Girneys are vocalizations - similar to human baby talk - used by adult female rhesus macaques, mandrills, and other large monkeys to establish friendly contact with infants which are not their own offspring. The vocalizations are made in a high-pitched sing-song. Dario Maestripieri, professor of comparative human development at the University of Chicago, says the sounds are "made with their mouths almost closed, sort of nasal and relatively soft." Professor Maestripieri suggests the similarity of girneys to human baby talk suggests the latter may be of biological origin. The research was made mostly by Maestripieri's PhD student, Jessica Whitman, who observed 19 adult females in a family of 65 rhesus macaques on the island of Cayo Santiago near Puerto Rico, every day for several months in 2004 and 2005. Adult males - which take no part in raising the young - do not use the girneys. Mothers never use them with their own offspring. The vocalization is often accompanied by tail-wagging, a very rare behavior for this species.
^Whitham, J.C., Gerald, M.S. and Maestripieri, D. (2007). Intended receivers and functional significance of grunt and girney vocalizations in free-ranging female rhesus macaques. Ethology, 113: 862-874