This research is a continuation of a study of the hormonal, demographic, and social mechanisms influencing seasonality in free-ranging sifaka (Propithecus verreauxi) in the Beza Mahafaly Special Reserve (BMSR), Madagascar. Prevailing theory suggests that reproduction is tightly entrained to seasonal variations in photoperiod, rainfall, and food abundance in many seasonally breeding mammals. Reproduction in wild sifaka is highly seasonal with 96% of births restricted to just a two month period. However, preliminary results using noninvasive methods of hormone analysis indicate that male reproduction is not so tightly entrained, suggesting that social factors, including aggression during group transfer in the birth season, may be as important as climatic factors in the regulation of male reproductive function in this species. The Specific Aim of this research is to test the relationship between birth season testosterone (T) levels and male dispersal, age, and migration success. The broader implications of this research reside in the insights it may provide into the role of androgens (T) in mediating male dispersal, life history, and reproductive strategies. Hormonal, behavioral and demographic data will be collected from 200 marked sifaka in 37 social groups at the research site in Madagascar during the July-August 1999, 2000, 2001, and 2002 birth seasons to examine androgen-behavior interactions associated with T-mediated migration and aggression. This research breaks new ground in the study of mammalian reproduction by employing field endocrinological approaches to studies of male dispersal patterns and seasonality in free-ranging endangered sifaka. More importantly, this study will broaden our understanding of male reproduction and provide new perspectives on its complexity, variation, and evolution.
