Spatiotemporal dynamics of biosonar in navigating Bornean Rhinolophid and Hipposiderid bats

Abstract

To investigate the active sensing strategies used by echolocating bats of the genera Rhinolophus and Hipposideros, we have constructed a 9-meter long flight tunnel, which incorporates an array of 32 ultrasonic microphones distributed throughout the tunnel. Rhinolophus and Hipposideros are of special interest because of their highly flexible biosonar system; these bats emit pulses from their nasal cavities, using complex noseleaf structures to quickly and precisely alter the beam-form and direction of emissions. Additionally, each species utilizes a unique combination of constant-frequency (CF) and frequency-modulated (FM) ultrasonic signals with varying durations, repetition rates, and frequencies. We plan to trap several species of wild Bornean bats of these genera and fly individual bats through the tunnel; a time-of-arrival algorithm will be used to localize the position of each bat at the time of each biosonar pulse emission, and an amplitude-comparison method to measure the horizontal and vertical direction of each emission from the bat’s noseleaf. We will also incorporate relatively simple foliage obstacles into the tunnel; this will create complex acoustic clutter and allow us to determine how bats of different species adjust their biosonar sampling strategies in order to navigate around novel obstacles in a cluttered environment.