Bats are the only true flying mammals. In Britain bats are insectivorous (eat insects), and contrary to popular misconception they are not blind; many can actually see very well (6). All British bats use echolocation to orient themselves at night; they emit bursts of sound that are of such high frequencies they are beyond the human range of hearing and are called 'ultrasound' (7). They then listen to and interpret the echoes bounced back from objects, including prey, around them, allowing them to build up a 'sound-picture' of their surroundings (7). The whiskered bat produces echolocation calls at frequencies between 35 and 80 kilohertz (5). They emerge at early dusk, and with rapid, weaving flight they hunt over water or at low levels through woodland (2), taking midges, beetles, moths, and small dragonflies (2).
Mating tends to occur in autumn (5), but fertilisation is delayed until the following spring (7). Female whiskered bats gather into maternity colonies of 20 to 50 females in summer (7), and give birth to a single young in June or July. At three weeks of age the young bat can fly, and it is able to forage independently by about six weeks of age (5). During the summer males are solitary (7). Whiskered bats are known to live to a maximum of 19 years (2), but the average is probably closer to four or five years of age (7).