Biosonar dynamics in horseshoe and old-world leaf-nosed bats

Abstract

Horseshoe bats (family Rhinolophidae) have evolved a capable biosonar system to allow the pursuit of prey amid dense vegetation that produces large amounts of clutter echoes. Horseshoe bats have long been known to employ dynamic effects such as Doppler effect compensation and large-scale rotations of their pinnae to realize these capabilities. Recent research has produced evidence of even more pervasive dynamical biosonar properties in horseshoe bat biosonar as well as in the related Old World leaf-nosed bats (family Hipposideridae). On the emission side, these animals employ elaborate baffle shapes that surround the exit points of their ultrasonic pulses (nostrils). During echolocation, multiple parts of these noseleaves such as the anterior leaf and the lancet in horseshoe bats are set in motion, typically in synchrony with pulse emission, hence creating a time-variant channel for the exiting wave packets. Similarly, the pinnae which diffract the incoming echoes on the reception side are frequently in motion while echoes impinge on them. These motions include non-rigid changes in shape. All these effects add a dynamic dimension to the interface of the bats' biosonar with the external world, which could allow the animals to enhance the quantity and quality of the sensory information they receive.