The aim of this project was to study the role of social housing group composition (presence/absence of sire, proportion of pregnant females in group, group size and stability) on various measures of reproductive outcome. We have continued this research by monitoring animals in the Seattle breeding colony for estrus cycle lengths, pregnancy outcome, interbirth intervals, and relative levels of social aggression. The presence of adult males has been manipulated as part of normal husbandry requirements. We are now completing analysis of the results and preparing them for publication. Supported by NIH grant RR00166.