Cheek Pouches

Cheek pouches are pockets between the jaw and the cheek used to temporarily store food.  Many rodents, marsupials and monkeys have them.

Apes and New World monkeys do not have cheek pouches.
Old World monkeys have cheek pouches but do not use them with the same frequency.  For instance, baboons in the wild don't seem to use their cheek pouches as much as they do in captivity.

It was long believed that cheek pouches were the result of an adaptation to ground foraging, to store food in high risk situation while on the ground and consume it later high in a tree, however Ciochon and Feagle argue that cercopithecines who live mostly arboreal have the largest cheek pouches. (Primate Evolution and Human Origins).

Unlike those of rodents, primates' cheek pouches secrete large quantities of amylase - which converts starches into sugar.  In her book "Primate Behavioral Ecology",  Karen Strier writes: "this adaptation for digesting unrip fruits, which are often high in starch, gives cercopithecines a competitive advantage over sympatric chimpanzees which tend to wait for fruits to ripen and may account for cercopithecines' high evolutionary success compared to apes (Lambert, 2005)." Cheek pouches also soften the fruit.  Gautier-Hion recorded in 1971 that cercopithecus talapoin used their cheek pouches to hold live prey - such as insects. Lindburg suggested that in addition to providing temporary storage for food monkeys could eat in a safer place away from danger and conspecific individuals, it also allowed the animal to continue feeding while engaging in social activities (like grooming and feeding the young).

In a study conducted in Japan between 1986-1995, scientists collected data related to seed dispersal via cheek pouches and compared the results to seed dispersal via feces.  (Japanese monkeys - Macaca fuscata yakui, on Yakushima Island, Japan - Takakazu Yumoto, Naohiko Noma, Tamaki Maruhashi).  They found that the seeds dispersed via cheek pouches were bigger than those spread through feces and a higher percentage (82%) germinated compared to those spread through feces.  They conclude that cheek pouch seed dispersal plays an important role in the evergreen forest of Yakushima.

More recently a study looked at the correlation between cheek pouch use and the use of a preferred hand.  The scientists wanted to find out if right or left-handedness evolved from the pre-existing laterality of basic brain functions and behavior of if the two evolved simultaneously.  (Do Right-Handed Monkeys Use the Right Cheek Pouch Before The Left?)

In captivity, it seems that primates use their cheek pouches more than in the wild - most likely because in a small environment where escape is not much of an option (apart from climbing up or hiding under a contraption), they feel more pressure to take as much food as they can before a higher ranking individual shows up.  I have seen this scenario many times with baboons - females will fill their cheek pouches as quickly as possible before the dominant male arrives and grabs all the enrichment items he can get his hands on.  What I have never seen is an individual stealing food directly from the cheek pouches ofa lower rank individual or a juvenile.  Yet, this situation occurs.  So cheek pouches are a safe  way to save food, but not always…