the reserve covers an area of 5030 hectares. the area features the diverse topography and geomorphology of a typical wetland swamp. lang sen area is heavily covered with flora varied to the seasonal tides of the mekong river (bassac river), especially planted cajuput forest which attracts a diverse fauna to inhabit here. according to the preliminary survey, there exists 156 wild species belonging to 60 families; 149 vertebrate species belonging to 46 families, of which 13 species are listed in vietnam's red data book; the aquatic species are abundant. among new species discovered are the wild mekong, a gecko with bright orange legs, a yellow neck, and a blue-grey body with yellow bars on its bright orange sides.