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This thesis details research into the ecology and behaviour of the black-shanked douc (Pygathrix nigripes Milne-Edwards, 1871), an Endangered colobine found in eastern Cambodia and southern Vietnam. The study was conducted in Seima Biodiversity
Conservation Area (SBCA), Mondulkiri Province, Cambodia, over a period of 20
months, from January 2003 to...
Citations
... Nasalis larvatus Yeager (1989), Rowe and Myers (2016) Presbytis melalophos Davies and Baillie (1988), Nijman et al. (2020) rubicunda Hanya and Bernard (2012) Pygathrix cinerea Long (2020), Long, Duc, et al. (2020) nemaeus Phiapalath et al. (2011) nigripes Rawson (2009), Roos et al. (2011) Rhinopithecus avunculus Rowe and Myers (2016), Hai (2012) bieti Present study; Rowe and Myers (2016) brelichi Xiang et al. (2013), Rowe and Myers (2016) roxellana Li (2007), Rowe and Myers (2016) strykeri Yang et al. (2019) Semnopithecus ajax Thakur et al. (2022) entellus Sayers and Norconk (2008) priam Vanaraj and Pragasan (2021) pileatus Solanki et al. (2008) TA B L E A 2 Data sources of dietary selection among Asian colobines. ...
Fallback foods (FBF), categorized into staple and filler types, are suboptimal food sources chosen by animals in response to a scarcity of preferred food items during specific periods. Using lichens as FBF by Yunnan snub‐nosed monkeys ( Rhinopithecus bieti ) represents a distinctive ecological adaptation and evolutionary development within nonhuman primates. This study delves into the annual dietary choices of the species to address issues, elucidate the nutritional value, and understand the ecological significance of lichens for this primate species, which resides at the highest altitudes and experiences the coldest weather among global primates. The findings reveal that the lichens consumed by the monkeys serve as the staple FBF, with Bryoria spp. and Usnea longissima being the primary dietary species. The former is the preferred choice, providing higher digestible fiber (neutral detergent fiber) levels but lower tannin, fat, ADF, and energy levels. During the dry season, lichens dominate as the monkeys' primary food and nutritional resources. In the wet season, they act as a fundamental food selection rather than an ideal dietary choice, substituting nutrients from fruits, seeds, and leaves. Compared to other Asian colobine counterparts, this species exhibits the highest lichen consumption but the lowest proportions of leaves, flowers, and seeds. This study provides valuable evidence and information for developing or amending conservation strategies and guidelines for the dietary management of captive breeding of monkeys, one of the world's critically endangered primate species.
... Mean densities of douc and silvered langur were similar or higher in 2022 compared to 2016 indicating that the threats which caused the declines in ground-dwelling ungulates did not impact population trends of either primate species. The relatively high density and abundance of douc in KSWS, compared to PPWS, and in PPWS compared to SWS, is likely related to the species' preference for evergreen habitat and general avoidance of DDF (Hoang, 2007;Rawson, 2009). The proportion of evergreen forest cover is highest in KSWS, followed by PPWS, and lowest in SWS, whilst the proportion of DDF follows the reversed pattern (Gray et al., 2014;Pin et al., 2013;Tani et al., 2007). ...
Snaring poses a significant threat to terrestrial animals in many parts of Southeast Asia. However, long-term population monitoring data to determine the impact of snaring on wildlife populations is limited. We used distance sampling to estimate wildlife densities and population trends and data collected from ranger patrols to assess snare numbers across two protected areas in Cambodia's Eastern Plains Landscape. We found that the populations of three ungulate species, including the globally endangered banteng (Bos javanicus), steeply declined as snare numbers appeared to increase. In the same time period, the populations of two globally threatened arboreal primates remained similar or increased. Our findings indicate that snaring likely impacts ground-dwelling ungulates whilst sparing arboreal primates. Current ungulate densities are at critically low levels with several species at the brink of extirpation in our study area. We recommend urgent and comprehensive conservation actions to restrict snaring and prevent irreversible wildlife population collapses in this landscape and across the broader region.
... This appears to be the highest number of food species recorded at a single site for any douc species to date (cf. Hoang Minh, Baxter & Page 2009;Rawson 2009). Relatively few food species overlapped between the two study areas within Kon Ka Kinh NP -just 25 species (10%) -suggesting that groups may vary in their preferences and-or flexibly adjust their diet based on the availability of plant species. ...
... The socioecology of the grey-shanked douc langur appears to be underpinned by multi-level group structure and 'fission-fusion' dynamics, as is also the case with the other douc langur species (Rawson 2009;Ulibarri & Gartland 2021). The smallest foraging units typically consist of One Male Units (OMUs), which are the breeding family groups, and All Male Units (AMUs), which are composed of 'bachelor' males. ...
... Data presented in the current study now make it possible to elaborate red-shanked douc feeding ecology and compare it to studies of the black-shanked douc (Pygathrix nigripes) conducted by Hoang (2007;Hoang, Baxter and Page 2009) in Vietnam and Rawson (2009) in Cambodia, and the grayshanked douc (Pygathrix cinerea) studied by Ha (2009) in Vietnam. ...
... Our third objective included comparing the feeding behavior of Son Tra's red-shanked doucs to other studies of studies of the species (Ulabarri 2013; Otto 2005). Son Tra red-shanked douc feeding behavior will also be compared to black-and gray-shanked douc feeding behavior (Hoang 2007;Rawson 2009;Ha 2009). Our objective was to characterize red-shanked douc feeding behavior along with general douc feeding behavior, and to compare it with the dietary behavior of other Asian colobines, such as the whiteheaded langur (Li and Rogers 2009), the Tonkin snub-nosed monkey (Boonratana and Le 1998;Dang 2007), and the proboscis monkey (Sha et al. 2011;Yeager 1989). ...
... The frequency of leaf items in Hoang's black-shanked douc samples was over 50%. In Rawson's (2009) study of black-shanked doucs at Keo Semia in Mondulkiri Province, Cambodia, the frequency of leaf consumption was lower than 40%. In both studies of red shanked doucs, the frequency of leaf consumption was over 60%: Son Tra doucs were over 80 % and in Otto's (2005) study the frequency was over 60%. ...
The first multi-year study of red-shanked doucs' (Pygathrix nemaeus) feeding ecology was conducted at Son Tra Nature Reserve, Danang City, Vietnam. Our goal was to discover the diet of red-shanked doucs at this nature reserve. Eleven years of data have been collected using scan sampling and video recording during group follows. Sixteen vegetation plots (50 m × 40 m) containing 160 trees from 60 species were established and monitored monthly for changes in fruit, flower, and young leaf production. A food calendar was constructed and used to estimate yearly food availability and abundance. Red-shanked doucs were found to depend primarily on buds and young leaves, while supplementing this intake with flowers, fruits, seeds, and bark. At least 226 plant species are used as food sources along with Acacia pruinescens, Ficus racemosa, Ficus sumatrana, Millettia nigrescens, and Shorea guiso that are consumed frequently. We found red-shanked doucs to be selective feeders since use of tree species was not based on relative density alone. The douc feeding strategy was to maintain a constant number of food resources monthly and seasonally while varying the plant species sources, resulting in dietary diversity. Our findings demonstrate that red-shanked doucs are more seasonally and dietarily flexible than was previously known, which may help explain why the species can survive in such a wide variety of forest habitats throughout its range.
... However, the potential distribution did not align well with its known distribution range, as described by Rawson et al. (2008) in the IUCN Red List of threatened species. The largest known population of the species was found in the Mondulkiri Province of Cambodia (Rawson et al., 2008;Rawson, 2010). However, this forested area was not predicted to be suitable for black-shanked doucs by Bett et al. (2012). ...
... Species occurrence data. We used a total of 472 points (350 points in Vietnam and 122 points in Cambodia; Fig. 1) where black-shanked doucs were recorded from previous studies, including those by Nadler et al. (2003), Phan et al. (2005), Hoang (2007), Hoang et al. (2010), Nguyen et al. (2010), Rawson (2010), O'Brien (2014), as well as ourselves. The animals were detected visually at these points during line-transect surveys. ...
... The area of high suitability seems to increase under the Access1-0 climate model due to the expected change in climate of the Lang Biang Plateau. Almost all current potential distributions in Khanh Hoa, Ninh Thuan, Dong Nai, and Binh Phuoc Provinces are predicted to become unsuitable for the species in 2070 under the RCP8.5 scenarios.DISCUSSIONOur predicted current potential distribution of the blackshanked douc was in accordance with the locations recorded byNadler et al. (2003),Phan et al. (2005), Hoang(2007),Hoang et al. (2010),Nguyen et al. (2010),Rawson (2010), and O'Brien (2014). The modelled potential distribution also aligned with the species' IUCN distribution map(Rawson et al., 2008) and the potential distribution predicted byBett et al. (2012). ...
Climate change has affected many animals, causing shifts in distributions across a wide range of vertebrate and invertebrate species. Many primate species have small distributions with narrow ecological niches and are therefore sensitive to changes in the environment. However, there exists a lack of predictions with regards to how the distribution ranges of primate species might shift given future climate changes. In this study, we assessed the potential effects of climate change on the distribution of the black-shanked douc, Pygathrix nigripes (Milne-Edwards, 1871). We generated climatic conditions projected for 2050 and 2070 under the two scenarios, RCP4.5 and RCP8.5, with three climate models, ACCESS1-0, GFDL-CM3, and MPI-ESM-LR. We predicted that the distribution of the black-shanked douc would be sharply reduced with 66.19% of the current distribution lost by 2070 under the RCP8.5 scenario. The species' suitable distributions were not projected to shift to higher latitudes but were instead expected to shift towards the centre of their current range. Under the context of climate change, higher priority in conservation efforts for the species should be given to the protected areas in the centre of the species' current distribution, especially in the north of Lam Dong, south of Dak Lak, and middle of Dak Nong provinces. Specifically, Bidoup-Nui Ba and Chu Yang Sin National Parks should receive the highest priority in terms of conservation attention for this species. Our study also indicated that more surveys should be conducted in several forested areas, both inside and outside the current protected area network, in order to gain a better understanding of the black-shanked douc langur populations and their distributions.
... Based on Delson et al. (2000); Lee et al. (1991); Smith and Jungers (1997) Phuong Anh et al. 2010;Ha Thang Long 2007Ha Thang Long et al. 2010;Hoang Minh Duc et al. 2009;Phiapalath 2009;Rawson 2009;Ulibarri 2013). However, a study of the socioecology of P. nigripes reported suspensory behavior to comprise 10% of males', and 3.7% of females' locomotor repertoire (Rawson 2009) and another study described extensive arm-swinging and suspensory postures in P. nigripes (Tran Van Bang et al. 2011). ...
... Based on Delson et al. (2000); Lee et al. (1991); Smith and Jungers (1997) Phuong Anh et al. 2010;Ha Thang Long 2007Ha Thang Long et al. 2010;Hoang Minh Duc et al. 2009;Phiapalath 2009;Rawson 2009;Ulibarri 2013). However, a study of the socioecology of P. nigripes reported suspensory behavior to comprise 10% of males', and 3.7% of females' locomotor repertoire (Rawson 2009) and another study described extensive arm-swinging and suspensory postures in P. nigripes (Tran Van Bang et al. 2011). Despite the anatomical evidence and captive data indicating that Pygathrix armswings, it remains unclear why they arm-swing when most other colobines do not. ...
... In an effort to tease apart this suggestion, we tested the hypothesis that body mass influences the frequency of arm-swinging in wild P. nemaeus. Given differences in mass between males and females, and between immatures and matures (and the sex differences in percentage of suspensory behavior observed in P. nigripes [Rawson 2009]), we predicted that males will arm-swing the most, followed by adult females with a ventral infant, adult females without an infant, subadults of any sex, and juveniles of any sex, respectively. ...
Across the primates, larger body mass often necessitates below-branch locomotion (such as arm-swinging or brachiation). While colobines are typically considered arboreal quadrupeds, Pygathrix exhibits a high degree of arm-swinging behavior in captivity (ca. 50% of locomotion time). However, little is known about their behavior in the wild. We examined two questions about the locomotion of Pygathrix nemaeus in the wild: 1) What is the proportion of arm-swinging in the locomotor repertoire? 2) Given the difference in sizes between the sexes and age categories in this species, do adult males, adult females, subadults, and juveniles differ in arm-swinging frequency? Based on the hypothesis that increased body mass is typically associated with below-branch locomotion, we predict adult males will arm-swing the most, followed by adult females with a ventral infant, adult females without an infant, subadults, and then juveniles. We recorded data between November 2016 and April 2017 in Son Tra Nature Reserve, Da Nang, Vietnam. This time frame encompasses the wet and dry seasons. We video-recorded P. nemaeus between dawn and dusk, 5 days a week, and recorded behavioral data from the footage. We found that juveniles used arm-swinging the most (34.3%), followed by subadults (21.7%), adult females (17.6%), adult females carrying infants (15.5%), and then adult males (9.8%). These results do not support the hypothesis that larger bodied individuals engage more in below-branch locomotion. It is not uncommon for colobine juveniles to show higher proportions of arm-swinging than adults, but more research is needed to understand the relatively high proportions of arm-swinging in adult P. nemaeus.
... Among the colobines, multilevel social organization has been documented in four genera: the doucs (Pygathrix spp.; Rawson, 2009), proboscis monkeys (Nasalis larvatus; Yeager, 1990), snub-nosed monkeys (Rhinopithecus spp.; Kirkpatrick & Grueter 2010;Qi et al., 2014), and recently Rwenzori colobus (Colobus angolensis ruwenzorii), which form temporary associations of more than 100 individuals at a lowland site in Uganda (Lake Nabugabo) (Arseneau-Robar, Joyce, Stead, & Teichroeb, 2018;Stead & Teichroeb, 2019), are confirmed to have a multilevel society with three social tiers (Stead & Teichroeb, 2019). A study at the same site on proximity and grooming patterns reveals opposite-sex bonding and weak same-sex bonds within dyads of the Rwenzori colobus (Arseneau-Robar et al., 2018). ...
Primates display broad diversity in their social organization. The social groups of a few primate species are organized in a multilevel fashion, with large groups composed of multiple, core one‐male units (OMUs). A characteristic of multilevel societies is that the higher levels can include hundreds of individuals. The Rwenzori black‐and‐white colobus (Colobus angolensis ruwenzorii) in the montane forests of Rwanda form supergroups and have been suspected to exhibit multilevel social organization. Here we present the first data on the “anatomy” of a supergroup numbering 500+ individuals. We identified subgroups within the supergroup based on progression data, extracting the social network structure from the time‐stamped spatiotemporal distribution of passing individuals identified to age–sex class, and selecting an optimal time window for each network using the two‐step approach developed by Uddin, Choudhury, Farhad, and Rahman (2017). We detail the existence of core units—multi‐male units (MMUs) with a mean of 1.7 adult males and 3.1 adult females, as well as OMUs, all‐female units and bachelor units composed of adult and sub‐adult males. More than two‐thirds of units are MMUs. These grouping patterns conform to a multilevel society with predominantly multi‐male core units, a social system that has recently also been described for a population of the same taxon in Uganda. Individual identification will be required to corroborate these interpretations.
Research Highlights
• We analyzed the “anatomy” of a supergroup of Rwenzori black‐and‐white colobus.
• Social network analyses point to a possible multilevel society.
• The majority of subunits contained multiple males and females.
... The estimator was done by using Vegan package and performed in R. We also used Spearman rank correlation coefficient test to identify significant correlations between examined variables. To understand if the diet of T. margarita at Takou Mountain is similar or different compared to other Trachypithecus species and to other genera of Asian colobine monkeys, we compiled the average consumption of food items for all selected species of the genera based on this and other studies (Newton, 1992;Kool, 1993;Sunderraj, 2001;Zhou et al., 2006;Le et al., 2007;Sayer & Norconk, 2008;Grueter et al., 2009;Ha et al., 2009;Matsuda et al., 2009;Rawson, 2009;Workman, 2010a;Hanya & Bernard, 2012;Le et al., 2015) into a contingency table before applying a Chi-square test. All statistical tests was done using R Version 3.4.1 for Windows. ...
... In Vietnam's Phuoc Binh and Nui Chua National Parks, Pygathrix nigripes also has a highly folivorous diet, followed by fruits/seeds and flowers . Trachypithecus margarita and the Vietnamese Pygathrix nigripes differ from Pygathrix nigripes in Cambodia, where langurs ate fruits and seeds as their primary food source (Rawson, 2009 (Sayers & Norconk, 2008). In addition, the similarity in dietary pattern between T. margarita with genus Semnopithecus is not significant. ...
... The number of plant food species was also fewer than that ingested by Pygathrix nigripes in semi-evergreen forest of Nui Chua and evergreen forest of Phuoc Binh NP in Vietnam ; Semnopithecus entellus in deciduous forest in India (Newton, 1992) and Presbytis rubicunda in dipterocarp forest of Borneo (Hanya & Bernard, 2012). However, the number of food species consumed by R. avunculus in limestone forests in Vietnam (Le et al., 2007) and Pygathrix nigripes in the semi-evergreen forest in Cambodia (Rawson, 2009) is similar to T. margarita at Takou Mountain with 31 and 35 species, respectively. ...
The Annamese langur (Trachypithecus margarita) was described in 1909 but its ecology, including its feeding behaviour, is still largely unknown. Based on current knowledge of feeding ecology of many Asian langurs, T. margarita is expected to be a generalist herbivore, with seasonal variation in diet. Feeding behaviour of one habituated group of Annamese langurs at Takou Mountain was studied from October 2009 to September 2011. The dietary pattern of these langurs was found to be similar to other Trachypithecus species, which is characterised by a high amount of leaf consumption (54.4% immature leaves, 7.1% mature leaves) and complemented by fruits (29.9%). The Annamese langurs ate plant parts from 31 species belonging to 20 families on Takou Mountain where 689 plant species were known for the mountain. Moraceae is the most important family in the langur’s diet with at least 10 species consumed and accounting for 41.1% of feeding time. Based on the current and previous feeding studies of Trachypithecus species, it could be concluded that the genus is a generalist folivore and the dietary pattern is similar among species
... Dietary information on the critically endangered R. avunculus and T. francoisi is largely lacking, but observations on Pr. rubicunda and Py. nigripes confirm that these two species frequently predate seeds (Davies 1991;Rawson 2009). Davies (1991) reported that the diet of Pr. rubicunda at Sepilok in Northern Borneo can comprise 80% seeds, depending on the season. ...
... Davies (1991) also reported that the resistant arils of fruits such as Xerospermum internedium, Wallucharia wallichii, and Knema laterica, are chiseled off and removed to access the seeds. While most colobines prefer young leaves over other food items (Bennett and Davies 1994;Oates 1994), Rawson (2009) pointed out that young leaves eaten by Py. nigripes were, on the contrary, fallback resources; seeds such as Sindora siamensis, Peltophorum cf. dasyrrhachis, Terminalia spp., and Dracontomelon appeared to be the most preferred food items, which may even determine group movements and, more particularly, fission-fusion behavior (Rawson 2009). ...
... While most colobines prefer young leaves over other food items (Bennett and Davies 1994;Oates 1994), Rawson (2009) pointed out that young leaves eaten by Py. nigripes were, on the contrary, fallback resources; seeds such as Sindora siamensis, Peltophorum cf. dasyrrhachis, Terminalia spp., and Dracontomelon appeared to be the most preferred food items, which may even determine group movements and, more particularly, fission-fusion behavior (Rawson 2009). Duc et al. (2009) observed that Py. nigripes in southern Vietnam fed more frequently on seeds from unripe fruits than ripe ones, using their canines to gouge out seeds so they could eat those alone. ...
Leaf-eating monkeys (colobines) are a highly diversified subfamily with 61 species in ten genera, in which patterns and constraints of morphological evolution are still poorly resolved. In the present study, we measured the skulls of 452 specimens collected from different museums worldwide. Using one of the most extensive samples ever employed, and geometric morphometric techniques, we aimed to elucidate the evolutionary processes that have led to the craniofacial diversification of colobines. Our comprehensive analyses of the colobine cranium demonstrated that phylogeny is the first order signal to emerge, with clear interspecific patterns of differentiation. Allometric trend constrains shape variation for most colobine taxa, but to a lesser degree than phylogeny. We also confirmed that diet is significantly associated with the variation in cranial shape among colobines. In particular, the mechanical advantage of the masseter for biting at the anterior dentition is linked to seed intake. We postulate that such ecomorphological patterns explain, in part, the non-phylogenetic and non-allometric variations in the colobine skull, and indicate the importance of diet in interspecific resource partitioning, allowing for species coexistence.
... Outside of the captive setting, information about douc langur locomotion, especially armswinging frequency data, is more limited. However, one study ( Rawson, 2009) has documented arm-swinging in nearly 10% of all travel bouts across all age and sex classes in wild black-shanked doucs (Pygathrix nigripes). While this is less frequent than what is reported for captive Douc langurs, it is likely safe to infer that armswinging is not simply an artifact of captivity. ...
Most colobine monkeys primarily move through their arboreal environment quadrupedally. Douc langurs (Pygathrix spp.), however, are regularly observed to use suspensory behaviors at the Endangered Primate Rescue Center (EPRC) in Northern Vietnam. Previous work has linked variation in scapular morphology to different modes of primate arboreal locomotion. Here we investigate whether the shape of the Pygathrix scapula resembles obligate brachiators (gibbons) or obligate arboreal quadrupeds (other cercopithecoids). Using a MicroScribe G2X 3D digitizer, the positions of 17 landmarks were recorded on 15 different species of nonhuman primates (n = 100) from three categories of locomotor behavior: brachiator, arboreal quadruped, and unknown (Pygathrix). All analyses were conducted in the R package geomorph. A Procrustes analysis uniformly scaled the shape data and placed specimens into the same morphospace. A Principal Component Analysis was used to examine scapular shape and a Procrustes ANOVA was conducted to test for shape difference in the scapulae. A pairwise analysis was used to compare the means of the locomotor categories and identify any statistically significant differences. A phylogenetically controlled Procrustes ANOVA was also conducted using a phylogeny from 10kTrees. Results show Pygathrix scapular morphology is significantly different from both arboreal colobine quadrupeds (p < 0.01) and hylobatid brachiators (p < 0.01). It does, however, share some features with each including a long vertebral border, like other cercopithecoids, and a more laterally projecting acromion process, like the hylobatids. The principal difference segregating Pygathrix from both the arboreal quadrupeds and the brachiators is the more medially placed superior angle. These nuanced morphological characteristics associated with suspensory behaviors may be useful for inferring suspensory locomotion in the primate fossil record.
