Modeling Developmental Class Provides Insights into Individual Contributions to Infant Survival in Callitrichids
Cooperative breeders live in social groups in which individuals in an age–sex class vary in reproductive development due to reproductive dominance by a few individuals in each group. Among callitrichids, adult males have been implicated in driving group reproductive output, but uneven sampling efforts, the underlying effects of group size, and pseudoreplication at the group and species levels are confounding variables in these analyses. We examined the drivers of group reproductive output in callitrichids by 1) conducting a meta-analysis of published studies of callitrichid group composition; 2) assigning developmental class based on reproductive morphology; and 3) using multivariate modeling to test whether the proportion of individuals of each developmental class predicts the presence and the number of surviving offspring among free-ranging Weddell’s saddleback tamarins (Leontocebus weddelli) and emperor tamarins (Saguinus imperator) in Peru. The meta-analysis revealed that the number of adult females and group size, but not the number of adult males, are significantly correlated with group reproductive output. Statistical models of the new dataset revealed that the proportion of primary breeding males, primary breeding females, and group size predicted whether groups had surviving infants, and that only the proportion of primary breeding females and group size predicted the number of surviving infants. Thus, primary breeding males appear to be necessary for groups to raise any infants, but a higher proportion of primary breeding females and a larger group size increase group reproductive output overall.
KeywordsCallitrichid Cooperative breeding Development Group composition Reproductive output
This study was funded by Field Projects International, the American Society of Mammalogists, Idea Wild, the Animal Behavior Society, Lambda Alpha, the International Primatological Society, the American Society of Primatologists, the Society for Integrative and Comparative Biology, Sigma Xi, and Trans World Airlines. We would like to acknowledge the logistical support of the Amazon Conservation Association, staff at EBLA, and the Ministry of Agriculture in Peru. In addition, we want to thank all wildlife handling research assistants who assisted in putting together this dataset with FPI and PrimatesPeru over the years. We also thank three reviewers and the editor of the International Journal of Primatology for their comments on a previous version of this manuscript.
Compliance with Ethical Standards
Conflict of interest
The authors declare that they have no conflicts of interest.
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