The Noctule (Nyctalus noctula) bat is one of the largest widespread British species, but it is still smaller than the palm of your hand. It is usually the first bat to appear in the evening, sometimes even before sunset.
Noctules’ calls sound like ‘chip chop’ with occasional clicks which can be heard during feeding. Calls can be heard by some adults and children.
Noctule bats are primarily tree dwellers and live mainly in rot holes and woodpecker holes. They occur rarely in buildings; most noctule roosts in buildings are only gathering roosts, the colonies moving off at the end of May and early June. The bats produce loud characteristic metallic chirping sounds so that noctule colonies can be heard up to 200-300m away on hot days. Noctule bats hibernate mainly in trees or rock fissures and hollows, but have also been found in bat boxes and buildings. and other man-made structures in winter. They can survive without feeding for four months.
Noctules have a characteristic powerful, direct flight on long narrow pointed wings. They fly in a straight line, very high and fast in the open, often well above tree-top level, with repeated steep dives when chasing insects. They can fly at 50 kph. Most food is caught on the wing and eaten in flight but occasionally prey is taken from the ground and in suburban areas noctules are attracted to street lamps to feed on moths. During spring noctules will feed mainly on smaller insects such as midges, changing their diet to take chafer and dung beetles and moths later in the season. They also feed on mayflies and winged ants.
A distinctive characteristic of this bat is that its inner ear lobe (the tragus) is mushroom shaped. Its head and body length is 37mm - 48mm and the adults fur colour is a sleek chocolate brown. The juveniles and some females have a dull chocolate brown fur. The wingspan is 320mm - 400mm and the noctule weighs 18g - 40g.
During the mating season, male noctules emit a series of shrill mating calls from a roost entrance, usually a tree hole, or during flight and produces a strong odour, attracting a harem usually of four or five (but up to 20) females, which stay with the male for 1 or 2 days. The young are born in late June or July in maternity colonies found often in trees. Females usually have one young. For 3 to 4 weeks the young are suckled solely on their mother’s milk, and they are fully weaned and able to forage for themselves within 6 weeks. The maternity colonies frequently change roosts, mothers carrying the smaller young between roosts. The young are left in crèches while the mothers go off to feed. Some females become sexually mature in their first autumn but many o not mate until their second year.
In Britain all bat species and their roosts are legally protected, by both domestic and international legislation.
To find out more about bats and how you can help these amazing but vulnerable animals, visit the Bat Conservation Trust’s website where you can become a member and discover the many ways you can get involved to do your bit for bats! The National Bat Helpline can be reached on 0845 1300 228.