Coexistence of the tiger and the common leopard in a prey-rich area: The role of prey partitioning

Ecological theory predicts that sympatric species should avoid competition through diet, spatial and/or temporal partitioning. In carnivores, interference is widespread between species with similar diets. Smaller species are expected to differentiate their diet from that of larger, dominant ones, to reduce the risk of potentially lethal encounters. Interference has been reported between tigers and common leopards, with the former dominant over the latter. In 2009–2011, in an area of Terai, South-West Nepal, we assessed food habits and prey selection of tigers and common leopards, to evaluate whether prey partitioning occurred between these large cats. Prey availability was high, both in terms of number of species (at least seven wild ungulates beside livestock, two primates and an array of smaller prey) and density (large ungulates, livestock and primates: 130.8–174.8 individuals per km2). Wild vertebrates were the staple of both cats (tigers: 82.7%; common leopards: 66.6%), but common leopards used livestock significantly more than tigers did. Diet breadth of leopards was c. 20% larger than that of tigers, indicating a broader trophic niche. Significant differences in prey use and selection occurred between tigers and leopards, with the former using large (i.e. >100 kg) prey more often and small (i.e. 5–25 kg) prey less often than the latter did. Medium-sized prey were taken in comparable proportions by the two cats, with a great overlap of diet (Pianka index: 0.85). In conclusion, in our study area, apparently tigers and leopards did not base their coexistence on diet partitioning, suggesting a major role for spatial and/or temporal partitioning.