Fecal carbon and nitrogen isotopic analysis as an indicator of diet in Kanyawara chimpanzees, Kibale National Park, Uganda.

Abstract

The shorter-term overview from feces provides scope to investigate dietary fluctuations. We assess the correlation of stable isotopic fecal values with recorded seasonal diet of 10 adult chimpanzees (P. t. schweinfurthii) of the Kanyawara community (Kibale National Park, Uganda) and whether fecal nitrogen levels (%N) indicate a change in crude protein intake. We recorded food eaten by each ape and collected both concurrent fecal samples (N = 115) and plant foods eaten by this community (N = 64). We compared fecal δ13 C and δ15 N values (also %N) with: (a) plant values; (b) feeding data; and (c) food-items found macroscopically in the fecal samples. Interspecies and intraspecies differences in plant and fecal isotope values (and %N) as well as seasonality in diet were determined using parametric and nonparametric tests. No difference in plant δ13 C and δ15 N values was found at intraspecies or interspecies level. Fecal isotope values reflected a diet of C3 plants from evergreen forest vegetation. Seasonal differences in δ13 C and δ15 N corresponded with aspects of feeding and fecal macroscopic data, but only at community level. A change in crude protein intake was not indicated from %N content. This study further validates the use of staple isotope analyses of primate feces to provide a dietary overview, revealing seasonal differences at community level; however, conclusive results may be limited for individuals when using short sampling periods. Further study of variables that influence fecal %N content is also suggested to interpret crude protein intake.