Variation in hair δ(13)C and δ (15)N values in long-tailed macaques (Macaca fascicularis) from Singapore.

Much of the primatology literature on stable isotope ratios of carbon (δ(13)C) and nitrogen (δ(15)N) has focused on African and New World species, with comparatively little research published on Asian primates. Here we present hair δ(13)C and δ(15)N isotope values for a sample of 33 long-tailed macaques from Singapore. We evaluate the suggestion by a previous researcher that forest degradation and biodiversity loss in Singapore have led to a decline in macaque trophic level. The results of our analysis indicated significant spatial variability in δ(13)C but not δ(15)N. The range of variation in δ(13)C was consistent with a diet based on C3 resources, with one group exhibiting low values consistent with a closed canopy environment. Relative to other macaque species from Europe and Asia, the macaques from Singapore exhibited a low mean δ(13)C value but mid-range mean δ(15)N value. Previous research suggesting a decline in macaque trophic level is not supported by the results of our study.