Bats are the only true flying mammals. In Britain they 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). Daubenton's bats produce echolocation calls of frequencies between 35 and 85 kHz, but most calls peak at 45 to 50 kHz (5). They emerge at twilight, and with fast, agile flight they hunt over water, close to the surface (2), taking small flies, midges, mayflies (5) and moths (2). Daubenton's bats have been seen taking prey from the surface of the water using the tail membrane or the feet (5), eating the prey whilst flying (2).
Mating tends to occur in autumn (5), but fertilisation is delayed until the following spring (7). Female Daubenton's bats gather into maternity colonies in summer, the young bats are suckled for several weeks, reaching independence at around 6 to 8 weeks of age (5). Males and non-breeding females may gather into communal roosts in the summer, or they may live in the maternity roosts (5), but in separate groups to the breeding females (7). Hibernation occurs between the end of September and late March or April (2). Daubenton's bats are known to live to a maximum of 20 years, although the average life expectancy is closer to 4 to 4.5 years (2).