Space use and habitat suitability model for post translocation sumatran tigers (Panthera tigris sumatrae, Pocock, 1929) based on monitoring of GPS collars

Abstract

Panthera tigris sumatrae is the last remaining Indonesian tiger after its relatives, the Bali and Javan tigers, became extinct in 1940s and 1980s respectively. Although translocation has been employed in mitigating human-tiger conflict in Sumatra for the last decade, the behavioral ecology of post-release animals is still poorly understood. Furthermore, the spatial modelling of tiger behavior based on global positioning system (GPS) collar tracking has never been done before. This information is urgently needed for improving Sumatran tiger translocation in the future. In this study we examine the movement and home range, activity pattern, and habitat selection of translocated tigers, as well as construct a habitat suitability model for identifying appropriate sites for future tiger translocation in Ulu Masen forest. Between July 2008 and December 2010 we translocated six Sumatran tigers, five males and one female. All tigers were fitted with GPS collars which were set to fix 24-48 location coordinates per day. The logistic regression equation was used to produce the habitat suitability prediction models and the tiger distribution map was overlaid with data on the relative abundance of tiger prey to determine suitable sites for future translocation. The mean distance traveled by the tigers varies from 2.8 to 4.0 km per day, but the female moved further than the males. In general, there was no difference in the mean distance traveled between day-time and night-time among the males, but the female traveled further in the day-time than during night-time. The length of time needed by each tiger to establish home range was significantly affected by the abundance of local tigers already in the area. The home range of each individual tiger, estimated using 95% fixed kernel, varies between 37.5 km2 and 188.1 km2 for males while for the female it was 376.8 km2. The most active period for translocated tigers is in the evening between 6 and 10 pm. However, on certain occasions, the tigers are most active in the morning between 6 and 10 am. The translocated tigers tend to range across all natural land cover types within the landscape, but forest availability within the landscape remains important for their survival. However, it seems that all translocated tigers prefer to conduct their daily activity within the mozaic landscape of lowland forest and regrowth vegetation. Modelling has shown that elevation, distance from rivers, distance from the edge of the forest, density of the forest canopy, and the slope of the terrain significantly influence the habitat model. Extrapolation of the model to the whole area of Ulu Masen forest (7,496.86 km2) has indentified 23.5% of the area as highly suitable habitat, 71.5% as suitable habitat, and 5.0% as less suitable habitat for the Sumatran tiger. It is also predicted that 5.2% of the ecosystem is highly suitable for future tiger translocation. Despite being preliminary, the findings of this study, the first ever conducted in Sumatra, highlight the conservation value of tiger translocation and provide valuable information for improving future translocation of rescued tigers.