Bats and their habitats are protected under the Wildlife and Countryside Act 1981 (as amended by the CRoW Act 2000), and by the Conservation of Habitats and Species Regulations 2017. Seven bat species are also listed as Species of Principal Importance under the provisions of the NERC Act 2006.

In undertaking an evaluation of the bat interest at a site, the following factors are taken into account: the value of roost types, commuting routes and foraging habitats; the rarity of the species involved; the approximate number of bats using them; the proximity to known roosts; and the nature and complexity of landscape features.

During development, bats can be disturbed in the short term by increased human presence at the site, increased noise or changes to the area’s layout, temperature or humidity (these can affect commuting routes).

In addition, changes to bat roosts can have long-term effects such as reduced roosting space or loss of roosts altogether, changed ventilation, increased human activity and / or external lighting near flight paths and commuting routes. Some bat species accept changes to their roosts better than others.

There are seventeen resident breeding species of bat in the UK, varying in size from our two smallest and most common Pipistrelle bats (which can fit into a match-box) to our two largest bats, the noctule and the greater horseshoe. Bats are most vulnerable to harm if disturbed during hibernation or the maternity period. However, all bats and their roosts are protected from harm and disturbance at all times by EU and UK law. Bats’ foraging habitats also receive some protection within the planning system.

All UK bats feed on insects, although they each have subtly different diets and are therefore best observed foraging where insects are most abundant: primarily, waterbodies and woodland, gardens and parks, and along hedgerows and tree lines. Bats often use linear features within the landscape such as hedgerows to navigate.

The calendar year for a bat usually starts with hibernation and they only emerge in the spring as the weather ameliorates. In the early summer, females form maternity roosts where most give birth to a single pup, usually in June or July. Just a month or so later, the juveniles are volant (i.e. able to fly) and these roosts will then often begin to disperse. Shortly after this, bats will begin to mate. Some species will head to communal ‘swarming’ sites, where mating and other social exchanges will occur between multiple bats on favourable nights through the autumn.

Often these sites are then used for hibernation, which typically takes place in an undisturbed place with a cool climate where bats will significantly lower their metabolic rate. Bats use very little energy when undisturbed, although some will occasionally stir on milder nights, perhaps even to mate.