Vertical stratification in foraging activity of Chaerephon plicatus (Molossidae, Chiroptera) in Central Thailand

Abstract

Chaerephon plicatus consumes large amounts of planthoppers, which are the most serious pest in Asian rice fields. Brown planthoppers (Nilaparvata lugens) are known to migrate at high altitude and can cause severe damage and economic loss over a large area. However, we lack evidence whether this bat species also forage at high altitudes. This study investigated the stratification in foraging activity of C. plicatus at approximately 0, 100, and 200 m above ground level by using a helium-filled balloon-kite. The activity of C. plicatus aloft (100 m and 200 m) on average was six to twelve times higher than that close to the ground. Peak activity corresponded with the top of the nocturnal stable boundary layer, which is also the layer of maximum temperature and wind speed. Nilaparvata lugens has been found flying at the altitude where peak bat foraging activity occurs, which suggests that C. plicatus actively follows these migratory insects in the air. Thus, C. plicatus bats potentially play an important role in insect pest suppression in the areas they inhabit as well as at the landscape scale. However, the height of peak activity also corresponds with the height of wind turbine blades, thus, such turbines may pose a serious threat to the species.