Estimation of White‐Handed Gibbon Density and Population Size in Huai Kha Khaeng Wildlife Sanctuary, Western Thailand

The massive ENSO-induced fires of 1982–1983 and 1997–1998 that burned across much of Borneo forced a critical re-evaluation of the role of fire in tropical forests. In Southeast Asia the occurrence of fires is generally associated with increasing rainfall seasonality. In aseasonal lowland rainforests fire is rare, but potentially devastating when it occurs. In the strongly seasonal regions of continental Southeast Asia deciduous forests and savannas may burn at low intensity every few years, but have little impact on the majority of trees. Between these two extremes of rainfall seasonality lie landscapes dominated by mosaics of evergreen and deciduous forests for which the role of fire and its potential impacts are poorly understood. Ecologists and conservationists across the region have expressed concern that changing fire regimes due to increasing human pressures and potential climate change may lead to a substantial loss of the evergreen forest component within these mosaics. However, there are few empirical data to address these concerns and to use in the development of robust landscape-scale fire management plans. Here we describe results from a study on the fire ecology of forests at the Huai Kha Khaeng Wildlife Sanctuary in western Thailand that was conducted in the wake of the 1998 ENSO fires that occurred there. We compared fire behavior, tree mortality, and stand-scale impacts of the fires across the three dominant forest types of the region: seasonal evergreen forest, mixed deciduous forest, and deciduous dipterocarp forest. Our data demonstrate that the fires are mostly low-intensity surface fires that generate a low level of mortality across the landscape. Mortality was primarily a function of tree size with 50% mortality occurring in trees ∼2 cm DBH (diameter at breast height). We found no evidence of heightened sensitivity to fire in the seasonal evergreen forest and suggest that the high levels of mortality among evergreen tree species in Bornean forests are indicative of differences in long-term exposure to fire between the seasonal evergreen forests of the continent and the aseasonal evergreen forests of insular Southeast Asia. We discuss these findings in the context of the design and implementation of fire management practices in the seasonal tropical forests of continental Southeast Asia.

Small apes are often characterized as inhabiting small home ranges and being dependent on evergreen forest due to their dietary specialization on ripe fruits. Yet few primate studies, particularly those with gibbons, have considered intraspecific variations in ranging behaviors in response to local ecological conditions. This study examines Endangered white-handed gibbon (Hylobates lar) ranging patterns in a heterogeneous landscape. We conducted 13months of behavioral observations on four white-handed gibbon groups living in Huai Kha Khaeng Wildlife Sanctuary in western Thailand, and combine these data with group location and transect-based productivity data. We compare home range area, site fidelity, and microhabitat preferences. Home range (HR) area varied considerably among the four groups (17-61 hectares). Site fidelity was higher in one of the groups with more evergreen forest in the HR (0.72 ± 0.1) than one of the groups with very little evergreen forest in the habitat (0.47 ± 0.07). While groups with more evergreen forest in the HR preferred evergreen forest areas, groups with very little evergreen forest within the HR demonstrated less preference for evergreen forest areas. We conclude that gibbons at this site exhibit a considerable degree of behavioral variation in response to local ecological conditions. These findings suggest that while gibbons exhibit significant ecological flexibility, this flexibility may be limited by habitat type and key food resources.

Home range size and daytime habitat selection of leopards in Huai Kha Khaeng Wildlife Sanctuary, Thailand

Five individuals of four civet species were captured and followed by radiotelemetry in a mosaic of dry tropical forest in Huai Kha Khaeng Wildlife Sanctuary, Thailand. Observations were made on a fifth, arboreal species which was never captured. Radio‐collared civets used overall areas ranging from 3.1 to 17 km2 with average monthly ranges from 0.72 to 5.4 km2. Average monthly ranges, home range centre shifts and activity radii showed a linear increase with weight and size of the individual, both within and between species. Despite individual differences, there were similar behavioural responses to extrinsic seasonal changes. Civets had activity levels of 50–55% and displayed nocturnal activity patterns. The four smallest civets used trees as resting sites extensively while the largest civet, Viuerra zibetha, was always located on the ground. Faecal analysis indicated that civets fed on at least 18 fruiting tree species as well as rodents, insects and crabs. At least one of the fruits found in civet faeces, Cassia fistula, was not eaten by other major frugivores in the area. The civets showed a preference for mixed deciduous and dry evergreen forest over dry deciduous dipterocarp forest, which had a lower abundance of known food items. The role that civets play as seed dispersal agents may help in the maintenance and structuring of tropical forest communities.

Multitemporal change detection was undertaken to investigate whether tropical evergreen forests in Huai Kha Khaeng Sanctuary, Thailand have declined as a result of wildfire. Unsupervised isodata classification was performed on four dry- season Landsat images. Two of the images, 1989 and 2000, were found to be radiometrically comparable with similar cluster classes identified and a near equidistant shift between cluster class means. Image spectral class recoding and subsequent union operation between the two images produced 36 change classes. Results show a significant net change of 14% between spectral classes of significance. The change detection process maps a clear decline in the area of evergreen forest and a shift to deciduous forest types.

Thailand's forest ecosystems contain a diverse vertebrate fauna and >30% of the species are thought to use cavities in trees. Forest management practices may significantly alter cavity availability for hole-nesting vertebrates. The effects of single-tree selection systems, commonly used in Thailand, on tree cavity abundance have not been extensively studied in any forest ecosystem, and no studies have been conducted in Thailand. We measured the effects of single-tree* selection harvest on cavity availability in mixed deciduous forests. We compared tree and cavity densities in unlogged and logged forests (5 stands in each type) in Huai Kha Khaeng Wildlife Sanctuary (HKKWS) in western Thailand. Tree densities (t = 2.89, 8 df, P = 0.02), cavity-tree densities (t = 4.27, 8 df, P = 0.003), and cavity densities (t = 4.44, 8 df, P = 0.004) were greater in unlogged than in logged stands. Ninety-two percent of cavity trees were alive; dead trees were uncommon, probably because of annual ground fires. Alangium salviifolium, Lagerstroemia spp., and Vitex spp. were the taxa most likely to form cavities, accounting for >30% of all trees and 66% of the cavities in unlogged habitats. Logging reduced tree densities of Vitex spp., but did not affect tree densities of Lagerstroemia spp. or A. salviifolium, nor cavity densities in Lagerstroemia spp. and Vitex spp. However, logging reduced cavity densities in A. salviifolium. Single-tree selection cutting reduced cavity abundances in these mixed deciduous forests. Maintenance of cavity-forming species and leaving more large-diameter trees may be required to maintain habitat for cavity-dependent wildlife.

Abstract. Charaspet K, Sukmasuang R, Khoewsree N, Pla-Ard M, Paansri P, Keawdee B, Chanachai Y, Bhumpakphan N. 2021. Spatial and temporal overlaps of top predators: Dhole, tiger and leopard, and their potential prey in Huai Kha Khaeng Wildlife Sanctuary, Thailand. Biodiversitas 22: 580-592. The study of the spatial-temporal overlap of top predators and their prey is important to understand competition among predators and predator-prey relationships so that the viable populations of predators and other animals can be sustained. This research aimed to study the abundance of three top predators: Dhole (Cuon alpinus), tiger (Panthera tigris) and leopard (Panthera pardus), and their potential wild prey in Huai Kha Khaeng Wildlife Sanctuary, Thailand, and to investigate the spatial-temporal overlap between those three predators, and their potential wild prey. We tested two significant hypotheses: (i) tiger and leopard had the highest spatial-temporal overlap and the spatial overlap of dhole and leopard was higher in comparison to dhole and tiger due to a higher prey overlap; (ii) the three species of large carnivore avoided spatial-temporal overlap even if they were in the same area. The study was conducted using camera traps. In addition, the spatial-temporal overlap of large carnivores and their potential prey was studied to understand the important species of prey of these large carnivores. The results showed that the spatial overlap of tiger and leopard was the highest. Dhole had significant spatial overlap with leopard, which was higher in comparison to dhole and tiger. A significant temporal overlap of dhole and leopard was not found. Also, a significant temporal overlap of tiger and leopard was not found. The results were based on hypotheses that conformed to the niche overlap index of the potential prey and the temporal overlap coefficient. There were ten important species of potential prey of large carnivores: Sambar deer (Rusa unicolor), red muntjac (Muntiacus muntjak), gaur (Bos gaurus), banteng (Bos javanicus), wild boar (Sus scrofa), Malayan porcupine (Hystrix brachyura), large Indian civet (Viverra zibetha), Asiatic black bear (Ursus thibetanus), pig-tailed macaque (Macaca nemestrina) and red jungle fowl (Gallus gallus). The important recommendation is the protection of the sanctuary from wildfires which spread from the outside in, especially in dry evergreen forest. Food resources of herbivores in the area must be managed, as well as the prevention of epidemics from livestock to wild animals.

Individual behavior of primates living in small groups is often seen to represent behavior of all group members due to close spatial cohesion. However, given that females expend more energy on reproduction than males (including lactation and infant carrying), females and males may exhibit different behaviors even when maintaining spatial proximity, particularly in highly seasonal or resource-poor environments. We collected 187 hours of data from three dyads (n= 6 individuals) of white-handed gibbons (Hylobates lar) living in a fruit-poor environment in western Thailand during the period of fruit scarcity. We calculated activity budgets, dyad behavioral synchronization, and dyad spatial cohesion. We hypothesized that activity budgets would differ significantly between sexes or pairs would engage in behaviors independently to provide females with an opportunity to obtain more resources. We also hypothesized that pairs would remain in close proximity. Overall, activity budgets exhibited significant variation when analyzed by sex (X2= 27.693, P ⩽ 0.001) and group (X2= 119.584, P ⩽ 0.001). Females spent less time resting and vocalizing and more time traveling compared to males. Percentages of synchronized behavior were lower than expected with only 55% of records synchronized (group B: 58.6%; group D: 58.5%; group L: 49.7%). Spatial cohesion, however, was relatively high overall with adults in the same or adjacent trees in 67.1% of paired records but significantly variable across groups (B: 89.4%; D: 73.1%; L: 48.2%; X2= 190.111, P ⩽ 0.001). We suggest that behavioral synchronization and spatial cohesion may be indicators of pair bond strength, not just the result of pair living. Given differences in activity budgets, low behavioral synchronization, and variable amounts of time pair mates spent apart, we conclude that pair mates should be considered individual actors who engage in behaviors independently from one another, particularly when coping with challenging ecological conditions.

Fire is a necessary disturbance in tropical deciduous forests, as it helps clear the understory community and allows regeneration of grasses and forbs for local wildlife. Huai Kha Khaeng Wildlife Sanctuary (HKK) and Huai Thab Salao-Huai Rabum Non-Hunting Area (HTS) are parts of a few places in Southeast Asia with deciduous forests. However, this area was heavily logged up until 1989, followed by a long period of fire suppression. The consequences of these changes on understory communities have not been investigated. Therefore, the current study aimed to examine the understory communities and their aboveground biomass before and after the annual prescribed burns in HKK and HTS. Understory plant composition and biomass were surveyed in November 2018 (before the fire) and May 2019 (three months after the fire) in 128 temporary plots, covering of deciduous dipterocarp forest, mixed deciduous forest, mixed deciduous forest with bamboo, and open area. We identified a total of 480 understory species, including 37 grass species, 214 forb species, 73 shrub species, 153 tree seedling species and three species of bamboo in the study plots. Grasses in the DDF plots were at 72.79 ± 22.41 kg ha−1, accounting for only ten percent of the understory plants in the plots. The understory community in the DDF plots was dominated by shrubs and tree seedlings of competing species, especially after the fire. The results suggested that past logging activities and long-term fire suppression had reduced the number of mature key dipterocarp forests and hindered the regeneration of grasses and forbs. Maintaining the structure of dipterocarp forests and sufficient food sources for the local wildlife species will require more active habitat management of the study areas.

Understanding the relationship between a species and its habitat is crucial for conservation action planning. The Endangered western hoolock gibbon (Hoolock hoolock) has a fragmented distribution in northeast India, Bangladesh and parts of western Myanmar. Namdapha National Park in Arunachal Pradesh contains the largest population of western hoolock gibbons in India. We carried out an auditory sampling survey and habitat analysis of western hoolock gibbons in the park from September to December 2012 in three potentially suitable forest types: tropical broad-leaved forest, tropical wet evergreen forest, and wet temperate forest. A new method of analysis of singing frequency revealed that only 21–23% of groups sing per day. Group detectability declined sharply beyond a listening radius of 600 m. Auditory sampling across 15 listening areas revealed an estimated mean density of 3.65 groups km−2. We found no significant differences in density among forest types. The habitat study revealed a total of 122 species of trees (girth at breast height ≥30 cm) in the three forest types, representing 73 genera in 41 families, with the highest number of tree species in wet evergreen forest (93) followed by tropical broad-leaved forest (52) and wet temperate forest (40). None of the vegetation traits we measured (mean canopy cover, girth, density, and total basal area of all trees) and no habitat disturbance factors correlated significantly with gibbon density. This lack of correlation may have been due to the prevailing anthropogenic effects that adversely affected gibbons and their habitat, such as forest degradation, road widening, and hunting, overriding the relatively smaller natural variation in vegetation. This study adds to our knowledge of the habitat requirements of hoolock gibbons and indicates that Namdapha National Park is more important to conservation of the western hoolock than previously thought.

Leaf phenology describes the seasonal cycle of leaf functioning and is essential for understanding the interactions between the biosphere, the climate and the atmosphere. In this study, we characterized the spatial patterns in phenological variations in eight contrasting forest types in an Indian region using coarse resolution NOAA AVHRR satellite data. The onset, offset and growing season length for different forest types has been estimated using normalized difference vegetation index (NDVI). Further, the relationship between NDVI and climatic parameters has been assessed to determine which climatic variable (temperature or precipitation) best explain variation in NDVI. In addition, we also assessed how quickly and over what time periods does NDVI respond to different precipitation events. Our results suggested strong spatial variability in NDVI metrics for different forest types. Among the eight forest types, tropical dry deciduous forests showed lowest values for summed NDVI (SNDVI), averaged NDVI (ANDVI) and integrated NDVI (I-NDVI), while the tropical wet evergreen forests of Arunachal Pradesh had highest values. Within the different evergreen forest types, SNDVI, ANDVI and INDVI were highest for tropical wet evergreen forests, followed by tropical evergreen forests, tropical semi-evergreen forests and were least for tropical dry evergreen forests. Differences in the amplitude of NDVI were quite distinct for evergreen forests compared to deciduous ones and mixed deciduous forests. Although, all the evergreen forests studied had a similar growing season length of 270 days, the onset and offset dates were quite different. Response of vegetative greenness to climatic variability appeared to vary with vegetation characteristics and forest types. Linear correlations between mean monthly NDVI and temperature were found to yield negative relationships in contrast to precipitation, which showed a significant positive response to vegetation greenness. The correlations improved much for different forest types when the log of cumulative rainfall was correlated against mean monthly NDVI. Of the eight forest types, the NDVI for six forest types was positively correlated with the logarithm of cumulative rainfall that was summed for 3–4 months. Overall, this study identifies precipitation as a major control for vegetation greenness in tropical forests, more so than temperature.

Seedlings are an important stage for plant populations, as the abundance and rigor of seedlings can indicate a changing forest structure in the future. Studying the different traits of the seedling can represent how the plant grows. Biomass is one of the traits that can represent the plant’s performance and many other growth processes of the seedling. Several allometric equations have been developed to estimate tree biomass. However, allometric equations for the biomass of seedlings remains poorly studied, especially those from the tropics. The objective of this research is to create and develop a model that can be used to predict the biomass of seedlings, including total biomass, aboveground biomass, and belowground biomass, from root collar diameter, shoot height, main stem length, and wood density from 205 two-year-old seedlings from twenty tree species found in dry evergreen forest in Huai Kha Khaeng Wildlife Sanctuary, Uthai Thani, Thailand. The results showed that the root collar diameter, shoot height, and wood density could be used to create a model to best predict the seedling biomass. This model should be tested with other seedlings in the wild and other datasets to evaluate the performance of the model. To our knowledge, this study is among the first to provide the first allometry for seedlings in tropical dry evergreen forest. The results from this study will allow ecologists to monitor and examine the growth of the seedlings at all stages of life in dynamic tropical environments in the future.

Recovery of globally threatened ungulate species in Huai Kha Khaeng Wildlife Sanctuary, Thailand

Disturbances influence forest dynamics across a range of spatial and temporal scales. In tropical forests most studies have focused on disturbances occurring at small spatial and temporal scales (i.e., gap dynamics). This is primarily due to the difficulty of reconstructing long‐term disturbance histories of forests in which most tree species lack annual growth rings. Consequently, the role of past disturbances in tropical forests is poorly understood. We used a combination of direct and indirect methods to reconstruct the historical disturbance regime and stand development patterns in mature and regenerating seasonal dry evergreen forest (SDEF) in the Huai Kha Khaeng Wildlife Sanctuary in western Thailand. Direct estimates of long‐term establishment and growth patterns were obtained from 12 tree species that form annual growth rings as a consequence of the region's strong intra‐annual rainfall seasonality. Indirect estimates of establishment patterns were obtained from analyses of stand structure and individual tree architecture and application of age‐estimation models to 10 dominant canopy‐tree species using demographic data from a large‐scale, permanent forest‐dynamics plot.The combination of direct and indirect methodologies revealed a complex disturbance history in the seasonal evergreen forest over the past 250 years. In the mid‐1800s, 200–300 ha of forest were destroyed by a catastrophic disturbance, which led to the synchronous establishment of many of the trees that presently dominate the forest canopy. Since then widespread disturbances of variable intensity have occurred at least three times (1910s, 1940s, and 1960s). These disturbances created discrete temporal pulses of establishment in small to large gaps in the forest matrix across several square kilometers. Background mortality and gap formation were evident in every decade since 1790, but these varied in intensity and frequency.The SDEF retains a distinct structural and floristic legacy from the catastrophic disturbance of the mid‐1800s. The single‐age cohort that established after the disturbance has developed a complex three‐dimensional structure as a consequence of differences in interspecific growth patterns of the canopy‐tree species and subsequent disturbances of moderate and low intensity. While no single methodological approach provided a complete picture of the disturbance history and stand development patterns of the seasonal evergreen forest, taken together they offered new insights into the long‐term dynamics of a primary tropical forest. In particular, the study highlighted the role of disturbance at multiple spatial and temporal scales and varying intensities in determining the structure and composition of a complex, species‐rich tropical forest and raises important questions about the role of rare, catastrophic events on tropical forest dynamics.

Three males and one female leopard cat were radio-collared and followed for periods of 1-13 months in Huai Kha Khaeng Wildlife Sanctuary, Thailand. The cats had overall home ranges from 1.5-7.5 km2 with core areas of 0.72 km2. A female leopard cat utilized an area of 6.6 km2 over 13 months while a male leopard cat, who shifted ranges, used 7.5 km2 over 3.5 months. Cats followed for longer periods of time generally showed larger overall ranges. The cats were active 50 percent of the time and displayed arrhythmic activity patterns. Leopard cats followed for at least several months showed seasonal variation in movement and ranging patterns. Fourteen prey items were identified in the feces of leopard cats, with small mammals, particularly Maxomys surifer, dominating the prey. Leopard cats preferred resting and moving on the ground, utilizing dry deciduous dipterocarp forest proportionally less than dry evergreen or mixed deciduous forest. Annual fires that help maintain the dry deciduous dipterocarp forest in the study area may affect both short and long term survival of leopard cats.