INFANT BABBLING IN A NONHUMAN PRIMATE - COMPLEX VOCAL SEQUENCES WITH REPEATED CALL TYPES

The pygmy marmoset is a small South American primate with a complex so cial system based on cooperative breeding. Infant pygmy marmosets are extremely vocal; most of their calling is a repetitive pattern of mixe d call types that is babbling-like. In a longitudinal study of vocal d evelopment in 8 infant pygmy marmosets, we recorded more than 750 call ing bouts which occurred in a wide range of behavioural contexts. The infants used 16 different call types that we grouped into three catego ries: Adult-Like (acoustic structure consistent with that of adult cal ls), Adult-Variant (acoustic structure with some adult features and so me variable features), and Infant (absent from the adult repertoire). The calling touts were highly conspicuous in their duration (ranging u p to more than 6.5 min/bout), complexity (up to 10 different call type s/bout), and call rate with nearly 3 calls/s. When the infants were ol der, their call rate slowed and they shifted to using several of the A dult-Like calls with greater frequency, and used fewer Adult-Variant t ypes. The infants did not use the Adult-Like call types appropriately when compared to the typical adult usage of those types. Caregivers we re significantly more likely to respond to an infant when it was vocal izing than when it was not.