Hylobates Agilis Research Articles

Stubby versus stabby: A preliminary analysis of canine microwear in primates: Implication for inferring ingestive behaviors.

Molar and incisor microwear reflect aspects of food choice and ingestive behaviors in living primates and have both been used to infer the same for fossil samples. Canine microwear, however, has received less attention, perhaps because of the prominent role canines play in social display and because they are used as weapons-while outside of a few specialized cases, their involvement in diet related behaviors has not been obvious. Here, we posit that microwear can also provide glimpses into canine tooth use in ingestion. Canines of Sumatran long-tailed macaques (Macaca fascicularis), agile gibbons (Hylobates agilis), lar gibbons (Hylobates lar), Thomas' leaf monkeys (Presbytis thomasi), and orangutans (Pongo abelii), and two African great apes, bonobos (Pan paniscus) and common chimpanzees (Pan troglodytes schweinfurthii), were considered. The labial tips of maxillary canine replicas were scanned using a white-light confocal profiler, and both feature and texture analyses were used to characterize microwear surface patterning. The taxa exhibited significant differences in canine microwear. In some cases, these were consistent with variation in reported anterior tooth use such that, for example, the orangutans, known to use their front teeth extensively in ingestion, had the highest median number of microwear features on their canines, whereas the gibbons, reported to use their front teeth infrequently in food acquisition, had the lowest.

PARASITIC WORM OF AGILE GIBBON (Hylobates agilis F. CUVIER 1821) AND SIAMANG (Symphalangus syndactylus RAFFLES 1821) AT SERULINGMAS ZOOLOGICAL GARDEN, BANJARNEGARA

Samples feces were collected from three heads of agile gibbon and three heads of siamang using direct smear, flotation, sedimentation, and McMaster methods. Identification is achieved by using faecal cultures to obtain larvae of parasitic worm. Identification result indicated that male agile gibbon (W/I) infected by two types of parasitic worms (Trichostrongylus and Strongyloides). In contrast, female agile gibbon (W/IIa and W/IIb), placed in the same cage as a male agile gibbon are uninfected by a parasitic worm. Male siamang (S/IA) put in a different cage with others is uninfected. Male siamang (S/IB) ia infected by three types of parasitic worms (Trichostrongylus, Strongyloides, and Cooperia) while the female siamang (S/IIB) that placed in the same cage with S/IB infected with one type of parasitic worm (Trichuris). Each egg account results showed no amount exceeding 300 eggs per gram of feces. This led to the degree of infection in agile gibbon and siamang at Serulingmas Zoological Garden, belonging to a common disease. It can be concluded that the type of parasitic worms found in the agile gibbon at Serulingmas Zoological Garden namely Trichostrongylus and Strongyloides while the variety of parasitic worms found in the siamang namely Trichuris, Trichostrongylus, Strongyloides, and Cooperia.

The effectiveness of artificial canopy bridges for the diurnal primates within a hydroelectric project in North Sumatra-Indonesia

Abstract Primates that live within fragmented and disturbed habitat are facing population declines and a higher probability of extinction due to gene flow inhibition. To address this problem, land managers, practitioners, and primatologists have applied several approaches to enhance primates’ habitat quality and connectivity through habitat restoration and canopy bridge installation. In some cases, artificial canopy bridges have shown to be effective to facilitate movement between fragmented habitats for several primates’ taxa. However, while several types of canopy bridge designs are available, there is no clear evidence on which is the best for primates. Here we evaluated the effectiveness of three artificial canopy bridge designs within a hydroelectric project in Sumatra, Indonesia from 2019 to 2021. The hydroelectric project was located at the edge of a forest block within the Batang Toru Ecosystem which could disconnect the primate’s population from this protected forest to the other forest blocks. During 595 days of camera trapping, we captured 988 independent crossing events from six diurnal primate species (Pongo tapanuliensis, Hylobates agilis, Symphalangus syndactylus, Presbytis sumatrana, Macaca nemestrina, and Macaca fascicularis). Our initial observation finds the ladder canopy bridge design was commonly used by primates and Presbytis sumatrana was the species that often crossed the canopy bridge. These findings are important to improve species management plans and primate conservation in Indonesia.

Population densities of Hylobates agilis in forests with different disturbance histories in Ulu Muda Forest Reserve, Malaysia.

Small ape habitat throughout Malaysia is rapidly being lost, degraded, and fragmented, and the effects of these changes on the abundance on this taxon are currently unknown. This study assessed the group density of Hylobates agilis in virgin forest, previously logged forest (1960s–1990s), and recently logged forest (2015–2017) of the Ulu Muda Forest Reserve (UMFR), Kedah, Malaysia. We conducted fixed‐point active acoustic triangulation at nine survey areas to estimate group density. We used vegetation “speed plots” and satellite imagery to quantify habitat characteristics and used model selection to identify ecological predictors of group density variation. The estimated group density of H. agilis in UMFR was 4.03 ± 0.14 groups km−2, with an estimated total of 2927 ± 102 groups in areas below 450 m a.s.l. in UMFR. Group density did not differ significantly among habitat types. The best ecological predictors for group density were canopy cover and proportion of deforested area. Areas with recent deforestation were associated with relatively high group densities, suggesting compression of the populations persisting in these habitat types. The consistently high group densities detected in all forest types emphasizes the importance of degraded forest as habitat for H. agilis. Because of the threats to small apes in Malaysia, and the uncertain status of most populations, we recommend a nationwide population census and regular monitoring to inform conservation planning and implementation. Most urgently, we call for immediate and permanent protection of UMFR and other forests in the Greater Ulu Muda landscape to protect the globally significant populations of H. agilis, as well as other charismatic and threatened megafauna, birds, and flora in the area.

Population density survey of white-bearded gibbons (Hylobates albibarbis) in high conservation value forest area of palm oil plantation company, Central Kalimantan, Indonesia

Abstract. Nurvianto S, Adrianti DT, Hamdan F, Triyanto J, Darmanto A. 2022. Population density survey of white-bearded gibbons (Hylobates albibarbis) in high conservation value forest area of palm oil plantation company, Central Kalimantan, Indonesia. Biodiversitas 23: 2245-2254. Bornean white-bearded gibbon (Hylobates albibarbis Lyon, 1911) or Bornean agile gibbon or southern gibbon is an endemic primate of Borneo and its distribution is limited to the forest areas in Central Kalimantan and West Kalimantan, Indonesia. However, its habitat is not restricted to the natural and undisturbed forest because this species also utilizes some forest blocks around rubber and palm oil plantation as habitats. This study aimed to estimate this species' population density and distribution in the five conservation blocks of PT Sawit Sumbermas Sarana (PT SSS), Indonesia and identify factors affecting its distribution. A field survey was conducted in five high conservation value forest areas inside the PT SSS management area, namely Pondok Duku Block, East Bravo Rangda Block, West Bravo Rangda Block, Tanjung Biru Block, and forest blocks around Kenambui Lake. Data was collected from April to May 2019 using the auditory sampling method through predetermined fixed Listening Posts (LP) to record population data. In addition, the protocol sampling technique was employed to systematically record the habitat features within the research site by establishing 0.04 ha plots systematically with a distance between plots of 400 m. Factors affecting gibbon distribution were identified using binary logistic regression. From the field survey, we identified that the southern gibbon was only found in East Bravo Rangda Block and Tanjung Biru Block with a population density of 4.26 ± 0.12 group/km² or 8.53 ± 0.34 individual/km² and 4.26 ± 0.12 group/km² or 8.53 ± 0.34 individual/km², respectively. Gibbon distribution was significantly associated with the number of seedlings (0.024±0.010, P=0.015), saplings (0.128±0.042, P=0.002), and trees (0.225±0.110, P=0.042. This result showed that vegetation condition strongly influences the presence of gibbon in an area.

Diversity and Distribution of Primates in the Gunung Basur Permanent Forest Reserve

This paper presents data regarding the diversity, population density, and distribution of primate species within the Gunung Basur Permanent Forest Reserve (GBPFR). The survey was conducted from the 3rd–8th of November in 2019, covering 7 survey locations (Terang Pump House, Suda Intake, Renyok 1 Intake, Renyok 2 Intake, Renyok 3 Intake, Long Intake, and Long 2 Intake) within the reserve. A total of 36 hours was spent to perform random sampling observations. The focus of this survey was to identify diurnal primate species. A total of 5 species (Symphalangus syndactylus, Hylobates agilis, Presbytis siamensis, Trachypithecus obscurus, and Macaca nemestrina), belonging to the families Hylobatidae and Cercopithecidae, were observed during the survey period. The density of Trachypithecus obscurus was high at the study site, with 60 individuals identified, followed by Symphalangus syndactylus, with 45 individuals, Presbytis siamensis, with 39 individuals, Hylobates agilis, with 20 individuals, and Macaca nemestrina with only 3 individuals. Two of the identified species are classified as Totally Protected (Symphalangus syndactylus and Hylobates agilis), whereas the other 3 species (Macaca nemestrina, Presbytis siamensis, and Trachypithecus obscurus) as classified as Protected, according to the Wildlife Conservation Act 2010 (Act 716). According to the International Union for Conservation of Nature (IUCN) Red List of Threatened Species, 2 species (Symphalangus syndactylus and Hylobates agilis) are considered to be Endangered, 2 species (Presbytis siamensis and Trachypithecus obscurus) are considered to be Near Threatened, and Macaca nemestrina is listed as Vulnerable. The data gathered from this study is crucial for designing a wildlife conservation plan for this reserve.

Are social media reports useful for assessing small ape occurrence? A pilot study from Peninsular Malaysia.

Citizen science-based research has been used effectively to estimate animal abundance and breeding patterns, to monitor animal movement, and for biodiversity conservation and education. Here, we evaluate the feasibility of using social media observations to assess the distribution of small apes in Peninsular Malaysia. We searched for reports of small ape observations in Peninsular Malaysia on social media (e.g., blogs, Facebook, Instagram, Twitter, YouTube, iNaturalist, etc.), and also used online, radio, print messaging, and word of mouth to invite citizen scientists such as birders, amateur naturalists, hikers, and other members of the public to provide information about small ape observations made during their activities. These reports provided new information about the occurrence of all three species of small apes (Hylobates agilis, Hylobates lar, and Symphalangus syndactylus) in Peninsular Malaysia. Social media users reported observations of small apes in almost every state. Despite the fact that small apes are believed to occur primarily in the interior of large forested areas, most observations were from fairly small (<100 km2 ) forests near areas of high traffic and high human population (roads and urban areas). This suggests that most outdoor enthusiasts primarily visit well-traveled and easily accessible areas, which results in biased sampling if only incidental observations reported on social media are used. A more targeted approach specifically soliciting reports from citizen scientists visiting large, less-accessible forests may result in better sampling in these habitats. Social media reports indicated the presence of small apes in at least six habitats where they had not been previously reported. We verified the reported data based on whether reports included a date, location, and uploaded photographs, videos and/or audio recordings. Well-publicized citizen science programs may also build awareness and enthusiasm about the conservation of vulnerable wildlife species.

Intestinal Parasites and the Occurrence of Zoonotic Giardia duodenalis Genotype in Captive Gibbons at Krabokkoo Wildlife Breeding Center, Thailand.

Intestinal parasitic infections can have an impact on health and growth of wildlife. The current study aims were to determine the prevalence of intestinal parasites and to molecular characterize Giardia duodenalis and Cryptosporidium spp. in captive gibbons at Krabokkoo Wildlife Breeding Center, Thailand. Fifty-five gibbons, 2 agile- (Hylobates agilis), 38 lar- (Hylobates lar) and 15 pileated gibbons (Hylobates pileatus) were included in this study. Fecal samples were collected individually at Krabokkoo Wildlife Breeding Center, Chachoengsao province, eastern Thailand, in November 2013. Intestinal parasitic infections were examined by zinc sulfate centrifugation flotation and by a commercially available immunofluorescent assay (IFA) for detection of G. duodenalis and Cryptosporidium spp.. Polymerase chain reaction targeting the Giardia glutamate dehydrogenase (gdh), beta- giardin (bg), triose phosphate isomerase (tpi) genes, and the Cryptosporidium small subunit-rRNA and heat-shock protein (hsp70) following by DNA sequencing were performed on the IFA positive samples. The overall prevalence of intestinal parasitic infection in gibbons at Krabokkoo Wildlife Breeding Center was 12.7% (95%CI: 5.3–24.5), Strongyloides spp. eggs or larvae were present in all positive samples. Co-infections with G. duodenalis were detected in 1.8% (95%CI: 0.1–9.7) of the samples. Based on the sequencing results of the three genes, the IFA Giardia positive isolate typed as the zoonotic genotype B. Since the data reveals the occurrence of zoonotic Giardia genotype, good hygiene management is suggested to prevent the transmission of this pathogen from gibbon to human, and vice versa.

Ex-Situ Wildlife Conservation in Taman Satwa Lembah Hijau Bandar Lampung

Ex-situ conservation carried out by Taman Satwa Lembah Hijau Bandar Lampung (TSLHBL) is an effort made to protect species of plants and animals outside the original habitat. This study aims to determine the suitability of ex-situ wildlife conservation efforts in TSLHBL using observation and interview methods. Data was processed by evaluative comparison methods with conformity indicators for wildlife welfare of the Indonesian Zoo Association (PKBSI) and the Indonesian Society for Animal Welfare (ISAW). The results of the study of the suitability of cages and animal playgrounds from twenty-five cages found 44% of cages that were not according to PKBSI and ISAW namely: Owa Jawa (Hylobates moloch), Owa Sumatera (Hylobates agilis), Merak Hijau (Pavo muticus), Rusa Timor (Cervus timorensis), Elang Hitam (Ictinaetus malayensis), Elang Brontok (Nisaetus cirrhatus), Elang Bondol (Haliastur indus), Beo (Gracula religiosa), Bangau Tong-tong (Leptoptilos javanicus), Binturung (Arctictis binturong), Buaya Muara (Crocodylus porosus), and Buaya Irian (Crocodylus novaeguineae). Of the twenty-six species of animals, only species of Merak Hijau (Pavo muticus) whose amount of feed does not match the amount of feed that should be given. Animals that produce offspring are only one deer in 2016, while other animals have no offspring. The utilization of wildlife in TSLHBL is for research, photo taking, visuals and animal attractions. Keywords: ex-situ conservation, wildlife conservation, wildlife parks lembah hijau

How conspecific primates use their habitats: Surviving in an anthropogenically-disturbed forest in Central Kalimantan, Indonesia

Kalimantan (Indonesian Borneo) is a biodiversity hotspot at risk because of severe forest loss, degradation and burning events. Habitat loss and anthropogenic altering of forest structures pose a threat to forest-dependent taxa, including multiple endemic primate species. Conservation management schemes may be enhanced by evaluating how forest-dependent primates use their habitat for fulfilling life-history requirements, the role of natural forest structures thereon, and any corresponding impacts from anthropogenic disturbance and modification of forests. We investigated how forest-structure variables and landscape scale anthropogenic disturbance factors influenced the life-history behaviours (sleeping, ranging and feeding) of two endemic and sympatric primate species, Presbytis rubicunda (red langur) and Hylobates albibarbis (Bornean agile gibbon), in Sabangau tropical peat-swamp forest, Central Kalimantan. We aimed to identify key factors that influence habitat suitability for both species, and determine the influence of similar factors when selecting habitat for various activities such as sleeping, feeding and ranging. GPS locational data for each behaviour were analysed in conjunction with forest-structure parameters present (derived from LiDAR, ALOS-PALSAR), landscape-scale habitat related factors, and proximity to landscape-scale disturbance factors including burned areas. A Maximum Entropy (MaxEnt) algorithm was employed for estimating habitat suitability for the different activities of each species based on the afore-mentioned variables. By using a combination of forest sub-class, structure and disturbance variables within the MaxEnt framework, distribution maps of suitable langur and gibbon sleeping, ranging and feeding habitats were produced. Langurs and gibbons had limited overlaps in terms of feeding, ranging and sleeping habitats. In all cases, landscape-scale variables including those related to landscape scale anthropogenic disturbance had the highest percentage contribution for explaining habitat suitability in comparison to forest-structure variables such as canopy heights (derived using LiDAR data). Additionally, variables influencing habitat selection varied between species; while langur feeding, ranging and sleeping were all influenced by distance from burned forests, gibbon sleeping habitat selection was influenced by distance from the forest edge, and ranging and feeding habitat selection was most affected by distance from burned areas. The insights gained from this study may help inform conservation management of these species and guide forest management strategies accordingly to ensure habitat structure is maintained to facilitate activities by sympatric primate species.

Species specificities among primates probed with commercially available fluorescence-based multiplex PCR typing kits.

To assess species specificities among primates of signals from short tandem repeat (STR) loci included in two commercially available kits, mainly the AmpFlSTR Identifiler kit and additionally the GenePrint PowerPlex 16 system, we analyzed 69 DNA samples from 22 nonhuman primate species representing apes, Old World Monkeys (OWMs), New World Monkeys (NWMs), and prosimians. Each prosimian species and the NWM cotton-top tamarin apparently lacked all STR loci probed. Only one peak, the amelogenin-X peak, was evident in samples from all other NWMs, except the owl monkey. In contrast, several loci, including the amelogenin-X peak, was evident in samples from each OWM species. Notably, for each ape sample, the amelogenin peaks were concordant with morphological gender of the individual. Among the primates, especially in apes, the numbers of alleles for STR loci were increasing according to their phylogenetic order: prosimians<NWMs<OWNs<apes, and so among apes: agile gibbons<white handed gibbons<orangutans<gorillas/common chimpanzees/bonobos. The species specificities among primates for a few commercially released multiplex STR kits examined in this study would contribute to forensic examinations.

The conservation value of degraded forests for agile gibbons Hylobates agilis

All gibbon species are globally threatened with extinction yet conservation efforts are undermined by a lack of population and ecological data. Agile gibbons (Hylobates agilis) occur in Sumatra, Indonesia and adjacent mainland Southeast Asia. Population densities are known from four sites (three in Sumatra) while little is known about their ability to tolerate habitat degradation. We conducted a survey of agile gibbons in Harapan Rainforest, a lowland forest site in Sumatra. The area has been severely degraded by selective logging and encroachment but is now managed for ecosystem restoration. We used two survey methods: an established point count method for gibbons with some modifications, and straight line transects using auditory detections. Surveys were conducted in the three main forest types prevalent at the site: high, medium, and low canopy cover secondary forests. Mean group density estimates were higher from point counts than from line transects, and tended to be higher in less degraded forests within the study site. We consider points more time efficient and reliable than transects since detectability of gibbons was higher from points per unit effort. We recommend the additional use of Distance sampling methods to account for imperfect detection and provide other recommendations to improve surveys of gibbons. We estimate that the site holds at least 6,070 and as many as 11,360 gibbons. Our results demonstrate that degraded forests can be extremely important for the conservation of agile gibbons and that efforts to protect and restore such sites could contribute significantly to the conservation of the species.

Immature male gibbons produce female-specific songs

Gibbons are apes that are well known to produce characteristic species-specific loud calls, referred to as "songs." Of particular interest is the sex specificity of the "great calls" heard in gibbon songs. However, little is known about the development of such calls. While great calls are given by female gibbons of various ages, they have never been recorded from males. Here, we report two observations of immature male gibbons from two different species, wild Hylobates agilis and captive H. lar, which spontaneously sang female-specific great calls. Based on the video clips, we conclude that immature males also have the potential to produce great calls. Our observations led us to propose a new hypothesis for the development of sexual differentiation in the songs of gibbons, and its implications for the general issue of sex-specific behavior in primates.

Travel adaptations of Bornean Agile Gibbons Hylobates albibarbis (Primates: Hylobatidae)in a degraded secondary forest, Indonesia

Data are presented on the locomotion of Bornean Agile Gibbons (Hylobatesalbibarbis) in a disturbed peat-swamp forest. Our results indicate that gibbons favour continuous-canopy forest, higher canopy heights and trees with a larger diameter at breast height. Gibbons select these trees despite the study site being dominated by broken-canopy forest and small trees. Gibbons also change frequently between brachiation, climbing, clambering and bipedal walking in this disturbed forest depending on the size of gap to be crossed. Gibbons are shown to be capable of adapting to some human-induced disturbances in forest continuity and canopy height, and to the presence of smaller trees, e.g., after selective logging. Despite this, gibbons are still limited to crossing gaps of =12m in a single movement, and more research is needed to quantify levels of disturbance gibbons can tolerate.

Sleeping Site Selection by Agile Gibbons: The Influence of Tree Stability, Fruit Availability and Predation Risk

Primates spend a significant proportion of their lives at sleeping sites: the selection of a secure and stable sleeping tree can be crucial for individual survival and fitness. We measured key characteristics of all tree species in which agile gibbons slept, including exposure of the tree crown, root system, height, species and presence of food. Gibbons most frequently slept in Dipterocarpaceae and Fabaceae trees and preferentially chose trees taller than average, slept above the mean canopy height and showed a preference for liana-free trees. These choices could reflect avoidance of competition with other frugivores, but we argue these choices reflect gibbons prioritizing avoidance of predation. The results highlight that gibbons are actively selecting and rejecting sleeping trees based on several characteristics. The importance of the presence of large trees for food is noted and provides insight into gibbon antipredatory behaviour.

Locomotion behavior of cao vit gibbon (Nomascus nasutus) living in karst forest in Bangliang Nature Reserve, Guangxi, China

The cao vit gibbon is a critically endangered species. Only approximately 110 individuals remain in degraded karst forest along the China-Vietnam border. Karst forest is unusual gibbon habitat. Currently, the canopy height of cao vit gibbon habitat is approximately 10 m. Research on the locomotor behavior of gibbons living in this particular forest type might provide important insight into locomotor stability and variability of gibbons. We used 5 min scan samples to record the locomotion mode, support use and canopy strata of gibbons in 3 groups for 2096 h between January 2008 and December 2009. Although cao vit gibbon habitat has a lower canopy in comparison to that of other forests inhabited by gibbons, cao vit gibbons displayed a similar overall locomotor pattern to other gibbon species (Symphalangus syndactylus, Hylobates lar and Hylobates agilis) in which brachiation dominate their locomotor behavior. Cao vit gibbons spent most of their time travelling on inclined branches (2-10 cm) in the middle stratum through the forest canopy. Adult females appear to more often employ safer modes of locomotion (bridging more often and brachiation less), while adult males choose riskier modes (leaping more and climbing less). As gibbons increased in body weight, as they grew from infant to adult, they tended to use larger supports. This research documented that locomotor behavior in Hylobatidae is strongly determined by anatomical characters, but cao vit gibbons also show the ability to use various supports, enabling them to survive in karst forest.

Male replacement and stability of territorial boundary in a group of agile gibbons (Hylobates agilis agilis) in West Sumatra, Indonesia

We report membership change in a group of wild agile gibbons, Hylobates agilis agilis, in West Sumatra, Indonesia. During 6-month observational periods, we focused on a particular unit of individuals known as the B group. We confirmed that the group consisted of five individuals: one adult female, one adult male, one subadult male, one subadult female, and one infant male. During our observations, the resident adult male and the two subadult individuals dispersed or disappeared, and a new adult male took over the group. We examined the effects of the male replacement on the territorial boundary, using the auditory census technique. The boundary was stable. We also documented the succession of the home range. Our results indicate a flexible social structure in this species and contribute some useful data to an ongoing debate on their social dynamics.

Localization of Nucleolar Organizer Regions (NORs) of 4 Gibbon Species in Thailand by Ag-NOR Banding Technique

Summary Localization of nucleolar organizer regions (NORs) of four gibbon species in Thailand was studied. Blood samples were taken from 1 male each of the following 3 species: white-handed gibbon (Hylobates lar), pileated gibbon (H. pileatus), and white-cheeked gibbon (Nomascus leucogenys): and 1 female of the dark-handed gibbon (H. agilis). These were subjected to standard whole blood T-lymphocyte culture. The samples were harvested by colchicine-hypotonic-fixation-air-drying technique and were followed by the Ag-NOR banding technique. The results showed that the H. lar had NORs on chromosome pair 13 (submetacentric chromosomes) while the H. agilis had NORs on chromosome pair 10 (submetacentric chromosomes) and H. pileatus had NORs on chromosome pair 15 (metacentric chromosomes). In addition, the N. leucogenys showed 5 positions with NORs on chromosomes pairs 23, 24 (acrocentric chromosomes) and the Y-chromosome (submetacentric chromosome). These results are useful to confirm marker chromosomes of gibbons and also comprise basic genetic information for these animals. Kew words Gibbon, Karyotype, Chromosome, Idiogram, Ag-NOR banding. Thailand is tropical country thus its weather and surrounding are suitable for organism that causes high diversity. Wild animals are one element that show the diversity and also important in ecology and food chain. The destruction of forest causes wild animal extinction or risk of extinction includes animal in family Hylobatidae. There were 13 families, 60 genera and 232 species of animals in order Primate (Wilson and Cole 2000); however, only 3 families, 5 genera, and 13 species were found in Thailand. Thai gibbon species consists of 4 species, white-handed gibbon (Hylobates lar Linnaeus 1771), agile gibbon or dark-handed gibbon (Hylobates agilis Cuvier 1821), pileated gibbon (Hylobates pileatus Gray 1842), and white-cheeked gibbon (Nomascus leucogenys Ogilby 1840) (Lekagul and McNeely 1988, Giessmann 1995) (Fig. 1). These species are listed as protected species in Wild Animal Reservation and Protection Act (1992), and in the International Union for the Conservation of Nature (IUCN) as vulnerable species. The Convention on International Trade in Endangered Species (CITES) of wild fauna and flora also listed these species in Appendix I (Brokelman 1981).

Demography of Agile Gibbons (Hylobates agilis) in a Lowland Tropical Rain Forest of Southern Sumatra, Indonesia: Problems in Paradise

Gibbons are among the best-studied Asian primates, but few studies address their demography and life history strategies. We used annual censuses to study the demography of agile gibbons (Hylobates agilis) between 1998 and 2009 in rain forests of Bukit Barisan Selatan National Park, Indonesia. The population declined from 22 individuals (9 groups) to 14 individuals (5 groups) over the 12 yr of study. Infant survival to the juvenile age class was 33.3%, and 16.7% of infants survived to the subadult age class. The interbirth interval was 3.83±1.15 yr and birth rate was 0.22-0.28 infants female -1 yr -1 . Two groups colonized the study area but subsequently disappeared. We documented 7 immigrations, 17 disappearances, and ≥10 transients in the population. Compared to lar gibbons (Hylobates lar) and Bornean white-bearded gibbons (Hylobates albibarbis), Way Canguk's agile gibbon population is characterized by slow reproduction, low survival, and high group turnover. We hypothesize that, although the habitat is high in fruit resources, agile gibbons may be displaced or excluded from the best fruit resources by larger and more numerous competitors, incurring costs of decreased opportunities to forage and increased travel, and leading to higher mortality for young agile gibbons. The reproductive potential of this agile gibbon population is insufficient to compensate for high mortality, and the population is unlikely to persist without immigration from outside the area. Given the agile gibbons' endangered status and limited capacity to respond demographically to change, it is likely that intensive management interventions will be required to conserve this species.

Pathological Changes in Captive Monkeys with Spontaneous Yersiniosis due to Infection by Yersinia enterocolitica serovar O8

An outbreak of fatal yersiniosis due to infection with Yersinia enterocolitica serovar O8 is documented in two species of captive monkey. Five of 50 squirrel monkeys (Saimiri sciureus) and one of two agile gibbons (Hylobates agilis) died following several days of diarrhoea. Necropsy examination revealed necrotizing enterocolitis and multifocal necrosis or abscesses in various organs. Microscopically, these lesions comprised multifocal necrosis with bacterial colonies, neutrophils and accumulation of nuclear debris. Occasional lesions included macrophages and abscess formation. Immunohistochemically, the bacteria were identified as Y. enterocolitica O8. In addition, Y. enterocolitica serotype O8 was isolated from animal organs in pure culture. This is the first report of fatal cases of infection with Y. enterocolitica serovar O8 in animals.