The limited information available suggests that the species is tied to evergreen forests of the hills and mountains of western Thailand and adjacent Myanmar (and perhaps further afield). The elevational range of the species is uncertain. In Myanmar evergreen forests are found down to the lowlands because of a relatively wet climate throughout the year, but on the more seasonal eastern Thai side lower elevations are predominantly clothed in drier often deciduous forest types. Its ecology appears to be similar to other muntjacs and it seems to share some of the widespread socio-ecological traits of other muntjacs, i.e. it is predominantly solitary and favours fruits and leaves in its diet (Lekagul and McNeely 1977).

Towards the centre of their known Thai range, in Kuiburi National Park, Fea’s appears to be relatively common in evergreen forest, being camera-trapped more frequently than Northern Red Muntjac even at elevations of 300 m asl. In open forest types, however, Northern Red Muntjac clearly dominates, and Fea’s doesn’t appear to use deciduous forest types much (if at all), for example in Kuiburi National Park it comes right to the edge of open habitat but doesn’t cross the line out of evergreen forest. In contrast, northern red muntjac overlaps with Fea’s in evergreen forest, including high elevation, although Fea’s may be the more common in montane evergreen forest above 1000 m asl (R. Steinmetz pers. comm. 2008, but see note under Distribution about provisional status of such records). Further north in Thung Yai Wildlife Sanctuary the species appears to be commoner (based on cameras, sightings and interviews) than Northern Red Muntjac in forest habitats up to at least 1,000 m asl (there has been little survey work at higher altitudes), although sign abundance of muntjac species certainly declines with increasing altitude, especially above 1,000 m asl (Steinmetz et al. 2008, Wanlop Chutipong pers. comm. 2014, R. Steinmetz pers. comm. 2008). In contrast within Huai Kha Khaeng Wildlife Sanctuary, which lies at a similar latitude to Thung Yai Wildlife Sanctuary, but further east, Fea’s Muntjac is rare even in montane evergreen forest. This may be due to a rain shadow effect which leaves forest in the east drier than forests in Myanmar or close to the border in westernmost Thailand (R. Steinmetz pers. comm. 2008). The animals camera-trapped in Kaeng Krachan National Park probably use both semi-evergreen forest and a narrow band of secondary mixed deciduous forest at elevations of around 350 m and above (Dusit Ngoprasert pers. comm. 2014).

Although the distribution of this species is usually given as from the Isthmus of Kra north and east through southern Myanmar and the adjacent Thai borderlands (Groves and Grubb 1990, Grubb 2005), there was until recently scant evidence of clearly identifiable records (i.e. those accompanied by information on diagnostic characters) from either country (i.e. some range localities appear to be based solely on reports from local people, Tun Yin 1967). Recent discoveries of new species of muntjac and extensions of known range for other muntjac species mean that some previous Thai and Myanmar localities for ‘M. feae’ (see Groves and Grubb 1990) should be viewed with caution. The presence in China remains unconfirmed (see taxonomic note). This leaves only the type locality of east of Moulmein, Myanmar, Muang district (9.08°N, 99.14°E), Surathani Province, and Raheng, Pangna Province (northeast of Phuket island), based on the origin of Thai captive animals and a Gairdner specimen in the Natural History Museum (NHM), London. Two other Gairdner specimens in the NHM, London are incomplete lacking skulls and heads (one of these was reportedly obtained at 300 m asl) and therefore cannot morphologically be confirmed as being this species (R.J. Timmins pers. comm. 2008).

Photographs of several muntjacs from Kaeng Krachan National Park (Thailand) appear to be of this species (R.J. Timmins pers. comm. 2008, based on Dusit Ngoprasert/WCS unpublished data). Camera-trapping in the western forest complex of Thailand has apparently documented the species on several further occasions, and animals have also been observed in the field (Wanlop Chutipong pers. comm. 2014, Anak Pattanavibool pers. comm. 2008, R. Steinmetz pers. comm. 2008), but identification of these animals could be considered provisional because it has been assumed that only two muntjac species inhabit this part of Thailand (M. feae and M. vaginalis), this might not be the case. Animals have usually been identified on the basis of dark pelage and especially the blackish tail (Anak Pattanavibool pers. comm. 2008, R. Steinmetz pers. comm. 2008), but such characters do not rule out some other muntjac species confirmed from neighbouring areas, including, M. gongshanensis and some animals in the, M. rooseveltorum species complex. Dark pelage does not even completely rule out M. vaginalis (R.J. Timmins pers. comm. 2008). The most northerly of the recent records assigned to this species is from Mae Wong National Park in montane forest at 1,450 m asl (16° 4' 46'' N, 99° 7' 4'' E) (Anak Pattanavibool pers. comm. 2008).

One photograph from 1,250 m asl in Hponkanrazi Wildlife Sanctuary in northern Myanmar shows a male with some features similar to M. feae (R.J. Timmins pers. comm. 2008, based on WCS unpublished data), and may refer to this species, particularly in the light of suggestions that the species is in China (see taxonomic note). This site lies far from the generally accepted Myanmar range of M. feae and raises the possibility that the species might have a much wider range in Myanmar than generally assumed. This record is not included in the distribution map (which should be considered highly provisional in any case). This record would also indicate sympatry with M. gongshanensis.

The species is presumed to be found within protected areas throughout its range; in Thailand, it is largely confined to protected areas (because most suitable habitat is now within protected areas), but it almost certainly will be found to persist both in and out of them in Myanmar.

There is a need for taxonomic work, including a re-evaluation of recent field and captive animals (there is a small captive population within Thai zoos) presumed to be M. feae with reference to the holotype, to determine that such animals are indeed this species. Diagnostic characters for the species also need to be clarified in light of recent discoveries of other muntjacs superficially similar in various morphological characteristics. Confirmation in particular is needed of camera trap records from Thailand and Myanmar as referring to this species rather than to any other darkish muntjac, and suggestions of the species' occurrence in China and far northern Myanmar need to be investigated (R.J. Timmins pers. comm. 2006). The species' status, habitat associations, and elevational limits need to be established with greater certainty (R.J. Timmins pers. comm. 2006).