Will groom mom for baby cuddles: market forces govern infant's value within monkey groups.
"Do my hair before you touch my baby" is the rule among mother vervet monkeys and sooty mangabeys when it comes to letting a neighbor snuggle their infants.
As in some other primates, monkey babies attract crowds of females eager to touch, hold and make silly lip-smacking noises at the little ones, says primatologist Cecile Fruteau of Tilburg University in the Netherlands. Her novel study of infant-touching etiquette in the vervets and mangabeys adds them to the short list of animals known to have "markets" for baby fondling: Moms must be groomed for a sufficient time before they let the groomer touch the baby.
What makes this exchange a market is the way sufficient grooming time changes with the baby supply, Fruteau and her colleagues explain in a paper posted online in Animal Behaviour. The price for access to a group's only infant, measured in grooming time for mom, fell when the number of little curies available for cuddling rose.
Price is sensitive to other variables as well, says Fruteau, who documented for the first time that infant age makes a difference in how much grooming the baby attracts to morn. Newborns earn their mothers the longest grooming sessions. One newborn mangabey, for example, the only baby in its group at the time, earned about 10 minutes of fur cleaning and combing for its mom. In contrast, another lone baby didn't even earn four minutes of grooming once it had reached the advanced age of almost 3 months.
Grooming time also correlated with access to vervet babies but not with fondling time or the degree of familiarity allowed. With enough grooming, moms permitted pretty much any female in their group to at least touch or sniff the baby. But it was mostly females with a history of grooming mom who could actually hold the baby.
"Prices" for a baby encounter also varied with rank, as in other infant-handling markets, Fruteau says. A female ranking lower in the group hierarchy of either species had to groom longer for access than a high-ranked monkey did.
Grooming-for-cooing trades have also been reported in chacma baboons and long-tailed macaques. In spider monkeys, the currency is hugging, not grooming.
Comparisons with markets can certainly be useful, says primatologist Rebecca E. Frank of Los Angeles Valley College in Valley Glen, Calif., "but it just leaves some aspects of female exchange unexplained." In her study of olive baboons, about two-thirds of grooming encounters, even without babies involved, don't get promptly or obviously reciprocated. These partners appear to have long-term relationships that don't require immediate settling of accounts.
It remains unclear whybabies stir such urges to fondle, Fruteau says. For vervets and mangabeys that's largely a female urge. Males interact more with older kids.
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|Date:||Dec 4, 2010|
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