐ognitively speaking, monkeys are
caught in the present,鈥� she says.
