The last supper: Conservation implications of Sumatran rhinos selective foraging ecology

Abstract

Centuries of overhunting and habitat loss have driven Sumatran rhinos (Dicerorhinus sumatrensis) to the brink of extinction, with the IUCN Red List estimating fewer than 30 mature individuals in the wild and only 11 in captivity. The scarcity of ecological research and the challenges of studying this critically endangered forest megaherbivore limit the effectiveness of conservation efforts. We conducted 28 h of focal observations on four Sumatran rhinos at the Sumatran Rhino Sanctuary in Way Kambas National Park to quantify their diet composition, feeding preferences, and foraging impacts in old-growth forest. Using a functional heterogeneity framework, we classified food resources into optimal, staple, buffer, and reserve categories based on preference ratios and availability. Sumatran rhinos were highly specialized browsers, feeding almost exclusively on the apical buds of dicot saplings. Of the 179 plant species from 45 families consumed, most belonged to optimal or staple categories, with limited use of buffer and reserve resources. Foraging impacts were less destructive than those of sympatric Asian elephants (Elephas maximus), with an estimated annual damage of ~7300 stem breakages—about one-fifth of the damage caused by an Asian elephant under similar conditions—and ~80,000 apical bud removals per rhino. These results emphasize the need to maintain diverse, structurally complex plant communities rich in optimal and staple resources when designing in-range captive breeding facilities and selecting post-breeding release sites. They also highlight the complementary ecological roles of Sumatran rhinos and other critically endangered Southeast Asian megaherbivores in sustaining forest ecosystem structure and function.