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 than 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 range 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 spotlit 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.

Tragulus napu, as constituted here (that is, excluding T. versicolor of Indochina and T. nigricans of the Philippines) occurs in the Sundaic subregion, 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 Viet Nam, 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.

Hunting and habitat loss occur at high levels almost throughout this species’s 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.