To Scream or to Listen? Prey Detection and Discrimination in Animal-Eating Bats

Abstract

All animal-eating bats are echolocators, and the vast majority can capture airborne prey (aerial hawking). The literature suggests that >40 % of these same species also take prey from surfaces (substrate gleaning). Innovations in acoustic recording have revealed bats’ high-frequency vocalizations and showed that hawking bats produce calls of greater intensity than calls produced by gleaning bats. In response to bat echolocation calls, many eared insects initiate evasive action, and some tiger moths produce sounds that deter a bat from completing an aerial attack. Bats abort their hawking attacks as a result of having had their echolocation interfered with by the moths’ sounds, by having had previous experience that taught them moths that make sounds tasted bad, or through some combination of the two. Among gleaning bats, the fringe-lipped bat has been well studied with respect to foraging. This bat uses the sexual advertisement calls of male frogs to localize them. Male frogs that produce calls with more complexity are more attractive to female frogs, but are more easily localized by fringe-lipped bats. It had been argued that gleaning bats are unable to locate perched or otherwise substrate-borne prey using echolocation. This is because background echoes were assumed to mask those reflected from prey. Gleaners were believed, instead, to use prey-generated sounds for detection and localization. It is now known that at least one species of bat is able to resolve echoes reflected from large insect prey from the echoes reflected from the vegetation on which the insect is perched.