Also known as Hainan Slope Deer, or Bog Deer, it belongs to the Cervidae family of Artiodactyla order. Its Latin scientific name is Cervus eldi, and its English name is Thamin.      

Its body bears considerable resemblance to Sika Deer, but slightly smaller in size, and with slimmer neck, body and limbs, which makes it seem especially strong and healthy. The male deer has horns, and its first brow tines protrude forward side-flatly from the basal portion, almost forming an arch with the trunk. The fur coat is yellowish brown, reddish brown or tan in color, and the median dorsal line is dark tan. On each side of the dorsal ridge there are a column of white spots, which are distinctive on fawns, but less discernible on adult deer in winter.

Thamin dwells in low hilly land and plain areas that are below 200 meters in elevation. By nature it is fond of living in groups, but long-pilose-antler male deer usually prefers solitude. It likes gathering at small river valleys. Thamin is highly vigilant and will raise its head and look around now and then even when eating. It will be frightened into running wildly by a slight sound and is able to cross a ravine of several meters wide at one jump. Feeding on grass and tender twigs and leaves, it is also fond of going to fire-burnt areas to lick the ash of grass and wood. Estrus and Copulation of Thamin usually take place in the period from April to May, during which fierce fights occur among males. The gestation period lasts 7 to 8 months, with one baby deer at a time.

Native to Hainan Island, its distribution is limited to certain areas, and the population is minor. By 1996 the number of Thamin has been increased to about 500 heads. It has been listed in Appendix I of International Trade Convention on Endangered Wild Animal and Plant Species.