The Javan slow loris Nycticebus javanicus is threatened by habitat decline and is classified as Critically Endangered on the IUCN Red List. Information on its distribution and habitat preferences is still lacking, and so far the distribution of the Javan slow loris has only been quantified via ecological niche modelling based on museum specimens and remotely derived environmental layers. We aimed to refine the modelled predictions and to verify the distribution of the Javan slow loris by collecting up-to-date occurrence data, which are fundamental for conservation and management of the species. Furthermore, we identify variables that predict its presence and give recommendations for future survey sites and conservation actions. From April to June 2012 we collected data on species presence, habitat preferences and levels of disturbance at priority sites throughout Java. We present a map of the predicted distribution of N. javanicus based on a maximum entropy model. We investigated habitat preferences using R (v. 2.14.1). During the study we sighted 52 lorises in 9 out of 14 investigated areas. The amount of bamboo in a forest had a positive effect on the encounter rates. Furthermore, we made 86% of sightings in forest plantations and agricultural areas located outside protected areas, with the majority located in areas with measured high levels of disturbance. We suggest that further ecological studies are needed to understand if and why densities may be higher in anthropogenically disturbed areas.
Simple SummaryWe investigated the niche separation of four macaque species (Macaca arctoides, M. assamensis, M. leonina, M. mulatta) occurring within Nakai-Nam Theun National Protected Area, central-eastern Laos using the environmental niche modelling software MaxEnt. The respective suitable habitat predicted for each species reveals niche segregation between the four species with a gradual geographical distribution following an environmental gradient of, notably, temperature, precipitation, elevation and slope within the study area. This means that the four species seem adapted to different ecological conditions within the area. This information has implications for future research on these species and for their management and conservation.AbstractSpecies misidentification often occurs when dealing with co-existing and morphologically similar species such as macaques, making the study of their ecology challenging. To overcome this issue, we use reliable occurrence data from camera-trap images and transect survey data to model their respective ecological niche and potential distribution locally in Nakai-Nam Theun National Protected Area (NNT NPA), central-Eastern Laos. We investigate niche differentiation of morphologically similar species using four sympatric macaque species in NNT NPA, as our model species: rhesus Macaca mulatta (Taxonomic Serial Number, TSN 180099), Northern pig-tailed M. leonina (TSN not listed); Assamese M. assamensis (TSN 573018) and stump-tailed M. arctoides (TSN 573017). We examine the implications for their conservation. We obtained occurrence data of macaque species from systematic 2006–2011 camera-trapping surveys and 2011–2012 transect surveys and model their niche and potential distribution with MaxEnt software using 25 environmental and topographic variables. The respective suitable habitat predicted for each species reveals niche segregation between the four species with a gradual geographical distribution following an environmental gradient within the study area. Camera-trapping positioned at many locations can increase elusive-species records with a relatively reduced and more systematic sampling effort and provide reliable species occurrence data. These can be used for environmental niche modelling to study niche segregation of morphologically similar species in areas where their distribution remains uncertain. Examining unresolved species’ niches and potential distributions can have crucial implications for future research and species’ management and conservation even in the most remote regions and for the least-known species.
Species distribution models are a key component for understanding a species' potential occurrence, specifically in vastly undersampled landscapes. The current species distribution data for the Assamese macaque Macaca assamensis are outdated, but suggest a patchy distribution in moist broadleaved forests in South and Southeast Asia. Therefore, in this study, we used a species distribution model to explore the potential climatic niche of this species and assess its distribution and potential barriers in 12 South and Southeast Asian countries. We combined primary and secondary species occurrence records from different countries. We applied Classification and Regression Tree (CART), TreeNet (boosting), RandomForest (bagging) and Maximum Entropy (MaxEnt) machine-learning algorithms with elevation as well as 19 bioclimatic variables for the first ensemble predictions ever completed for this species. Our results suggested that the predicted distribution of the Assamese macaque is strongly associated with precipitation of warmest quarter (BIO18), temperature annual range (BIO7) and temperature seasonality (BIO4). Our prediction shows a continuous potential climatic niche of the species from east of the Kaligandaki River in Nepal to Lao People's Democratic Republic. There are also potential niche patches in Bhutan, Southeast China, Thailand and Cambodia, while Pakistan and Afghanistan have no potential niche for the species. We believe that our workflow presents a new conservationoriented open access research template to progress empirical primate conservation worldwide.
The endangered red-shanked douc (Pygathrix nemaeus), endemic to Lao PDR, Vietnam, and perhaps Cambodia, remains little known. The Lao population is highly threatened. To improve conservation prospects of the species there, we here update a status review from 1999. Subsequent literature (mostly not readily available to the outside scientific community) was reviewed critically. Doucs and their habitat in Lao PDR faced continuous, increasing threats in the past 10 years through large development projects and heavy hunting. Many locations with records from the 1990s were not surveyed in the last decade, so douc persistence remains uncertain in them. Given the poor status of the species in Vietnam and Cambodia, the Lao population is surely the world's largest and the best hope for the species' global conservation. Resources for conserving species are very limited in the country, urging prioritization of populations, so available resources have maximum effect. Nakai-Nam Theun and Hin Namno National Protected Areas hold the largest populations of P. nemaeus, but face great threats from hunting. Management of these areas (and secondary priority areas) should focus on control of this illegal activity.
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