The 84th Annual Meeting of the American Association of Physical Anthropologists (2015)

Age belies reproductive status in a wild population of Saguinus fuscicollis and S. imperator in southeastern Peru


1Department of Physical Anthropology, Washington University in St. Louis, 2Department of Biology, University of Missouri-St. Louis, 3Research Committee, PrimatesPeru

March 28, 2015 2:15, Grand Ballroom E/F/G Add to calendar

Given the difficulty of raising twin offspring, and the necessity for assistance from the group, ideal breeding-opportunities are rare among callitrichids. Additionally, reproductive success is dependent on the physiological capability of an individual to attract a mate, copulate, and raise offspring. We studied Saguinus fuscicollis and S. imperator from southeastern Peru via a capture and release program. Using morphometrics and age data, we created a mechanism for determining primary, secondary or non-breeding status, which was correlated with reproductive success to detect reproductive suppression. We found no significant differences between species in the size of their genitalia or scent glands, despite differing markedly in their physical appearance. Primary breeding males had higher testicular volumes than secondary breeding males (44-287% higher in S. fuscicollis and 24-80% higher in S. imperator), indicating possible subtle reproductive suppression of males. Secondary breeding females had lower vulvar indices and suprapubic scent gland areas than primary breeding females, and required 2-3 y to acquire secondary breeding status compared to 1 y for males. While vulvar indices initially grow faster than testicular volumes in both species, by 1.5 years of age, males have fully developed genitalia while females still appear underdeveloped. Morphological scores assigned to genitalia and glands could be used to distinguish infants from adults, but not other age classes. Overall, we found evidence of reproductive suppression, and highlight the importance of evaluating age based on dentition and not reproductive measures for either species, as reproductive suppression can cause animals to appear younger than they actually are.

This project was funded by grants from PrimatesPeru, IdeaWILD, Explorer’s Club, ASM, IPS, Lambda Alpha, ABS, Harris Center, UMSL TWA, Sigma Xi, and Washington University in St. Louis