Stable Carbon and Nitrogen Isotope Analysis of Captive Northern Galagos (Otolemur garnettii) Fed Experimental “Frugivorous” and “Invertebrate” Diets

Abstract

Otolemur garnettii are small (~ 770g), semi-solitary, omnivorous primates and although there have been studies examining the behavioral ecology of the species very little is known about its diet. This is due in part to the species cryptic nature, fast and sporadic movements, and nocturnal activity patterns. To address this gap in the literature this study employs stable isotope analysis (SIA) on a captive population (n=11) of O. garnettii that resided at the University of Southern Mississippi to examine dietary patterns and establish feces-diet isotopic fractionation. Over a six-week period, the population was fed experimental diets that mimic the seasonal availability of food resources, these diets have been traditionally referred to as 'frugivory' and 'insectivory.' As part of a larger galago digestibility project examining the nutritional properties of these foods and feces, this study used isotope ratio mass spectrometry (IRMS) to additionally record the stable carbon ([delta]13C) and stable nitrogen ([delta]15N) values of these samples. I hypothesize that the [delta]13C and [delta]15N values of the feces will track the dietary changes presented to the galagos and that each diet will be isotopically distinct from one another. This study revealed that inter-individual variation in the digestibility of the diets can be identified but may not lead to an overall significant degree of difference among a large captive colony, isotopically speaking. This study demonstrated that even short-term dietary changes can be tracked accurately using SIA which is an important result for field primatologists studying free-ranging galagos and other small, nocturnal strepsirrhine primates. The implementation of these methods in field settings may prove useful to researchers attempting to understand nonhuman primate dietary patterns across time which has become increasingly more difficult to observe as primate populations decline globally.