Factors influencing bat road casualties in a Neotropical savanna

Abstract

Collision with vehicles is one of the main causes of death for many vertebrates; however, little is known about bat roadkill. Thus, in this study we described bat roadkill in an area of Neotropical savanna and evaluated factors potentially affecting its occurrence. We surveyed 114km of roads on the margins of protected areas in the Brazilian Federal District for 5 years. We analysed bat roadkill on three types of roads (dirt roads, two-lane paved highways, and four-lane paved highways) and recorded distance from water and presence of artificial light. Bat roadkill was calculated for 2-km sections and analysed using generalized linear mixed models (GLMMs) with the following independent variables: season, road type, presence of light, and distance from water. We used section nested within road as a random effect. We estimated a total of 4740 roadkilled bats and identified individuals from three families. Bat road casualties were more numerous in the rainy season and on four-lane highways, whereas proximity to water and presence of artificial light were not related to roadkill number. The higher roadkill rate during the rainy season may be explained by higher bat activity due to the increased availability of resources. Regarding the influence of road type, four-lane highways have the highest traffic volumes in the area and the highest speed limits, which are associated with higher roadkill rates. Bats represent the most diverse order of mammals in the Cerrado, where they provide many important ecological services, which need to be preserved.