D. Mark Rayan

The importance of selectively logged forests for tiger Panthera tigris conservation: a population density estimate in Peninsular Malaysia.

To obtain information on density of tiger Panthera tigris in selectively logged forest, a 9-month camera-trapping survey was conducted over elevations of 190–850 m in lowland and hill/upper dipterocarp and lower montane forests in Gunung Basor Forest Reserve, Peninsular Malaysia. Capture-recapture sampling methods were used to estimate tiger population density in the Reserve. The number of individual tigers captured was six. Using the M h jackknife estimator the average capture probability per sampling occasion was 0.28 and the corresponding estimate of population size 8 ± SE 1.89. The overall probability of photo-capturing a tiger present in the sampled area was 0.75. Using an approach based on distances between photo-captures, a buffer width of 3.22 km and an effectively sampled area of 308 km 2 was estimated. This resulted in a density estimate of 2.59 ± SE 0.71 adult tigers per 100 km 2 . The results indicate that selectively logged forests such as Gunung Basor Forest Reserve have the potential to accommodate a high density of tigers. Decision makers and conservation planners should not therefore perceive selectively logged forests to have limited conservation value. Further research on the ecology of tigers and their prey in selectively logged forests is urgently needed. Such research would enable conservationists to recommend tiger-friendly management guidelines for sustainable forest management and thereby significantly contribute to tiger conservation in Malaysia.

Estimating the population density of the Asian tapir (Tapirus indicus) in a selectively logged forest in Peninsular Malaysia

The endangered Asian tapir (Tapirus indicus) is threatened by large-scale habitat loss, forest fragmentation and increased hunting pressure. Conservation planning for this species, however, is hampered by a severe paucity of information on its ecology and population status. We present the first Asian tapir population density estimate from a camera trapping study targeting tigers in a selectively logged forest within Peninsular Malaysia using a spatially explicit capture-recapture maximum likelihood based framework. With a trap effort of 2496 nights, 17 individuals were identified corresponding to a density (standard error) estimate of 9.49 (2.55) adult tapirs/100 km(2) . Although our results include several caveats, we believe that our density estimate still serves as an important baseline to facilitate the monitoring of tapir population trends in Peninsular Malaysia. Our study also highlights the potential of extracting vital ecological and population information for other cryptic individually identifiable animals from tiger-centric studies, especially with the use of a spatially explicit capture-recapture maximum likelihood based framework.

Monitoring tigers with confidence.

With only 5% of the worlds wild tigers (Panthera tigris Linnaeus, 1758) remaining since the last century, conservationists urgently need to know whether or not the management strategies currently being employed are effectively protecting these tigers. This knowledge is contingent on the ability to reliably monitor tiger populations, or subsets, over space and time. In the this paper, we focus on the 2 seminal methodologies (camera trap and occupancy surveys) that have enabled the monitoring of tiger populations with greater confidence. Specifically, we: (i) describe their statistical theory and application in the field; (ii) discuss issues associated with their survey designs and state variable modeling; and, (iii) discuss their future directions. These methods have had an unprecedented influence on increasing statistical rigor within tiger surveys and, also, surveys of other carnivore species. Nevertheless, only 2 published camera trap studies have gone beyond single baseline assessments and actually monitored population trends. For low density tiger populations (e.g. <1 adult tiger/100 km(2)) obtaining sufficient precision for state variable estimates from camera trapping remains a challenge because of insufficient detection probabilities and/or sample sizes. Occupancy surveys have overcome this problem by redefining the sampling unit (e.g. grid cells and not individual tigers). Current research is focusing on developing spatially explicit capture-mark-recapture models and estimating abundance indices from landscape-scale occupancy surveys, as well as the use of genetic information for identifying and monitoring tigers. The widespread application of these monitoring methods in the field now enables complementary studies on the impact of the different threats to tiger populations and their response to varying management intervention.

Tiger Ecology in Relation to Monitoring Issues

Early naturalists recorded descriptive accounts of tigers in tropical Asia during the past two to three centuries (Karanth 2001).