Moisture and nutrients determine the distribution and richness of India's large herbivore species assemblage

The goal of this study was to test whether body-mass based foraging principles, guided by plant available moisture (PAM) and plant available nutrients (PAN), could explain large mammalian herbivore species distribution and richness in India. We tested (1) whether the occurrence of larger-bodied herbivore species increases with PAM, but is independent of PAN, (2) whether the occurrence of smaller-bodied herbivore species decreases with PAM, but increases with PAN, and (3) whether herbivore species richness is highest in areas with intermediate PAM and high PAN. We analyzed the distribution and richness of the 16 large (>10 kg) herbivore species found in sub-Himalayan mainland India. Since the distributions of large herbivores in India have been altered by historic human activity, we only used India's largest 76 protected areas as data points, with respect to PAM (log10(rainfall/potential evapotranspiration)), PAN (soil cation exchange capacity), elevation, tree cover, and fire frequency. Using regression and null models to analyze the data, we found positive relations between PAM and the occurrences of the larger-bodied species (elephant and gaur), and negative relations between PAM and the occurrences of smaller-bodied species (chinkara, four-horned antelope and blackbuck). We also found positive relations between the occurrence of the smaller-bodied species and PAN. Large herbivore species richness in India is highest in Kanha and Indravati, areas with high PAN and intermediate PAM. We found that elevation, tree cover and fire frequency were insignificant predictors of herbivore species richness, although elevation and tree cover explained the distribution of a few species. Based on our null model analyses results, we conclude that moisture and soil nutrients are important in determining large herbivore species distribution and richness in sub-Himalayan India.