The matrix of riverine grasslands and grassland-forest mosaics in the Ganges and Brahmaputra river valleys in the Himalayan foothills is one of the 200 eco-regions of the world that harbor important biodiversity (Dinerstein, 1979). These grassland forest mosaics, which have been variously described as grasslands, savannas, and wooded savannas (Dabadghao and Shankarnarayan, 1973; Lehmkuhl, 1994; Yadava, 1990) and known as the Terai-Duar savanna, are under severe threat due to expanding human influence and in urgent need of conservation attention (Dinerstein, 1979). The sub-tropical tall grasslands found in this eco-region are some of world's tallest and most productive, and the biomass of large herbivores they support equals many of the savanna ecosystems in East Africa (Lehmkuhl, 1994; Sarma et al., 2008). These tall grassland forest mosaics are the last remaining examples of subtropical tall grasslands in the Indian subcontinent (Lehmkuhl, 1994), and contain some of the highest densities of tiger, rhino, and ungulates in Asia. They also support exceptionally rich and abundant bird, amphibian, reptile, and fish communities.