This slow motion video of a bat drinking from a pool of water was made by German scientists Stefan Greif and Björn Siemers. The pair set out to investigate the sensory cues that help animals recognise features in their environment: in this case, the ponds and rivers that bats use for orientation and foraging. We know a lot about how bats use echolocation to target insect-sized objects, but this is the first study to show how they recognise large, flat objects like ponds. Stefan and Bjorn caught wild bats in Bulgaria and tested them in a large, dark flight room. They presented the bats with either smooth or textured plates positioned on the flight room’s sandy floor. When presented with a smooth plate of metal, the bats treated it like water and tried to drink. Even when the metal plate was put on a table – a very unnatural position for a pond – the researchers watched as the bats attempted to quench their thirst. A smooth metal plate reflects sound in the same way as a body of water so this behaviour supported the researchers’ hypothesis that bats rely on the mirror-like echo reflection properties of smooth surfaces to recognize water in their environment. When a bat flies above a smooth surface most of the sound waves in its call are reflected away, but a small proportion hit the surface immediately below and then bounced back… a tell-tale sign of water if you’re a bat. Stephan and Bjorn also tested young bats that had never encountered a pond or river before. These naive bats also tried to drink from the metal plate. This was the first time in their lives these youngsters had encountered a large, smooth surface so this suggests that water recognition in bats is hardwired into the brain. And the researchers claim this is the first evidence for innate recognition of a habitat cue, such as a pond, in a mammal.