Danum Valley Conservation Area Research Articles

Occurrence of Volatile Organic Compounds and Extrafloral Nectaries in Tropical Rainforest Species in Danum Valley Conservation Area, Sabah, Malaysia

Plants synthesize numerous classes of secondary metabolites that are crucial in plant defense. Two of the common but non-ubiquitous defenses are the emission of volatile organic compounds (VOCs) and production of extrafloral nectaries (EFN). This study investigates the occurrence of emission of VOC and production of EFN in forest species in Danum Valley Conservation Area, Sabah, Malaysia. From the 165 species screened, 131 species were found to emit VOC while 41 species were EFN-bearing plants. There are 34 species that are both emitting VOC and producing EFN, while 97 species were found to be emitting VOC with no EFN observed. On the other hand, there are 7 species that were EFN bearing but non-VOC emitter, while 27 species were neither emitting VOC nor producing EFN. All 12 dipterocarp species were observed to emit VOC, of these 3 are non-EFN bearing. VOC emissions were further classified into isoprene (C5) and monoterpene (C10) compounds. There are 46 species that were detected to emit both isoprene and monoterpenes, while there are more exclusive monoterpene emitters (62 species) than isoprene-only emitters (23 species). This study showcased the ability of plants to produce a wide array of secondary metabolites as plant defense making them successfully adapt to the complexities of tropical rainforest ecosystem.

MOLECULAR PHYLOGENY STUDY OF SCHISMATOGLOTTIS FROM DIFFERENT REGIONS IN SABAH USING INTERNAL TRANSCRIBED SPACER REGION

The Schismatoglottideae tribe, primarily in Borneo, is notably diverse within the Araceae family. It encompasses various rainforest herbs, adapting to terrestrial, lithophytic, and rheophytic habitats. The Schismatoglottis genus, with over 175 species, mostly exclusive to Borneo due to geological preferences, stands out. A study aimed to understand genetic relationships among Schismatoglottis species from Kadamaian-Kinabalu Park, Kionsom Recreational Area, Imbak Canyon Conservation Area, Mensalong Forest Reserve, Danum Valley Conservation Area, Tawau Hills Park, and Mantailang Crocker Range Park. The Internal Transcribed Spacer (ITS) regions of twelve Schismatoglottis species were sequenced. Genomic DNA was extracted from dried-silica-gel leaf tissue using a commercial kit (Promega, USA). ITS region lengths ranged from 528 bp to 708 bp. BLAST analysis accurately identified species within the Schismatoglottis genus (95% to 98% similarity). Phylogenetic analysis revealed a highly supported sister clade, uniting Schismatoglottis porpax species from Mensalong and Kionsom, despite differing elevational habitats. This pioneering study delves into Schismatoglottis phylogenetics, particularly in Sabah, with seven of the twelve species showing potential for new species classification, pending further research.

Assessing Forest Carbon Accumulation Potential Across Different Treatments using Field Inventory Data

Deforestation and forest degradation lead to an increase in the level of carbon in the atmosphere and disrupted the global carbon cycle. The tropical forest has received a lot of interest since it contributes around 60% of the total global forest carbon. By enhancing carbon sink, tropical forests have a great potential in mitigating climate change. Assessing aboveground biomass (AGB) and carbon stock through field inventories is crucial for this purpose as it provides the most accurate result. The research was conducted at Danum Valley Conservation Area and INFAPRO in Sabah, Malaysia. An earlier study over 35 years ago at this site suggests that restored forests accrue AGB at twice the rate of regenerating forests, though the cause of this difference between treatments is unclear. Thus, this study will focus on three principal study sites which are restored, naturally regenerating and old-growth forests to determine the forest’s potential to sequester and store carbon in the forest ecosystem. These three sites were chosen because it is a well-established plot from the earlier inventory over the last seven years. The field measuring method is a non-destructive methodology. Tree parameters such as diameter at breast height (DBH), tree height and tree species diversity were collected for calculating AGB using a species-specific allometric equation. Results showed a positive correlation between tree species, diameter at breast height, and biomass/carbon stock across three different forest treatments. The active restoration increases up to 151% carbon stock whilst the old-growth forest increased by 34% and natural regeneration increased by 73%, which active restoration can be the best solution for forest treatment. The outcome of this study will increase the ability of forest authorities and the Malaysian government to effective monitoring of carbon stock for establishing reliable standard guidelines in measuring deforestation and forest degradation toward achieving sustainable forest management.

On the Cypariini (Coleoptera: Staphylinidae: Scaphidiinae) of Borneo

Surveys of the Insects of the Danum Valley Conservation Area in Sabah, Malaysia yielded species of the Scaphidiinae genus Cyparium Erichson, 1845. In the present paper, four are described while a fifth potential new species, only represented by a single female, is left undescribed. A key to the ten species of Cyparium known at present to occur in the Sundaland is provided.

Evidence for acoustic niche partitioning depends on the temporal scale in two sympatric Bornean hornbill species

AbstractUnderstanding niche partitioning of closely related sympatric species is a fundamental goal in ecology. Acoustic communication space can be considered a resource, and the acoustic niche hypothesis posits that competition between species may lead to partitioning of communication space. Here, we compare the calling behavior of two sympatric Bornean hornbill species—the rhinoceros hornbill (Buceros rhinoceros) and the helmeted hornbill (Rhinoplax vigil)—to test for evidence of acoustic niche partitioning. Both hornbill species emit calls heard over many kilometers and have similar habitat preferences which is predicted to result in interspecific competition. We collected acoustic data on sympatric populations of both hornbill species using 10 autonomous recording units in Danum Valley Conservation Area, Sabah, Malaysia. We found that there was substantial spectral overlap between the calls of the two species, indicating the potential for competition for acoustic space. To test for evidence of acoustic niche partitioning, we investigated spatial and temporal patterns of calling in each species. Both hornbills were strictly diurnal and called throughout the day, and we were equally likely to detect both species at each of our recorders. We did not find evidence of temporal acoustic avoidance at a relatively coarse timescale when we divided our dataset into 1 h bins, but we did find evidence of temporal acoustic avoidance at a finer timescale when we used null models to compare the observed duration of overlapping calls to the expected amount of overlap due to chance.Abstract in Malay is available with online material.

Increase in social interactions of wild Northern Gray gibbons (Hylobates funereus) during the mast fruiting period in the Danum Valley Conservation Area, Sabah, Malaysia

In Southeast Asian forests, there are dramatic supra-annual peaks in fruit availability known as mast fruiting, followed by low-fruit periods. Gibbons are frugivorous small apes. In this study, we investigated how gibbons varied their social and calling behaviors in response to changes in fruit availability. Activity budget, travel distance, sleeping time, and song duration of two wild Northern Gray gibbon (Hylobates funereus) groups were investigated during both mast and non-mast fruiting periods at the Danum Valley Conservation Area, Sabah, Malaysia. Gibbons traveled longer, entered the sleeping tree later, and spent more time engaged in singing, playing, and grooming behaviors during the mast fruiting period. Playing and grooming are intra-group social interactions. Gibbon songs were sung antiphonally within and among groups, indicating that singing is both an intra- and inter-group social interaction. Furthermore, copulatory behaviors that occurred during female pregnancy were observed during the mast fruiting period, suggesting this might be a social interaction behavior rather than a reproductive activity. Our results show that gibbons extended their daily activity schedules during the mast fruiting period and spent this extra time on social interactions. We examined whether male song complexity increased during the mast fruiting period by using the Levenshtein distance method, but we did not find such a trend. In the mast fruiting period, gibbons may consume more energy than in the non-mast fruiting period. Social and calling behaviors are energetically costly. Our results show that there is a link between energy intake and social and calling behaviors.

Three decades of post-logging tree community recovery in naturally regenerating and actively restored dipterocarp forest in Borneo

Selective logging has affected large areas of tropical forests and there is increasing interest in how to manage selectively logged forests to enhance recovery. However, the impacts of logging and active restoration, by liberation cutting and enrichment planting, on tree community composition are poorly understood compared to trajectories of biomass recovery. Here, we assess the long-term impacts of selective logging and active restoration for biomass recovery on tree species diversity, community composition, and forest structure. We censused all stems ≥2 cm diameter at breast height (DBH) on 46 permanent plots in unlogged, primary forest in the Danum Valley Conservation Area (DVCA; 12 plots, totalling 0.6 ha) and in sites logged 23–35 years prior to the census in the Ulu Segama Forest Reserve adjacent to DVCA (34 plots, totalling 1.7 ha) in Sabah, Malaysian Borneo. Active restoration treatments, including enrichment planting and climber cutting, were implemented on 17 of the logged forest plots 12–24 years prior to the census. Total plot-level basal area and pole (5–10 cm DBH) stem density were lower in logged than unlogged forests, however no difference was found in stem density amongst saplings (2–5 cm DBH) or established trees (≥10 cm DBH). Neither basal area, nor plot-level stem density varied with time since logging at any size class, although sapling and pole stem densities were lower in actively restored than naturally regenerating logged forest. Sapling species diversity was lower in logged than unlogged forest, however there were no other significant effects of logging on tree species richness or diversity indices. Tree species composition, however, differed between logged and unlogged forests across all stem size classes (PERMANOVA), reflected by 23 significant indicator species that were only present in unlogged forest. PERMANOVA tests revealed no evidence that overall species composition changed with time since logging or with active restoration treatments at any size class. However, when naturally regenerating and actively restored communities were compared, two indicator species were identified in naturally regenerating forest and three in actively restored forests. Together our results suggest that selective logging has a lasting effect on tree community composition regardless of active restoration treatments and, even when species richness and diversity are stable, species composition remains distinct from unlogged forest for more than two decades post-harvest. Active restoration efforts should be targeted, monitored, and refined to try to ensure positive outcomes for multiple metrics of forest recovery.

Habitat use by a primate community in a lowland dipterocarp forest in Danum Valley, Borneo.

Knowledge of niche partitioning with respect to habitat is indispensable to understand the mechanism of coexistence of multiple species. Among primates, however, data are still deficient because repeated survey for a sufficiently long time, covering seasonal changes over a large area, is the only way to clarify habitat segregation within a seasonally fluctuating environment. Southeast Asia is particularly interesting because of the supra-annual, highly unpredictable seasonality in fruiting known as mast fruiting. We conducted repeated route census, habitat monitoring, and group tracking for 25 months in two study sites (ca. 10 km apart) in the largely primary lowland dipterocarp forest of the Danum Valley Conservation Area, eastern Sabah, northern Borneo, Malaysia. The five species of diurnal primates (Bornean orangutan Pongo pygmaeus, Müeller's gibbon Hylobates muelleri, red leaf monkey Presbytis rubicunda, long-tailed macaque Macaca fascicularis, and southern pig-tailed macaque M. nemestrina) did not show horizontal spatial segregation. Red leaf monkeys showed preferences for places with short tree height, but their distribution was not confined to such places. In response to the fruiting peak observed once during the study period, orangutans increased their numbers simultaneously in the two study sites. The average tree height used by the five species was different, but their range overlapped substantially. Compared with other primate communities, the lack of horizontal spatial segregation and the suggested long-distance movement of orangutans seem to be unique characteristics in Borneo, although the use of different forest strata is a widespread phenomenon among primate communities throughout the world.

Copulation calls in wild Mueller’s gibbons (Hylobates muelleri)

AbstractMating activity of a wild Mueller’s gibbon group (Hylobates muelleri) was observed in the Danum Valley Conservation Area, Sabah, Malaysia. The purpose of this study was to investigate the function of copulation calls in gibbons. The female emitted copulation calls at the time of intromission and pelvic thrusting. Copulation calls were composed of two notes and one of them was sung only while mating. Approximately half of copulation calls were sung near the range boundary. Mating with copulation calls sometimes occurred while singing. According to the model that female copulation calls have evolved under the selective pressures of risk of infanticide and sperm competition, copulation calls should be rare in species with little female promiscuity. As gibbons usually live in pair-living social organization and have a monogamous mating system, no vocal signals by female gibbons are considered to be needed. However, clear copulation calls were emitted by the female. It suggests that the relationship between paired gibbons is unstable. Copulation calls by the female Mueller’s gibbon may function to increase mate guarding and strengthen the pair bond.

Developmental changes in the endocrine stress response in orangutans (Pongo pygmaeus)

Non-invasive measures of stress are crucial for captive and conservation management programs. The adrenal hormone dehydroepiandrosterone-sulfate (DHEAS) has recently been adopted as a stress marker, but there is little investigation of its relationship to glucocorticoids (GC), well-known indicators of stress. This study examined the influence of age, reproductive state and environment on GC and DHEAS levels in orangutans, to test whether the GC/DHEAS ratio can provide an index of stress response in primates. We measured fecal GC (fGC) and fecal DHEAS (fDHEAS) concentrations in 7 captive orangutans from zoological parks in Japan and 22 wild orangutans from Danum Valley Conservation Area, Malaysia. We found that in a stressful condition (transportation), fDHEAS levels increased 2days after the fGC response, which occurred 1day after the stressor. One pregnant female had elevated levels of both hormones, and a higher fGC/fDHEAS ratio than baseline. Females in the first year of lactation had fGC levels and the fGC/fDHEAS ratio significantly higher than both baseline and females in the second and subsequent years of lactation. There was no effect of age on fGC levels, but the fGC/fDHEAS ratio was higher in infants than adults and adolescents. fDHEAS concentrations were lower in infants than juveniles, adolescents and adults, a phenomenon known as adrenarche, shared with humans and other great apes. We suggest that changes in DHEAS during orangutan life history are associated with changes in the dynamics of maintaining homeostasis that vary with age and reproductive state. The GC/DHEAS ratio index is useful to evaluate age-related abilities of responding to stressful challenges.

Studies on Schismatoglottideae of Borneo LXVIII: two new species of Schismatoglottis endemic to the Danum Valley Conservation Area, Sabah, Malaysian Borneo

Schismatoglottis clivemarshii and Schismatoglottis priapica are described and illustrated as new species from the Danum Valley Conservation Area, Tawau, Lahad Datu, Sabah, to where both are endemic.

Short Communication: Growth patterns of Shorea leprosula and Dryobalanops lanceolata in Borneo’s forest managed with Selective Cutting with Line Replanting System

Abstract. Tirkaamiana MT, Partasasmita R. Kamarubayana L. 2019. Growth patterns of Shorea leprosula and Dryobalanops lanceolata in Borneo’s forest managed with Selective Cutting with Line Replanting System. Biodiversitas 20: 1160-1165. Dryobalanops lanceolata is a species of plant in the family Dipterocarpaceae, which indigenous of Borneo. It is found in at least five protected areas (Kabilli-Sepilok Forest Reserve, Danum Valley Conservation Area, Ulu Temburong, Lambir, and Gunung Mulu National Parks), but is threatened elsewhere due to habitat loss. The demand for its timber is very high, so it requires conservation efforts while at the same time maintaining its productivity to meet the timber demand. One of the efforts to increase productivity of production forest in Indonesia is implementing Selective Logging with Line Replanting System (TPTJ). In this system superior species are planted in the planting lines. This study aimed to determine the growth of Shorea leprosula and Dryobalanops lanceolata planted in different planting line widths. Data of diameter increment of S. leprosula and D. lanceolata were obtained by observing 4 permanent sample plots (PUP) at concession areas of PT Balikpapan Forest Industries in Penajam Paser Utara, East Kalimantan, Indonesia. The results showed that the average diameter increment of S. leprosula and D. lanceolata at the planting line width of 3 meters was 1.47cm/yr and 0.74 cm/yr respectively, and at the planting line width of 6 meters was 2.08 cm/yr and 1.14 cm/yr respectively. The differences in planting line width had very significant effect on the growth and diameter increment of S. leprosula, presumably due to the increase of light intensity to optimal level which accelerates stomata opening and transpiration rate, thus affecting the rate of photosynthesis.

Studies on Schismatoglottideae (Araceae) of Borneo LXVII: Bucephalandra danumensis, a new species from Sabah, Malaysian Borneo

Bucephalandra danumensis is described from the Danum Valley Conservation Area, Tawau, Lahad Datu, Sabah, where it is restricted to streams and waterfalls on igneous outcrops in forests on Cretaceou...

The freshwater crabs of Danum Valley Conservation Area in Sabah, East Malaysia, with a description of a new species of Thelphusula Bott, 1969 (Crustacea, Brachyura, Gecarcinucidae, Potamidae, Sesarmidae).

Seven species of freshwater crabs from three families are recorded from and around the Danum Valley Conservation Area in Sabah, Malaysian Borneo: Thelphusula capillodigitus sp. n., Thelphusula dicerophilus Ng & Stuebing, 1990, Arachnothelphusa terrapes Ng, 1991, Terrathelphusa secula Ng & Tan, 2015, Parathelphusa valida Ng & Goh, 1987 (new record) (Gecarcinucidae); Isolapotamon ingeri Ng & Tan, 1998 (Potamidae); and Geosesarma danumense Ng, 2002 (Sesarmidae). The new species of Thelphusula Bott, 1979, can be distinguished from all congeners by a unique combination of morphological features, most notably the presence of dense patches of short setae on the fingers of the adult male chelipeds, as well as the structure of the male first gonopod. Arachnothelphusa terrapes is confirmed to be a phytotelm species. A key to all species in the conservation area is provided.

Combinatory rules and chunk structure in male Mueller’s gibbon songs

Understanding whether the long and elaborate songs of male gibbons (Hylobates muelleri) have syntax and hierarchical structures (chunks) is an interesting question in the evolution of language, because gibbons are near humans in the phylogenetic tree and a hierarchically organized syntax is considered to be a basic component of human language. We conducted field research at Danum Valley Conservation Area in northern Borneo to test the hypothesis that gibbon songs have syntax and chunks. We followed one Mueller’s gibbon group for 1 week in the dry and rainy seasons every year from 2001 to 2009, collecting vocal and behavioral data. Results show that songs emitted by the studied male gibbon were governed by combinatory rules. Some context-dependent songs had different combinatory rules, although they overlapped with the songs whose contexts were uncertain. The male Mueller’s songs had characteristics that suggest existence of chunk structure. These results provided an important perspective in the study of language origin.

Behavioral and physiological changes in a juvenile Bornean orangutan after a wildlife rescue

We report a case of a juvenile female orangutan (Pongo pygmaeus morio) that remained in a durian tree (Durio zibethinus) for about one month, nearby a road delimiting Danum Valley Conservation Area (DVCA), East Borneo. The juvenile was rescued and brought to Sepilok Orangutan Rehabilitation Centre (SORC). Before rescue and after release, we recorded the juvenile’s activity and collected fecal samples for the determination of fecal glucocorticoids (fGC). We compared the behavior and stress levels between the two conditions and made comparisons with DVCA juveniles. Additionally, we obtained hematological and biochemical parameters pre and post-quarantine, to monitor her health condition and recovery. The pre-quarantine diagnosis revealed dehydration, malnourishment and slight anemia, but after quarantine her condition stabilized. The juvenile showed abnormal activity in both conditions, with high bark consumption before rescue and a high proportion of resting time after release. fGC levels were higher in comparison to DVCA juveniles, and showed a marked increase after the release. The results suggest that rescue programs help reestablish health parameters, but release processes are stressful for wild orangutans. Early separation from the mother in orangutans may occur more often than reported, particularly in fragmented habitats, and result in poor health that could hasten death.

Reduced damage and epiphyll cover of leaves ofKorthalsiarattans that hostCamponotusants in the rain forest of Malaysian Borneo

Abstract:Many species of palm produce chambers called domatia that are used by ants as nesting spaces. However, the ecological nature of this association is not well understood, and the information on palm–ant interactions is primarily anecdotal. Here, we conducted a field study in the secondary forest of the Danum Valley Conservation Area, Malaysian Borneo, on 41 individuals of the rattanKorthalsia furtadoana. All studied plants showed signs of a past or present partnership with domatia-nesting ants, as indicated by entry holes in domatia. In 14 plants, our physical disturbance of a stem provoked the appearance of patrolling ants ofCamponotussp. We compared the leaf conditions of rattans with and without patrolling ants, testing whether the presence of ants is linked to improved leaf health. The leaflets of plants with patrolling ants were significantly less physically damaged and less covered by epiphylls. On average, 19% of the leaflets of plants with patrolling ants were damaged (52% in plants without patrolling ants), and the epiphyll cover of their leaflets was 0.2 on our scale of 0–4 (1.3 in plants without patrolling ants). Our results suggest that this poorly studied plant–ant association has a mutualistic character. It seems that the ants take advantage of the nesting space created by the plant partner, while the plants gain protection for their photosynthetic apparatus against herbivores and epiphylls.

The First Estimates of Marbled Cat Pardofelis marmorata Population Density from Bornean Primary and Selectively Logged Forest.

The marbled cat Pardofelis marmorata is a poorly known wild cat that has a broad distribution across much of the Indomalayan ecorealm. This felid is thought to exist at low population densities throughout its range, yet no estimates of its abundance exist, hampering assessment of its conservation status. To investigate the distribution and abundance of marbled cats we conducted intensive, felid-focused camera trap surveys of eight forest areas and two oil palm plantations in Sabah, Malaysian Borneo. Study sites were broadly representative of the range of habitat types and the gradient of anthropogenic disturbance and fragmentation present in contemporary Sabah. We recorded marbled cats from all forest study areas apart from a small, relatively isolated forest patch, although photographic detection frequency varied greatly between areas. No marbled cats were recorded within the plantations, but a single individual was recorded walking along the forest/plantation boundary. We collected sufficient numbers of marbled cat photographic captures at three study areas to permit density estimation based on spatially explicit capture-recapture analyses. Estimates of population density from the primary, lowland Danum Valley Conservation Area and primary upland, Tawau Hills Park, were 19.57 (SD: 8.36) and 7.10 (SD: 1.90) individuals per 100 km2, respectively, and the selectively logged, lowland Tabin Wildlife Reserve yielded an estimated density of 10.45 (SD: 3.38) individuals per 100 km2. The low detection frequencies recorded in our other survey sites and from published studies elsewhere in its range, and the absence of previous density estimates for this felid suggest that our density estimates may be from the higher end of their abundance spectrum. We provide recommendations for future marbled cat survey approaches.

Detection of urinary estrogen conjugates and creatinine using near infrared spectroscopy in Bornean orangutans (Pongo Pygmaeus).

For promoting in situ conservation, it is important to estimate the density distribution of fertile individuals, and there is a need for developing an easy monitoring method to discriminate between physiological states. To date, physiological state has generally been determined by measuring hormone concentration using radioimmunoassay or enzyme immunoassay (EIA) methods. However, these methods have rarely been applied in situ because of the requirements for a large amount of reagent, instruments, and a radioactive isotope. In addition, the proper storage of the sample (including urine and feces) on site until analysis is difficult. On the other hand, near infrared (NIR) spectroscopy requires no reagent and enables rapid measurement. In the present study, we attempted urinary NIR spectroscopy to determine the estrogen levels of orangutans in Japanese zoos and in the Danum Valley Conservation Area, Sabah, Malaysia. Reflectance NIR spectra were obtained from urine stored using a filter paper. Filter paper is easy to use to store dried urine, even in the wild. Urinary estrogen and creatinine concentrations measured by EIA were used as the reference data of partial least square (PLS) regression of urinary NIR spectra. High accuracies (R(2) > 0.68) were obtained in both estrogen and creatinine regression models. In addition, the PLS regressions in both standards showed higher accuracies (R(2) > 0.70). Therefore, the present study demonstrates that urinary NIR spectra have the potential to estimate the estrogen and creatinine concentrations.

Intergroup and intragroup antiphonal songs in wild male Mueller’s gibbons (Hylobates muelleri)

Mueller’s gibbons (Hylobates muelleri) sing both sex-specific and duet songs. These songs are thought to be involved in territory maintenance, as well as the maintenance of pair or family bonds. However, few observational studies have examined how gibbons interact with their neighbors through song in the wild. We have been conducting field observations of wild gibbon groups in northeast Borneo since 2001. In the Borneo Rainforest Lodge (BRL) and Danum Valley Field Center (DVFC) at the Danum Valley Conservation Area (DVCA), we observed seven episodes of alternating songs between males. Here, we describe the process of song exchange between males. During male interactions, song bouts rarely overlapped and were alternately emitted. Several studies have reported antiphonal vocalizations in New World and Old World primate species, but rarely in apes. Our observations of antiphonal songs in gibbons indicate that gibbons not only unilaterally advertise information, but also interactively communicate with neighbors and family members through songs. Since gibbons are phylogenetically similar to humans, and turn-taking has an important role in human conversation, our research on gibbon communication may provide insight into the evolution of human language.