Biological Market examples

grooming in primates: baby markets

A striking example of the exchange of grooming against a social favour is the so-called 'baby market': the fewer infants in a group the higher the price that has to be paid in the form of grooming to gain the mother's permission to inspect and handle it. This was first described for chacma baboons, but similar results have been found in other primate species, such as sooty mangabeys and vervet monkeys (Fruteau et al. 2011), longtailed macaques (Gumert 2007), spider monkeys (Schaffner & Aureli 2005; Slater et al. 2007) and golden-snub nosed monkeys (Wei et al 2013). The latter is a highly interesting example of baby markets in a harem-species.

One should not expect baby markets to operate in all species, for example not in non-seasonal breeders in which fluctuations in numbers of small infants are generally low and also not in species that lack steep dominance hierarchies and in which mothers are permissive towards other females eager to handle their infants. The latter can notably be expected in groups with high degrees of kinship among the adult females. A good example can be found in Caselli et al (2021). 

Negotiating the price of access to an infant

The video shows members of our captive group of vervet monkeys held in the Primate Center of Strasbourg (France).

Two females groom a mother holding her infant. The groomers once in a while attempt to grab the infant, but the mother does not allow this as long as she reckons she can refuse and demand more grooming

(video by Yann Gobrecht)

Baby-grooming vervet (small).mp4

last update: 29 SEP 2021