Geology topics

Siew Te Wong

Publications and source records attributed to Siew Te Wong.

3 recordsLinked to original sources

USGS2022

Review of field methods for monitoring Asian bears

Efficient and effective monitoring methods are required to assess population status and gauge efficacy of conservation actions for threatened species. Here we review the spectrum of field methods useful for monitoring distribution, occupancy, abundance, and population trend for the five species of Asian terrestrial bears. Methods reviewed include expert opinion, local knowledge, bear sign, visual observations, camera traps, DNA-based methods (hair and scat derived), and radio telemetry. We examine the application of each method in terms of realizing specific monitoring objectives, their assumptions, challenges, and advantages. Our goal is to assist researchers in matching appropriate field methods with sought-after project objectives and to highlight shortfalls and trade-offs. Methods vary greatly in terms of cost, logistics, required number and expertise of staff, and the reliability of the data they provide. Many Asian bear population assessments have relied on expert opinion, local interviews, and sign surveys to provide estimates of distribution, abundance, and trend, in part because these are inexpensive and relatively easy to employ. However, increasing use of camera traps and DNA-based methods now allow for better monitoring via occupancy or rigorous capture–recapture population estimation, with the caveat that these methods may be restricted by inadequate budgets or logistical constraints. For distribution monitoring, camera traps and DNA yield the most definitive records of presence, but in low density bear populations, sign and local knowledge may be more effective. For occupancy, camera traps and DNA are advantageous in providing definitive detections in known time periods. For abundance/density or population trend monitoring in relatively small areas (<10,000 km 2 ), bears must be individually identified and used in a mark-recapture design. This requires DNA from collections of hair or scat, or a camera-based survey in which natural chest marks are clearly visible and individually distinguishable. DNA-methods or camera traps within individual identification is best for population trend when sufficient funding is available. Alternatively, careful use of local knowledge or expert opinion may be viable options, but come with greater uncertainty. For the foreseeable future, we believe that expert opinion will likely continue to play a large part in monitoring Asian bears, but these opinions should be informed by more rigorous data from the other methods we discuss.

Global Ecology and Conservation↗

USGS2021

Mammal species composition and habitat associations in a commercial forest and mixed-plantation landscape

Commercial forest plantations of fast-growing species have been established globally to meet increasing demands for timber, pulpwood, and other wood products. Industrial plantations may contribute to tropical forest conservation by reducing exploitation of primary and secondary natural forests. Whether such plantations can support critical elements of biodiversity, including provision of habitat and movement corridors for species of conservation concern, is an important question in Southeast Asia. Our objectives were to investigate relationships between habitat gradients and community attributes of medium-sized to large mammals in a mixed plantation mosaic in Bengkoka Peninsula, Sabah, East Malaysia. Data on mammals were collected using 59 remote camera stations deployed for a minimum of 21 days (24-hour sampling occasions) in three major land-use types: natural forest, Acacia plantations, and non- Acacia plantations (oil palm, rubber, young Eucalyptus pellita ). We used sample-based rarefaction to evaluate variation in species richness with land use. We used generalized linear models and ordination analyses to evaluate whether variation in mammal detections and species composition was associated with habitat gradients. We recorded >22 mammal species over 1572 sampling occasions. Natural forest area was positively associated with mammal species richness and detections of threatened mammals. Overall detections of mammals increased with decreasing elevation, but decreased within, and close to, Acacia plantations. Detections of threatened mammals increased with greater proportions of natural forest and Acacia and increasing proximity to roads. Sample-based rarefaction indicated that species richness of mammals in Acacia and natural forest was considerably higher than observed. Both natural forest and Acacia plantations shared similar values for species richness and diversity, but non- Acacia plantations scored lower in both metrics. Mammal species composition differed among different types of land use. Smaller generalists used non- Acacia plantation forests. A variety of other mammals including some threatened species used natural forest, Acacia , or a combination of the two. Acacia plantations possess attributes supporting a diversity of mammal species, including those we defined as threatened based on IUCN criteria. However, this is likely a function of the habitat mosaic with natural forest in the study area and the mangrove forests on the fringes of the peninsula serving as refuges of mammal diversity. Retention and restoration of natural and mangrove forests may therefore enhance the conservation potential of industrial Acacia plantations. Additionally, controlled road access in conjunction with anti-poaching operations and strengthening public awareness are essential to reduce the threat of overexploitation.

Forest Ecology and Management↗

USGS2020

An evaluation of noninvasive sampling techniques for Malayan sun bears

Traditional mark–recapture studies to estimate abundance and trends of Malayan sun bear ( Helarctos malayanus ) populations are impeded by logistics of live-trapping wild individuals. The development of noninvasive sampling techniques for monitoring sun bear populations is therefore crucial for targeted conservation action. Sun bears have short fur, and conventional hair-snagging devices are ineffective. Moreover, scats are rapidly decomposed by the warm, humid environment, as well as by invertebrates. In combination with camera-sampling, we tested 2 designs of hair traps ( n = 45) in situ at Tabin Wildlife Reserve in Sabah, Malaysia, during April–October 2017, to obtain hair samples from wild sun bears. We also deployed 4 types of hair traps in rainforest enclosures with captive sun bears to evaluate hair-capture success and the effects of weathering, lure, and adhesive on polymerase chain reaction (PCR) amplification success. Wild adult male sun bears displayed back-rubbing behavior at hair traps and 6 individuals were identified based on unique chest marks. We collected 30 hair samples from wild sun bears, including 15 chest mark images of 6 individuals over 1,260 trap-nights. We detected adult males at hair traps more frequently than females and subadults. We obtained 39 hair samples in the captive trials. Extracted DNA from hair roots successfully amplified with mitochondrial (wild bears: 95%; captive bears: 97%) and microsatellite primers (wild bears: 100%; captive bears 87%). Adhesive and lure type did not affect PCR amplification, but weathering reduced amplification of microsatellite loci. This study is the first successful attempt to obtain genetic samples from wild sun bears using inexpensive, readily available materials such as duct tape, polybutyl glue, and locally sourced lures. The quality of genetic material from these genetic samples should be suitable for studies of population size and gene flow.

Sabah↗