The proposal covers tow broad areas: infant care and infant behavioral development in cooperatively breeding monkeys, and the ontogeny of vocal communication in the same species. In a longitudinal study of ten families (5 newly formed and 5 established families) we will use non- invasive methods for measuring hormonal changes (estrogen, cortisol, prolactin and testosterone) in mothers, fathers and other helpers during late pregnancy and after the birth of infants. The hormonal data will be correlated with direct observations on the amount and quality of infant care. By comparing new parents with well-established parents we will determine how quality of caretaking changes with experience, and what, if any, hormonal correlates exist. We will determine the role of infants in affecting the care they receive and will determine the role of early hormonal environment, sex, and social interactions on infant social and physical development. Experimental studies will determine if males can detect when their mates are pregnant and if there is long-term olfactory recognition of familiar, but separated, relatives. Three models of vocal development will be pursued: the development of food-associated calls in cotton-top tamarins and pygmy marmoset, the """"""""babbling"""""""" of pygmy marmoset infants and its relationship to vocal production and vocal usage, and changes in call structure occurring with changes in social environment. Complementary studies on vocal communication and social interactions will be carried out on wild monkeys in the field. The results should provide a better understanding of the factors involved in successful infant care in cooperatively breeding species and should contribute to our understanding of the evolution of vocal communication. These species have social systems much more similar to human families than most other primate species, and the results of these studies should increase our understanding of factors affecting successful development of human infants.
