[Show abstract][Hide abstract] ABSTRACT: The orangutan is the world's largest arboreal mammal, and images of the red ape moving through the tropical forest canopy symbolise its typical arboreal behaviour. Records of terrestrial behaviour are scarce and often associated with habitat disturbance. We conducted a large-scale species-level analysis of ground-based camera-trapping data to evaluate the extent to which Bornean orangutans Pongo pygmaeus come down from the trees to travel terrestrially, and whether they are indeed forced to the ground primarily by anthropogenic forest disturbances. Although the degree of forest disturbance and canopy gap size influenced terrestriality, orangutans were recorded on the ground as frequently in heavily degraded habitats as in primary forests. Furthermore, all age-sex classes were recorded on the ground (flanged males more often). This suggests that terrestrial locomotion is part of the Bornean orangutan's natural behavioural repertoire to a much greater extent than previously thought, and is only modified by habitat disturbance. The capacity of orangutans to come down from the trees may increase their ability to cope with at least smaller-scale forest fragmentation, and to cross moderately open spaces in mosaic landscapes, although the extent of this versatility remains to be investigated. T he Bornean orangutan Pongo pygmaeus is the largest arboreal species in the world and its survival is linked to forest habitat 1,2 . Despite the orangutan's iconic value and millions of dollars spent annually on its conser-vation 3 , the species is declining throughout its range. In Borneo, more than 70% of orangutans occur in OPEN SUBJECT AREAS: izw-berlin.de) or A.W. (firstname.lastname@example.org) * These authors contributed equally to this work. SCIENTIFIC REPORTS | 4 : 4024 | DOI: 10.1038/srep04024 1 fragmented multiple-use and human-modified forests that have lost many of their original ecological characteristics 4,5 . The consequences of these drastic habitat changes on orangutan survival, behaviour and ecology are only just starting to be documented 3,4,6,7 . Some authors have proposed that forest degradation may force the species to the ground more frequently 8,9 . We can suppose that increased terrestri-ality would increase predation risk, interactions with and persecution by humans, and exposure to novel pathogens. On the other hand, terrestrial behaviour could also facilitate movement and, therefore, dispersal, especially in degraded or fragmented landscapes as a result of natural or man-made processes. It could also create new oppor-tunities to access different food sources 10
[Show abstract][Hide abstract] ABSTRACT: The orangutan is the world's largest arboreal mammal, and images of the red ape moving through the tropical forest canopy symbolise its typical arboreal behaviour. Records of terrestrial behaviour are scarce and often associated with habitat disturbance. We conducted a large-scale species-level analysis of ground-based camera-trapping data to evaluate the extent to which Bornean orangutans Pongo pygmaeus come down from the trees to travel terrestrially, and whether they are indeed forced to the ground primarily by anthropogenic forest disturbances. Although the degree of forest disturbance and canopy gap size influenced terrestriality, orangutans were recorded on the ground as frequently in heavily degraded habitats as in primary forests. Furthermore, all age-sex classes were recorded on the ground (flanged males more often). This suggests that terrestrial locomotion is part of the Bornean orangutan's natural behavioural repertoire to a much greater extent than previously thought, and is only modified by habitat disturbance. The capacity of orangutans to come down from the trees may increase their ability to cope with at least smaller-scale forest fragmentation, and to cross moderately open spaces in mosaic landscapes, although the extent of this versatility remains to be investigated.
[Show abstract][Hide abstract] ABSTRACT: Keywords:
Climate;ectomycorrhizal associations;large tree density;pan-tropical analysis;soils;species traits;tree size;tropical forest biomass;wood density;wind dispersal
Large trees (d.b.h. ≥ 70 cm) store large amounts of biomass. Several studies suggest that large trees may be vulnerable to changing climate, potentially leading to declining forest biomass storage. Here we determine the importance of large trees for tropical forest biomass storage and explore which intrinsic (species trait) and extrinsic (environment) variables are associated with the density of large trees and forest biomass at continental and pan-tropical scales.
Aboveground biomass (AGB) was calculated for 120 intact lowland moist forest locations. Linear regression was used to calculate variation in AGB explained by the density of large trees. Akaike information criterion weights (AICc-wi) were used to calculate averaged correlation coefficients for all possible multiple regression models between AGB/density of large trees and environmental and species trait variables correcting for spatial autocorrelation.
Density of large trees explained c. 70% of the variation in pan-tropical AGB and was also responsible for significantly lower AGB in Neotropical [287.8 (mean) ± 105.0 (SD) Mg ha−1] versus Palaeotropical forests (Africa 418.3 ± 91.8 Mg ha−1; Asia 393.3 ± 109.3 Mg ha−1). Pan-tropical variation in density of large trees and AGB was associated with soil coarseness (negative), soil fertility (positive), community wood density (positive) and dominance of wind dispersed species (positive), temperature in the coldest month (negative), temperature in the warmest month (negative) and rainfall in the wettest month (positive), but results were not always consistent among continents.
Density of large trees and AGB were significantly associated with climatic variables, indicating that climate change will affect tropical forest biomass storage. Species trait composition will interact with these future biomass changes as they are also affected by a warmer climate. Given the importance of large trees for variation in AGB across the tropics, and their sensitivity to climate change, we emphasize the need for in-depth analyses of the community dynamics of large trees. http://onlinelibrary.wiley.com/doi/10.1111/geb.12092/abstract
Global Ecology and Biogeography 11/2013; 22:1261-1271. · 7.22 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: A multitude of factors influence how natural populations are genetically structured, including dispersal barriers, inhomogeneous habitats, and social organization. Such population subdivision is of special concern in endangered species, as it may lead to reduced adaptive potential and inbreeding in local subpopulations, thus increasing the risk of future extinctions. With only 6600 animals left in the wild, Sumatran orangutans (Pongo abelii) are among the most endangered, but also most enigmatic, great ape species. In order to infer the fine-scale population structure and connectivity of Sumatran orangutans, we analyzed the most comprehensive set of samples to date, including mitochondrial hyper-variable region I haplotypes for 123 individuals and genotypes of 27 autosomal microsatellite markers for 109 individuals. For both mitochondrial and autosomal markers, we found a pronounced population structure, caused by major rivers, mountain ridges, and the Toba caldera. We found that genetic diversity and corresponding long-term effective population size estimates vary strongly among sampling regions for mitochondrial DNA, but show remarkable similarity for autosomal markers, hinting at male-driven long-distance gene flow. In support of this, we identified several individuals that were most likely sired by males originating from other genetic clusters. Our results highlight the effect of natural barriers in shaping the genetic structure of great ape populations, but also point toward important dispersal corridors on northern Sumatra that allow for genetic exchange.
The Journal of heredity 10/2012; · 2.05 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: To conserve species it is essential to understand which factors determine their distribution and density. Here we focus on the critically endangered Sumatran orang-utan and examine factors that influence the distribution and density in the Batang Toru area, the southernmost area where wild orang-utans occur on Sumatra. We contrast a scenario in which orang-utan distribution is mainly determined by ecological, and topographic variables with a model that includes hunting and human impact. We show that orang-utan distribution and density are best explained by hunting pressure and elevation. These results indicate that an assessment of anthropogenic factors that might influence density such as hunting needs to be included in surveys that aim to predict orang-utan distribution and density. As anthropogenic impact becomes higher with increasing human population density and increased forest access in most areas where orang-utans occur the consequence is that orang-utan conservation will have to be achieved in an environment modified by humans. In such areas the potential for a range of conflicts such as hunting that lead to human-caused mortality for orang-utans will remain a constant threat and need to be mitigated.
[Show abstract][Hide abstract] ABSTRACT: The geographic distribution of Bornean orang-utans and its overlap with existing land-use categories (protected areas, logging and plantation concessions) is a necessary foundation to prioritize conservation planning. Based on an extensive orang-utan survey dataset and a number of environmental variables, we modelled an orang-utan distribution map. The modelled orang-utan distribution map covers 155,106 km(2) (21% of Borneo's landmass) and reveals four distinct distribution areas. The most important environmental predictors are annual rainfall and land cover. The overlap of the orang-utan distribution with land-use categories reveals that only 22% of the distribution lies in protected areas, but that 29% lies in natural forest concessions. A further 19% and 6% occurs in largely undeveloped oil palm and tree plantation concessions, respectively. The remaining 24% of the orang-utan distribution range occurs outside of protected areas and outside of concessions. An estimated 49% of the orang-utan distribution will be lost if all forest outside of protected areas and logging concessions is lost. To avoid this potential decline plantation development in orang-utan habitats must be halted because it infringes on national laws of species protection. Further growth of the plantation sector should be achieved through increasing yields in existing plantations and expansion of new plantations into areas that have already been deforested. To reach this goal a large scale island-wide land-use masterplan is needed that clarifies which possible land uses and managements are allowed in the landscape and provides new standardized strategic conservation policies. Such a process should make much better use of non-market values of ecosystem services of forests such as water provision, flood control, carbon sequestration, and sources of livelihood for rural communities. Presently land use planning is more driven by vested interests and direct and immediate economic gains, rather than by approaches that take into consideration social equity and environmental sustainability.
PLoS ONE 01/2012; 7(11):e49142. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The marked biogeographic difference between western (Malay Peninsula and Sumatra) and eastern (Borneo) Sundaland is surprising given the long time that these areas have formed a single landmass. A dispersal barrier in the form of a dry savanna corridor during glacial maxima has been proposed to explain this disparity. However, the short duration of these dry savanna conditions make it an unlikely sole cause for the biogeographic pattern. An additional explanation might be related to the coarse sandy soils of central Sundaland. To test these two nonexclusive hypotheses, we performed a floristic cluster analysis based on 111 tree inventories from Peninsular Malaysia, Sumatra, and Borneo. We then identified the indicator genera for clusters that crossed the central Sundaland biogeographic boundary and those that did not cross and tested whether drought and coarse-soil tolerance of the indicator genera differed between them. We found 11 terminal floristic clusters, 10 occurring in Borneo, 5 in Sumatra, and 3 in Peninsular Malaysia. Indicator taxa of clusters that occurred across Sundaland had significantly higher coarse-soil tolerance than did those from clusters that occurred east or west of central Sundaland. For drought tolerance, no such pattern was detected. These results strongly suggest that exposed sandy sea-bed soils acted as a dispersal barrier in central Sundaland. However, we could not confirm the presence of a savanna corridor. This finding makes it clear that proposed biogeographic explanations for plant and animal distributions within Sundaland, including possible migration routes for early humans, need to be reevaluated.
Proceedings of the National Academy of Sciences 07/2011; 108(30):12343-7. · 9.81 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Various studies have shown that the population densities of a number of forest vertebrates, such as orangutans, are higher on Sumatra than Borneo, and that several species exhibit smaller body sizes on Borneo than Sumatra and mainland Southeast Asia. It has been suggested that differences in forest fruit productivity between the islands can explain these patterns. Here we present a large-scale comparison of forest fruit production between the islands to test this hypothesis.
Data on fruit production were collated from Sumatran and Bornean sites. At six sites we assessed fruit production in three forest types: riverine, peat swamp and dryland forests. We compared fruit production using time-series models during different periods of overall fruit production and in different tree size classes. We examined overall island differences and differences specifically for fruiting period and tree size class. The results of these analyses indicate that overall the Sumatran forests are more productive than those on Borneo. This difference remains when each of the three forest types (dryland, riverine, and peat) are examined separately. The difference also holds over most tree sizes and fruiting periods.
Our results provide strong support for the hypothesis that forest fruit productivity is higher on Sumatra than Borneo. This difference is most likely the result of the overall younger and more volcanic soils on Sumatra than Borneo. These results contribute to our understanding of the determinants of faunal density and the evolution of body size on both islands.
PLoS ONE 01/2011; 6(6):e21278. · 3.53 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Interviews with farmers (1998–2000) in 5 communities along the edge of the Sungai Wain Protection Forest, East Kalimantan, Indonesian Borneo, indicated that crop damage caused by sun bears (Helarctos malayanus) was higher than normal following the 1997–98 El Niño Southern Oscillation Event. Widespread drought and forest fires reduced habitat and fruit availability for sun bears on the islands of Borneo and Sumatra. The main source of antagonism toward bears resulted from the damage they caused to stands of old coconut trees, which frequently killed the trees. This prompted farmers to seek removal of the bears. Bear damage to annual crops generally spurred a less hostile reaction. Experiments with metal sheeting affixed to the trunks of coconut trees to deter climbing by bears were successful, at least in the short term (<3 years). Inexpensive and easily applicable crop-protection devices such as this could help protect sun bears in the future, as increased human–bear conflicts are anticipated due to rapid human population growth, unabated forest destruction and fragmentation, and increased susceptibility of remaining forests to fires.
[Show abstract][Hide abstract] ABSTRACT: Droughts and forest fires, induced by the El Niño/Southern Oscillation (ENSO) event, have increased considerably over the
last decades affecting millions of hectares of rainforest. We investigated the effects of the 1997–1998 forest fires and drought,
associated with an exceptionally severe ENSO event, on fruit species important in the diet of Malayan sun bears (Helarctos malayanus) in lowland dipterocarp forest, East Kalimantan, Indonesian Borneo. Densities of sun bear fruit trees (≥10cm DBH) were reduced
by ~80%, from 167±41 (SD) fruit treesha−1 in unburned forest to 37±18 fruit treesha−1 in burned forest. Densities of hemi-epiphytic figs, one of the main fallback resources for sun bears during periods of food
scarcity, declined by 95% in burned forest. Species diversity of sun bear food trees decreased by 44% in burned forest. Drought
also affected sun bear fruit trees in unburned primary forest, with elevated mortality rates for the duration of 2years,
returning to levels reported as normal in region in the third year after the ENSO event. Mortality in unburned forest near
the burn-edge was higher (25±5% of trees ≥10cm DBH dead) than in the forest interior (14±5% of trees), indicating possible
edge effects. Combined effects of fire and drought in burned primary forest resulted in an overall tree mortality of 78±11%
(≥10cm DBH) 33months after the fire event. Disturbance due to fires has resulted in a serious decline of fruit resources
for sun bears and, due to the scale of fire damage, in a serious decline of prime sun bear habitat. Recovery of sun bear populations
in these burned-over forests will depend on regeneration of the forest, its future species composition, and efforts to prevent
subsequent fire events.
[Show abstract][Hide abstract] ABSTRACT: The distributions, basic ecology and conservation status of bats in Indonesian Borneo is not well documented. Few surveys have been conducted and most are limited to using mist nets. We report the presence of 12 bat species recorded during a harp-trap training workshop in Sungai Wain Protection Forest near Balikpapan, East Kalimantan. Most of these species are considered forest specialists. Our record of Hipposideros ridleyi, is the second for Indonesia. Sungai Wain is an important refuge for this rare and threatened species amongst the highly disturbed forests between Balikpapan and Samarinda. Despite the lack of caves in the vicinity of Sungai Wain it is likely that further survey work will uncover more bat species.