Bats' avoidance of real and virtual objects: implications for the sonar coding of object size

Area of Science:

• Animal Behavior
• Bioacoustics
• Neuroethology

Background:

• Fast movement in complex environments necessitates effective obstacle evasion.
• Bats utilize biosonar (echolocation) to navigate and detect objects by analyzing echo acoustics.
• Object echo features, such as amplitude and spectro-temporal characteristics, correlate with physical properties like size.

Purpose of the Study:

• To investigate sonar-based obstacle evasion in bats emerging from a roost.
• To determine how bats perceive object size using sonar.
• To differentiate the roles of spectro-temporal and spatial echo features in object size coding.

Main Methods:

• Video-recording bats' flight behavior during emergence from a day roost.
• Presenting a real, small object (ultrasonic loudspeaker) to elicit evasion.
• Generating a virtual object echo via real-time convolution of bat calls with an impulse response, played from the loudspeaker.

Main Results:

• Bats successfully evaded the small, real object.
• Bats did not evade the larger virtual object, despite spectro-temporal echo similarity.
• Virtual object echoes lacked the angular spread (sonar aperture) characteristic of large objects.

Conclusions:

• Bats' evasion behavior is influenced by a combination of echo features.
• The sonar aperture of object echoes is critical for coding object size.
• A mismatch in spectro-temporal and spatial echo features can prevent evasive maneuvers.