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Camera-trap evidence that the silver-backed chevrotain Tragulus versicolor remains in the wild in Vietnam

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In an age of mass extinctions, confirming the survival of lost species provides rare second chances for biodiversity conservation. The silver-backed chevrotain Tragulus versicolor, a diminutive species of ungulate known only from Vietnam, has been lost to science for almost three decades. Here, we provide evidence that the silver-backed chevrotain still exists and the first photographs of the species in the wild, and urge immediate conservation actions to ensure its survival. Interviews with local people and camera-trap surveys have led to the first scientifically confirmed sightings of the silver-backed chevrotain for more than 25 years. The news that this species is not extinct is tempered by major threats of habitat loss and poaching in the region.
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Brief CommuniCation
1Global Wildlife Conservation, Austin, TX, USA. 2Leibniz Institute for Zoo and Wildlife Research, Berlin, Germany. 3Southern Institute of Ecology,
Vietnam Academy of Science and Technology, Ho Chi Minh City, Vietnam. 4NCNP, Ninh Thuan Province, Vietnam. 5Borneo Futures, Bandar Seri Begawan,
Brunei Darussalam. 6University of Queensland, Brisbane, Queensland, Australia. 7Center for the Conservation of Tropical Ungulates, Punta Gorda, FL, USA.
8These authors contributed equally: An Nguyen, Andrew Tilker. *e-mail:
In an age of mass extinctions, confirming the survival of lost
species provides rare second chances for biodiversity con-
servation. The silver-backed chevrotain Tragulus versicolor,
a diminutive species of ungulate known only from Vietnam,
has been lost to science for almost three decades. Here, we
provide evidence that the silver-backed chevrotain still exists
and the first photographs of the species in the wild, and urge
immediate conservation actions to ensure its survival.
The Greater Annamites Ecoregion of Vietnam and Lao PDR
contains one of the highest concentrations of endemic mammal
species found anywhere in a continental setting1; it has a par-
ticularly diverse suite of endemic ungulates1. Unfortunately, the
distribution and population sizes of its endemic ungulate species
have been severely reduced from historical levels due to anthro-
pogenic pressures24. Habitat loss has been a major factor in these
declines1, especially in Vietnam5, but a more substantial threat to
the regions ungulates is the widespread and intensive hunting,
which supplies the thriving wildlife trade in Indochina6,7. Hunting
of terrestrial mammals in the Annamites is primarily accomplished
by the setting of indiscriminate wire snares8,9. Snaring is almost
ubiquitous across the Annamites and has resulted in widespread
empty forest syndrome’10. Exceptionally high levels of snaring have
driven two endemic ungulates, the saola Pseudoryx nghetinhensis
and the large-antlered muntjac Muntiacus vuquangensis, to the
brink of extinction24.
Among the least-known ungulates in the Greater Annamites
Ecoregion is the silver-backed chevrotain T. versicolor11. The silver-
backed chevrotain was first described in 1910 from four specimens
that were obtained near the city of Nha Trang, Vietnam12 (Fig. 1).
The exact localities for the specimens were not provided in the
original publication12, possibly because they were acquired in trade.
Several morphological features distinguish the silver-backed chev-
rotain from the more widespread lesser chevrotain Tragulus kanchil.
The most distinctive external characteristic of the silver-backed
chevrotain is its unique two-tone pelage coloration, with an ocher-
ous-buff anterior and a silver or grey posterior1215. The grey hairs
are conspicuously tipped with white, giving the posterior a grizzled
appearance13. Another distinguishing characteristic is the absence
of the dark transverse throat stripe that is present in the lesser chev-
rotain. In the silver-backed chevrotain, the ocherous throat lines
converge but do not touch; the white ventral coloration is therefore
contiguous from the throat to the underbelly1315.
Other than the four specimens that were used to describe the
species, only a single verifiable record exists11. In 1990, a joint
Vietnamese–Russian expedition in the Gia Lai province obtained a
hunter-killed chevrotain in the vicinity of Dak Rong and Buon Luoi
that was later identified as silver-backed chevrotain13. The specimen
shows the pronounced bi-coloration and non-convergent throat
markings that are characteristic of the species (Fig. 2a). Notably, an
additional 24 chevrotain specimens were collected from the area
between 1978 and 1993 as part of the joint expeditions, but there are
no additional silver-backed chevrotain records13. The Gia Lai speci-
men provides limited insights into the ecology of the species. The
area that the specimen was recorded from was described as mature
lowland semi-evergreen tropical forest13. The record suggests sym-
patry with the lesser chevrotain13, although locality information is
not precise enough to indicate syntopy11. However, the most impor-
tant consequence of the Gia Lai specimen was the confirmation that
the silver-backed chevrotain was still extant13,16.
Following the identification of the Gia Lai specimen, Kuznetsov
and Borissenko13 and Meijaard etal.16 called for follow-up surveys
to assess the distribution and conservation status of silver-backed
chevrotain. In their 2004 publication describing the Gia Lai sil-
ver-backed chevrotain, Kuznetsov and Borissenko noted that,
by the mid-1990s, the area around Dak Rong and Buon Luoi had
undergone severe deforestation13. The authors also suggested that,
over the course of the 1978 to 1993 surveys, hunting pressure had
already resulted in chevrotain declines13. Despite these warnings,
no follow-up search efforts appear to have taken place, and there
were no confirmed records of the species for more than 25 years.
Given the considerable increase in hunting pressure that has
occurred in Vietnam since the early 1990s17, it was unclear whether
the species still existed. Once again, the silver-backed chevrotain
became a lost species.
We conducted targeted surveys to search for the silver-backed
chevrotain. First, we used interview surveys to obtain information
on the occurrence of potential silver-backed chevrotains in the
vicinity of Nha Trang, then conducted follow-up camera-trapping
in the most promising area. Interviews were conducted in three
Vietnamese provinces and covered four forest blocks, only one of
Camera-trap evidence that the silver-backed
chevrotain Tragulus versicolor remains in the
wild in Vietnam
An Nguyen1,2,8, Van Bang Tran 3, Duc Minh Hoang 3, Thi Anh Minh Nguyen3, Dinh Thang Nguyen4,
Van Tiep Tran4, Barney Long1, Erik Meijaard 5,6, Jeff Holland7, Andreas Wilting 2 and
Andrew Tilker 1,2,8*
Content courtesy of Springer Nature, terms of use apply. Rights reserved
... Those that were perceived as high risk included the white-faced plover, Gongshan muntjac (Muntiacus gongshanensis), silver-backed chevrotain (Tragulus versicolor), Williamson's chevrotain (Tragulus williamsoni), and the leaf muntjac (Muntiacus putaoensis). These Cetartiodactyla species are herbivorous ground foragers and are all recent discoveries to science being described from only a small number of specimens (Kloss, 1916;Ma et al., 1990;Amato et al., 1999) and a recent rediscovery in 2018 of the silver-backed chevrotain (Nguyen et al., 2019). Although the primary threats to these Cetartiodacyla species is habitat degradation and poaching Meijaard et al., 2017;Nguyen et al., 2019) any additional pressures from domestic dogs could halt their recovery. ...
... These Cetartiodactyla species are herbivorous ground foragers and are all recent discoveries to science being described from only a small number of specimens (Kloss, 1916;Ma et al., 1990;Amato et al., 1999) and a recent rediscovery in 2018 of the silver-backed chevrotain (Nguyen et al., 2019). Although the primary threats to these Cetartiodacyla species is habitat degradation and poaching Meijaard et al., 2017;Nguyen et al., 2019) any additional pressures from domestic dogs could halt their recovery. Doherty et al. (2017) found that only 30 species across Southeast Asia had domestic dogs listed as a threat by the IUCN Red List. ...
The global population of domestic dogs is estimated at 900 million, making them the world’s most abundant carnivore. Southeast Asia is considered extremely vulnerable to wildlife declines linked to free-ranging dogs, yet few studies report specific cases of dog-wildlife interactions in this region. To overcome this lack of data, the perceived risk to bird and mammal species from free-ranging domestic dogs was modelled using Bayesian networks considering the life history traits of each individual species. The spatial distribution of perceived risk across Southeast Asia was then modelled using a Bayesian network incorporating landscape and demographic characteristics. The number of species considered as high perceived risk in the region was over five times that previously reported. Overall, 11% of bird species and 10% of mammal species were classified as at high perceived risk from free-ranging domestic dogs and eight of these species were listed as Critically Endangered or Endangered by the IUCN Redlist. Furthermore, 50% of mainland Southeast Asia was predicted to be of high perceived risk from free-ranging domestic dogs with only 9% of the region considered as low perceived risk. When empirical data is lacking on IUCN Redlist assessments, incorporation of single threat models can provide missing information critical for accurate evaluation. It is recommended that species are re-evaluated considering domestic dogs as a threat and that this study be used as a template to assist in the development of species action plans and to define key areas where dog management needs to be considered. Management practices should be culturally appropriate and overall promote responsible pet ownership.
... Habitat fragmentation is associated with increasing poaching and logging, and it adversely affects behavioral patterns of animal species, reproduction, and survival of animals (Azlan, 2006;Chaves et al., 2019;Laurance & Arrea, 2017;Ngoprasert et al., 2007). Across its range, wild populations of chevrotain or mouse-deer are declining because of habitat fragmentation, habitat destruction for timber extraction, and poaching (Adila et al., 2017;Heydon & Bulloh, 1997;Jamhuri et al., 2018;Nguyen et al., 2019;Tee et al., 2018). Chevrotain species inhabit primary and secondary lowland rainforests and, in all parts of their range, are hunted for food (Azhar et al., 2014;Luskin et al., 2014). ...
... The mouse-deer populations have been threatened by extensive land clearing and poaching across their known habitat (Azhar et al., 2013;Petersen et al., 2020). Nguyen et al. (2019) suggest that snares laid by hunters have pushed the species to the brink of extinction in ...
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... Camera traps are the standard tool for assessing population status of many terrestrial mammals, describing species distributions, and confirming the presence of some of the rarest terrestrial species (e.g. [1,2]). Camera traps log detections of all species that trigger the sensors, including rare detections of previously unknown species (e.g. ...
... Camera traps log detections of all species that trigger the sensors, including rare detections of previously unknown species (e.g. [2]). It has been assumed that species that overlap in their geographic ranges and are considered sympatric in some areas can be effectively detected under survey designs that do not necessarily take into consideration mark-recapture or occupancy modelling tend to be data hungry and so may be unsuitable for use with sparse 'by-catch' data, leaving only RAIs for making weak inferences about the population. ...
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... This can help to evaluate animal's role in ecosystems and to optimize the conservation programs aimed at reducing the negative effect of human activities and preventing population decrease or species extinction (Caravaggi et al. 2017). Unusual animal behaviour can often be discovered or a species that was believed to be extinct can reappear on camera trap photo (for example, Nguyen et al. 2019), especially when the geographic range of the species is hard to reach. With recent technological advances, modern cameras can now be deployed in the most extreme environments, including rainforests (Bowler et al. 2016), deserts (Tichon et al. 2016), underwater (Williams et al. 2014), and polar regions (Jones et al. 2018). ...
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... While there is a prevailing demand for wildlife for various uses, Gray et al. (2017) argue that indiscriminate hunting in the region persists primarily to satisfy demand for meat from wild animals (hereafter 'wild meat'). Vietnam is one of the countries where wildlife has been gravely affected by unsustainable offtake and where demand for wild meat has been highlighted as a key driver (MacMillan & Nguyen, 2013;Nguyen et al., 2019;Sandalj et al., 2016;Shairp et al., 2016). In Vietnam, poor law enforcement fails to deter poaching and trafficking, while pervasive demand for wildlife continues to drive illegal exploitation (Duckworth et al., 2012;Gray et al., 2017;MacMillan & Nguyen, 2013). ...
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Although deforestation and forest degradation have long been considered the most significant threats to tropical biodiversity, across Southeast Asia (Northeast India, Indochina, Sundaland, Philippines) substantial areas of natural habitat have few wild animals (>1 kg), bar a few hunting-tolerant species. To document hunting impacts on vertebrate populations regionally, we conducted an extensive literature review, including papers in local journals and reports of governmental and nongovernmental agencies. Evidence from multiple sites indicated animal populations declined precipitously across the region since approximately 1980, and many species are now extirpated from substantial portions of their former ranges. Hunting is by far the greatest immediate threat to the survival of most of the region's endangered vertebrates. Causes of recent overhunting include improved access to forests and markets, improved hunting technology, and escalating demand for wild meat, wildlife-derived medicinal products, and wild animals as pets. Although hunters often take common species, such as pigs or rats, for their own consumption, they take rarer species opportunistically and sell surplus meat and commercially valuable products. There is also widespread targeted hunting of high-value species. Consequently, as currently practiced, hunting cannot be considered sustainable anywhere in the region, and in most places enforcement of protected-area and protected-species legislation is weak. The international community's focus on cross-border trade fails to address overexploitation of wildlife because hunting and the sale of wild meat is largely a local issue and most of the harvest consumed in villages, rural towns, and nearby cities. In addition to improved enforcement, efforts to engage hunters and manage wildlife populations through sustainable hunting practices are urgently needed. Unless there is a step change in efforts to reduce wildlife exploitation to sustainable levels, the region will likely lose most of its iconic species, and many others besides, within the next few years. This article is protected by copyright. All rights reserved.
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Camera trapping is a widely applied method to study mammalian biodiversity and is still gaining popularity. It can quickly generate large amounts of data which need to be managed in an efficient and transparent way that links data acquisition with analytical tools. We describe the free and open-source R package camtrapR, a new toolbox for flexible and efficient management of data generated in camera trap-based wildlife studies. The package implements a complete workflow for processing camera trapping data. It assists in image organization, species and individual identification, data extraction from images, tabulation and visualization of results and export of data for subsequent analyses. There is no limitation to the number of images stored in this data management system; the system is portable and compatible across operating systems. The functions provide extensive automation to minimize data entry mistakes and, apart from species and individual identification, require minimal manual user input. Species and individual identification are performed outside the R environment, either via tags assigned in dedicated image management software or by moving images into species directories. Input for occupancy and (spatial) capture-recapture analyses for density and abundance estimation, for example in the R packages unmarked or secr, is computed in a flexible and reproducible manner. In addition, survey summary reports can be generated, spatial distributions of records can be plotted and exported to gis software, and single- and two-species activity patterns can be visualized. camtrapR allows for streamlined and flexible camera trap data management and should be most useful to researchers and practitioners who regularly handle large amounts of camera trapping data.
THE RECENT HANOI Conference on Illegal Wildlife Trade (16 to 18 November 2016) has further highlighted the extent to which Southeast Asia's wildlife is facing an extinction crisis driven by unsustainable levels of commercial hunting ([ 1 ][1]). This threat affects species both outside and within