Acoustic discrimination of fine surface textures by echolocating free-tailed bats uri icon

abstract

  • Surface texture is an integral cue used by echolocating mammals for characterizing and forming a mental representation of an ensonified target. Bats need to be able to recognize and discriminate between different target surface textures. Previous work showed that bats rely on spectral cues embedded in echoes to resolve textures, but the resolution limits for this behavior are unknown. Mexican free-tailed bats (Tadarida brasiliensis) are fast, high-flying insectivorous bats that emit broadband FM multi-harmonic sonar pulses. We trained three bats to perform a two-alternative forced-choice assay in which they compared and selected the coarser of two sandpaper samples of different grit size. Commercial sandpaper grits decrease in mean particle size following an exponential function. We tested the bats ability to discriminate between 10 different grit sizes varying from 40 to 240 grit, corresponding to mean particles diameters varying from 425 to 50 m. Bats discriminated all grits from a smooth plexiglass control and almost all grits from each other up to 180versus 220 grit (82 vs 68 m) but not 220 vs 240 (68 vs 54 m), indicating an extraordinary minimum difference threshold of about 14 m, which rivals human performance using tactile active sensing by finger touch.

published proceedings

  • The Journal of the Acoustical Society of America

author list (cited authors)

  • Smotherman, M., Odunsi, S., Hobbs, M., & Croft, T.

complete list of authors

  • Smotherman, Michael||Odunsi, Stephen||Hobbs, Mikayla||Croft, Thomas