Hog Deer is usually reported from habitat consisting of wet or moist tall grasslands, often associated with medium- to large-sized rivers (Bhowmik et al. 1999, Biswas and Mathur 2000, Biswas 2004), and appears to reach its highest densities in floodplain grasslands (Seidensticker 1976, Dhungel and O’Gara 1991, Karanth and Nichols 2000, Odden et al. 2005). It avoids closed-canopy forest, but will use coastal grasslands (e.g., Peacock 1933). Johnsingh et al. (2004) considered Hog Deer to be an obligate grassland species in the Terai Arc Landscape of India, and studies in India and Nepal have shown a preference for grasslands dominated by Imperata cylindrica (Biswas 2004 and references therein). Similar alluvial floodplain grassland seems to be used in Thailand and Indochina (Maxwell et al. 2007, Clark undated, R.J. Timmins pers. comm. 2006). In Bardia National Park, measured densities were much higher in the floodplain association than in the riverine association, and no Hog Deer was found in adjacent Sal Shorea robusta forest at all (Odden et al. 2005). In the hilly areas of northeastern India, it occurs in small grassy areas, light woodland and abandoned juhms with grass (Choudhury 2013, A. Choudhury pers. comm 2014). The highest elevation where it has been recorder was 1,500 m asl in Nagaland (Choudhury 2013). These seem to be marginal habitats supporting only low-density subpopulations (A.U. Choudhury pers. comm. 2006): they may historically have been primarily ‘sink’ subpopulations. The remnant population in Bangladesh is located in grassy, lightly wooded, hill country (Khan 2004). In the southwestern coastal lowlands of Cambodia, where apparently the species was once common (Dumas 1944), the species appears to use an open habitat mosaic including brackish Eleocharis sedge marshes and ‘upland’ tall Imperata cylindrica grasslands, and areas of scrubby open secondary woodland interspersed with ‘dry’ short stature grasslands; cane-grass floodplain grasslands are essentially absent in this region (Timmins and Sechres 2010, R.J. Timmins pers. comm. 2014). The reintroduced semi-wild subpopulations in Thailand occupy a variety of habitats for which there is no evidence of use by wild subpopulations in Thailand, Lao PDR, Viet Nam or Cambodia. One of the few detailed historical accounts of an abundant subpopulation in Southeast Asia was from extensive tall floodplain grasslands in the Dong Nai catchment, Viet Nam (Clark undated). Hog Deer is a primarily a grazer of young grasses, particularly Imperata cylindrica and Saccharum spp.; it also takes herbs, flowers, fruits and browse (young leaves and shoots of shrubs; Bhowmik et al. 1999, Dhungel and O’Gara 1991, Bisawas 2004, Wegge et al. 2006). It is much more a grazer and less a browser than is the Sambar Rusa unicolor. Animals occur in scrub and cinnamon gardens in Sri Lanka, where they cause considerable damage to home crops (McCarthy and Dissanayake 1992).

Where undisturbed, Hog Deer tend to be crepuscular, with significant day-time activity and some at night, especially in the hot and wet seasons (Dhungel and O’Gara 1991). In some areas it seems to have become more nocturnal and solitary (e.g., Cambodia; R.J. Timmins pers. comm. 2008), presumably through hunting pressure. The main social group is a female and fawn. When more Hog Deer are together, they do not form a strong "unit", fleeing when flushed in different directions rather than as one. In Chitwan, aggregations of up to 20 animals have been observed feeding on new shoots following fire (Dhungel and O’Gara 1991). In Kaziranga, aggregations of 40–80 animals are frequently seen on grazing grounds created by Great Indian Rhinoceros Rhinoceros unicornis and/or short grasslands near large water bodies (N.S. Kumar pers. comm. 2008, based on observations in 1996). Home ranges vary widely in size, but average about five to 70 ha, depending on how the range is defined (Dhungel and O’Gara 1991, Odden et al. 2005). In Chitwan, Hog Deer is essentially sedentary (Dhungel and O’Gara 1991), but in cultivated landscapes (Sri Lanka) movements are reported to be influenced by agricultural seasons (McCarthy and Dissanayake 1992). Hog Deer moves into higher-lying grasslands in response to monsoon flooding in India, Myanmar and presumably throughout their range (Peacock 1933, Q. Qureshi pers. comm. 1995). The rut is during September–October in Nepal and India and (presumably based on captives) during September–February in China. One to two fawns are born during April–May in Nepal and during April–October in China. Gestation period is 220–230 days (Dhungel and O’Gara 1991, Sheng and Ohtaishi 1993). Fawns wean at six months, reaching sexual maturity at eight to 12 months. The maximum recorded life span is 20 years.

Hog Deer historically occurred from Pakistan, throughout northern and northeastern India, including the Himalayan foothill zone, east across non-Sundaic Southeast Asia and, marginally, southern China (southern Yunnan province), but it is now reduced to isolated subpopulations within this range. It is almost extirpated from east of Myanmar. It is extinct in Thailand (where it has, however, been reintroduced) and almost certainly in Viet Nam and Lao PDR (Humphrey and Bain 1990, Duckworth et al. 1999, Tordoff et al. 2005, R.J. Timmins pers. comm. 2008). Very small numbers have been found recently in Bangladesh and in five areas in Cambodia (Khan 2004, Maxwell et al. 2007, Timmings and Sechrest 2010, Brook et al. 2015). A report on the internet in 2007 from China turned out to refer to a young Sambar (B.P.L. Chan pers. comm. 2012). Hog Deer still probably occurs in at least several areas of Myanmar (J.W. Duckworth in litt. 2008, from various sources), and localised subpopulations survive in northern and northeastern India, Nepal, Bhutan (few recent data) and Pakistan (status uncertain; Biswas and Mathur 2000, Biswas 2004). Hog Deer has been introduced (not mapped) into Australia (specifically the coastal regions of south and east Gippsland; Moore and Mayze 1990), the United States (Texas, Florida and Hawaii; Grubb 2005) and it is presumed introduced into Sri Lanka; however there remains some discussion as to whether the species is native or introduced into Sri Lanka (Vishvanath et al. 2014) so the species is retained here as non-native until definitive information is received.

Hog Deer is fully protected in Bangladesh, India, and probably most or all other range states. One subspecies is listed on CITES Appendix I as Axis porcinus annamiticus.

Wetlands, especially floodplain grasslands, have traditionally been ignored by the protected area systems and other conservation initiatives of Lao PDR, Viet Nam and Cambodia (Tordoff et al. 2005, R.J. Timmins pers. comm. 2006). Most of the area supporting the single known subpopulation in Cambodia has been proposed for protected area status, but the situation is complicated by the inclusion of agricultural lands and traditional use areas of local people, and the high human population immediately nearby (Maxwell et al. 2007, Bezuijen et al. 2008); as of 2014 no protected status has been granted to this area (R.J. Timmins pers. comm. 2014). As soon as the subpopulation was found, a small conservation programme with external funding from WWF was started to support a small number of forestry rangers and local guardians to carry out patrolling and community outreach activities, in addition to basic research. These measures ceased due to a combination of factors including lack of funding and motivation in part brought on by the failure to establish the site as as protected area in c. 2008 (R.J. Timmins pers. comm 2014), but may be re-established by WWF with the Forestry Administration (Brook et al. 2015). Probably the bulk of the southwest Cambodian subpopulation lies outside of protected areas, although there was marginal inclusion within one protected area Botum Sakor National Park and the proposed Southwest Elephant Corridor, with confirmed occurrence near to the Dong Peng Multiple Use Area. However, in all of these areas deer are in peripheral areas, while conservation attention, is focused on extensive forest at their heart (R.J. Timmins pers. comm. 2014).

In 2013 a national action plan was developed for the conservation of Hog Deer in Indochina. The plan recommends securing the Kratie subpopulation and one of the Southwest subpopulations (Andoung Teuk) thourgh establishing anti-poaching patrols, engaging local communities in the conservation oh Hog Deer, stabilizing land-use and formalizing protection for the sites. It also recommends the establishment of a conservation breeding programme for the species from ideally to other known small and isolated subpopulations in the Southwest (Forestry Administration, 2014). The plan has not yet been approved by the Ministry of Agriculture, Forestry and Fisheries. To ensure protection and survival of animals, consideration should be given as to whether it would be useful for part of the areas to be strategically fenced to help deter poaching, agricultural encroachment and predation by dogs; but this would need to consider seasonal movements.

There are few areas in Viet Nam where suitable habitat is thought to remain, but if reasonable extents of alluvial grassland survive in the following areas surveys for Hog Deer may be warranted: Cat Tien National Park, the Kon river in the Kon Cha Rang Nature Reserve area, and the Sa Tay area of Kon Tum and Gia Lai Provinces; although given the high hunting pressure in Viet Nam it is becoming very unlikely that any animals could still survive (R.J. Timmins pers. comm. 2014). Cat Tien National Park retains significant areas of alluvial grasslands, and could potentially in the future become a site for reintroduction, however park management appears to be to some extent ignorant of the importance of these grasslands with ongoing schemes to re-establish forest and a fire management policy that is probably leading to woody encroachment of grasslands (R.J. Timmins pers. comm. 2014, based on a visit in December 2013).

It is not certain what conservation measures are in place (if any) for the rediscovered subpopulation in Bangladesh.

There has been no comprehensive assessment of Hog Deer in Myanmar, but it probably exists mostly in unprotected plains grassland areas which, as in the Mekong countries, are conventionally seen as of low conservation value (Peacock 1933, J.W. Duckworth pers. comm. 2006). In 2010 an 11,000 km² extension of the Hukaung valley was established. Hog Deer were camera-trapped in three localities in the grasslands along the Tawang River; one in the core area and the other two on the edge of the core area and the extension. In the last two years (since 2012) this area has seen the development of human settlements and agricultural expansion (Than Zaw pers. comm.) resulting in considerable loss of grassland habitat (R.J. Timmins pers. comm. 2014). A clarification of the status of Hog Deer in Myanmar is urgent: there may yet remain areas supporting animals which have high conservation potential if they do not disappear before being known to conservation. This lack of conservation profile is the chief challenge to Hog Deer in Myanmar at the moment, as it was in Peacock’s (1933) day: “the butchery of these little deer and the failure to provide more than one small sanctuary for their preservation is certainly one of the weak spots in Myanmar game legislation...the existing legislation is singularly ineffective in preventing their wholesale destruction. Moreover, there are few forest reserves which are suitable for the Hog Deer, and the legislation concerned with such forests is little more than a gesture”. If not met head-on, there are no grounds to assume that Hog Deer national conservation status will not replicate that shown by all range states to the east (major population collapse), if indeed it has not already done so.

Most Hog Deer subpopulations remaining in India, Nepal and Bhutan are in protected areas where animals are at least somewhat, and in some cases well, protected from poaching (Biswas et al. 2002, Biswas 2004, Johnsingh et al. 2004, Pralad Yonzon pers. comm. 2006, H. S. Baral pers. comm. 2008, A. Choudhury pers. comm. 2006, N.S. Kumar pers. comm. 2008). Wildlife protection laws in India have also helped in retaining the specialized habitat of Hog Deer, arresting habitat loss and habitat conversion in some protected areas. Johnsingh et al. (2004) found a strong correlation with Hog Deer subpopulations and protected areas in the Terai Arc Landscape of India (similar to that for Barasingha Rucervus duvaucelii), in contrast to other deer which occur relatively widely outside protected areas. Some protected areas are not big enough to allow adequate ranging during heavy flood periods, and thus prevent heavy mortality during such periods, and all suffer from being too small to be allowed unfettered habitat succession, because new grasslands are not now being created by natural processes elsewhere (see Habitat and ecology). In India and Nepal, Hog Deer has benefited from conservation measures taken for Great Indian Rhinoceros and Barasingha in the same wet grassland habitats (Q. Qureshi pers. comm. 1995, Biswas 2004). However, grassland management for rhinoceros may in some cases be deleterious to Hog Deer (Biswas 2004).

In South Asia there is an urgent need to update the status review of Biswas and Mathur (2000), even though some large Hog Deer subpopulations inhabit some of the best-secured protected areas in the world. Even assuming that these protected areas continue to receive sufficient material and political support, such a review is necessary because all subpopulations face uncertain futures from a multitude of factors, some of which originate outside protected areas and beyond the zone of influence of protected area managers. The review needs to determine roughly the numbers remaining and the locations of all sizeable or potentially sizeable subpopulations, and especially for each make assessments of current and likely future conservation status and population trends, bearing in mind threats from poaching, agricultural encroachment, livestock grazing, natural habitat succession, perverse habitat management, invasive plant species, the risk of disease epidemics from domestic livestock, changes to water levels and flows (e.g. from upstream dams), further fragmentation of subpopulations and habitats, episodic mortality through flooding and abiotic risks such as insurgency (which can collapse protected area management, although it does not always do so). Confinement of subpopulations to small habitat patches isolated from other such patches raises the intrinsic threat of subpopulation loss significantly when considering the wide gamut of threats facing such subpopulations (Biswas and Singh 2002, Biswas 2004), and in some sites challenges may be so pervasive that long-term retention of Hog Deer subpopulations may be so difficult as to be an inefficient use of resources. An integrated South Asia-wide conservation plan may be the best route to direct resources to a representative set of areas where long-term persistence of large Hog Deer subpopulations can be assured provided sufficient resources are mobilised and deployed in the appropriate way.

By contrast, in Southeast Asia, any subpopulation found east of central Thailand (i.e. within the historical range of A. p. annamiticus, the western limit of which is not clear) warrants immediate attention. It is plausible that the recently found small and fragile subpopulation in Cambodia is the last stock of this taxon. The isolated small subpopulations in Bangladesh, although presumably of the nominate race, warrant priority protection in maintaining the ancestral geographic and habitat range of Hog Deer. Species-specific intervention in Myanmar should probably, given the great challenges in the country (and, specifically, the uneven success to date with Eld’s Deer Rucervus eldii conservation), be fitted within larger initiatives such as conservation of the Hukaung Valley, probably the largest floodplain in tropical Asia retaining largely natural ecological processes of stream geography and habitat dynamics.

In Sri Lanka, where the species is restricted to privately-owned gardens, its survival depends on the goodwill of the landowners. The conservation value of this introduced subpopulation needs re-evaluation, considering approximate size, recent trend, ecological integrity and any genetic uniqueness, balanced against the likely cost of conservation interventions to secure the subpopulation’s future. Needs of other introduced subpopulations are not considered here.

There is a large total of animals in zoos of tropical Asia. Although at least one Mekong animal appeared in a zoo recently (in Cambodia in the mid 1990s, C.M. Poole pers. comm. 1998), so far as is known, all captive herds are derived from subpopulations from Thailand and Myanmar and further west. Reintroduction of animals in the range of the nominate, should it be needed, thus has many options. There is no captive buffer for A. p. annamiticus.