Payne et al. (1985) stated that “available data suggests that this species predominates over the Red Muntjac in low hill ranges and coastal regions”, but Meijaard and Sheil (2008) pointed out that still “no robust quantitative data exist to support this [pattern]”. An incomplete review of altitudes associated with museum specimens by R.J. Timmins (pers. comm. 2008) suggests no readily apparent difference between M. atherodes and M. muntjak in the altitudes of historically collected animals, in fact there appear to have been very few muntjacs collected at altitudes over 900 m, presumably partly reflecting the relatively small area of Borneo above such altitudes (Timmins et al. pers. comm. 2008). There is, however, an opinion by many field observers that Bornean Yellow Muntjac is genuinely absent from mountains (Timmins et al. pers. comm. 2008), yet there are specimen records from over 900 m and camera-trap records from over 1,100 m (R. J. Timmins pers. comm. 2015, Hearn et al. unpub. data).

Based on camera-trapping undertaken between 2008 and 2010 in Sabah in three forest areas all identifiable muntjac photographs were of M. atherodes. The three forest areas were Deramakot (FSC certified and well managed) [below 400 m] in which there were 1,916 trap-days of effort, where muntjacs were recorded from 27 of 48 camera stations, and out of these 18 had confirmed M. atherodes, Tangkulap (more disturbed by conventional selective logging but logging stopped 10 years ago) [below 400 m] in which there were 2,203 trap-days of effort, where muntjacs were recorded from 6 of 64 camera stations, at all six with confirmed M. atherodes, and Segaliud Lokan (also more disturbed by conventional selective logging, only RIL logging is being continued) [below 400 m] in which there were 2,933 trap-days of effort, where muntjacs were recorded from 11 of 58 camera stations, and out of these 10 locations had confirmed M. atherodes. M. muntjak by comparison was not definitely recorded, although single individuals photographed in Deramakot might have been this species and a female and fawn in Segaliud Lokan were probably this species. All three sites are lowland forest reserves and both Deramakot and Tangkulap had high patrol effort by rangers from Sabah Forestry Department during the study, no evidence of hunting was found during the project. In Segaliud Lokan rangers reported that sometimes they encountered hunters in the forest during patrolling, although no evidence of hunting was found during the project (all information from A. Mohamed and A. Wilting pers. comm. 2014).

It was common in Sungai Wain forest, Kalimantan, which spans 30–150 m asl, and clearly out numbers M. muntjak there (G.M. Fredriksson pers. comm. 2008). It also seems to be the predominant species in Sarawak Planted Forests, Bintulu Division, a mix of Acacia mangium plantation and natural forest, where it uses mature and immature plantation, freshly logged forest and relict tall forest, nearby it has also been found in oil palm (Belden et al. 2007, Belden Giman pers. comm. 2008). Since the 2008 assessment the population in this lowland area seems stable (Belden Giman pers. comm. 2014). In this mosaic region the majority of camera-trap photos have come from plantation areas rather than natural forest, and although harvesting has taken place in the plantations this seems not to have affected the muntjac population (Belden Giman pers. comm. 2014). In the Ulu Segama area of Danum Valley Conservation Area, Sabah, mostly at about 300 m Asl, M. atherodes was slightly more common than M. muntjak (Siew Te Wong pers. comm. 2008). Muntjacs were frequently seen, suspected to comprise roughly equal numbers of the two species, in the Batang Ai National Park, Sarawak, which lies mostly at 100–760 m asl (Meredith 1996). M. atherodes occurs down to sea-level (in e.g. Similajau National Park, Sarawak, Duckworth 1997) and up to at least 3,000 feet (approximately 900 m asl), based on specimens in the Field Museum (Chicago, USA, R. J. Timmins pers. comm. 2008). Mohd Azlan J. (pers. comm. 2008) has recorded muntjacs provisionally recorded as this species in hill dipterocarp forest at both Lambir Hills National Park and Lanjak Entimau Wildlife Sanctuary. Field observation suggests that it occurs naturally only below 1,000 m asl, although semi-captive individuals live as high as 3,000 m asl (Belden Giman pers. comm. 2006). Camera-trapping between 2010 and 2012, in 15 sites in Sabah and Sarawak recorded many muntjacs, based on provisional identification of the photos, it appeared that the two species may have had approximately similar abundance below ca 300 m, but M. atherodes abundance declined very quickly with increasing elevation, the preliminary review of the data also suggested that M. atherodes abundance was lower in logged areas than in unlogged areas, while M. muntjak abundance was not discernably affected by logging (Brodie unpublished data, J. Brodie in litt. 2014).

Preliminary camera-trapping results from nine different forest reserves and protected areas across Sabah found high naive occupancy results for Yellow Muntjac from lowland sites, but low occupancy at highland sites, however the highest detections were from over 1,100 m (Hearn, Ross and Macdonald, unpublished data). It uses both primary and secondary forest (Matsubayashi and Sukor 2005, Belden Giman pers. comm. 2008), although no specific information is available on its tolerance to severe degradation and fragmentation. Preliminary analysis of muntjac records from camera-trapping between 2010 and 2012, in eight sites in Sabah and Sarawak, suggest the species might have lower abundance in newly logged forest, whilst M. muntjak abundance potentially was higher, compared with unlogged forest (Brodie unpublished data, J. Brodie in litt. 2014). Preliminary results from 9 different forest reserves and protected areas across Sabah also suggest Yellow Muntjac may be negatively affected by logging whilst Red Muntjac may be less affected (Hearn, Ross and Macdonald, unpub. data). Presumably M. atherodes cannot survive complete forest conversion, but this has not been demonstrated or even, it seems, specifically investigated.

Its diet includes herbs, seeds, grass and fruits (Payne et al. 1985). It is mostly active during the daytime (Payne et al. 1985, Yasuma and Abdullah 1997, Ross et al. 2013) but at least sometimes at night (Duckworth 1997). It lives in small territories and moves either in pairs or alone (Payne et al. 1985). Breeding seasonality is unknown.

This species occurs only on Borneo, and lives throughout the island; many specific localities are given in Groves and Grubb (1982). No information was traced concerning its presence in Brunei but presumably it lives there. It is present in both Indonesia (Kalimantan) and Malaysia (Sabah and Sarawak). The Bornean Yellow Muntjac is known from most of the forest protected areas in Sarawak, including Bako National Park, Lanjak-Entimau Wildlife Sanctuary, Similajau National Park, Lambir Hills National Park, Samunsam National Park, Gunung Gading National Park (in the lowland part), Mulu and Niah National Park, and has also been recorded in logged forest in the Bintulu area and in oil palm adjacent to recently logged forest in north-east of Bintulu (Belden Giman pers. comm. 2008).

Yellow Muntjac is known from many protected areas in Malaysia and Indonesia. Protected area coverage in the lowland plains is still relatively limited in Borneo, and many areas are, in terms of forest ungulate protection, sufficiently small (under 100 sq. km) that long-term persistence cannot be assumed; most places will require continuous hands-on activities against poaching. Even protected areas are not securing lowland forest on current trends, at least in some parts of Borneo: Curran et al. (2004) demonstrated substantial loss of lowland forest within protected areas of Indonesian Borneo. Indonesian forestry law protects all species of muntjac (D. Martyr pers. comm. 2008).

Heavy hunting with shotguns was found to be a severe problem for larger mammals and birds across Sarawak and the need for its control (of guns and of sale of ammunition, with firm legal underpinnings) was recognised in the Master Plan for Wildlife in Sarawak (Wildlife Conservation Society and Sarawak Forest Department 1996). As everywhere, people devise ways for circumventing the controls (illegal trade in bullets and locally made shot-guns, called bekakok, which have no administrative or legal paper-trail) and strong enforcement is required for the foreseeable future.

The long-term persistence of large populations of Bornean Yellow Muntjac, as distinct from isolated populations in well-secured protected areas, will depend upon their ability to use plantation landscapes of oil palm, rubber, acacia and others. Clarification of this is needed to assess the species’s conservation priorities. Of particular concern is the finding from Sabah suggesting that M. atherodes may be more a species of old-growth forest and M. muntjak the predominant species of logged areas (Heydon 1994). It is urgent to determine whether this is a generally applicable pattern across Borneo.

Close liaison with plantation estates and other employers of large numbers of labourers is essential as this offers the best medium to control hunting by employees. As the proportion of plantation rises this will become ever more important. Similar arrangements are needed with logging concession-holders, even more importantly because of the high hunting levels by and/for loggers.

In future studies, ways of enhancing information specific to muntjac species need to be sought and implemented. Many of the studies reviewed here would not, for example, have detected wild changes in the relative proportions of the two muntjac species within their results concerning muntjac spp. This is a major concern, given that M. atherodes is likely to be most everywhere sympatric with M. muntjak. With cheap digital cameras now available, some form of photography, by the hunter, of each animal killed should be considered (and this would be beneficial for other Bornean genera with closely similar species, e.g. chevrotains Tragulus). Most of the grey literature was not available to the present review and much could be learnt from a more comprehensive trawl of it and of active surveyors.