It's Monkey Business

VIGOTHA THARMARAJAH REPORTS ON THE BOOMING BABYSITTING INDUSTRY IN THE PRIMATE WORLD IN A NEW REGULAR SERIES, TELLING US ALL THAT WE DIDN’T AND NEED TO KNOW ABOUT THE ANIMAL KINGDOM.

“Next up a pay-per-play for a three month old infant spider monkey. Let’s start the bidding at one hug.”

While it’s unlikely you’ll witness the described scenario in any auction house, it’s one that regularly occurs among spider monkeys in albeit leafier settings.

The concept of an exchange of commodities for benefits is well practised within our own society. It is less well-known that some of our non-human primate relatives also participate in this exchange. Specifically, access to a shiny new infant is a commodity that can be ‘sold’. Now unlike us, their currency is not money but grooming and, unique to spider monkeys, hugs – paid to the mother.

Group female attraction to new infants is thought to be a by-product of selection; females which show greater interest in maternal care will likely make better mothers. Similar to how your lady friends may coo at the sight of a baby. Sometimes this interest in infants leads to allomothering. This is when group members help the mother with care of the infant. However, at times non-mothers don’t want to deal with the actual care giving an infant requires. Instead they just want a few minutes to coddle a baby and not deal with the feeding or carrying. In such cases non-mothers have been observed to significantly increase affiliative behaviour: i.e. initiating hugs/grooming sessions towards the mother. Rather than return the favour, the mother repays non-mothers with quality time with her sprog. No hug means no access, and any attempt to take an infant without due payment leads to mothers taking their ‘goods’ elsewhere.

So what does mama monkey get out of this deal? Among golden snub-nosed monkeys and other primates which use grooming as currency, grooming provides the mother with the beneficial fitness effect of removing those pesky, unwanted freeloaders like the dreaded nits or fleas. It’s also been shown grooming causes the release of β-endorphins which is linked to stress-relief; also known as natures natural high. Though the beneficial effect of hugs in spider monkeys is not so clear. It is thought that the embraces represent benign intent and reassures the mother.

There are exceptions to the ‘hugs for babies’ scheme. If you are one of the privileged spider monkey females of your group to also have spawned, you can ‘baby swap’ with another mother without incurring hug fees.

The infant biological market amongst the mentioned primates is unfortunately for them not immune to the curse of supply and demand. Much like how shops can charge us an obscene amount for the latest trends, younger infants can demand more hugs. Older infants (3-6 months old), on the other hand, face a decrease in value and can be played with for bargain basement prices. It’s thought the increased anxiety a mother of a younger infant may experience, requires increased reassurance via increased grooming duration or number of hugs. Another parallel is when there is an excess of infants (or cheap knock-offs in Primark) the ‘cost’ of an infant decreases. So availability and demand of young infants determine the grooming frequency exchange rate of monkey infants.

Among some of the primates other factors also play a role. Vervet, sooty mangabey, chacma baboon and golden snub-nosed monkey mothers require a longer duration of grooming if the rank distance between the mother and non-mother is greater than if a female with a higher rank than the mother wanted to play with the infant. Effectively a higher ranking non-mother can pay a lower price than the current market asking price.  Golden snub nosed monkeys also have a ‘loyalty card’ scheme, where frequent patrons can play with infants in exchange for shorter grooming sessions compared to the infrequent petitioner. This is likely to do with the mother trusting the former more.

It’s clear that non-human primates can have biological markets and those that do subscribe to some form of monkey economics. There certainly is booming business in babies, and one that is sophisticated enough to modify exchange rates according to variables such as supply as well as hierarchy. They’re not monkeying around; the spider monkey hug-dealers mean business.