Fur colour and texture Juvenile bats of all British species are darker and greyer than the adults. This is not always obvious, especially if the bats are born early in the year, when they may moult before hibernation. Fur of juveniles is often matt and frizzy rather than glossy or sleek. Wing membrane colour/texture Wing membranes of juvenile bats are often clean and unblemished and feel soft and tacky. The colour is generally darker than in adults. These juvenile characteristics maybe detectable for up to a year. Moult Except for juveniles, bats have a single annual moult, usually in June and July. The moult usually starts from the back of the head and shoulders.