Traffic noise affects foraging behavior and echolocation in the Lesser Bulldog Bat, Noctilio albiventris (Chiroptera: Noctilionidae)

Abstract

Urban noise, such as that of traffic, can affect the sensory capabilities in animals. Foragers acting optimally are expected to exploit feeding patches depending on the cost/benefit ratio, and some noises can cause increased foraging costs. We hypothesized that traffic noise affects foraging patch quality for aerial-insectivorous bats and predicted that there are measurable differences in their foraging activity and in their echolocation signals between nights with or without traffic noise. We tested these predictions in the Lesser Bulldog Bat, Noctilio albiventris, foraging over aquaculture fishponds, by recording bat activity on nights playing traffic noise and on traffic-sound free control nights. We measured foraging activity by counting the number of search passes and feeding buzzes made by the bats and measured several characteristics of echolocation signals. Foraging activity was higher during noisy nights than during control ones, probably due to the need of more time to obtain information about prey under noisy conditions. When exposed to traffic noise, the bats changed the spectral and temporal characteristics of echolocation signals. We suggest that exposure to traffic noise increases foraging costs for N. albiventris and posit that these bats continue foraging under noisy conditions because they can modulate their echolocation signals to obtain enough information.