To determine the habitat usage and movement patterns of the viviparous aquatic snake Oocatochus rufodorsatus (formerly Elaphe rufodorsata), we radio-tracked 21 snakes on agricultural lands during two active seasons in 2007 and 2008. Male and female snakes stayed close to aquatic habitats such as paddy fields and agricultural ponds during both breeding and non-breeding periods, except when the snakes moved to dry terrestrial areas to hibernate in late fall. The use of different structural features in the habitat, such as ground, tree, underground, and water, varied depending on the air and water temperatures, female's reproductive conditions, and the time of day. Male and female snakes moved about 17 m daily and postpartum females moved farther than antepartum females. The home ranges of males and females were 0.45 ha and 0.47 ha, respectively, and the year-round home range of this species was approximately 1.54 ha (95% fixed kernel). Thus, to conserve a population of O. rufodorsatus in our study area, areas including both aquatic and terrestrial habitats within a radius of 150 m from a core pond habitat must be preserved.