Robert Steinmetz

The Shared Preference Niche of Sympatric Asiatic Black Bears and Sun Bears in a Tropical Forest Mosaic

Background Ecologically similar species often coexist by partitioning use of habitats or resources. Such partitioning can occur through divergent or shared niches. We investigated overlap in habitat use and spatial co-occurrence by sympatric Asiatic black bears and sun bears in three habitats in Thailand, and thereby assessed which niche model best accounts for their coexistence. Methods/Principal Findings We used density of species-specific signs to assess habitat use. Signs of both bear species occurred in all three habitats, and on >60% of sampling transects. Both species fed mostly on fruit; insect feeding signs were uncommon, and were mostly from sun bears. Significant differences in habitat use occurred only in montane forest, the habitat in which fruit was most abundant; incidence of black bear sign there was six times higher than that of sun bears. Habitat use was similar between the two species in the other habitats, which comprised 85% of the area. Of 10 habitat attributes examined, fruiting tree density was the best predictor of occurrence for both species. Models that included interspecific competition (fresh foraging activity of the other species) were less supported than the top models without competition. Conclusions/Significance Bear species co-occurrence at both coarse and fine spatial scales and use of the same resources (fruit trees) indicated common niche preferences. However, their habitat use differed in ways expected from their physical differences: larger black bears dominated in the most fruit-rich habitat, and smaller sun bears used less-preferred insects. These results indicate broadly overlapping fundamental niches combined with asymmetric competition—features consistent with the concept of shared preference niches. This model of the niche has received little attention in ecology, but appears to be relatively common in nature.

Gaur (Bos gaurus) and Banteng (B. javanicus) in the lowland forest mosaic of Xe Pian Protected Area, Lao PDR: abundance, habitat use, and conservation

Gaur (Bos gaurus) and banteng (Bos javanicus) populations throughout South-east Asia have declined severely because of hunting and habitat fragmentation. Important remnant populations persist in Xe Pian national protected area in southern Lao P.D.R., where sign-based surveys were carried out between 1996 and 1998 to determine their distribution, abundance, and patterns of habitat use. Xe Pian is comprised of a largely intact lowland mosaic of semi-evergreen, mixed deciduous, and dry dipterocarp forest types. Gaur used a broader diversity of these habitat types than banteng, attaining moderate densities in homogeneous semi-evergreen forest as well as expanses of deciduous dipterocarp and mixed deciduous forests. Mixed deciduous forest was the least abundant forest type but was commonly used by gaur. Banteng showed a strong affiliation with drier and more open habitats, especially dry dipterocarp forest, despite increased vulnerability to hunting in these areas in the past. Banteng were not found within large expanses of semi-evergreen forest. Their distribution within Xe Pian was therefore more restricted than gaur, though they were relatively more numerous within two isolated corners of the protected area. Signs of calves and juveniles indicated that both species retained breeding populations in Xe Pian. Remaining herds were small – composed of two to five individuals – but bamboo understories in semi-evergreen forest were a food source that attracted larger congregations of gaur in the rainy season. The banteng population in Xe Pian is globally significant for conservation, while that of gaur is nationally significant. The existence of extensive high quality habitat and on-going collaboration of local people lends hope that Xe Pians wild cattle will increase, given protection from hunting.

Foraging ecology and coexistence of Asiatic black bears and sun bears in a seasonal tropical forest in Southeast Asia

Abstract Asiatic black bears (Ursus thibetanus) and sun bears (Helarctos malayanus) are ecologically similar and coexist extensively across Southeast Asia. We used foraging signs identified to bear species to examine their food selection and dietary overlap relative to food abundance, nutrition, and phenology in 3 habitats in Thailand. We posited, based on ecological theory, that coexistence of these 2 species would be explained through resource partitioning; our data, however, did not support this hypothesis. We conducted 71 sign transects and recorded 730 bear signs, mainly claw marks on trees that bears climbed for food. Both species fed predominantly on fruit; we documented 93 plant species from 42 families that bears consumed. Insects were of secondary importance. Bears of the 2 species selected fruit trees of the same families and genera in each habitat, especially lipid-rich Lauraceae and Fagaceae, tracking fruiting phenology through time. Diet overlap was high, even during periods of diminished fruit availability. We propose a number of mechanisms that may have promoted coexistence of these 2 species. For example, sun bears consumed proportionately more insects than did black bears; insectivory may help sustain the smaller-sized sun bears in the face of competition over fruits with black bears. Also, competition over fruits was reduced by both species cropping a lower proportion of common fruit trees than rarer fruit trees, thereby leaving a potential surplus for the other species. Furthermore, food resources were generally abundant and available year-round: about half the trees in the forest were potential food trees for bears. Bear populations likely were depressed below carrying capacity by previous hunting; as they recover, more competition for resources and greater niche divergence could ensue.

Influence of Fruit on Habitat Selection of Asian Bears in a Tropical Forest

ABSTRACT Wild bear populations in Southeast Asia are threatened with extinction, but the ecology and distribution of the 2 species occurring in the regions protected areas is poorly known, so there is little scientific basis underlying conservation strategies. We used bear signs, primarily claw marks on climbed trees, to study habitat selection and distribution of Asiatic black bear (Ursus thibetanus) and sun bear (Helarctos malayanus) across Khao Yai National Park, Thailand from March to December 2008. We found black bear claw marks in 24 of 30 random sample blocks (80%), indicating that this species was widely distributed across Khao Yai. Sun bear signs were much scarcer: their claw marks occurred in 11 blocks (37%); data were too sparse for sun bear so we limited our focus to Asiatic black bear. Using logistic regression, we found that fruit abundance best explained variation in presence of black bear, whereas human disturbance, distance to park edge, elevation, and ground cover had little influence. Fruits appear to be a key resource for Asiatic black bears, and factors affecting fruit abundance or shifts in seasonality (e.g., climate change) will impact bear populations. Knowledge of this relationship will allow managers to be more proactive in managing bears. We recommend using sign surveys for monitoring changes in black bear occupancy as they are inexpensive, efficient, and can be conducted by trained park rangers.

Distinguishing Asiatic Black Bears and Sun Bears by Claw Marks on Climbed Trees

Abstract Asiatic black bears (Ursus thibetanus) and sun bears (Helarctos malayanus) are sympatric in mainland Southeast Asia and face similar threats of habitat loss and commercial poaching. They are rarely seen but leave distinct signs, especially claw marks on climbed trees. These markings, which are potentially valuable indicators of presence, population status, and behavior of black bears and sun bears, have limited usefulness if the 2 species cannot be differentiated. We measured 121 claw mark imprints on climbed trees from 43 known (mainly captive) individual black bears and sun bears of both sexes in Thailand and Cambodia. The span across the markings made by 3, 4, or 5 claws from the hind foot was significantly greater for black bears than sun bears. We developed discriminant function models with these variables and arranged them in a 3-step process that distinguished claw marks as either sun bear, black bear, or indeterminate. This procedure correctly classified 95% of claw marks from the experimental animals. Tested on wild bears (at sites where only one species occurred), the procedure correctly classified 91% of claw marks of black bears in China (n = 94) and 100% of claw marks of sun bears in Indonesia (n = 32). The main limitation of the method was in distinguishing young, small black bears (cubs and yearlings) from sun bears. Nevertheless, application of these findings will be valuable in bear research and monitoring programs throughout Southeast Asia, where sign surveys have, until now, been hampered by the inability to differentiate these 2 ecologically and behaviorally similar species.

Mapping the distribution of dholes, Cuon alpinus (Canidae, Carnivora), in Thailand

Abstract No recent attempt has been made to survey dhole distribution, or to estimate remaining population numbers. We surveyed 15 protected areas in Thailand with camera traps from 1996 to 2010. We used the photo locations of dholes (n=96) in the maximum entropy (MaxEnt) model along with six environmental variables to model current dhole distribution, as well as species predictive occurrence layers for sambar, red muntjac, wild boar, tiger, and leopard. The MaxEnt model identified the predicted probability of the presence of leopards and sambar as positive and the most important variables in modeling dhole presence, indicating that maintaining a sufficient prey base may be the most important factor determining continued survival of dholes. Roughly 7% of the total land area in Thailand is potentially suitable for dholes. However, surveys to date have focused on protected areas, which make up just a third of the potential suitable areas for dholes. Only in four protected areas do they occur across the entire landscape, suggesting that in the majority of places where they occur, habitats are not uniformly suitable. Using the model, we identified several potential areas where dholes have not been reported, and therefore status surveys are needed, and where future research of the species might be focused.

Comparative sensitivity to environmental variation and human disturbance of Asian tapirs (Tapirus indicus) and other wild ungulates in Thailand

Southeast Asias tropical forests suffer the highest rates of deforestation and disturbance of any on Earth, with poorly understood impacts on native fauna. Asian tapirs (Tapirus indicus) are among the least studied of the large mammals in these forests. Using records from 9 camera trap surveys in 7 of the largest (>1000 km(2) ) protected area complexes, we assessed the influence of environmental variation and human-induced disturbance on tapir occurrence. Tapirs were detected at 13% of locations sampled, significantly associated with evergreen forest (P < 0.001). A multiple logistic regression model predicted tapir presence 87% of the time. According to this model, tapir occurrence was positively influenced by annual rainfall and proximity to the forest edge. However, tapirs may not avoid edges but instead prefer wetter evergreen forest, a habitat type that tended to occur further from the forest edge at higher elevations in our particular study sites (P < 0.001). By comparison, 4 other wild ungulate species that share habitats with tapirs showed a range of differing responses. Tapirs are expected to be less sensitive to disturbance because they are not targets for hunting and trade, and are almost entirely active at night, so avoid peak traffic periods in parks. Tapir populations in Thailand may be more stable than in other parts of their global range because rates of forest loss have decreased >40% over the past 20 years. We recommend surveys to fill gaps in the understanding of the status in lesser-known protected areas, research to better understand the fine-scale environmental influences on behavior and habitats of tapirs, and other forest ungulates, and continued legal status for tapirs in the highest category of protection.

Political transition and emergent forest-conservation issues in Myanmar

Political and economic transitions have had substantial impacts on forest conservation. Where transitions are underway or anticipated, historical precedent and methods for systematically assessing future trends should be used to anticipate likely threats to forest conservation and design appropriate and prescient policy measures to counteract them. Myanmar is transitioning from an authoritarian, centralized state with a highly regulated economy to a more decentralized and economically liberal democracy and is working to end a long-running civil war. With these transitions in mind, we used a horizon-scanning approach to assess the 40 emerging issues most affecting Myanmars forests, including internal conflict, land-tenure insecurity, large-scale agricultural development, demise of state timber enterprises, shortfalls in government revenue and capacity, and opening of new deforestation frontiers with new roads, mines, and hydroelectric dams. Averting these threats will require, for example, overhauling governance models, building capacity, improving infrastructure- and energy-project planning, and reforming land-tenure and environmental-protection laws. Although challenges to conservation in Myanmar are daunting, the political transition offers an opportunity for conservationists and researchers to help shape a future that enhances Myanmars social, economic, and environmental potential while learning and applying lessons from other countries. Our approach and results are relevant to other countries undergoing similar transitions.

Estimating ages of bear claw marks in Southeast Asian tropical forests as an aid to population monitoring

Abstract Asiatic black bears (Ursus thibetanus) and sun bears (Helarctos malayanus) in Southeast Asia leave claw marks on climbed trees that provide a cumulative history of their presence and activities, but this record can be difficult to interpret without knowing the age of the marks. We conducted an experiment to estimate ages of bear claw marks by monitoring 212 fresh claw mark sets (most of which we created to mimic real claw marks) on 122 trees from 17 families in Thailand. We categorized marks as looking fresh (presence of woody grit, sharp edges), recent (absence of woody grit), or old (bark growth in the gouges), and estimated the duration of these age categories using Kaplan-Meier survival analysis. Most marks (81%) remained fresh for at least 2 months, but by 3 months, 75% had transitioned to recent (median 2.6 months). By 10 months, 90% of fresh marks became old (median 7.3 months). Wood hardness had no effect on aging rates. Marks created in the rainy season and those on thin-barked trees aged slightly faster than dry season marks or marks on thick-barked trees, but these differences were slight enough that they could be disregarded in population monitoring programs based on abundance of sign. Simulation models we constructed indicated that the density of fresh (or fresh plus recent) sign would more closely correspond with the number of bears in an area than would the density of all sign or the ratio of new∶old sign, because old sign persists for a long (≥24 months) and variable time, so would tend to be a poor reflection of bear abundance. Fresh claw marks also can be linked to phenology and fruit production of climbed trees, so could provide information on bear feeding habits.

Habitat Use of the Saola Pseudoryx nghetinhensis (Mammalia; Bovidae) Based on Local Sightings in the Northern Annamite Mountains of Lao PDR:

The Saola Pseudoryx nghetinhensis (Mammalia; Bovidae) is IUCN Critically Endangered, but its ecology remains almost entirely unknown. Here we present the first characterization of Saola habitat use. We assessed Saola macrohabitat and microhabitat characteristics using Saola sighting location data obtained from local people. The study focused on the Phou Sithon Endangered Species Conservation Area in the northern Annamites of Lao PDR. A geographical information system was used to characterize macrohabitat variables including elevation, abundance of streams, and distance to nearest village associated with each observation. Infinitely weighted logistic regression models were used to assess relationships between detection of Saola and these macro variables. Direct measurements for microhabitat variables for each Saola observation were also collected and compared with other available vegetation data. Twenty-two observations from 18 independent observation points were analyzed. Elevations of the points ranged from 592 to 1,112 m (Median = 747 m) matching previous studies (500–1,400 m). Our regression model indicated abundance of streams affected detection of Saola suggesting it was more likely detected in areas with higher abundances of streams; however, streams were also associated with human travel routes. Our analysis also suggested that Saola were more frequently encountered in primary forest with a high density of trees but were occasionally observed in secondary growth. Most encounters were on animal trails. This information represents an important baseline for future assessments of Saola priority areas, which may assist in searching for possible sites that might harbor this elusive species; however, additional studies of its ecology are urgently needed to guide future management.