Abstract: Echolocation or biosonar is an alien sense to humans. For us as visually guided mammals it is hard to imagine what an echolocator's acoustic perception of its surroundings 'looks' like. Part of this difficulty arises because vision and biosonar differ fundamentally in a number of ways: a) Vision is based on two dimensional data, i.e. images focused on the retina in the eye, while bats evaluate a linear stream of echoes and have to reconstruct all directional/spatial information from the temporal and spectral properties of the echo stream; b) the number of sensory cells in hearing is much lower than in vision and c) biosonar is a case of active sensing, i.e. bats actively produce the signals with which they probe the environment, while vision (in the vast majority of cases) relies on external light sources. This combination of traits, i.e. limited bandwidth and active sensing has led to a number of behavioural adaptive strategies by which bats control what information about the environment becomes available to them. In a sense, external mechanisms to extract the relevant information from the plethora of available data are far more important in biosonar than in vision.
Hence, biosonar offers unique opportunities to study behavioural strategies of information flow control by active sensing. We employed high resolution acoustic tracking techniques and 3D laser scanning of natural habitats to study free flying bats in forests. We investigated how they adapt flight patterns, calling behaviour and sonar signal design to optimize information flow.
