Z01 HD 01124-09 LCE and a companion project investigate auditory communication in primates from receptors to the rainforest. The overall goal of these studies is to provide a comprehensive understanding of primate auditory communication in terms of development, neural mechanisms, related endocrine factors, and social context. Two non-human primate species, the squirrel monkey and the common marmoset, are the main subjects of study, with additional data collected in collaborative studies from a wider range of species, including rhesus macaques and humans. The present project studies primate communication from a bioacoustic perspective, focusing on the detailed acoustic structure of vocalizations and the relationship of structural differences to individual variables such as age, gender, and experience, as well as the broader factors of social context and genetic background. New findings during FY99 were (a) evidence that male squirrel monkeys in a free-ranging troop produced the same vocalizations following female calling observed the previous year in our social groups at the NIH; (b) the vocal behavior of female squirrel monkeys living as members of established social groups strongly depends on the physical characteristics of the testing environment; (c) infant common marmosets engage in apparent babbling during the first month of life, but this seems to be a reflection of immature brain development rather than an obligatory experiential stage of development; (d) the vocal behavior of infant rhesus macaques experiencing brief periods of social separation in a naturalistic and a controlled environment was found to be similar in rate of calling, but differed in that the calling behavior in the controlled setting consisted of long sequences of similar vocalizations, whereas the calling behavior in the naturalistic setting consisted of frequent alternation of different call types. - behavioral development, primates, bioacoustics
