Bornean Populations Research Articles

Capacity for recovery in Bornean orangutan populations when limiting offtake and retaining forest

AbstractAimWe assess the potential long‐term viability of orangutan populations across Borneo, considering the effects of habitat loss, and various forms of population reduction, including hunting, retaliatory killings and capture and translocation.LocationThe study focused on the island of Borneo, a region that has experienced substantial deforestation over the past four decades, resulting in the degradation and fragmentation of its lowland forests, thereby threatening the island's unique biodiversity, including orangutan populations.MethodsTo evaluate the long‐term viability of orangutan populations, we employed a spatially explicit individual‐based model. This model allowed us to simulate various scenarios, including the impact of removing habitat fragments or individuals from the population.ResultsOur findings revealed that small forest fragments facilitate orangutan movement, thereby increasing the number of individuals settling in non‐natal patches. Crucially, orangutan populations proved highly vulnerable to even small levels of offtake. Annual removal rates exceeding 2% diminished the positive role of small forest patches in sustaining population connectivity, the long‐term viability of populations and prospects for recovery.Main ConclusionsOur results suggest that orangutan populations in Borneo could potentially recover from recent declines if removal of orangutans by hunting, retaliatory killings, capture and translocation is reduced, and habitat connectivity is maintained within human‐modified landscapes. These findings emphasize the urgent need for conservation strategies that mitigate negative human–wildlife interactions, and/or help preserve habitat and fragments as stepping stones. Measures could include promoting coexistence with local communities and translocating orangutans only in rare cases where no suitable alternative exists, to ensure the long‐term survival of orangutan populations in Borneo.

Killing of orangutans in Kalimantan ‐ Community perspectives on incidence and drivers

AbstractDespite decades of conservation management, many orangutan populations are on the brink of extinction. This is primarily due to habitat loss and direct killings. A study from 2008/2009 suggested that killing was impacting orangutan populations at a rate sufficient to cause local extinctions. As an illegal and taboo behavior that is difficult to measure, killing has been severely understudied since. We conducted 431 interviews in 79 villages across Kalimantan in 2020/2021. Ours is the first quantitative field study in more than 10 years to assess the state of killing of orangutans. We aimed to: (1) assess the current state of killing of orangutans in Kalimantan and compare this to the previous study; (2) determine whether conservation projects are affecting killing; and (3) explore drivers of killing. We examined killing of orangutans across villages with forest conservation projects, orangutan conservation projects, and no conservation projects. We assessed the existence of killing and used scenarios to examine perceived norms about illegal behavior relating to orangutans. We then used matching techniques to assess whether projects have any impact on these indicators. Overall, our findings suggest that killing has occurred in recent times, and our data does not indicate a clear attenuation of the behavior. As such, we argue that killing may still present a substantial threat to Bornean orangutan populations. We also found no statistically significant evidence that conservation projects are reducing killing. Conservation project managers could seek to understand the drivers of killing, and to invest in interventions that address these drivers. Research suggests that current allocation of conservation funding has been ineffective at abating orangutan population decline. We argue that a key part of improving Bornean orangutan conservation practice involves directly addressing killing of orangutans and the underlying drivers of killing.

Phylogenetic and multivariate analyses of Gekko smithii Gray, 1842 recover a new species from Peninsular Malaysia and support the resurrection of G. albomaculatus (Giebel, 1861) from Sumatra

AbstractAn integrative taxonomic analysis of Sundaic populations ofGekko smithiifrom the Thai-Malaya Peninsula, Sumatra, and Borneo recovered four deeply divergent mitochondrial lineages that are separated by major geographic barriers (mountains and seaways). Furthermore, they bear a number of concordant statistically significant differences in meristic and morphometric features, morphospatial separation in multivariate space, and discrete differences in color pattern.Gekko smithiisensu strictois restricted to southern Thailand south of the Isthmus of Kra and Peninsular Malaysia west of the Banjaran (mountain range) Titiwangsa, being that the type locality is on Penang Island, Penang.Gekko hulksp. nov.is a new species from extreme southern Thailand and Peninsular Malaysia east of the Banjaran Titiwangsa and five east coast islands—the type locality being Pulau (island) Tioman, Pahang. Gekko cf. albofasciolatus is tentatively used to include Bornean populations west of the Iran Mountains in Sabah and Sarawak which, in the absence of molecular data, cannot unequivocally be separated morphologically fromG. albofasciolatusfrom the type locality at Banjarmasin, Kalimantan, Indonesia east of the Iran Mountains. In the absence of molecular data,G. albomaculatusis resurrected to include mainland Sumatran, Nias Island, and Banyak Islands populations which, based on their morphology, cannot be separated from descriptions ofG. albomaculatusfrom the type locality of Bangka Island, 15 km off the southeast coast of mainland Sumatra. Further integrative analyses of all Sumatran and Bornean populations are currently underway as well as the enigmatic Wallacean populations from Sulawesi. Data are presented that strongly suggest all references toG. smithiifrom Java stem from a 151 year-old misidentification of a specimen ofG. geckoof unknown provenance. Additionally, there are no vouchered records ofG. smithiifrom Myanmar. The phylogeographic patterns of Sundaic populations of theG. smithiicomplex are concordant with those of a plethora of other Sundaic lineages.

Fear of COVID-19 and COVID-19 Stress and Association with Sociodemographic and Psychological Process Factors in Cases under Surveillance in a Frontline Worker Population in Borneo.

COVID-19 stress and fear of COVID-19 is an increasingly researched construct in the general population. However, its prevalence and association with sociodemographic factors and psychological process variables has not been explored in frontline workers under surveillance in a Bornean population. This study was a cross-sectional study using a sociodemographic questionnaire incorporating two specific epidemiological risk variables, namely specific questions about COVID-19 surveillance status (persons under investigation (PUI), persons under surveillance (PUS), and positive cases) and the nature of frontline worker status. Furthermore, five other instruments were used, with three measuring psychopathology (namely depression, anxiety and stress, fear of COVID-19, and stress due to COVID-19) and two psychological process variables (namely psychological flexibility and mindfulness). Kruskal–Wallis and Mann–Whitney tests were performed to assess if there were significant differences in psychopathology and psychological process variables between sociodemographic and epidemiological risk variables. Hierarchical multiple regression was further performed, with depression, anxiety, and stress as dependent variables. There were significant differences in the fear of COVID-19 between positive cases, PUI, and PUS. The fear of COVID-19 scores were higher in positive cases compared to in PUS and PUI groups. Upon hierarchical multiple regression, mindfulness and psychological flexibility were significant predictors of depression, anxiety, and stress after controlling for sociodemographic and epidemiological risk factors. This study demonstrates that exposure to COVID-19 as persons under investigation or surveillance significantly increases the fear of COVID-19, and brief psychological interventions that can positively influence mindfulness and psychological flexibility should be prioritized for these at-risk groups to prevent undue psychological morbidity in the long run.

Ecogeographic variation and taxonomic boundaries in Large Treeshrews (Scandentia, Tupaiidae:Tupaia tanaRaffles, 1821) from Southeast Asia

AbstractThe Large Treeshrew, Tupaia tana Raffles, 1821, is a small mammal (~205 g) from Southeast Asia with a complicated taxonomic history. Currently, 15 subspecies are recognized from Borneo, Sumatra, and smaller islands, and many were originally differentiated based on minor pelage differences and small sample sizes. We explored intraspecific variation in T. tana using quantitative osteological data obtained from the hands and skulls of museum specimens. Multivariate analyses reveal extensive overlap among T. tana populations in morphospace, indicating that the majority of currently recognized subspecies are not morphometrically distinct. In contrast, the separation between Bornean and Sumatran populations of T. tana is sufficient to recognize them as different subspecies. Comparisons of Bornean specimens to those on small, offshore islands reveal that the latter average smaller body size. This pattern is inconsistent with Foster’s island rule, which predicts that island populations of small mammals (< 5 kg) will average larger body size relative to mainland forms. A similar lack of support for ecogeographic rules has been noted in T. glis (Diard, 1820), suggesting that these “rules” are poor predictors of geographic variation in treeshrews.

Killer cell immunoglobulin-like receptors (KIR) genes can be an adequate tool in forensic anthropological studies: evaluation in a wide Caucasian Spanish population

ABSTRACT Most immune system polymorphisms have undergone molecular evolution largely due to natural selection driven primarily by host-pathogen interactions, showing significant human geographic expansion signs. Killer cell immunoglobulin-like receptors (KIRs) show great genetic and allelic variation among different populations. The aim of this study was to analyse the frequency of KIR genes in a large cohort of healthy Spanish Caucasians (SC) to be able to compare them with other world populations. A total of 609 healthy SC unrelated individuals were analysed and compared with 16 worldwide populations. KIR genotyping was analysed by PCR-SSO technique. Our results showed that all KIR genes were present in the Spanish population. iKIR2D genes of the Spanish population were similar in different European populations like Danish, Finland, Irish and Italian populations, Czech and Turkish populations but very different to Australian, Bornean, Chinese, Indian, Venezuelan, and Russian populations. KIR3DL1 gene frequency in the Australian population was significantly lower than the Spanish population. aKIR genes frequencies of the Spanish population were similar to European populations, but slight differences were found in English, Finnish, Irish and Macedonian populations. In conclusion, our results enrich the Caucasian genetic information resources of the KIR gene pool for genetic susceptibility diseases and forensic anthropological studies.

Taxonomy, Evolutionary and Dispersal Events of Pig-Tailed Macaque, Macaca nemestrina (Linnaeus, 1766) in Southeast Asia with Description of a New Subspecies, Macaca nemestrina perakensis in Malaysia.

The pig-tailed macaque, Macaca nemestrina, which is distributed in Peninsular Malaysia, Thailand, Borneo, and Sumatra, has been the subject of unstable and changing taxonomic entity in the M. nemestrina group. This species is involved with a human-macaque conflict in Malaysia and at the same time played an important role in the ethnozoological culture of Malaysian. Even so, comprehensive phylogenetic, population genetics and biogeographical analysis of M. nemestrina in Malaysia are non-existent after decades of intensive research on the genus itself. Thus, we conducted the first comprehensive genetic study of M. nemestrina in Malaysia, based on three mitochondrial loci-Cytochrome b (567 bp), D-loop (398 bp), and COI (577 bp)-from 27 individuals representing Malaysia, plus an additional 26 sequences of Southeast Asian macaques from Genbank. Comparative biogeographical analysis in this study supports the positions of M. nemestrina in M. nemestrina groups as opposed to the silenus or Sulawesi groups. Results from this study also indicate that Bornean populations are the first extant lineages to separate from the other examined lineages of M. nemestrina, M. leonina, M. pagensis, and M. siberu in Southeast Asia. Molecular clock analysis suggested that M. nemestrina arrived in the Malay Peninsula about 0.32 million years ago (MYA). Our results indicate that the population of pig-tailed macaque from Perak (west Peninsular Malaysia) differs genetically based on all phylogenetic and population genetic analyses. Morphologically, Perak's pig-tailed macaque shows brighter coloration than M. n. nemestrina. Thus, we proposed a new subspecies for Perak's pig-tailed macaque as Macaca nemestrina perakensis distributed in the state of Perak, Peninsular Malaysia. This research helps resolve the taxonomic position and population genetics of pig-tailed macaque in Malaysia, which contribute directly to conservation and management of the species in Malaysia.

The cost of associating with males for Bornean and Sumatran female orangutans: a hidden form of sexual conflict?

Sexual coercion, in the form of forced copulations, is relatively frequently observed in orangutans and generally attributed to their semi-solitary lifestyle. High ecological costs of association for females may be responsible for this lifestyle and may have prevented the evolution of morphological fertility indicators (e.g., sexual swellings), which would attract (male) associates. Therefore, sexual conflict may arise not only about mating per se but also about associations, because males may benefit from associations with females to monitor their reproductive state and attempt to monopolize their sexual activities. Here, we evaluate association patterns and costs for females when associating with both males and females of two different orangutan species at two study sites: Suaq, Sumatra (Pongo abelii), and Tuanan, Borneo (Pongo pygmaeus wurmbii). Female association frequency with both males and females was higher in the Sumatran population, living in more productive habitat. Accordingly, we found that the cost of association, in terms of reduced feeding to moving ratio and increased time being active, is higher in the less sociable Bornean population. Males generally initiated and maintained such costly associations with females, and prolonged associations with males led to increased female fecal cortisol metabolite (FCM) levels at Tuanan, the Bornean population. We conclude that male-maintained associations are an expression of sexual conflict in orangutans, at least at Tuanan. For females, this cost of association may be responsible for the lack of sexual signaling, while needing to confuse paternity.Significance statementSocioecological theory predicts a trade-off between the benefits of sociality and the ecological costs of increased feeding competition. Orangutans’ semi-solitary lifestyle has been attributed to the combination of high association costs and low predation risk. Previous work revealed a positive correlation between association frequencies and habitat productivity, but did not measure the costs of association. In this comparative study, we show that females likely incur costs from involuntary, male-maintained associations, especially when they last for several days and particularly in the population characterized by lower association frequencies. Association maintenance therefore qualifies as another expression of sexual conflict in orangutans, and especially prolonged, male-maintained associations may qualify as an indirect form of sexual coercion.

Social interactions and interaction partners in infant orang-utans of two wild populations

Temporary associations with conspecifics provide critical opportunities for the acquisition and development of socioecological skills, especially in species where these interaction opportunities are not readily available. In fact, social interactions can have far-reaching consequences for the cultural and communicative repertoire on both the species and population level. However, to what extent interaction rates are linked to association patterns, which depend on individual and ecological factors, is often overlooked. Here, we examined the sources of variation in immatures’ social behaviour, in relation to both activity and partner type, in one Sumatran (Suaq) and one Bornean population (Tuanan) of wild orang-utans ( Pongo spp.) that are known to differ in sociability. Specifically, we examined to what extent the time spent in social interactions and with specific social partners was related to study population, but also individual (e.g. age), ecological (food availability) and social variables (e.g. presence of specific associates). Overall, we found that study population and the presence of specific associates (siblings, peers, adult males) had a profound effect on the occurrence of different social activities, while local variation in food availability did not appear to play a major role. Although proportions of time spent in interactions was overall higher at Suaq, we found no difference between the two sites regarding the use of interaction opportunities when partners were available. Begging was mainly directed at mothers, whereas peers and older siblings served primarily as play partners, and unflanged males were frequent targets of social gazing. Our study suggests that orang-utan infants use interaction opportunities differently depending on social partners and interaction type. • We examined social interactions in infant orang-utans of two wild populations. • Analyses focused on three specific social activities with different partners. • Study site and presence of specific associates affected interaction rates. • Population differences in interaction time mirror differences in sociability.

Species delimitation within the Glaucidium brodiei owlet complex using bioacoustic tools

BackgroundThe taxonomy of the Collared Owlet (Glaucidium brodiei) species complex is confused owing to great individual variation in plumage colouration seemingly unrelated to their distribution. Although generally recognised as a single species, vocal differences among the subspecies have been noted by field recordists. However, there is no study assessing the vocal differences among these four subspecies.MethodsWe obtained 76 sound recordings of the G. brodiei species complex comprising all four subspecies. We conducted bioacoustic examinations using principal component analysis and the Isler criterion to quantitatively test species boundaries within the G. brodiei complex. In addition, we compared plumage colouration among 13 specimens of the G. brodiei complex deposited at the Natural History Museum at Tring, UK and the Lee Kong Chian Natural History Museum, Singapore to ascertain the presence of plumage differences across taxa.ResultsWe found the Bornean and Sumatran populations vocally similar to each other, but distinctly different from the mainland and Taiwan populations. The vocal pattern seems to corroborate plumage distinctions in the colouration of neck collars: the Bornean and Sumatran taxa share a white neck collar, whereas the continental and Taiwan taxa share a rufous neck collar.ConclusionsWe propose the taxonomic elevation of the Sumatran and Bornean populations to species level as Sunda Owlet G. sylvaticum, with one subspecies on Sumatra (G. s. sylvaticum) and Borneo (G. s. borneense) each. Our study corroborates the importance of bioacoustics in ascertaining species boundaries in non-passerines, and emphasises the significance of incorporating multiple species delimitation approaches when making taxonomic decisions.

A cryptic new species of bulbul from Borneo

Cream-vented Bulbul Pycnonotus simplex of Borneo was previously considered to be polymorphic in iris colour, having either red or white (creamy-yellow) irides. Mitochondrial DNA sequence comparisons, however, indicate that white- and red-eyed Bornean individuals are not closely related to one another. Instead, white-eyed birds are sister to Ashy-fronted Bulbul P. cinereifrons of Palawan Island, in the south-west Philippines, and red-eyed birds are sister to white-eyed P. simplex of the Thai-Malay Peninsula. Consequently, we elect to treat the white-eyed Bornean population as a distinct, previously overlooked species. In respect to plumage, white- and red-eyed individuals are almost identical, varying only slightly in the amount of yellow coloration in their feathers. The two taxa are sympatric at some localities, but white-eyed individuals are rarer and more consistently associated with mature forest than red-eyed birds.

Substrate moisture, particle size and temperature preferences of trap‐building larvae of sympatric antlions and wormlions from the rainforest of Borneo

1. Larvae of antlions (Neuroptera: Myrmeleontidae) and wormlions (Diptera: Vermileonidae) display a convergently evolved sit‐and‐wait hunting strategy of building pitfall traps in sandy areas. This study investigated a sympatric population of antlions and wormlions in the lowland rainforest of Borneo for substrate moisture, particle size and temperature preferences. It was hypothesised that these animals would show different preferences regarding these microhabitat traits.2. The results showed that antlions had a higher aversion to moisture compared with wormlions, but that wormlions had a higher preference for small‐particle sand. Furthermore, thermal preferences in antlions and wormlions were significantly different, with antlions choosing higher temperatures.3. The detected differences between antlions and wormlions might contribute to their niche partitioning in the mixed Bornean population and thus facilitate coexistence of these animals. It is possible that the hotter and dryer microhabitat edges are preferred by antlions.

Genetic Diversity of Five Native Populations (Dusun, Rungus, Sonsogon, Murut and Sungai-Lingkabau Paitan) of North Borneo, East Malaysia based on 17 Y-chromosomal Short-Tandem Repeats Polymorphism

In this study, we typed 51 male individuals from North Borneo using 17 Y-chromosome STRs contained in the AmpFLSTR® Yfiler® kit (Applied Biosystems). These individuals constitute five indigenous ethnic populations representing the three major linguistic groups (Dusunic, Murutic and Paitanic): the Dusun ( n =7), Rungus ( n =12), Sonsogon ( n =12), Murut Paluan ( n =12), and Sungai Lingkabau Paitan ( n =8). A total of 37 haplotypes were identified, of which 30 individuals were represented by a single haplotype. The mean ± S.D. haplotype diversity was 0.600±0.181 and the discrimination capacity was 0.725. The results also showed that the haplotype H33 was the most frequent haplotype observed in the sampled male populations occurring exclusively in the Murut population. Comparative analysis between Y-haplotype populations of North Borneo and the ethnic populations (Bidayuh, Iban, and Melanau) of neighbouring Sarawak (East Malaysia) i.e. indicated that the Sungai Lingkabau Paitan was more closely associated with the Melanau with respect to Y-haplotype descent (RST=- 0.0023). In addition, the Multidimensional Scaling (MSD) analysis managed to clearly differentiate the eight groups from Borneo. We concluded that the 17 Y-chromosome STRs data of North Bornean populations are valuable resources in the applications of forensic and population genetics of the ethnic groups.

Morphometric, Behavioral, and Genomic Evidence for a New Orangutan Species

Six extant species of non-human great apes are currently recognized: Sumatran and Bornean orangutans, eastern and western gorillas, and chimpanzees and bonobos [1]. However, large gaps remain in our knowledge of fine-scale variation in hominoid morphology, behavior, and genetics, and aspects of great ape taxonomy remain in flux. This is particularly true for orangutans (genus: Pongo), the only Asian great apes and phylogenetically our most distant relatives among extant hominids [1]. Designation of Bornean and Sumatran orangutans, P.pygmaeus (Linnaeus 1760) and P.abelii (Lesson 1827), as distinct species occurred in 2001 [1, 2]. Here, we show that an isolated population from Batang Toru, at the southernmost range limit of extant Sumatran orangutans south of Lake Toba, is distinct from other northern Sumatran and Bornean populations. By comparing cranio-mandibular and dental characters of an orangutan killed in a human-animal conflict to those of 33 adult male orangutans of a similar developmental stage, we found consistent differences between the Batang Toru individual andother extant Ponginae. Our analyses of 37 orangutan genomes provided a second line of evidence. Model-based approaches revealed that the deepestsplit in the evolutionary history of extant orangutans occurred ∼3.38 mya between the Batang Toru population and those to the north of Lake Toba,whereas both currently recognized species separated much later, about 674 kya. Our combinedanalyses support a new classification of orangutans into three extant species. The new species, Pongo tapanuliensis, encompasses the Batang Toru population, of which fewer than 800 individuals survive. VIDEO ABSTRACT.

Phylogeography of the reticulated python (Malayopython reticulatus ssp.): Conservation implications for the worlds' most traded snake species.

As an important economic natural resource in Southeast Asia, reticulated pythons (Malayopython reticulatus ssp.) are primarily harvested from the wild for their skins—which are prized in the luxury leather goods industry. Trade dynamics of this CITES Appendix II listed species are complex and management approaches on the country or regional level appear obscure. Little is known about the actual geographic point-of-harvest of snakes, how genetic diversity is partitioned across the species range, how current harvest levels may affect the genetic viability of populations, and whether genetic structure could (or should) be accounted for when managing harvest quotas. As an initial survey, we use mitochondrial sequence data to define the broad-scale geographic structure of genetic diversity across a significant portion of the reticulated python’s native range. Preliminary results reveal: (1) prominent phylogenetic structure across populations east and west of Huxley’s modification of Wallace’s line. Thirty-four haplotypes were apportioned across two geographically distinct groups, estimated to be moderately (5.2%); (2) Philippine, Bornean and Sulawesian populations appear to cluster distinctly; (3) individuals from Ambon Island suggest recent human introduction. Malayopython reticulatus is currently managed as a single taxonomic unit across Southeast Asia yet these initial results may justify special management considerations of the Philippine populations as a phylogenetically distinct unit, that warrants further examination. In Indonesia, genetic structure does not conform tightly to political boundaries and therefore we advocate the precautionary designation and use of Evolutionary Significant Units within Malayopython reticulatus, to inform and guide regional adaptive management plans.

First integrative trend analysis for a great ape species in Borneo

For many threatened species the rate and drivers of population decline are difficult to assess accurately: species’ surveys are typically restricted to small geographic areas, are conducted over short time periods, and employ a wide range of survey protocols. We addressed methodological challenges for assessing change in the abundance of an endangered species. We applied novel methods for integrating field and interview survey data for the critically endangered Bornean orangutan (Pongo pygmaeus), allowing a deeper understanding of the species’ persistence through time. Our analysis revealed that Bornean orangutan populations have declined at a rate of 25% over the last 10 years. Survival rates of the species are lowest in areas with intermediate rainfall, where complex interrelations between soil fertility, agricultural productivity, and human settlement patterns influence persistence. These areas also have highest threats from human-wildlife conflict. Survival rates are further positively associated with forest extent, but are lower in areas where surrounding forest has been recently converted to industrial agriculture. Our study highlights the urgency of determining specific management interventions needed in different locations to counter the trend of decline and its associated drivers.

Threatened but understudied: supporting conservation by understanding the genetic structure of the flat-headed cat

The flat-headed cat (Prionailurus planiceps) is a wetland specialist, currently facing habitat loss on a serious scale due to massive destruction of lowland forests and wetlands in Southeast Asia. Despite its ‘endangered’ status in the IUCN Red List, there has virtually been no investigation on the population structure nor on the evolutionary history of the flat-headed cat. To fill this gap, we used full mitochondrial genome sequences, obtained from archival samples, covering the historical distribution of the flat-headed cat. Our data revealed a high genetic differentiation (F st = 0.81, P < 0.001) between mitochondrial lineages from Borneo and those from Thai-Malay Peninsula/Sumatra, a split that was dated to ~575 Kya. Such a significant differentiation clearly distinguishes the Bornean flat-headed cat population from all other populations and suggests that there should be a reassessment of the flat-headed cat’s intraspecific taxonomy. However, morphological and nuclear data are required to corroborate our mtDNA results. Until such data become available, we recommend that for future conservation efforts and captive breeding programmes the two genetically distinct flat-headed cat populations are managed separately as two lineages to maintain the original genetic diversity of this endangered species.

Erratum to: Development and behavior of wild infant-juvenile East Bornean orangutans (Pongo pygmaeus morio) in Danum Valley.

Orangutans have a long period of immaturity and the longest inter-birth interval (IBI) of all mammals, which can be explained by their solitary life style, preventing the mother from rearing two offspring simultaneously (solitary life hypothesis) [corrected]. We collected data on mother-offspring dyads living in a primary lowland forest in Danum Valley, East Borneo in an effort to examine the developmental and behavioral patterns of the subspecies Pongo pygmaeus morio. We analyzed developmental changes in mother-offspring distance, contact, and activity budgets in orangutans ranging from 1 to 7 years of age. The results indicated decreased resting and playing with increasing age, whereas feeding, traveling and social play all increased significantly. Mothers' feeding and traveling time were good predictors of their offspring's feeding and traveling activities. Mother-offspring contact lasted longer in resting contexts; contact during traveling was almost non-existent after 4 years of age. Comparisons with previously published data on the Sumatran species Pongo abelli revealed no fundamental differences in these behavioral measures. However, a shorter association time with the mother after behavioral independence is documented for this East Bornean population in comparison to Sumatran populations. These results are best explained by the solitary life hypothesis, in agreement with previous studies. We suggest that environmental constraints in Bornean forests, as well as a lower population density, should be considered when interpreting the differences between Sumatran and Bornean orangutans in both the period of association with mother and the IBI.

Development and behavior of wild infant-juvenile East Bornean orangutans (Pongo pygmaeus morio) in Danum Valley.

Orangutans have a long period of immaturity and the longest inter-birth interval (IBI) of all mammals, which can be explained by their solitary life style, preventing the mother from rearing two offspring simultaneously (solitary life hypothesis) [corrected]. We collected data on mother-offspring dyads living in a primary lowland forest in Danum Valley, East Borneo in an effort to examine the developmental and behavioral patterns of the subspecies Pongo pygmaeus morio. We analyzed developmental changes in mother-offspring distance, contact, and activity budgets in orangutans ranging from 1 to 7years of age. The results indicated decreased resting and playing with increasing age, whereas feeding, traveling and social play all increased significantly. Mothers' feeding and traveling time were good predictors of their offspring's feeding and traveling activities. Mother-offspring contact lasted longer in resting contexts; contact during traveling was almost non-existent after 4years of age. Comparisons with previously published data on the Sumatran species Pongo abelli revealed no fundamental differences in these behavioral measures. However, a shorter association time with the mother after behavioral independence is documented for this East Bornean population in comparison to Sumatran populations. These results are best explained by the solitary life hypothesis, in agreement with previous studies. We suggest that environmental constraints in Bornean forests, as well as a lower population density, should be considered when interpreting the differences between Sumatran and Bornean orangutans in both the period of association with mother and the IBI.

Unusually high genetic diversity in the Bornean Limnonectes kuhlii-like fanged frogs (Anura: Dicroglossidae)

A fanged frog Limnonectes kuhlii was once thought to be wide-ranging in Southeast Asia, but is now confined to its type locality Java through recent phylogenetic studies, which clarified heterospecific status of non-Javanese populations, and monophyly of Bornean populations. However, large genetic differences among Bornean populations suggest occurrence of cryptic species, which we test using dense geographic sampling. We estimated the phylogenetic relationships among samples of Bornean populations together with their putative relatives from the continental Southeast Asia, using 2517bp sequences of the 12S rRNA, tRNAval, and 16S rRNA of mitochondrial DNA, and 2367bp sequences of the NCX1, POMC, and RAG1 of nuclear genes. In the mtDNA trees, Bornean L. kuhlii-like frogs formed a monophyletic group split into 18 species lineages including L. hikidai, with the deepest phylogenetic split separating L. cintalubang from the remaining species. Almost all of these lineages co-occur geographically, and two to three lineages were found syntopically in each locality. Co-occurrence of more than one lineage may be maintained by differential morphology and microhabitat selection. These syntopic lineages should be regarded as distinct species. Our results clearly indicate that taxonomic revision is urgent to clarify many evolutionary problems of Bornean L. kuhlii-like frogs.