Excellent question! Barbastelle bats, like most other bats, use echolocation to ‘see’ the world around them and hunt insects and other prey. Bats emit high frequency squeaks and listen carefully for the echoes that return from objects, and they use information in these echoes to build a picture of their surroundings in their mind. Barbastelles call more quietly than most other bats, mainly to avoid being heard by the moths that they love to eat, and so they need big ears to detect the faint echoes of their calls. Bats that call much louder tend to have smaller ears!