Stress, life history and dental development: a histological study of mandrills (Mandrillus sphinx)

Abstract

Dental development is frequently used to reconstruct life history in primates for which little other information exists. In addition to the regular growth increments visible in histological tooth sections, accentuated lines are thought to form at the time of stressful events in the lives of individual animals. However, our understanding of when, how and why such accentuated lines form in relation to stressful events is limited. In this thesis, I tested the hypothesis that accentuated lines in the enamel and dentine are associated with stressful events in the lives of semi-free-ranging mandrills (Mandrillus sphinx, Cercopithecidae) from the Centre International de Recherches Médicales de Franceville, Gabon. I used dates of birth and death to calibrate dental histology to calendar time and individual age. I then reconstructed dental development sequences for individual mandrills, providing a detailed overview of mandrill dental development. I report sex-specific dental development chronologies, crown extension rates and stages of dental development, and compare these to mandrill life history. Based on this dental development data, I matched the observed accentuated lines in the mandrill teeth with the dates of events in the mandrills’ lives. My results suggest that accentuated lines can correspond to potentially stressful events, including resumption of reproductive cycling in the mother and menstrual cycles, and in some occasions with parturitions. My results show that male mandrills might form accentuated lines at the time of potentially stressful events too, but most potentially stressful life history events for males take place after dental development is complete. Furthermore, my findings suggest that the number of accentuated lines recorded in teeth varies between individuals in a population, reflecting differences that may influence reproductive success.