Impact of social environment on variation in menstrual cycle length in captive female olive baboons (Papio anubis)

Factors affecting menstrual cycles and conception were explored for captive female olive baboons. We evaluated the relationship between the social environment and adequacy of the menstrual cycle in 55 non-conceptive and 21 conception cycles from 23 females. More abnormal cycles were expected for low-status females, and social stress levels were associated with variation in menstrual cycle length. Mean cycle length was 39.9 days (median=38) with a mean follicular phase duration of 23.7 (median=22) days. The duration of the follicular phase was more variable than that of the luteal phase (mean=15.8 days). The first cycle after postpartum resumption of cycling was not markedly different from subsequent cycles in terms of duration or probability of conception. Dominance rank was one significant factor affecting female fertility. Low-ranking females experienced more cycles prior to conception, longer cycles once cycling was well established and had smaller sexual swellings (anogenital area) than did high-ranking females. Both acute and chronic stresses may play important roles in fertility outcomes for these baboons and further research is needed to understand the role of stress and subtle menstrual cycle abnormalities in female mammal fertility.