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Tragulus williamsoni

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Taxonomy [top]

Kingdom Phylum Class Order Family
ANIMALIA CHORDATA MAMMALIA CETARTIODACTYLA TRAGULIDAE

Scientific Name: Tragulus williamsoni
Species Authority: Kloss, 1916
Common Name(s):
English Williamson's Chevrotain, Williamson's Mousedeer
Taxonomic Notes: Meijaard and Groves (2004) wrote that "Although [T. williamsoni] is based on one specimen only, we provisionally assign it to species level because of its very large size"; previously it was almost universally placed as a subspecies of T. kanchil, usually under the name T. javanicus (e.g. Lekagul and McNeely 1977). Because it is known only from one specimen, it is difficult to determine the taxonomic significance of its large size (compared with T. kanchil and T. javanicus). This is compounded by the lack of available specimens of chevrotains from close to the type locality of T. williamsoni (in the northern highlands of Thailand) to test for conspecificity with T. kanchil and, if the taxon is validated, to determine the nature of the boundary with T. kanchil (sympatry or parapatry). More material is needed both of T. williamsoni and of T. kanchil, if it occurs, from the northern highlands of South-east Asia and adjacent southern China, for a more informed judgment. Although Meijaard and Groves (2004) considered T. williamsoni to be “very large”, this is under conditions of museum measurement (“larger than the means of all other mouse-deer from the Asian mainland...for most of the individual measurements it was also larger than the maximum values for the ....mainland Asia T. kanchil subspecies”. No difference is likely to be apparent if measurements are not taken, so records hitherto assigned to T. kanchil (mostly under the name T. javanicus) from areas of northern South-east Asia and China which have not been validated by specimens must now be regarded as indeterminate. Even measurements need careful interpretation: Kuznetzov and Borissenko (2004) measured skulls from southern Viet Nam (far from the holotype of T. williamsoni) of what they assigned to T. kanchil and found sizes exceeding those documented for Indochinese T. kanchil by Meijaard and Groves (2004) and even approaching those of T. williamsoni. They underlined how differences between individual people in style of skull measurement can be as significant as actual differences size in terms of apparent size results when measuring skulls of similar species. If T. williamsoni is a valid taxon, confirming additional specimens as such will clearly require great care.

Assessment Information [top]

Red List Category & Criteria: Data Deficient ver 3.1
Year Published: 2008
Date Assessed: 2008-06-30
Assessor(s): Timmins, R.J., Duckworth, J.W. & Meijaard, E.
Reviewer(s): Black, P.A. & Gonzalez, S. (Deer Red List Authority)
Justification:
The species' status cannot be assessed due to some taxonomic uncertainty and a paucity of data on extent of occurrence, threats, habitat preferences and altitudinal range. Speculation about the extent of occurrence is prevented by the paucity of data on Tragulus populations in northern highland areas of Thailand, China and Indochina, thereby forestalling application of this Red List criterion. While hunting is heavy in the species' likely range and habitat perturbation is increasing there, the lack of understanding of the population-level effects on the species rule out inferential application of decline-based criteria. Although until very recently there was no record since 1916, there seemed no reason to consider it a Possibly Extinct Candidate, because the lack of records is assumed to reflect the lack of suitable survey (see above).

It is likely that even modest amounts of current information would allow categorization of the species, and that it would warrant either Near Threatened or one of the threatened categories.

Geographic Range [top]

Range Description: Tragulus williamsoni is only known from the holotype which was collected at Meh Lem, Muang Pre, Song forest of Thailand (18°25'N, 100°23'E); also referred to as Me Song (Meijaard and Groves 2004). The species' true range cannot be determined until more material of Tragulus is examined from the northern highlands of South-east Asia and adjacent southern China; this will require serious further collecting. The lack of subsequent records of T. williamsoni may largely reflect the paucity of collecting in recent decades, the fact that most surveyors and other biologists in the region have been unaware of the taxon’s distinctiveness, and so have not sought it and may well have overlooked it when they came across it. The collections in China and Thailand (and Viet Nam), where additional specimens of T. williamsoni would be most likely to be found, were not studied by Meijaard and Groves (2004) and remain to be critically examined. Thus, the current restriction of records to the type locality cannot be seen as even weakly indicative of a genuinely restricted distribution. The type locality is west of the Mekong and this river is a biogeographic barrier for some species (Meijaard and Groves 2006, Timmins and Duckworth in press) but it should not be assumed to be so for T. williamsoni. While all specimens (about four) examined from east of the Mekong from localities lying along the southern edge of the northern highlands of Indochina have all proved to be T. kanchil (E. Meijaard pers. comm. 2008), this is a small sample size and does not represent the actual highland area. Most significantly, two specimens from Yunnan province (China) here provisionally assigned to this species (below) come from east of the Mekong. Specifically, given the known presence of Tragulus across a large area of the northern highlands of Lao PDR far from any specimens validated to either T. williamsoni or T. kanchil (Bergmans 1995, Duckworth et al. 1999: 269; Johnson et al. 2003), it is an open question whether T. williamsoni occurs in Lao PDR. Records from the area of north Lao PDR west of the Mekong (Xaignabouli province), based on village interviews but surely reliably indicative of the genus given the strength of the distribution pattern in Lao PDR from this nation-wide dataset (Duckworth et al. 1999: 269), should be priorities to determine to species. Two specimens from Mengla, Xishuanbanna, southern Yunnan province, China (21°32’ N, 101°36’ E) appear to be T. williamsoni on the basis of some skull measurements (the skulls are damaged and knowledge of intraspecific variation in this taxon is obviously weak given only a single specimen from the region of the type locality) (Wang Yingxiang in litt. to E. Meijaard pers. comm. 2008). Tragulus, nominally identified as T. javanicus (=, here, T. kanchil) occur in northern Viet Nam (Dang Huy Huynh et al. 1994), but the distributional map suggests records are likely to have been from the lowlands.

The type locality and the data from China suggest that this species might be associated with highland terrain and higher altitudes than T. kanchil, but this is no more than speculation at present. The genus Tragulus has an odd northerly distribution within South-east Asia, being entirely unrecorded from Myanmar (except the far south) (Tun Yin 1967, Lynam 2003, Meijaard and Groves 2004; Shan state, adjacent to highland areas of northern Lao PDR and Thailand which hold the genus, has not been well investigated and may yet be found to hold the species), apparently absent from the east of Lao PDR’s northern highlands (and the central northern highlands remain to be investigated; Duckworth et al. 1999: 269), present in northern Viet Nam but quite probably restricted to the lowlands (see above), and penetrating China only in the far southwest, in Xishuangbanna prefecture of Yunnan Province (Smith and Xie 2008). The T. williamsoni holotype appears to be the only Tragulus record critically identified to species from this extensive area, making the absence of confirmed T. kanchil records biologically uninformative.
Countries:
Native:
Thailand
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The population status is unknown, but there are indications of the status of Tragulus as a genus from the northern highlands of South-east Asia. Chevrotains (which may or may not comprise or include T. williamsoni) are clearly common in and around Nam Ha National Protected Area, Lao PDR: they are one of the most commonly hunted (mostly with snares, some with guns), eaten, and traded wildlife. Only 3% of households interviewed considered the genus to be in decline (Johnson et al. 2003) (However, because no wildlife taxon was considered to be in decline by more than 13% of households questioned and even such heavily traded species such as pangolin, otter, tiger and sambar were assessed as being in decline by fewer than a tenth of villagers questioned, there was either a major mismatch of villagers’ perceptions with reality or of surveyors’ records with villagers’ beliefs: so nothing should be concluded from this statement of villagers’ perception of decline.) An intensive hunting study of two villages in Thailand’s northern highlands in the general areas of the type locality did not record the species at all (Tungittiplakorn and Dearden 2002). Given the genus’s prominence in hunting bags when it is present, it can safely assumed to be absent from around the two study villages; and given that the study was specifically investigating species extirpation sequence, it is safe to assume that it never occurred in these two areas. Neither village is located precisely. This suggests the genus’s populations may be localised in Thai northern highlands.
Population Trend: Decreasing

Habitat and Ecology [top]

Habitat and Ecology: Its habitat is currently speculated to be evergreen forest, though it is essentially unknown. Meijaard and Groves (2004) thought it might be restricted to higher elevation forests; this is plausible but currently entirely speculative (see above). Other Tragulus species appear to be associated especially with forest microhabitats with dense undergrowth, such as especially edges (see other species’ 2008 Red List accounts).
Systems: Terrestrial

Threats [top]

Major Threat(s): There is no applicable knowledge of threats, because even though hunting and habitat change patterns in the region can be presented even without resolution of the species' actual distribution, there is no information whatsoever on the effects these patterns have on the genus. The northern highlands of Thailand, China and Indochina are generally subject to heavy hunting from local people, often with high densities of snares suitable to catch animals like chevrotains. At least in Indochina, chevrotains are a favoured quarry (Tungittiplakorn and Dearden 2002; Johnson et al. 2003; Anak Pattanavibool pers. comm. 2006; R.J. Timmins pers. comm. 2008). There is an enormous trade in wild meat from rural areas to markets in adjacent towns, those further afield, across international borders and up into, particularly, Viet Nam and China (e.g. Compton and Le Hai Quang 1998; Compton et al. 1999; Noreen and Claridge 2001). However, whether the species would be significantly threatened by such activity is unknown (R.J. Timmins pers. comm. 2008); it might be one of several ungulates that is remarkably resilient. Despite extensive forest disturbance through shifting cultivation in the species' likely range, habitat-related factors may only have been a relatively minor threat to date, if indeed one at all, given the adaptability of the genus to disturbed and secondary habitats (see other species 2008 Red List accounts). This may be changing fast, because the northern highlands of Lao PDR and adjacent areas are currently seeing heavy conversion of forest (albeit mostly secondary and regrowth, which is all that survives in large areas) to plantations to supply the burgeoning Chinese market for rubber. This will have three linked negative effects on ground-dwelling mammals: direct loss of forest habitat, decline and destabilisation of the forest resource-base (including wild-meat sources) for subsistence-level communities, leading to higher hunting levels in remaining wildlife areas (C. Wood pers. comm. 2005 to J.W. Duckworth, based on emerging patterns across several provinces in Lao PDR’s northern highlands); and shrinkage of the size of natural habitat blocks and thereby reduction and, locally, loss, of the cushioning effect which allows hunted wildlife to persist in large blocks of forest when eradicated from smaller blocks. Although this habitat trend is not in doubt, it is entirely unknown to what extent rubber plantations will support chevrotains in northern South-east Asia, so effects on the genus cannot be predicted. Hunting and habitat loss are provisionally seen as threats to the species, pending actual data.

Conservation Actions [top]

Conservation Actions: Much more research is required; in particular it is a priority to reassess the taxonomic validity of the species. This requires collecting more material of Tragulus from across the northern highlands of South-east Asia but an immediate and possibly highly informative first step would be critical examination of material already held in collections in the region (particularly China, Thailand, and Viet Nam). Distributional surveys focusing on relative species status (of T. williamsoni and T. kanchil) and altitudinal range, perhaps focussed on acquiring remains from hunters, should be carried out in widely spaced localities in northern Thailand, northern Lao PDR (both east and west of the Mekong), southern China, and perhaps also Viet Nam and Shan State, Myanmar (such surveys could sensibly be combined with those for other taxa, for instance Muntiacus spp.).

Because of the species' presumed external similarity to T. kanchil, it will be necessary to collect specimens in order to distinguish the two species. Most unfortunately it seems likely that while data collected from camera-trapping studies will be helpful in establishing the genus’s distribution and conservation status, until specimen-based clarification of ranges, particularly the extent of geographic and ecological overlap, is clear, species-specific conclusions will not be possible from this method. Similarly, hunting studies such as those of Johnson et al. (2003) which do not systematically collect voucher specimens will be of limited use in determining this species' conservation needs.
Because this species might have a small range it might therefore be a conservation priority and clarification of chevrotain status in degraded and fragmented forests and in plantations in its possible range is urgently needed.

Many protected areas exist within the northern highlands of South-east Asia. Whether any hold the species is as yet unclear. Few of those that might do are effectively reigning in hunting levels.

Citation: Timmins, R.J., Duckworth, J.W. & Meijaard, E. 2008. Tragulus williamsoni. The IUCN Red List of Threatened Species. Version 2014.2. <www.iucnredlist.org>. Downloaded on 30 October 2014.
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