The study was carried out in the rice fields of the Bachhauli and Kumroj Village Development Committee (VDC) of Chitwan district, Nepal (Fig. 1). The study area lies in the buffer zone of Chitwan National Park, which is listed as a World Heritage Site by the United Nations Educational, Scientific and Cultural Organization (UNESCO) and has high levels of biodiversity (Bhattarai and Kindlmann, 2011 and Straede and Helles, 2000). The climate is subtropical. January is the coldest month (mean temperature 10 °C) and the warmest months are May to August (mean temperature 32 °C). Monsoonal rainfall occurs between June and September and the area receives the majority of annual rainfall during this period. However, short showers are common throughout the year. The average annual rainfall for 2003–2007 was 2429 mm/year for the nearby weather station of Bharatpur Airport