Bats in your neighbourhood

There are 18 species of bat in the UK, and even in the middle of a town you probably have at least one living within a few hundred metres of your back door. Step outside about twenty minutes after sunset on a mild evening between April and October and you may see them: small dark shapes flicking over the hedge line, turning sharply, vanishing against the rooftops. Those are most likely pipistrelles — the common and the soprano pipistrelle together make up the majority of records in most counties. If you have mature trees, a pond and an unlit corner, you may also have brown long-eared bats, which are far quieter and seldom seen but regularly found roosting in older houses.

Bats are not blind, they are not flying mice, and they will not get caught in your hair. They are long-lived mammals — some pipistrelles reach their teens — and their numbers have fallen sharply over the last fifty years, largely because of insect decline, roost loss and artificial light. The good news is that a garden can genuinely help.

Where British bats roost

Different species use very different places, which is why a scruffy, varied garden is better than a tidy one.

• Common pipistrelle and soprano pipistrelle: crevice roosters. They squeeze behind hanging tiles, under ridge tiles, into gaps beneath soffits and bargeboards, inside cavity walls, behind window shutters, and in narrow tree holes and crack willow. Soprano pipistrelles are especially associated with water and damp woodland.
• Brown long-eared bat: a roof-void specialist. It needs open, uncluttered lofts and barns where it can hang free, and it also uses tree cavities and old buildings. It gleans moths, beetles and spiders straight off leaves and window frames.
• Daubenton's bat and Natterer's bat: both roost in bridges, culverts and stone arches over streams, as well as in trees and old masonry. A bridge in your local park is a genuine bat roost.
• Ivy, dead wood and veteran trees: dense ivy on a tree or wall holds warmth and gives shelter for many species. Standing dead trees and cracked limbs are prime real estate — leave them if it is safe to do so.

All British bats and their roosts are protected by law, whether bats are present at the time or not. Never block, repair or light a suspected roost without advice from your local bat group or the relevant statutory body.

Growing a better larder

A pipistrelle can eat around 3,000 small insects in a single night, so the single most useful thing you can do is produce more insects. That means native plants, rough edges and no pesticide.

• Plant native trees and shrubs — oak, willow, birch, hawthorn, blackthorn, hazel and field maple. These support the caterpillars and beetles that bats eat.
• Leave a patch of long grass, nettles and wildflowers to overwinter, and let leaf litter and log piles build up.
• Add night-scented natives such as honeysuckle and wild privet, which draw in moths after dark.
• Dig a small pond with shallow, unfenced edges. Bats drink on the wing, and still water hatches clouds of midges and caddisflies.

Switch off, and let the dark back in

Artificial light is one of the quietest ways we harm bats. Lighting delays emergence, breaks up commuting routes and makes roosts too warm or too exposed. Use warm-white, downward-facing fittings with hoods or shields, keep them low and on motion sensors, and leave the boundary of your garden genuinely dark. If a bat box or a suspected roost is nearby, no light at all is the best answer.

Putting up a bat box

Boxes are no substitute for a good tree, but they work — particularly for pipistrelles in suburban gardens. Choose a timber or woodcrete box with a narrow entrance slit of about 15–20mm for pipistrelles; larger boxes suit brown long-eared bats.

• Site it 3–5 metres up, on a tree, wall or building, facing south or south-west for warmth.
• Give it a clear flight approach and shelter from prevailing wind and rain.
• Hang two or three in a group, at slightly different heights and aspects — bats move between them as temperatures change.
• Fix with a bracket or strap rather than nails into the tree, and check from the ground only.

Autumn and late winter are the best times to put boxes up, ahead of the maternity season in May to July.

Watch, count and lend a hand

Standing quietly at dusk with a cup of tea is proper citizen science. Count the bats leaving a roost, note the time and the weather, and record it. A basic heterodyne bat detector will separate the two pipistrelles: common pipistrelles peak at around 45kHz, sopranos at about 55kHz, while brown long-eared bats are whisper-quiet and easy to miss. Keep cats in from an hour before sunset, never handle a grounded bat with bare hands, and if you find one, call a local bat care helpline for advice. Report what you see to your county bat group — those records shape planning decisions, and they start in gardens like yours.