Both captured wild bats and juvenile bats that had never previously encountered large bodies of water were placed in a room with smooth and textured wood, metal and plastic plates. Bats of all species repeatedly attempted to drink from the smooth plates, but never from the textured plates.
This is because the smooth plates replicate the mirror-like echo reflection exhibited by bodies of water. Such surfaces reflect most of the bats’ echolocation energy away from it, but some energy hits the surface perpendicularly, sending an echo back directly beneath the bat. Water is the only such surface that behaves this way found in nature, so when the bats encountered similar properties in this artificial environment, they assumed the smooth plates were water.