Common. They hunt insects over water – they use mostly wooded areas by rivers or lakes. Food – small diptera, mayflies and butterflies are caught and eaten in flight. The food eaten by one bat per night exceeds half the animal’s weight. Colonies of these bats can be found in natural caves, tree cavities as well as in man-made hiding places – basements, ruins, tunnels or even under bridges. They hibernate from September to April in the same places.