Bats are small flying mammals that belong to the large family of Chiroptera, which today represents between 1000 & 1200 species worldwide. The most common is the common pipistrelle. These nocturnal animals are predominantly insectivorous, with the exception of the largest species which may be carnivorous, & therefore feed on small flying insects. To hunt the latter use ultrasound which they emit either by mouth or through the nostrils & which come back to their ears.