[4] Swamp deer were once common in many areas, including parts of the Upper Narmada Valley and to the south, in Bastar, prior to the 19th century.

[6] They frequent flat or undulating grasslands, floodplains and marshes, and generally stay on the outskirts of forests.

Today, the distribution is further reduced and fragmented, due to major losses in the 1930s–1960s following unregulated hunting and conversion of large tracts of habitat into cropland.

In Nepal, they can be primarily found in the western areas of the country, south of the Himalayas, in Shuklaphanta and Bardiya National Parks.

They are found in Kanha National Park, in Madhya Pradesh, and have also been observed across the state border in Chhattisgarh (near to Dhamtari),[8] likely the most southerly extent of their distribution.

They are regionally extinct in West Bengal,[9] and are also likely extirpated from Arunachal Pradesh, Bihar, Jharkhand, Meghalaya, Nagaland and Odisha.

[11][12][13][14] In 2005, a small population of about 320 individuals was discovered in the Jhilmil Jheel Conservation Reserve in Haridwar district, Uttarakhand, on the east bank of the Ganges.

[4] They largely feed on grasses and aquatic plants, foremost on Saccharum, Imperata cylindrica, Narenga porphyrocoma, Phragmites karka, Oryza rufipogon, Hygroryza and Hydrilla.

The breeding season lasts from September to April, and births occur after a gestation of 240–250 days in August to November.

Swamp deer lost most of its former range because wetlands were converted and used for agriculture so that suitable habitat was reduced to small and isolated fragments.

[9] The remaining habitat in protected areas is threatened by the change in river dynamics, reduced water flow during summer, increasing siltation, and is further degraded by local people who cut grass, timber and fuelwood,[1] and by illegal farming on government land.