Hearing in a Megachiropteran Fruit Bat (Rousettus aegyptiacus)

The Egyptian fruit bat (Rousettus aegyptiacus) is one of the few megachiropteran bats capable of echolocation. However, it uses rudimentary tongue clicks rather than laryngeally produced echo calls. We determined the audiogram of 2 bats using a conditioned avoidance procedure with fruit puree reward. At an intensity of 60 dB sound pressure level, the bats' hearing extended from 2.25 kHz to 64 kHz, with a region of good sensitivity between 8 kHz and 45 kHz. A dip in sensitivity at 32 kHz appears to be due to pinna directionality. The hearing of Egyptian fruit bats is typical for a mammal of that size and is not as limited as previously reported. Methodological issues, specifically training an animal to listen for low-intensity signals and imposing a significant cost for failing to report signals (i.e., misses), are discussed as the basis for the discrepancy between our results and earlier reports. The Egyptian fruit bat, Rousettus aegyptiacus, is a megachiropteran bat from the Middle East and sub-Saharan Africa. Unlike other megachiropterans that do not echolocate, Egyptian fruit bats, as well as other members of its genus, roost in caves and possess an echolocation system that uses tongue clicks. Such a system is quite different from the laryngeally produced echolocation calls of microchiropterans and is believed to have evolved independently (Griffin, Novick, & Komfleld, 1958; Kulzer, 1956). Thus, Egyptian fruit bats provide an interesting contrast to the microchiropteran bats with their more sophisticated echolocation abilities. Given the differences between the tongue click echoloca