Population Status of a Cryptic Top Predator: An Island-Wide Assessment of Tigers in Sumatran Rainforests

Large carnivores living in tropical rainforests are under immense pressure from the rapid conversion of their habitat. In response, millions of dollars are spent on conserving these species. However, the cost-effectiveness of such investments is poorly understood and this is largely because the requisite population estimates are difficult to achieve at appropriate spatial scales for these secretive species. Here, we apply a robust detection/non-detection sampling technique to produce the first reliable population metric (occupancy) for a critically endangered large carnivore; the Sumatran tiger (Panthera tigris sumatrae). From 2007–2009, seven landscapes were surveyed through 13,511 km of transects in 394 grid cells (17×17 km). Tiger sign was detected in 206 cells, producing a naive estimate of 0.52. However, after controlling for an unequal detection probability (where p = 0.13±0.017; ±S.E.), the estimated tiger occupancy was 0.72±0.048. Whilst the Sumatra-wide survey results gives cause for optimism, a significant negative correlation between occupancy and recent deforestation was found. For example, the Northern Riau landscape had an average deforestation rate of 9.8%/yr and by far the lowest occupancy (0.33±0.055). Our results highlight the key tiger areas in need of protection and have led to one area (Leuser-Ulu Masen) being upgraded as a ‘global priority’ for wild tiger conservation. However, Sumatra has one of the highest global deforestation rates and the two largest tiger landscapes identified in this study will become highly fragmented if their respective proposed roads networks are approved. Thus, it is vital that the Indonesian government tackles these threats, e.g. through improved land-use planning, if it is to succeed in meeting its ambitious National Tiger Recovery Plan targets of doubling the number of Sumatran tigers by 2022

Cryptic mammals caught on camera: assessing the utility of range wide camera trap data for conserving the endangered Asian tapir

The loss and fragmentation of substantial areas of forest habitat, in combination with rampant hunting, has pushed many of Southeast Asia's megafauna species to the verge of extinction. However, the extent of these declines is rarely quantified, thereby weakening lessons learned and species-based management. This need not be the case as a proliferation of camera trap surveys for large-bodied mammals across Southeast Asia, which use a standardized sampling technique, presents a rich yet under-utilized wildlife data set. Furthermore, advances in statistical techniques for assessing species distribution provide new opportunities for conducting comparative regional analyses. Here, we focus on one of Southeast Asia's least known species of megafauna, the Endangered Asian tapir (Tapirus indicus), to investigate the performance of a camera trap-based spatial modeling approach in conducting a range-wide species assessment. Detection data were collectively collated from 52,904 trap days and 1,128 camera traps located across 19 study areas drawn from the Asian tapir's entire range. Considerable variation in tapir occurrence was found between study areas in: Malaysia (0.52–0.77); Sumatra, Indonesia (0.12–0.90); Thailand (0.00–0.65); and, Myanmar (0.00–0.26), with generally good levels of estimate precision. Although tapirs were widespread (recorded in 17 of the 19 study areas), their occurrence was significantly and negatively correlated with human disturbance. Thus, this study extends the previously known applicability of camera traps to include a threatened and cryptic species by identifying where and how tapirs persist (including new records of occurrence), where future surveys should be conducted and providing a benchmark for measuring future conservation management efforts

Summary of Sumatra-wide field survey effort for each landscape.

<p>*I = global priority; II = regional priority; III = long-term priority.</p>1<p>Kerinci Seblat National Park and Batang Hari Protection Forest and their surrounding forests.</p>2<p>Bukit Barisan Selatan National Park and Bukit Balai Rejang Selatan.</p>3<p>Pasir Pangaraian, Giam Siak, Duri, Balaraja, Tapung.</p>4<p>Tesso Nilo, Bukit Bungkuk, Bukit Rimbang-Baling, Bukit Batabuh, Bukit Tigapuluh, Kerumutan.</p>5<p>Dangku, Bukit Duabelas, Berbak.</p

Estimated Sumatran tiger site occupancy and sites with actual indirect tiger sign detections (black dots).

<p>Estimated Sumatran tiger site occupancy and sites with actual indirect tiger sign detections (black dots).</p

Sumatran tiger site occupancy () and density () estimates for the best model, averaged for each study area.

<p>The two right-most columns show the estimates conditional to the data observed. Standard errors are shown in brackets.</p