Добірка наукової літератури з теми "Delacour's langur"

During 2019 and 2020, 14 areas in Northern Vietnam were surveyed for Delacour’s langur Trachypithecus delacouri (Osgood, 1932) to confirm the status of distribution, estimated populations and intensity of hunting pressure. People from elected local authorities, as well as other individuals, were interviewed to determine their awareness of the langur’s conservation. These data were combined for statistical analysis. The results showed that protection status was negatively correlated with hunting pressure (Rs = -0.601; p = 0.006). Hunting pressure also had a negative relationship with the growth of the number of langur populations (Rs = -0.616; p = 0.005) and the number of langur individuals (Rs = - 0.578; p = 0.01). However, placing an area under State protection had no correlation with the growth of the population of Delacour's langur living there (p > 0.05). People's awareness in Van Long Nature Reserve was very high (over 99% strongly supported the conservation of Delacour’s langur) which corresponded to the growth of Delacour's langur population in that area. To protect both the langurs and people's livelihoods, we, therefore, recommend turning the areas where Delacour's langurs are distributed into protected areas and also promoting people’s awareness through legal dissemination and activities. The reintroduction of the species into suitable protected habitats should be carried out scientifically.

AbstractThis study draws on the local ecological knowledge of 58 hunters from seven communes in the Ngoc Son Ngo Luong Nature Reserve (Hoa Binh province, North Vietnam) to examine the local status of 40 threatened vertebrates. The reserve forms part of a biodiversity-rich mountainous corridor. Respondents were shown photographs of the species and asked to rate their abundance on a scale of 0–3 (0, extinct; 3, very abundant) in two periods: pre-1975 (before Doi Moi) and in 2009. The results show that 39 species have lived in the area and five are now extinct (Delacour's langur Trachypithecus delacouri, northern white-cheeked crested gibbon Nomascus leucogenys, dhole Cuon alpinus, oriental small-clawed otter Aonyx cinereus, Indochinese tiger Panthera tigris corbetti) and the presence of another six is doubtful (Phayre's leaf-monkey Trachypithecus phayrei ssp. crepuscula, sun bear Helarctos malayanus, binturong Arctictis binturong, fishing cat Prionailurus viverrinus, leopard Panthera pardus, wreathed hornbill Anorrhinus undulatus). The results show a general decline in numbers and abundance, with mammals declining fastest, especially carnivores and primates. The differences in abundance between species have narrowed since 1975, converging towards trends of general impoverishment at similar low abundances. The survey results were similar among communes and also concord with the findings of research in nearby areas. This study demonstrates the usefulness of local ecological knowledge for planning, decision-making and management of protected areas in the absence of historical records or financial resources for conducting intensive fieldwork in remote and little-known areas.

Abstract One of the three Critically Endangered and endemic primate species in Viet Nam, Delacour's langur Trachypithecus delacouri, is restricted to the north of the country. The largest remaining population is in Van Long Nature Reserve, Ninh Binh Province, and the second largest is in nearby Kim Bang Protection Forest, Ha Nam Province, with other populations believed to be too small for recovery. The population in Van Long has been well studied but the status of that of Kim Bang has not previously been adequately evaluated. To address this, a survey was conducted during 10 August–7 October 2018. In total, we recorded 13 groups comprising a total of at least 73 individuals, almost doubling the highest number reported in previous studies. We documented six new groups in Lien Son and Ba Sao communes in Kim Bang. Our findings indicate there is a high likelihood that Delacour's langur population in Kim Bang will recover and could be important for the long-term conservation of this Critically Endangered species. However, immediate and appropriate conservation measures need to be implemented to protect the population from major anthropogenic threats, namely poaching and habitat destruction, detected during our survey.

Delacour's langurs (Trachypithecus delacouri), one of the six limestone langur taxa of Southeast Asia, inhabit isolated, rugged limestone karst mountains in Northern Vietnam, although the reason for their current restriction to this habitat is unclear. The occupation of karst habitats by limestone langurs has been attributed to the refuge these rocky outcrops provide in a dramatically anthropogenically-altered landscape. Conversely, several ecological explanations have been proposed to account for their distribution, though the ecology of wild Delacour's langurs had yet to be studied. In this dissertation, I quantified the foraging ecology of Delacour's langurs living on Dong Quyen Mountain in Van Long Nature Reserve, Vietnam to address if these langurs show special adaptations to limestone karst or if they are exploiting a refuge habitat into which they have been pushed. I quantified their foraging ecology by systematically investigating their diet and feeding ecology, the chemisty of their eaten leaves, and the locomotions and substrates they utilized.

From August 2007 through July 2008, I used instantaneous focal-animal sampling during all-day follows of Delacour's langurs on Dong Quyen Mountain. I collected data on activity budget, diet, and positional behavior. I also collected samples of soils and eaten and uneaten leaves which were tested for phytochemical content.

With nearly 79% leaves in the diet, 60% of which were young leaves, Delacour's langurs are among the most folivorous of studied colobines, and- along with the closely related T. leucocephalus of southern China- the most folivorous of the Asian langurs. None of the plants that were important in the Delacour's langur diet were endemic limestone plants, and therefore feeding dependence alone cannot explain the current distribution of limestone langurs on karst habitat. Langurs ate leaves with high protein:fiber ratios, and despite a high percentage of carbon in the soil, young leaves were available throughout the year and plant defenses did not seem to have a large impact on eaten leaves. Delacour's langurs spent nearly 80% of their time on rocks. Quadrupedalism was their dominant locomotor style, more than double that of climbing. Terrestrialism, however, does not adequately describe the dangerous locomotion of these langurs; they are cliff-climbers. Delacour's langurs leapt only 6% of the time, much less than other African and Asian colobines, but their morphology (intermembral index) does not suggest terrestrialism or an evolutionary adaptation for limestone karst. Delacour's langurs appear to be a flexible taxon occupying a refuge habitat into which they have pushed. However, this restricted limestone habitat does not appear limiting in resources. The population at Van Long Nature Reserve is increasing which means that- if protected- this local population can rebound. Persistent hunting for traditional medicine and the more recent emergence of quarrying limestone for cement, however, threatens their survival.

Dissertation

Delacour’s langur (Trachypithecus delacouri) is a critically endangered Southeast Asian colobine, found in the karst outcrops of northern Vietnam. Half of the remaining population (estimated at fewer than 200 individuals) resides within Van Long Nature Reserve, Ninh Binh Province. This thesis aims to further the conservation of T. delacouri by reviewing the first release of captive-bred individuals as a potential conservation tool for the species, along with acquiring a greater understanding of the species’ behaviour. Behavioural focal observations were conducted throughout 2011, both on wild groups at Van Long and captive individuals at the Endangered Primate Rescue Center (EPRC) at Cuc Phuong National Park. A group of three individuals was released by the EPRC into Van Long in August 2011 in an aim to connect populations and promote interbreeding, and was tracked using GPS radio collars for a period of up to 13.5 months, with the release then evaluated in line with IUCN reintroduction guidelines. Activity budgets of the wild versus captive T. delacouri populations showed significant differences, although both were in line with typical colobine budgets. Inactivity dominated (wild 75.0%, captive 61.9%), with feeding behaviours also playing a major part (wild 21.3%, captive 29.0%). Sex differences were minimal, but age differences showed that young were more social, and adults spent more time inactive and less time feeding. Both affiliative and antagonistic social interactions were common, with females and young most likely to be involved in affiliative behaviours. Infants showed significant changes in their behaviour as they aged, becoming increasingly social and independent, with allomothering witnessed. Vocalisations were predominantly performed by adult males, with grunts the most common call (61.2%) of the seven identified. An individual’s sex/age class was significantly linked to the type of vocalisation performed. T. delacouri vocalisation behaviour was relatively similar to that of other limestone langurs, although some differences in call structure were found. The released individuals all survived for a minimum of five months before tracking was disrupted for one, showing some wild-like behaviours, although their behaviours were largely atypical. The group quickly separated to travel as individuals, and ranged extensively with the adult male covering 1020ha in 9.5 months. Average day journey lengths were comparable to other limestone langurs (453m–735m), but the individuals did not develop distinct home ranges. A strong diurnal trend in movement showed two peaks at early morning and late afternoon, but minimal seasonal differences were detected. More extensive monitoring is needed to determine whether or not the release was a success, but the project fulfilled an important role as a pilot study to learn how best to conduct a release and how the animals will behave. In reviewing the release it was found to have broadly followed the IUCN guidelines, although gaps were identified suggesting more formalised planning, risk assessments, and consultation was needed. Moving forward, the possibility of translocating existing T. delacouri subpopulations, rather than conducting further captive releases, should be explored as a conservation strategy, along with continuing the effective protection measures in place at Van Long.