Species richness and activity of insectivorous bats in cotton fields in semi-arid and mesic Mediterranean agroecosystems

Abstract

Insectivorous bats play a significant role in regulating the populations of nocturnal insects, including important agricultural pests in various agroecosystems, such as corn and cotton fields. Using bat detectors, we recorded species richness, bat activity, and the response of the bats to major insect pests in two major cotton-growing regions located in Revadim in a semi-arid area and in Emek Hefer in the Mediterranean habitats, Israel, for two growing seasons in 2014 and 2015. In 2016, we directly tested the response of the bats to chemical spraying by recording their activity before and after the spraying events. In both regions bat activity and species richness increased as the cotton growth progressed, reaching a peak when pest abundance was high. In Revadim, bat activity was significantly higher at the edge of the plots than in the center of the plots. There was a positive correlation between bat activity and the cotton leafworm (Spodoptera littoralis) insect pest, indicating that bats may exploit pest irruptions in the cotton fields. Bat activity was significantly lower after spraying events and remained low for several nights, suggesting a strong negative effect of chemical spraying on bats. Seven and nine species of bats and the genus Myotis were recorded in Revadim and Emek Hefer, respectively; most of them are locally categorized as threatened species. The edges of cotton fields may serve as potential foraging areas for insectivorous bats under bat-friendly management schemes that aim to increase their suitability for these bats, which in turn enhances their potential contribution to pest control.