Journal of Threatened
Taxa | www.threatenedtaxa.org | 26 May 2026 | 18(5): 28739–28749
ISSN 0974-7907 (Online) | ISSN 0974-7893 (Print)
https://doi.org/10.11609/jott.9807.18.5.28739-28749
#9807 | Received 10 February 2026 | Final received 09 March 2026| Finally
accepted 16 April 2026
Large mammal diversity of
Vietnam’s Chu Yang Sin National Park and the first experimental assessment of their
vulnerability to snaring
Minh Thi Anh Nguyen 1 , Thuy Thi Bich
Vo 2 , Quy Tan Le 3 ,
Vy Tran Nguyen 4 , Vu Linh Nguyen 5 , R.J. Timmins 6 & Anthony J. Giordano 7
1 Department of Fish, Wildlife and
Conservation Biology, Warner College of Natural Resources, Colorado State
University, Fort Collins, CO 80523, USA.
2,5 Faculty of
Environment and Natural Resources, Nong Lam
University – Ho Chi Minh City, Thu Duc City, Ho Chi Minh City 70000, Viet Nam.
1,6 Saola Foundation for Annamite Mountains Conservation, Milwaukee, WI 53208, USA.
3 Center for Ecology and Resources,
Institute of Advanced Technology, Viet Nam Academy of Science and Technology, 1B
TL 29, Thanh Loc Ward, District 12, Ho Chi Minh City,
Viet Nam.
4 Institute of Life Sciences,
Vietnam Academy of Science and Technology, District 3, Ho Chi Minh City, Viet
Nam.
4,7 S.P.E.C.I.E.S.
– The Society for the Preservation of Endangered Carnivores and their
International Ecological Study, Ventura, CA 93006, USA.
7 Center for Human-Carnivore
Coexistence, Colorado State University, Fort Collins, CO 80523, USA.
1 Minh.Nguyen@colostate.edu
(corresponding author), 2 thuy.vothibich@hcmuaf.edu.vn, 3 tanquyle.2409@outlook.com,
4 vychim@gmail.com, 5 vu.nguyenlinh@hcmuaf.edu.vn, 6
rjtimmins@saolafoundation.org, 7 species1@hotmail.com
Abstract: The Annamite
Mountains of Indochina have high mammal endemism but also face a mammalian
extinction crisis, primarily from the indiscriminate use of snares. Chu Yang
Sin National Park in the southern Annamites of
Vietnam is one of the few forests in Vietnam where the Critically Endangered Annamite endemic Large-antlered Muntjac is predicted to be
present. The objectives of this study were to experimentally investigate and
quantify the relative impact of snaring on local mammal populations by using
camera trapping, with a focus on muntjac, and to provide a checklist of the
large mammal species of the park. In 2020, a preliminary survey was executed to determine
a study site in the park by observing the prevalence of signs indicative of
large mammals. From December 2020 to February 2021, a 515-m long simulated
continuous snare-line was constructed at the study site by five experienced
local hunters. Camera-traps were then set up along 240-m of the snare-line to
monitor animal movement. A total of 4,747 working camera-trap nights were
logged and recorded the Large-antlered Muntjac and 10 other large mammal
species along the snare-line. It was found that the Large-antlered Muntjac was
more vulnerable to snares relative to the other mammals detected, exhibiting
the highest probability of being ‘captured’ by a snare if an individual animal
encountered the snare-line (p = 0.67). The finding suggests, as already
theorized, that prolonged exposure to a snare-line will greatly reduce local
large mammal populations, because with repeated encounters by an individual
animal, the probability of capture increases close to p = 1. The study
demonstrates here for the first time how some species are potentially more
susceptible to snaring than others. Building on the experimental approach,
future research could yield new insights into managing snare hunting more
efficiently, using more data from other locations and over longer periods.
Keywords: Annamite Mountains,
snare, Large-antlered Muntjac, tropical forests, Indochina, camera-trapping,
poaching.
Abbreviations: CR—Critically Endangered | CT—Camera-Trap |
EN—Endangered | LC—Least Concern | MTAN—Minh Thi
Anh Nguyen | NP—National Park | O—Observation |
p(C/Cr)—the probability of capture by the
theoretical snare noose if the animal crossed the snare-gap, as a function of
all snare-gap crossing events for a species | p(C/E)—the probability of capture by any
theoretical snare-noose if the animal was detected along the snare-line
(snare-line encounter event), as a function of all snare-line encounter events
for a species | p(Cr)—the probability
of crossing the snare-gap if the animal encountered (was camera-trapped
adjacent to) the snare-gap, as a function of all snare-gap encounter events for
a species | p(E)—daily encounter rate with the
snare-line for a species | p(Sn/E)—the probability of encountering at least one
snare-gap if the animal was detected along the snare-line, as a function of all
snare-line encounter events for a species | VU—Vulnerable.
Editor: Bhargavi Srinivasulu,
Zoo Outreach Organisation, Hyderabad, Telangana,
India. Date of publication: 26
May 2026 (online & print)
Citation: Nguyen,
M.T.A., T.T.B. Vo, Q.T. Le, V.T. Nguyen, V.L. Nguyen, R.J. Timmins & A.J.
Giordano (2026). Large mammal diversity of Vietnam’s Chu Yang Sin National Park
and the first experimental assessment of their vulnerability to snaring. Journal of Threatened Taxa 18(5): 28739–28749. https://doi.org/10.11609/jott.9807.18.5.28739-28749
Copyright: © Nguyen et al. 2026. Creative Commons Attribution 4.0 International License.
JoTT allows unrestricted use, reproduction, and
distribution of this article in any medium by providing adequate credit to the
author(s) and the source of publication.
Funding: Conservation Leadership Programme (Project No. 03121520), Saola Working Group – Women for Annamites Conservation Fund (awarded on July 2018), and Nong Lam University – Ho Chi Minh City (Project No.
CS-CB21-MTTN-08), S.P.E.C.I.E.S.
Competing interests: The authors declare no competing interests.
Author details: Minh Thi Anh Nguyen (MTAN) is a PhD candidate at Colorado State University and a research associate at the Saola Foundation, working on mammal conservation in Viet Nam and Lao PDR. Thuy Thi Bich Vo (TTBV) is a lecturer at Nong Lam University – Ho Chi Minh City and a specialist in eco-tourism. Quy Tan Le (QTL) is a field researcher at the Center for Ecology and Resources, Institute of Advanced Technology, Viet Nam Academy of Science and Technology in Viet Nam. Vy Tran Nguyen (VTN) is the head of the Department of Biological Resources, Institute of Life Sciences. Vu Linh Nguyen (VLN) is a lecturer at Nong Lam University – Ho Chi Minh City and possess expertise in and environmental management and engineering. R.J. Timmins is the technical director at the Saola Foundation for Annamite Mountains Conservation, with three decades of fieldwork and conservation experience in Indochina. Dr. Anthony J. Giordano (AJG) holds the position of CEO and Chief Conservation Scientist at S.P.E.C.I.E.S. with more than three decades of field work on carnivores and other mammals; he is also an adjunct professor at the Centers of Human-Carnivore Coexistence, and Collaborative Conservation, at Colorado State University.
Author contributions: MTAN and RJT conceived and designed the study. VLN, MTAN, and TTBV obtained funding. TTBV obtained permissions for the study in CYS, managed logistic and communication with local government and local communities. MTAN and QTL conducted fieldwork, collected and collated data and performed the analysis. RJT identified the survey locations for the pre-survey, drafted the annotated checklist of large mammal species in CYS, conceptualized the data analysis, and revised the manuscript. AJG helped with the writing, significant editing, and revision of the manuscript and advised on data analysis and design. AJG and RJT helped with the structure and content of the paper. AJG and VTN contributed the mammal species list from their wider scale camera trap data in CYS in 2022. MTAN led the writing with QTL’s assistance;
all authors edited and approved the manuscript.
Acknowledgments: We would like to express our gratitude to the Department of Agriculture and Rural Development of Dak Lak Province for supporting our project and granting permission for fieldwork. We sincerely thank Mr. Do Van Lam, Mr. Dang Hung Phi, the Ranger Station 5, especially Mr. Nguyen Viet Hang, and Mr. Nguyen of Chu Yang Sin National Park; Mr. Ket, vice head of Cho village; and local villagers for assisting field survey.
Introduction
Southeast Asia has some of the
richest biodiversity in the world (Hall 1998; Sodhi
et al. 2010). It encompasses four of the 25 global biodiversity hotspots (Myers
et al. 2000), and harbors one of the highest proportions of country-endemic
mammal species (Sodhi et al. 2010). The Annamite Mountains of Indochina are perhaps best known for
their particularly high levels of mammal endemism. This region has seen many
extraordinary recent discoveries of large mammals (Coudrat
2022). Despite receiving significantly increased attention to conservation over
the past few decades, continued survey and research efforts are needed to
thoroughly investigate and monitor the ecosystems of the Annamite
Bioregion (Hughes 2017).
The biodiversity of the Greater Annamites Ecoregion is experiencing a severe mammal
extinction crisis; it also currently has the highest proportion of threatened
species globally, many of which are large mammals (Conrad 2012; Duckworth et
al. 2012). Forming much of the border between Vietnam, Laos, and Cambodia, the Annamites have been experiencing high-intensity illegal
hunting, which is almost singularly driving the depletion of the region’s large
mammal populations; consequently, this is causing the spread of “empty forest
syndrome” (Corlett 2007; Duckworth et al. 2012; Harrison et al. 2016). Given
that illegal hunting is behind these current population declines (Rija et al. 2020), improved knowledge around how it impacts
large mammals differently may be critical to developing effective and nuanced
management responses and more effectively deploying law enforcement.
Large mammals (following the list
noted by Duckworth et al. 1999) are hunted by many means, but primarily
ground-dwelling large mammals are mainly hunted in the Annamite
Mountains using snares, which can be categorized as primarily
“opportunistic/passive”, based on the way hunters use them (Harrison et al.
2016; Dobson et al. 2019). Snares are widely employed across large areas of
tropical forests in the Annamite Mountains to meet
the intensive demand of domestic and international trade markets (Duckworth et
al. 2012). They are easily made from readily available cable wires, cheap to
make and deploy, resilient for months in the forests, require less effort and
skill than using a gun (per unit of catch), are hard to detect, and can be
indiscriminate in what species they catch (Harrison et al. 2016; Gray et al.
2018; Dobson et al. 2019). The use of snares can be particularly effective when
combined with simple “drift fences” made from forest undergrowth, which leads
to a “snare-line” of alternating fences and “snare-gaps” (O’Kelly et al. 2018).
Snare-fences function as a channeling device, encouraging animals to ‘seek’ the
‘gaps’ as a way to pass through the fence, and thus encounter the actual snare
strategically placed in the ‘gap’. Each local hunting team might create several
kilometers of these snare-lines, altogether incorporating hundreds of snares
(Harrison et al. 2016). Despite this massive effort, many animals that get
caught are left to die and rot, especially when snares are not checked in a
timely way or ultimately abandoned by the hunters (Gray et al. 2017, 2018).
Somewhat counter intuitively, snares have been found to be used more
intensively in very depleted forests relative to those with more intact fauna
as a way to catch any remaining wildlife in the area (Branch et al. 2013);
although this may not be a widespread phenomenon, especially in the Annamite Mountains. Among those cultures where hunting rare
wildlife is celebrated, and the established norm is that “wild meat is
healthier than domestic meat”, this extinction driver can be a particularly
serious challenge to overcome (Brodie et al. 2009; Drury 2009; Dobson et al.
2019). The primary driver challenging effective solutions to snaring in the Annamite Mountains is poor legislation and poor enforcement
due to a paucity of government resources and capacity.
In this study, we conducted the
very first experimental effort to investigate the impact of snaring on large
mammal species in the context of events occurring at a snare line. A checklist
of large mammal species is presented for Chu Yang Sin National Park (NP), a
critically important protected area located in the southern Annamite
Mountains range of Vietnam.
Materials
and Methods
Study Area
Chu Yang Sin NP covers an area of
590 km2 in southeast Dak Lak Province in
southern Vietnam with elevations ranging from less than 600 m to 2,442 m at the
summit of Mount Chu Yang Sin (BirdLife International
2010) (Image 1). It is part of an extensively forested landscape in the
southern Annamites, and is connected to several other
protected areas, such as Bidoup–Nui Ba National Park
to the south. Chu Yang Sin NP harbours exceptionally
high biodiversity: its diverse forest types are home to at least 65 mammals,
250 birds, 112 amphibians and reptiles, 81 fish, and 248 butterflies
species (BirdLife International 2010). Chu Yang Sin
NP is one of only a few areas in Vietnam that may still hold a viable
population of Large-antlered Muntjac Muntiacus
vuquangensis, a ‘Critically Endangered’ (CR)
ungulate endemic to the region (Timmins et al. 2016). Although there had been
no further records of the species in the park since 2009, there had also not
been sufficient survey effort in the intervening period. It was believed that
extensive suitable habitat, and its connection with large, protected forested
areas, would have helped increase the probability that Large-antlered Muntjac
persist in the park. It was also determined that for this reason, Chu Yang Sin
NP was a potential site for the present study on the impact of snaring, with a
particular focus on the species.
Snare experimental design
From 27 August to 02 September 2020, Minh Thi Anh Nguyen (MTAN) conducted a pilot survey to identify
a field site inside Chu Yang Sin NP for the experimental snare-line project.
The survey involved walking a 58 km route spanning various habitats at
elevations ranging 750–1,300 m to record large mammal signs. Positive
indications included direct species observations, frequent sightings of fresh
tracks, and a diversity of track types, reflecting the presence of a diverse
assemblage of mammal species. From 10–18 December 2020, work was conducted with
local communities to identify five experienced hunters and learn about their snaring
methods. At the field site, each hunter independently walked us through what a
“real snare-line setup” would entail, even though no actual snares were ever
set. Hunters explained how and where to set up the snare-line and snares, and
this information was carefully recorded. Following this, all the hunters were
asked to agree on where to place a single snare-line (Image 1). A typical
snare-line, of alternating snare-fence and snare-gaps, but without actual
snares, 515 m long, with 70 snare-gaps, was then constructed by the hunters.
101 camera-traps (Covert illuminator) were deployed along 240 m of the
snare-line, beginning at the 28th snare-gap from the starting location of its
construction. Two camera-traps in video mode, one on either side of the snare-line
were used for monitoring animal movement at 35 consecutive snare-gap locations
along the snare-line. The remaining camera-traps in photo mode were used to
monitor animal movement along the snare-fence between snare-gaps; one camera
between successive snare-gaps, with cameras alternating between the two sides
of the snare-fence. This setup allowed us to understand which species
encountered the snare-line, and whether, once encountering the snare-line, an
individual animal subsequently crossed the snare-line through a snare-gap (or
not), and whether (if they crossed) they would have been captured (or not) by
putting a foot within the simulated (theoretical) snare-noose. All camera-traps
were active between 18 December 2020 and 03 February 2021 (a total of 4,747
camera-trap nights, 47 camera-trap nights for each camera-trap unit).
Consecutive photo and video captures less than 30 min
apart for the same species, at any camera-trap location, were treated as a
single snare-line encounter event. If there was more than one animal in a
photograph or other evidence indicating the presence of two animals in the
event, the single event was divided into a number of events equal to the number
of animals. Note, there was no evidence of detections of individual animals at
impossibly distant locations in quick succession, which would have indicated
the presence of spatially separated individual animals being counted as a
single event. The impossible distance is defined as the scenario where two
photos taken within a 1-min interval cannot be captured by two cameras
positioned more than 30 m apart. The exception to this was macaques, which
proved problematic because they occur as groups of multiple individuals; thus,
a minimum number of certainly different individuals were recorded in an event.
But this is probably an underestimate of the number of actual individuals
present at an event. This allowed us to calculate the daily encounter rate with
the snare-line p(E) for an individual animal of each species as the total number
of events divided by 47 camera-trap nights.
For analysis of capture
probabilities resulting from snare-line encounter events, the following
protocol was used. For each snare-line encounter event (i.e., captured by any
camera-trap adjacent to the snare-fence and or snare-gap within a 30-min
period), the outcome of an individual animal’s interaction with snare-gaps, and
the simulated (theoretical) snare-noose at each snare-gap, was recorded. This
included recording how many snare-gaps the animal encountered (snare-gap
encounter event), and for each one, recording firstly whether it crossed the
snare-gap (with potential outcomes recorded as - yes/no/unclear), and secondly,
if it did cross the snare-gap, whether it put a foot within the simulated
(theoretical) snare-noose (with potential outcomes recorded as —
yes/no/unclear). In one snare-line encounter event, an individual animal might
cross snare-gaps multiple times; for this analysis, each was counted as an
independent ‘snare-gap crossing’ event, and for each such event, the outcome
with regard to putting a foot within the simulated snare-noose was recorded. In
the rare event of an animal crossing a snare-gap, and then subsequently in the
same event recrossing the very same snare-gap (from
the opposite side of the fence), this was treated as an additional snare-gap
encounter event, with the outcome relative to the simulated snare-noose
recorded for that event. Probabilities of theoretical capture in the simulated
snare-noose p(C/E) were thus calculated as:
Total number of times the species
crossed snare - gaps for all snare - line encounter events
p(Cr) =
–––––––––––––––––––––––––––––––––––––––––––––––––––
Total number of snare - gaps the
species encountered for all
snare - line encounter events
Total number of times the species stepped
into the simulated
snare noose (was captured) for all snare - line encounter events
p(C/Cr) =
–––––––––––––––––––––––––––––––––––––––––––––––––
Total number of times the species
crossed snare-gaps for all snare - line encounter events
Number of snare - line encounter events the animal encountered at least
one snare-gap
p(Sn/E) =
–––––––––––––––––––––––––––––––––––––––––––––––––
Total number of snare - line encounter
events
p(C/E) = p(Sn/E)p(Cr)p(C/Cr)
where p(Cr) is the probability of
the animal crossing the snare-gap if the animal encountered (was camera-trapped
adjacent to) the snare-gap; p(C/Cr) is the probability of capture by the
theoretical snare-noose if the animal crossed the snare-gap; p(Sn/E) is the
probability of the animal encountering at least one snare-gap per snare-line encounter event; p(C/E) is the probability of
being captured by the theoretical snare-noose per snare-line
encounter event.
Results
and Discussion
Species detected
A total of 4,747 working
camera-trap nights identified a total of 27 species of birds and mammals along
the simulated snare-line; 11 of these were large mammals (excluding squirrels
and treeshrews), two of which are classified as
‘Vulnerable’ (VU), and another as CR (Table 1). In addition, on 02 September
2020, during the pilot survey, a group of Black-shanked Douc Pygathrix nigripes
was observed at 12.31° N, 108.56° E at 0700 h, and a
male Stump-tailed Macaque Macaca arctoides killed by a real snare-line in the
study area (Image 2) was brought back to the camp by team members, but neither
species were captured by the camera-traps.
Although we only surveyed a small
area of forest with the camera-traps (total ca. 240 m x 10 m = 2.40 ha) for 47
total nights, this intensive survey (i.e., a high density of sampling units)
revealed that a good diversity of ground-dwelling large mammals was still
present. This helps confirm Chu Yang Sin NP is still potentially important as a
key protected area for large mammal conservation, especially for Annamite endemics like the Large-antlered Muntjac, which we
successfully documented. Not surprisingly, our list of recorded species
reflects a similar checklist of mammals compiled from a previous camera-trap
survey by BirdLife International (2010) (see Table
1), except for the Sambar Rusa unicolor
and Large Indian Civet Viverra zibetha which we did not detect during the survey. A
similar pattern of occurrence was also found during a recent camera-trap survey
in Chu Yang Sin NP to investigate more widely the occupancy of mammals (Vy T. Nguyen & Anthony J. Giordano, unpub.
data). In this camera-trap survey, Vy T. Nguyen and
Anthony J. Giordano recorded four more mammal species including Long-tailed
Macaque Macaca fascicularis,
Asian Brush-tailed Porcupine Atherurus macrourus, Sunda Pangolin Manis
javanica, and Lesser Chevrotain Tragulus kanchil
(see Table 1 & Image 3a–c). Together, findings from these surveys provide a
representative picture of the diversity and abundance of large mammals still
present in the protected area (Table 2).
This survey is also a commentary
on the impact of illegal hunting on large mammal populations in Chu Yang Sin
NP, especially ungulates and carnivores. It was noted that high levels of
hunting had previously been recorded during surveys by Birdlife International
between 2006 and 2009, especially the use of snares. In 2020, for example,
signs of hunting were observed that included areas of forest undergrowth burnt
for hunting purposes, snare-lines, single snares, and hunting camps; in
addition, hunters were encountered in the forest almost every day during the
pilot survey. The carcass of a rotten muntjac was observed that had died in an
abandoned snare-line, and a male Stump-tailed Macaque that died similarly. Vy T. Nguyen and Anthony J. Giordano recorded a male
Northern Red Muntjac Muntiacus vaginalis
missing his left hind leg on their camera-traps. Prolonged and high intensity
snare hunting is a primary reason for the disappearance of many mammal species
in the region (Harrison et al. 2016). Carnivore species with large home ranges
and long ranging movements, including Leopard Panthera
pardus, Asian Golden Cat Pardofelis
temminckii, Mainland Clouded Leopard Neofelis nebulosa,
and Dhole Cuon alpinus,
are among the most vulnerable to snaring (Gray 2013; Sukmasuang
et al. 2020; Giordano 2022). Although during 2006–2009, surveys conducted by
Birdlife International detected two individuals of Asian Golden Cats in Chu
Yang Sin NP, neither this species nor other larger carnivores, including
Leopard, and Mainland Clouded Leopards, have officially been confirmed in
southern Vietnam for more than a decade (Wilcox et al. 2014; Hoffmann et al.
2019). These species probably have been extirpated from the national park given
that our and the other survey by Vy T. Nguyen and
Anthony J. Giordano (unpub. data) have failed to
detect them in Chu Yang Sin NP.
Populations of large-bodied
ungulates are following the same declining pattern as the country’s large
carnivores, including the Large-antlered Muntjac (Timmins et al. 2015, 2016).
This species has declined rapidly in recent years and has now disappeared from
most of the Annamite landscape (Timmins et al. 2016).
Recent intensive camera-trapping surveys in Vietnam have largely confirmed that
remaining Large-antlered Muntjac populations now appear small, fragmented, and
isolated (Alexiou et al. 2022; Nguyen et al. 2024; Tilker
et al. in press). The presence of Large-antlered Muntjac might suggest a
potential source population for the recovery of this CR species. This can only
occur if illegal hunting can be successfully controlled in the very near
future. Because Chu Yang Sin NP is part of one of the largest remaining
contiguous forested landscapes in Vietnam, connecting with Bidoup–Nui
Ba National Park, Phuoc Binh National Park, other
nature reserves, and state forest companies through its eastern and southern
borders, recovery could have significant ramifications for the species’
long-term future.
Species vulnerability to snares
Among all species we detected, we
recorded the highest encounter rate for Ferret Badger (Melogale
sp.) (p(E) = 0.91); this was followed by Mainland Leopard Cat Prionailurus bengalensis,
East Asian Porcupine Hystrix brachyura, Northern Pig-tailed Macaque Macaca leonina,
Masked Palm Civet Paguma larvata, and Northern Red Muntjac (p(E) varied from
0.17 to 0.11). Western Serow Capricornis
sumatraensis, Eurasian Wild Pig Sus scrofa, and
Northern Common Palm Civet Paradoxurus hermaphroditus had the lowest encounter rates (p(E)
0.02 – 0.06). Large-antlered Muntjac and Yellow-throated Marten Martes flavigula
also showed low encounter rates of p(E) 0.09 and 0.11, respectively (Table 3).
Although our sample size is small
for most species, our data suggested that overall, most ground-dwelling large
mammals are vulnerable to snares in some way. One of the most compelling
results was the apparent effectiveness of the construction of the snare-gap in the
resulting probability of an animal being captured by a snare strategically
placed in the snare-gap. Every snare-gap crossing event recorded (n = 25; Table
3), across all species (n = 8), with a single exception, resulted in the
theoretical capture of the animal. In other words, if an animal crosses a
snare-gap, its probability of capture would appear to be very high. However,
other factors interact to determine the theoretical probability of capture at a
snare-line; for example, Large-antlered Muntjac was the most vulnerable with a
high probability of capture per snare-line encounter
event (p(C/E) = 0.67), thus although the species’ encounter rate was low,
theoretically most animals in the vicinity of the snare-line were likely to
have been captured. Data for the Large-antlered Muntjac came mostly from a
single juvenile animal and one event of an adult female; if the snare-line had
real snares the probability of capture of the juvenile over the entire period
would have been p(C/E) = 1 (100%). In contrast, Ferret Badger was less likely
to be captured per event (p(C/E) = 0.18), the high encounter rate (p(E) = 0.91)
is likely to ensure in reality a high probability of being captured over the
lifetime of the snare-line. Based on our conversations with hunters, we know
that hunters in Chu Yang Sin NP often abandon actual snare-lines after three
months, with no snares ever being removed from the forest. Interestingly,
Western Serow, Northern Pig-tailed Macaques, Eurasian
Wild Pig, and Yellow-throated Marten, all had low capture rates with evidence
visible on the videos and photographs to suggest that behaviour
might play a crucial role in lowering their susceptibility to being captured in
snares; including potentially increased wariness and active avoidance of the
snare-gap, avoidance of crossing snare-gaps for other reasons and crossing the
snare-line by other means (e.g., through the fence or climbing vegetation
adjacent to the snare-line). For example, in the only encounter of Western Serow (one individual) with the snare-line the animal
appeared to show a high level of caution. It appeared to actively avoid
crossing the first three snare-gaps that it met, attempted but failed to get
through/over the vegetation of a section of snare-fence, before finally crossing
the fourth snare-gap, but in a way that avoided placing any of its feet within
the theoretical snare. Yellow-throated Marten tended to move over/through the
snare-line by climbing trees or jumping over the gap directly, rather than
going through the center of the snare-gap (five events with eight
snare-gaps encountered and one crossing but none captured). Northern Red
Muntjac (at least two different individuals encountered) also appeared to show
indications of wariness on the videos and photographs with the probability of
being captured four times lower than Large-antlered Muntjac (p(C/E) = 0.16).
The data for Large-antlered Muntjac was largely based on a single juvenile
animal, and it is plausible that significant differences exist in behaviour between juveniles and adults.
This experiment showed important
empirical evidence supporting the assumption that different species display
different levels of vulnerability to capture in snare-lines. From this it can
be theorized that different species potentially have very different thresholds
to ‘intensity’ of snaring that affect their population viability. Understanding
these thresholds potentially opens the door to better management of the snaring
crisis. Tackling the snaring crisis is a highly complex problem, requiring both
in situ and ex situ interventions at multiple levels, with many different
stakeholders. Knowledge of population viability thresholds can guide
conservation planning by prioritizing the protection of species most sensitive
to snaring. Since snares are difficult to detect and snare eradication efforts
are constrained by limited resources, achieving zero snaring is unrealistic at
least in the short-term. Biodiversity conservation effort and resources
therefore need to be strategically targeted to interventions that prevent local
population extirpation of priority species. To achieve this, continuously
monitoring population viability thresholds in response to ‘intensity’ of
snaring can help answer critical questions about the intensity of snaring that
could be tolerated to prevent species’ local population extirpations.
Determining the effort and spatial scale required for snare removal activities
to reduce snare intensity below species viability thresholds to ensure the
continued survival of large mammal populations is essential for guiding law
enforcement actions. Over the long term, this approach can potentially help
identify priority areas for in situ conservation where targeted snare removal
supports population recovery.
Conclusion
This study is the first of its
kind in the world to use camera-traps in an innovative context to directly
simulate the impact of snare hunting on large mammals. Although the analysis
was simple and the sampling period was short, our
results yield new insights into the snaring crisis and “empty forest syndrome”
especially highlighting the potential differential vulnerability among species.
It is believed that with more replication and analysis of larger datasets based
on similar methods, these approaches may offer promising new opportunities to
address the snaring crisis. Until such time, greatly enhanced, strategic, and
highly focused law enforcement is needed in critical protected areas of Vietnam
to effectively mitigate illegal hunting in key locations and ultimately prevent
widespread extirpation of many species, but particularly the Annamite endemic species.
Table 1. Large mammals recorded
in Chu Yang Sin National
Park.
|
Species |
Scientific name |
IUCN Red List 2023 |
BirdLife International 2010 |
Pilot survey 2020 |
Snare-line experiment 2021 |
Vy T. Nguyen &
Anthony J. Giordano (unpubl. data) |
|
East Asian Porcupine |
Hystrix brachyura |
LC |
|
O |
CT |
CT |
|
Asian Brush-tailed Porcupine |
Atherurus macrourus |
LC |
|
|
|
CT |
|
Northern Pig-tailed Macaque |
Macaca leonina |
VU |
CT |
|
CT |
CT |
|
Stump-tailed Macaque |
Macaca arctoides |
VU |
CT, O |
O |
|
CT |
|
Long-tailed Macaque |
Macaca fascicularis |
EN |
|
|
|
CT |
|
Black-shanked Douc |
Pygathrix nigripes |
CR |
O |
O |
|
|
|
Southern Yellow-cheeked Gibbon |
Nomascus gabriellae |
EN |
O |
|
|
|
|
Sunda Pangolin |
Manis javanica |
CR |
|
|
|
CT |
|
Mainland Leopard Cat |
Prionailurus bengalensis |
LC |
CT |
|
CT |
CT |
|
Large Indian Civet |
Viverra zibetha |
LC |
CT |
|
|
|
|
Northern Common Palm Civet |
Paradoxurus hermaphroditus |
LC |
|
|
CT |
CT |
|
Masked Palm Civet |
Paguma larvata |
LC |
|
|
CT |
CT |
|
Owston’s Civet |
Chrotogale owstoni |
EN |
O |
|
|
|
|
Yellow-throated Marten |
Martes flavigula |
LC |
|
|
CT |
CT |
|
Ferret Badger |
Melogale sp(p). |
LC |
|
|
CT |
CT |
|
Lesser Chevrotain |
Tragulus kanchil |
LC |
|
|
|
CT |
|
Eurasian Wild Pig |
Sus scrofa |
LC |
|
|
CT |
CT |
|
Sambar |
Rusa unicolor |
VU |
CT |
|
|
CT |
|
Northern Red Muntjac |
Muntiacus vaginalis |
LC |
CT |
|
CT |
CT |
|
Large-antlered Muntjac |
Muntiacus vuquangensis |
CR |
CT |
|
CT |
CT |
|
Western Serow |
Capricornis sumatraensis |
VU |
|
|
CT |
CT |
Key: CT—camera-trap detection |
O—direct observation | IUCN—International Union for Conservation of Nature |
CR—Critically Endangered | EN—Endangered | VU—Vulnerable | LC—Least Concern. Note:
Scientific and common names used are following Wildlife Conservation Society
(WCS) 2024. Only species recorded by camera-traps and direct observation in Chu
Yang Sin NP are included
Table 2. Annotated checklist of large mammal
species historically presumed native to Chu Yang Sin National Park.
|
Name used following WCS (2024) |
IUCN Red List scientific name |
Current status |
|
Elephas maximus Asian Elephant |
Elephas maximus |
EX |
|
Tupaia belangeri Northern Treeshrew |
Tupaia belangeri |
Y* |
|
Dendrogale murina Northern Slender-tailed Treeshrew |
Dendrogale murina |
Y* |
|
Galeopterus sp. Indochinese
Colugo |
Galeopterus variegatus |
Y |
|
Nycticebus pygmaeus Pygmy Loris |
Nycticebus pygmaeus |
Y |
|
Macaca leonina Northern Pig-tailed Macaque |
Macaca leonina |
Y* |
|
Macaca arctoides Stump-tailed Macaque |
Macaca arctoides |
Y* |
|
Macaca fascicularis Long-tailed Macaque |
Macaca fascicularis |
?M1 |
|
Trachypithecus germaini Indochinese Silvered Leaf Monkey [including 'margarita'] |
Trachypithecus margarita |
?M |
|
Pygathrix nigripes Black-shanked Douc |
Pygathrix nigripes |
Y |
|
Nomascus gabriellae Southern Yellow-cheeked Gibbon |
Nomascus gabriellae |
Y |
|
Nesolagus timminsi Annamite
Striped Rabbit |
Nesolagus timminsi |
Y |
|
Hystrix brachyura East Asian Porcupine |
Hystrix brachyura |
Y* |
|
Atherurus macrourus Asian Brush-tailed Porcupine |
Atherurus macrourus |
Y |
|
Ratufa bicolor Black Giant
Squirrel |
Ratufa bicolor |
Y |
|
Callosciurus erythraeus Pallas's Squirrel |
Callosciurus erythraeus |
Y* |
|
Menetes berdmorei Berdmore's Squirrel |
Menetes berdmorei |
?M |
|
Tamiops rodolphii Cambodian Striped Squirrel |
Tamiops rodolphii |
? |
|
Tamiops maritimus Eastern Striped Squirrel |
Tamiops maritimus |
Y* |
|
Dremomys rufigenis Red-cheeked Squirrel |
Dremomys rufigenis |
Y* |
|
Hylopetes spadiceus Red-cheeked Flying Squirrel |
Hylopetes spadiceus |
? |
|
Hylopetes alboniger Particolored Flying Squirrel |
Hylopetes alboniger |
? |
|
Hylopetes phayrei Phayre's Flying Squirrel |
Hylopetes phayrei |
? |
|
Petinomys setosus White-bellied Flying Squirrel |
Petinomys setosus |
? |
|
Belomys pearsonii Hairy-footed Flying Squirrel |
Belomys pearsonii |
? |
|
Biswamoyopterus laoensis Lao Giant Flying Squirrel |
Biswamoyopterus laoensis |
? |
|
Petaurista petaurista Red Giant Flying Squirrel |
Petaurista petaurista |
? |
|
Petaurista philippensis Indian Giant Flying Squirrel |
Petaurista philippensis |
Y |
|
Petaurista elegans Lesser Giant Flying Squirrel |
Petaurista elegans |
Y |
|
Manis pentadactyla
Chinese
Pangolin |
Manis pentadactyla |
? |
|
Manis javanica
Sunda Pangolin |
Manis javanica |
Y |
|
Prionodon pardicolor Spotted Linsang |
Prionodon pardicolor |
Y |
|
Prionailurus viverrinus Fishing Cat |
Prionailurus viverrinus |
?M |
|
Prionailurus bengalensis Mainland Leopard Cat |
Prionailurus bengalensis |
Y* |
|
Catopuma temminckii Asian Golden Cat |
Catopuma temminckii |
EX |
|
Pardofelis marmorata Marbled Cat |
Pardofelis marmorata |
Y |
|
Neofelis nebulosa Mainland Clouded Leopard |
Neofelis nebulosa |
EX |
|
Panthera pardus Leopard |
Panthera pardus |
EX |
|
Panthera tigris Tiger |
Panthera tigris |
EX |
|
Viverra zibetha Large Indian Civet |
Viverra zibetha |
Y |
|
Viverricula indica Small Indian Civet |
Viverricula indica |
?M |
|
Paradoxurus hermaphroditus Northern Common Palm Civet |
Paradoxurus hermaphroditus |
Y* |
|
Paguma larvata Masked Palm Civet |
Paguma larvata |
Y* |
|
Arctictis binturong Binturong |
Arctictis binturong |
Y |
|
Arctogalidia trivirgata Small-toothed Palm Civet |
Arctogalidia trivirgata |
Y |
|
Chrotogale owstoni Owston's Civet |
Chrotogale owstoni |
Y |
|
Urva javanicus Javan Mongoose |
Herpestes javanicus |
?M |
|
Urva urva Crab-eating Mongoose |
Herpestes urva |
Y |
|
Canis aureus Golden Jackal |
Canis aureus |
?M |
|
Cuon alpinus Dhole |
Cuon alpinus |
EX |
|
Ursus thibetanus Asian Black Bear |
Ursus thibetanus |
Y |
|
Ursus malayanus Sun Bear |
Helarctos malayanus |
Y |
|
Mustela kathiah Yellow-bellied Weasel |
Mustela kathiah |
Y |
|
Mustela strigidorsa Stripe-backed Weasel |
Mustela strigidorsa |
Y |
|
Martes flavigula Yellow-throated Marten |
Martes flavigula |
Y* |
|
Arctonyx collaris Greater Hog Badger |
Arctonyx collaris |
Y |
|
Melogale personata Large-toothed Ferret Badger |
Melogale personata |
?M |
|
Melogale moschata Small-toothed Ferret Badger |
Melogale moschata |
Y |
|
Lutra lutra Eurasian Otter |
Lutra lutra |
Y |
|
Lutra sumatrana Hairy-nosed Otter |
Lutra sumatrana |
?M-EX |
|
Lutrogale perspicillata Smooth-coated Otter |
Lutrogale perspicillata |
?M-EX |
|
Aonyx cinereus Oriental Small-clawed Otter |
Aonyx cinereus |
Y |
|
Rhinoceros sondaicus
Javan
Rhinoceros |
Rhinoceros sondaicus |
EX |
|
Dicerorhinus sumatrensis Sumatran Rhinoceros |
Dicerorhinus sumatrensis |
EX |
|
Sus scrofa Eurasian Wild Pig |
Sus scrofa |
Y* |
|
Tragulus kanchil Lesser Chevrotain |
Tragulus kanchil |
Y |
|
Rusa unicolor Sambar |
Rusa unicolor |
Y |
|
Muntiacus vaginalis Northern Red
Muntjac |
Muntiacus vaginalis |
Y* |
|
Muntiacus vuquangensis Large-antlered Muntjac |
Muntiacus vuquangensis |
Y* |
|
Bos gaurus
Gaur |
Bos gaurus |
Y |
|
Pseudoryx nghetinhensis Saola |
Pseudoryx nghetinhensis |
? |
|
Capricornis sumatraensis Western Serow |
Capricornis sumatraensis |
Y* |
Key: Y—Presumed native and still
to be present | EX—Presumed to be extirpated | ?EX—Possibly
extirpated | M—Possibly present, but would be very marginal (lowland and open
country species) | ?—Presence and distribution (historically and at present)
are uncertain in the southern Annamites | *—Species
detected during the study | 1—Although detected by Vy
T. Nguyen and Anthony J. Giordani (unpub. data, Image 3B), it is unclear if the species is
native to Chu Yang Sin NP, as animals confiscated from the wildlife trade network
in Vietnam are routinely released in protected areas, and the habitats in Chu
Yang Sin NP are somewhat atypical for this species. Note: Presumed historical
status was determined by R.J. Timmins via reference to a large number of
published and unpublished studies and other data sources on species
distribution and ecological factors relevant to compatibility of habitats in
Chu Yang Sin NP with species native presence; key references included but are
not limited to Dang et al. (1994), Duckworth et al. (1999), Duckworth &
Hills (2008), Francis (2017), Hoffmann et al. (2019), Nguyen & Timmins
(2020), WCS (2024), along with reference to current IUCN Red List species
accounts (iucnredlist.org) to provide further data on most likely current
status.
Table 3. Summary of encounters
with the simulated snare-line (events) and snare-gaps,
crossing the snare-gap and being captured
by the simulated
snare-noose, and capture probabilities.
|
Species |
Total number of events |
Total number of snare-gaps
encounters for all events |
Number of events with at least
one snare-gap encounter |
Total number of times
snare-gaps were crossed for all events |
Total number of captures by
simulated snares for all events |
p(E) |
p(Cr) |
p(C/Cr) |
p(Sn/E) |
p(C/E) |
|
Large-antlered Muntjac |
4 |
9 |
4 |
6 |
6 |
0.09 |
0.67 |
1 |
1 |
0.67 |
|
Mainland Leopard Cat |
8 |
9 |
7 |
4 |
4 |
0.17 |
0.44 |
1 |
0.88 |
0.39 |
|
Common Palm Civet |
3 |
2 |
2 |
1 |
1 |
0.06 |
0.5 |
1 |
0.67 |
0.34 |
|
East Asian Porcupine |
7 |
10 |
7 |
3 |
3 |
0.15 |
0.3 |
1 |
1 |
0.3 |
|
Ferret Badger |
43 |
29 |
28 |
8 |
8 |
0.91 |
0.28 |
1 |
0.65 |
0.18 |
|
Masked Palm Civet |
5 |
6 |
5 |
1 |
1 |
0.11 |
0.17 |
1 |
1 |
0.17 |
|
Northern Red Muntjac |
5 |
5 |
4 |
1 |
1 |
0.11 |
0.2 |
1 |
0.8 |
0.16 |
|
Northern Pig-tailed Macaque |
6 |
5 |
5 |
0 |
0 |
0.13 |
0 |
0 |
0.83 |
0 |
|
Western Serow |
1 |
5 |
1 |
1 |
0 |
0.02 |
0.2 |
0 |
1 |
0 |
|
Eurasian Wild Pig |
2 |
1 |
1 |
0 |
0 |
0.04 |
0 |
0 |
0.5 |
0 |
|
Yellow-throated Marten |
5 |
8 |
5 |
1 |
0 |
0.11 |
0.125 |
0 |
1 |
0 |
For
images. - - click here for full PDF
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