Facial displays in young tufted Capuchin monkeys (Cebus apella): appearance, meaning, context and target.

Facial displays are important for communication, and their ontogeny has been studied primarily in chimpanzees and macaques. We investigated the ontogeny, communicative function and target of facial displays in Cebus apella. Our results show that facial displays are absent at birth and develop as infants grow older. Lip-smacking appears first (at about 1 month of age), followed by scalp-lifting, relaxed open-mouth, silent bared-teeth, open-mouth silent bared-teeth displays and finally the open-mouth threat face. Infants perform most facial displays in the same contexts as adults, with the exception of the silent bared-teeth display that young capuchins use primarily, or exclusively, in affiliative contexts. Interestingly, facial displays are exchanged very often with peers, less frequently with adults and almost never with the mother.