Introducing Fecal Stable Isotope Analysis in Primate Weaning Studies
Version of Record online: 21 JUN 2012
© 2012 Wiley Periodicals, Inc.
American Journal of Primatology
Volume 74, Issue 10, pages 926–939, October 2012
How to Cite
REITSEMA, L. J. (2012), Introducing Fecal Stable Isotope Analysis in Primate Weaning Studies. Am. J. Primatol., 74: 926–939. doi: 10.1002/ajp.22045
- Issue online: 17 AUG 2012
- Version of Record online: 21 JUN 2012
- Manuscript Accepted: 14 MAY 2012
- Manuscript Revised: 13 MAY 2012
- Manuscript Received: 18 NOV 2011
- Contract grant sponsor: American Society of Primatologists.
- François’ langur
This research investigates the potential of a new, noninvasive method for determining age of weaning among primates using stable carbon and nitrogen isotope ratios in feces. Analysis of stable isotope ratios in body tissues is a well-established method in archeology and ecology for reconstructing diet. This is the first study to investigate weaning in primates using fecal stable isotope ratios. Diets of a single François’ langur (Trachypithecus francoisi) mother–infant pair at the Toledo Zoo are reconstructed using this technique to track changes in infant suckling behavior over the weaning period. Stable isotope ratios in feces are sampled instead of more traditional samples such as bone or hair to enable daily, noninvasive snapshots of weaning status. Isotopic assessments of weaning status are compared to visual assessments to identify any discordance between the two. Three measurements documented the transition from breast milk to solid foods: stable carbon isotope ratios (δ13C), stable nitrogen isotope ratios (δ15N), and nitrogen content of feces (%N). It appears that solid foods were introduced at approximately 2 months of infant age, but that nursing continued into the 12th month, when sample collection ceased. Stable isotope data exposed a much longer weaning period than what was expected based on previously published data for captive langurs, and clarified visual estimates of weaning status. This reflects the method's sensitivity to suckling at night and ability to distinguish actual nursing from comfort nursing. After testing this method with zoo animals, it can readily be applied among wild populations. An isotopic approach to weaning provides a new, accurate, and biologically meaningful assessment of interbirth intervals, and facilitates a better understanding of mother–infant interactions. Both of these outcomes are critical for developing successful conservation strategies for captive and wild primates. Am. J. Primatol. 74:926-939, 2012. © 2012 Wiley Periodicals, Inc.