Satyawan Pudyatmoko

Non-invasive genotyping of Sumatran elephants: implications for conservation

Reliable baseline information necessary for the monitoring and conservation of Sumatran elephants is scarce. We here combine non-invasive molecular genetics methods and capture-recapture modeling to estimate elephant population size, distribution, sex ratio, and age structure for the Bukit Tigapuluh landscape in Sumatra, Indonesia. Two separate subpopulations were found, for which we estimated a population size of 99 (95% CI = [86,125], PCCL = 38.59%) and 44 elephants (95% CI = [37, 56], PCCL = 43.18%), respectively. Low elephant densities are likely the result of patchy habitat usage and anthropogenically increased mortality, the latter assumption being supported by strong skews in both sex ratio and age structure as well as direct evidence of elephant killing. Still, the Bukit Tigapuluh landscape currently holds the largest known population of elephants in central Sumatra, representing one of the most important areas for their conservation in Indonesia. Conservation of both the elephant population and their habitat in this region should thus be of high priority. We identified several threats to the population, including (i) the risk of inbreeding and subsequent loss of genetic diversity, (ii) illegal elephant killing, and (iii) the lack of protected habitat. In order to overcome these challenges we suggest: (i) the implementation of a meta-population management program, (ii) monitoring and safeguarding elephants and improving law enforcement, and (iii) providing sufficient safe habitat to mitigate human-elephant-conflict (HEC) and ensure elephant survival.

Spatiotemporal inter-predator and predator–prey interactions of mammalian species in a tropical savanna and deciduous forest in Indonesia

An understanding of the interspecific interactions within communities is required to explain the mechanisms promoting carnivore co-existence and how prey respond behaviorally to predators. In this research, inter-predator and predator–prey interactions in the tropical savanna and deciduous forests in Baluran National Park, East Java, Indonesia, were investigated. The pattern of interactions was assessed with respect to intraguild predation theory for inter-predator interactions and landscape of fear theory for predator–prey interactions. Data from camera traps were used to examine spatiotemporal activities of animals. The results indicated no evidence of spatial avoidance of solitary predator leopards (Panthera pardus ssp. melas) caused by the presence of social predator dholes (Cuon alpinus), and the data showed that the probability of the occupancy of leopards increases when dholes are present. Within the predator–prey interaction, only dhole and banteng (Bos javanicus) showed a significantly negative spatial interaction. The probability of occupancy of Javan deer increased when dholes and leopards were present; that of the muntjac and the buffalo increased when dholes were present and decreased when leopards were present. By contrast, the segregation of temporal activity was confirmed for all pairs of species, both for inter-predator and predator–prey species. The findings of this research affirmed that temporal interaction was stronger than spatial interaction in determining the inter-predator and predator–prey co-occurrence in the tropical savannah and deciduous forests.

AKDEC home range size and habitat selection of Sumatran elephants

Abstract Context. Understanding ranging behaviour and habitat selection of threatened species is crucial for the development of conservation strategies and the design of conservation areas. Our understanding of the actual needs of the critically endangered Sumatran elephant in this context is insufficient. Aims. Provide reliable subspecies-specific information on home range size and habitat selection of Sumatran elephants. Methods. Using both the new area-corrected autocorrelated kernel density estimation (AKDEC) and two commonly applied conventional methods, the home range sizes of nine Sumatran elephants were estimated. Elephant habitat selection was studied using Manly’s selection ratios. Key results. AKDEC home ranges of adults ranged from 275 km2 to 1352 km2. Estimates obtained using conventional KDE and minimum convex polygon (MCP) ranged between 156 km2 and 997 km2. Overall habitat selection was significant for both slope and land-cover type, whereas individual preferences varied to some extent. On the basis of global selection ratios, we found natural forest, pulpwood plantations and gentle slopes (≤4°) to be significantly selected, whereas most areas affected by human activities and steeper slopes were avoided by the majority of animals included in the study. Conclusions. As expected, AKDEC estimates were much larger than those obtained using conventional methods because conventional methods have a tendency to underestimate home range size when confronted with autocorrelated movement data and produce estimates that refer to the limited study period only, whereas AKDEC estimates include the predicted animal’s long-term space use. The extremely large AKDEC estimate obtained for a subadult male most likely represents a combination of population dispersal range and temporary home range rather than its final adult home range. Regardless, it appears that Sumatran elephants roam over much larger areas than previously assumed. Natural forests and relatively flat areas are of great importance for Sumatran elephants. The observed intensive use of pulpwood plantations by one individual is likely because of limited availability of alternative suitable habitats. Implications. A landscape-wide approach to elephant conservation that takes large home ranges into account, is required, and should include forest protection and restoration and elephant friendly management of existing pulpwood concessions, with special focus on areas with relatively gentle slopes.