Dietary partitioning in the sympatric Paradoxurinae civets in Borneo suggested by compound-specific nitrogen isotope analysis of amino acids

The sympatric four wild Paradoxurinae civet species in Borneo share similar ecological characteristics, but the coexistence mechanism of these species is unclear. We investigated their faunivory, reflected in their tropic positions (TP), by carbon and nitrogen stable isotope analysis of bulk hair and compound-specific nitrogen isotope analysis of amino acids. The bulk stable isotope analysis showed distinctly lower nitrogen isotope ratios in binturongs among the four subject species, suggesting the lowest degree of faunivory. The compound-specific stable isotope analysis confirmed little faunivory in binturong and showed a probably varying degree of faunivory in the other species. The estimated TP was the lowest in binturongs (2.0–2.1) and higher in small-toothed palm civets (2.4–2.5), masked palm civets (2.7), and common palm civets (2.9). Although the number of the measured sample for the compound-specific stable isotope analysis is small (n = 2 for each species), our results suggest the varying degree of consumption of animal food sources, such as insects, is the key mechanism of niche partitioning in these four Paradoxurinae civet species in Borneo. Such subtle but important differences in closely related sympatric species would maintain high biodiversity in tropical regions.