Sumatran elephant Elephas maximus sumatranus density and habitat use in relation to forest characteristics in the Leuser Ecosystem, North Sumatra.

Abstract

Forest loss as a result of human activities is causing widespread habitat loss for the critically endangered Sumatran elephant Elephas maximus sumatranus. An increase in the global demand for natural resources is believed to be the greatest driver of widespread deforestation throughout the Sumatra and Indonesia, accelerated by the demand of agricultural development and legal and illegal logging. If deforestation continues, remaining populations of Sumatran elephants will become more vulnerable to extinction as their habitat becomes dominated by human landscapes. Continuation of habitat reduction for the Sumatran elephant will likely increase the occurrence of negative human-elephant interactions. Sumatran elephants also remain one of the least understood mammals in regards to their habitat requirements, distribution and population numbers. This study gained a first density estimate of a North Sumatran population residing within Sikundur, a rare lowland forest in the Gunung Leuser National Park and aimed to increase our overall knowledge of elephant habitat use. Ten transects were each walked a minimum of 3 times, totalling 34km. Dung found on the transects were recorded alongside 5m circular vegetation plots that were also undertaken every 125m along the transects. A dung decay rate of 0.0097 was estimated from 14 dung piles residing under different conditions. Elephant density was calculated using the method of McClanahan (1986) & Barnes and Jensen (1987). The density of Sumatran elephants estimated for the lowland forest area of 379km2 was 71 elephants (0.188 per km2). Habitat use was determined by comparing vegetation plots near dung piles and those >125m away from dung piles. Ground and understory vegetation and canopy cover did not vary between plots. Tree density was significantly lower and median DBH of trees was greater in areas where dung was present compared to control areas. Elephants were found in all habitat types of the lowland forest, including hill habitats with steep slopes, but were found more often in areas of low elevations (20-55 m.a.s.l). Elephants were found to inhabit areas close to human-dominated landscapes significantly more than areas further away. Elephants also utilised a trail system that exposed them to human traffic but did so less than they used other areas of the forest. Overall, this study brings attention to a previously un-studied elephant population residing in a North Sumatran forest, that remains at risk to habitat loss through on-going deforestation.