Early maternal recognition of offspring vocalizations in rhesus macaques (Macaca mulatta)

This study investigated the development of maternal recognition of infant c alls in rhesus macaques (Macaca mulatta). Fifteen mothers and their offspri ng, of age ranging from several hours to 28 days, served as subjects of an experiment in which the offspring's distress vocalizations were recorded an d then played back to their mothers simultaneously with those of an age-mat ched control infant. The proportion of time looking at, but not the proport ion of orientations to the speaker playing the offspring's vocalizations in creased significantly as a function of infant age. Specifically, mothers of infants older than 1 week of age responded longer to the playback of their own infant's calls than did mothers of younger infants. These findings pro vide the first evidence that offspring recognition in macaques develops bet ween the first and second week of the infant's life and are consistent with the hypothesis that mothers need to be exposed to their infants' calls in order to learn their acoustic characteristics.