Abstract # 170:

Scheduled for Friday, August 19, 2005 07:00 PM-09:00 PM: (Cambridge/Oxford Room) Poster Presentation

Developmental changes in separation vocalizations of infant common marmosets

M. V. Rakhovskaya, M. L. Becker, D. Bernhards, J. Norcross, J. Zehr and J. Newman
National Institutes of Health, NIH Animal Center, Laboratory of Comparative Ethology NICHD, Poolesville, MD 20837, USA
     Rearing conditions play an important role in primate social development, yet little research has been conducted on “normal” vocal maturation in New World monkeys. Anecdotally, the pattern of distress vocalizations in callitrichids drastically changes during the first year of life. We examined audio recordings from 44 infant common marmosets, Callithrix jacchus. Subjects lived in small family groups, consisting of one breeding pair and their offspring. At regular intervals during the first year of life infants were separated from their groups for 5-10 minutes to tape record their vocalizations. Audio recordings were digitized and the first 30-second interval of the third minute was chosen from each session. Within these intervals we counted the number of 1-second periods with particular call types or silence. We found age-related changes in call diversity and organization that culminated in adult-like vocal behavior after three months. Silent intervals showed a statistically significant increase with the age of the vocalizer during the first three months of life (P < 0.0001, ANOVA). The proportion of time devoted to isolation calls did not dramatically change during that period. However, squeals, combined calls and soft vocalizations typically produced by adults during affiliative social behaviors significantly decreased in separated infants by months 1 and 2 (P < 0.0001, ANOVA). Results suggest social feedback as a primary mechanism of primate vocal development.