As the evenings lengthen and temperatures increase, our night skies once more become home to one of Britain’s most enigmatic and elusive mammals. After hibernating through the long cold Winter, Bats begin to emerge in early March and by April they are out most nights taking advantage of the warmer evenings to feed. If suitable quantities of food are available, by early summer, pregnant female bats will form maternity roosts to give birth, writes our Conservation Officer, Will Scott-Mends.

Bat pregnancy can last between six and nine weeks and each bat gives birth to a single pup. They will suckle and nurture the pup for around five weeks as they grow rapidly. After this point the young bat is old enough to fly and will begin to make foraging flights away from the roost, no longer requiring its mother’s milk and instead feeding on the insects it catches.

We have 17 species of bat that permanently reside in the UK, meaning they make up almost a quarter of all our mammal species! Sadly many of these species have undergone significant decline in the last few decades with populations of some species declining by as much as 70%. This is predominantly due to habitat loss but many other factors such as artificial lighting, disease and diminished food supply play a role as well. Fortunately, thanks to the efforts of conservationists and bat groups nationwide, bat populations seem to be stabilising but there is more work to be done.

You can help bats living in your area by turning off outside lights and limiting light usage at night in order to combat light pollution. It might not sound like much, but light pollution can have a major effect on nocturnal wildlife, in particular bats. Studies have shown that excess artificial light at night can have a serious impact on bat behaviour. Artificial lighting near a bat roost can disrupt or even prevent emergence from roosts, causing the bats to miss their key feeding window just after dusk when most insects are out. Slower flying species will avoid certain foraging areas or pathways if they are well lit which can reduce their feeding potential and faster flying species will favour feeding under streetlamps (which attract large numbers of insects) making them more visible and therefore more vulnerable to predation.

Barnes Common Ltd is once again be running monthly batwalks around the Leg O’Mutton Reservoir which is an excellent site for bats. Last year’s walks were very popular with many interesting sightings (including a range of bat species and a Tawny Owl) so please book early to avoid disappointment. Tickets will be available on Eventbrite from the beginning of each month and there will be further walks every month until October. Sign up for our Friends newsletter to get notified of new events added to the calendar.