Napu (Tragulus napu)
Tragulus napu, as constituted here (that is, excluding
T. versicolor of Indochina and T. nigricans of the Philippines)
occurs in the Sundaic sub region, extending some way up the Thai–Malay
peninsula, in the following countries: Brunei, Indonesia (Kalimantan, Sumatra,
and many small islands), Malaysia (West Malaysia, Sabah, Sarawak, and many small
islands), Myanmar (far south only), Singapore (Pulau Ubin only), and Thailand
(south only) (Meijaard and Groves 2004, Chua et al. 2009). Grubb (2005) also
included Cambodia, Lao PDR, and ‘Indochina’ in the range of T. napu; but
this was founded on the assumption that because T. versicolor, formerly
considered a subspecies of T. napu, occurred in Vietnam, T. napu must
presumably occur in intervening Lao PDR and Cambodia. There is, for example, a
map of such a conterminous range for T. napu in Corbet and Hill (1992).
There is no evidence of such a distribution and, given the distribution patterns
of other species, absolutely no reason to expect that it would have such a
range, even if T. napu and T. versicolor are closely allied.
Recent surveys in both countries have not suspected the species (Duckworth et
al. 1999, R.J. Timmins pers. comm. 2008).
The northern limit on the Thai–Malay peninsula is not well clarified. Despite fairly intensive camera-trapping in Kuiburi National Park, Thailand (12°N and thus within the generally-assumed range for T. napu), Greater Chevrotain has not been photographed there. It must be scarce in this park if it occurs at all (Steinmetz et al. 2007, R. Steinmetz pers. comm. 2008).
Caution is needed in interpreting modern records of T. napu from anywhere outside the specimen- and photograph-validated range (as presented in Meijaard and Groves 2004); some camera-trap studies seem to have taken an essentially arbitrary attitude on naming their photographs of chevrotains, resulting in published listings of T. napu from, for example, northern Thailand. Because such listings never highlight the significance of such records, let alone discuss them, all are assumed to be in error, and are not discussed further, here.
Brunei Darussalam; Indonesia (Kalimantan, Sumatera); Malaysia (Peninsular Malaysia, Sabah, Sarawak); Myanmar; Singapore; Thailand
Greater Oriental Chevrotain populations are not well studied,
in part reflecting a general lack of research interest in the genus and in part
its almost complete sympatry with the Lesser Oriental Chevrotain, from which
separation requires care under field conditions (Duckworth 1997; Matsubayashi
and Sukor 2005). It seems to be relatively common on at least Borneo (Payne et
al. 1985; Belden Giman pers. comm. 2008). In Thailand, at the northern margin of
its range, it is generally rare (Anak Pattanavibool pers. comm. 2008); for
example, during the flooding of the Chiew Larn Reservoir (Surat Thani province;
about 9°00′N, 98°45′E; 20–130 m asl), only six Greater Chevrotains were
‘rescued’ compared with 172 Lesser Chevrotains (Nakasathien 1989). The genus is
commonly camera-trapped and recorded by signs on Sumatra and in West Malaysia
(Laidlaw 2000; O'Brien et al. 2003; Kawanishi and Sunquist 2004; Azlan 2006) and
in far southern Myanmar (Lynam 2003; the identifications to species should be
disregarded). At the Danum Valley, Sabah (East Malaysia), densities were
recorded as 32–72 animals per km² in primary habitat; they were more scarce in
selectively logged areas, with densities of 6–16 animals per km², indicating a
marked decrease in T. napu in selectively logged forest vs unlogged
(Heydon and Bulloh 1997, Davies et al. 2001). Because population densities of
Southern Red Muntjac Muntiacus muntjak and Sambar Rusa unicolor rose in the
logged areas in this same study, the decline in chevrotains presumably reflects
habitat factors rather than the secondary complication of logging-induced
hunting. Population densities for Tragulus spp. (presumably including this
species) in Taman Negara, Malaysia, were taken to be 0.37–0.83 per km²
(Kawanishi and Sunquist 2004). Duckworth (1995) considered that the chevrotains
demonstrably common at Similajau National Park in 1986 and 1995 were largely or
entirely Greater (see Habitat and Ecology).
Population Trend: Decreasing
Habitat and Ecology:
The Greater Oriental Chevrotain is almost completely sympatric
with T. kanchil, but the degree of syntopy is less clear. In the lowlands
of Borneo both occur but T. napu apparently ranges to higher altitudes (up to at
least 1,000 m asl) than does the latter (Payne et al. 1985). Relevant
comparisons have not been traced for the other main occupied landmasses.
Duckworth (1995) considered that the chevrotains demonstrably common at
Similajau National Park were largely or entirely Greater, but on altitude use as
given in Payne et al. (1985) it would seem surprising if Lesser did not occur.
However, Matsubayashi and Sukor (2005) found at Tabin Wildlife Reserve, Sabah,
that T. kanchil was almost absent from mature forest, all animals in such
habitats being T. napu. Almost all observations from Similajau were from
climax forest. Much more information of chevrotain habitat use in areas of
sympatry is desirable before firm species-level conclusions can be drawn. T.
napu was found typically to range 19 ha in old logged forest and 7 ha in primary
forest, this difference again suggesting an association with primary forest
(Heydon 1994). Heydon and Bulloh (1997) suggested the obligate frugivory of
chevrotains limited their ability to compensate for logging-led loss of fruit
trees by browsing the abundant regrowth of logging areas. The abundance of
Tragulus spp. (T. napu and T. kanchil combined, with no information on the
proportions or even confirmation that both species were present) was higher
(strongly statistically significantly so) in areas within 1 km inside the
boundary of Bukit Barisan Selatan National Park, Sumatra than in the interior of
the park, suggesting higher numbers in somewhat encroached habitat. Also at this
site, Tragulus was more then nine times as abundant in areas of the park with
low than with high human population density within 10 km of the park boundary,
suggesting limited resilience to human presence, presumably the effects of
hunting (O'Brien et al. 2003); note that it is not confirmed that this
information refers, even in part, to T. napu. The genus (presumably
including this species) was ubiquitous in a study of virgin jungle reserves
(VJRs) of West Malaysia which paired each of seven VJRs with a nearby
unprotected area with seriously encroached habitat (Laidlaw 2000). The ability
of T. napu to use plantations is probably low, because all (the
admittedly relatively few) sources agree that it does not persist well in
secondary or logged forest. Moreover, Belden Giman (pers. comm. 2008), in
extensive observations at Sarawak Planted Forests, Bintulu, Sarawak, has never
recorded T. napu in any of the blocks of monoculture plantations there, despite
many records of T. kanchil. Given the pace of conversion of forests to
plantations across the rane of T. napu, clarification of its degree of
plantation use is urgent.
Competition with T. kanchil is not pronounced. In Tabin Wildlife Reserve, Sabah, T. napu was largely confined to mature forest with T. kanchil only in immature forest (Matsubayashi and Sukor 2005). In unlogged forest at Danum Valley, Sabah, T. napu was significantly more common than T. kanchil, but following logging, the numerical dominance of T. napu declined, and in 2–5-year-old regrowth T. kanchil was the commoner species. By 12 years post-logging, T. napu had reasserted its numerical predominance (Heydon 1994). Tragulus spp. are generally thought to be nocturnal, and at two sites in Borneo, they comprised over half the contacts of spot-lighting surveys (Duckworth 1997), but Matsubayashi and Sukor (2005) found substantial amount of both day- and night-time activity in this species. Duckworth (1997: 186–187) pointed out that most chevrotains spotlight in Similajau National Park, Sarawak, (identified as T. napu) were sitting around resting. The related T. kanchil was considered highly solitary by Matsubayashi et al. 2006) and this may also be somewhat true for T. napu; Duckworth (1995: 177) observed chevrotains identified as T. napu 14 times, of which 12 records involved singles and two involved duos in apparent association. Collation of information from general sources suggests the following, but the contribution of information from T. nigricans to these conclusions is unknown, so their reliability for T. napu s.s. should be considered preliminary. Females gestate for 152–155 days and give birth to one or, rarely, two young. Young wean at 2–3 months, and reach sexual maturity at 4.5 months. Animals live up to 14 years. The female can be pregnant throughout her adult life, often having just an 85–155 minute 'breather' between giving birth and becoming pregnant again. The young are born fully developed, and can stand within 30 minutes of birth. Mothers nurse their young standing on three legs. They are generally solitary.
Hunting and habitat loss occur at high levels almost
throughout Greater Chevrotain’s range, but the species is said to be relatively
resilient. However, few data to support this assessment have been traced,
particularly because most key studies have not within the Sundaic region
identified chevrotains to species. Thus, while clear that the genus remains
widespread and common in the face of these threats, there seems to be little
publicly available evidence that T. napu specifically does so, and reasonable
evidence that it is not very adaptable to forest degradation (see Habitat and
ecology). However, on the assumption that most chevrotains above 100 m asl on
Borneo are this species rather than T. kanchil, Borneo at least retains
large populations. Greater Oriental Chevrotain is extinct on Singapore (K. Lim
pers. comm. 2008), although the relative contributions of hunting versus habitat
perturbation are not known. Poaching pressure in Kerinci-Seblat National Park,
Sumatra, among snared ungulates was greatest for muntjacs and lowest for
chevrotains, as assessed by diameter of the cable (Linkie et al. 2003).
Chevrotains were scarcer in areas of higher human use (and thus hunting) of
Bukit Barisan Selatan National Park, Sumatra (O'Brien et al. 2003; see Habitat
and ecology). Bennett et al. (2000) profiled the effects of hunting in both
Bornean states of Malaysia (Sarawak and Sabah), each with eight study areas,
upon chevrotains (not distinguished to species) through a lengthy hunting study
in February 1993 to June 1995. They constituted 8–9% of animals killed. No
direct or index measure of chevrotain densities was possible at these sites to
determine what effects, if any, such heavy hunting was having on chevrotains.
Chevrotains are among the most favoured wild meat by inhabitants of the Sarawak
Planted Forests area, Bintulu, Sarawak, after Sambar Rusa unicolor and wild pigs
Sus (Belden Giman pers. comm. 2008).
Hunting and habitat loss occur at high levels almost throughout this species' range. Adequate legal basis exists in all range states to control both threats (through protected areas and regulations governing wildlife trade and hunting). The chief need is for effective translation of these laws into action. There are no obvious species-specific needs additional to general consolidation of protected areas and enforcement of hunting and wildlife trading laws. The paucity of Sundaic studies determining chevrotains to species shows admirable caution but hinders assessments of this species’s status. Better data would be useful to confirm the opinion-based conclusion here that this is a resilient species, and to investigate further habitat use, in areas where it overlaps with T. kanchil and in those (probably, primarily at higher altitude) where it does not.