Focus on bats

Different species of bats need specific roosting requirements. Bats have adapted to make full use of man-made structures, often without us being aware of their presence. Unlike rats and mice, roosting bats do not wander about in a buildings in search of food  and causing damage to cables etc. Bats do minimal damage to the building, unless they roost in particularly large numbers, when the characteristic smell and accumulation of droppings can sometimes become an issue.

Crevice-dwelling species, such as Soprano Pipistrelles (Pipistrellus pygmaeus) and Common Pipistrelles (Pipistrellus pipistrellus) are often found roosting in modern buildings. Cavity walls, and the narrow spaces between roof tiles or slates and sarking or felt lining below, provide perfect roosting spaces, often accessed through small gaps behind soffits (a gap of just 10mm is sufficient for a bat).

Brown long-eared bats (Plecotus auritus) like open attic-spaces, usually in older buildings. They often roost in the apex of the roof or in the gap between rafters and a wall. Natterer’s Bats (Myotis nattereri) tend to use old, stone-walled buildings and often roost in gaps in beam joints.

Daubenton’s bats (Myotis daubentonii) are linked to aquatic habitats and feed on insects over water. These are often the bats you can see at dusk skimming the surface of ponds, lakes and rivers catching insects on the wing. They usually roost close to water and tend to seek holes and crevices in stone or concrete-built structures, such as bridges.

In my line of work, I often get asked the same questions regarding bats and buildings:

1.      Why are bats and their roosts protected?

2.      What does it mean if I have bats in my building – can I develop?

3.      Why would I want to encourage bats to my garden/building if they are not there already?

1 – Bats are a European protected species, the numbers and geographic ranges of some species in the UK are showing signs of increasing, but generally the trend across Europe is that the numbers of bats are in decline. Reasons for this decline range from agricultural intensification to habitat modification or removal and/or roost destruction, increasingly as a result of development. As bats are loyal to their roost sites (including very important maternity roosts and hibernation roosts), often returning year on year to the same roost, any changes in roost availability or condition is likely to impact local populations. They also only give birth to one pup each year. These are the reasons why both the bats and their roosts are protected by law.

2 – Often people think if they have bats in their building or bats are discovered through a survey, that the works they wanted to do to the building will not be possible. This is not the case. What it does mean is that if works are to go ahead and there is no reasonable alternative, works will need to be done under a European Protected Species (also known as a mitigation) licence, which permits otherwise illegal works in relation to bats to proceed with respect to development. This licence is supported by additional survey work, and detailed mitigation will need to be designed to ensure that the bats themselves are not harmed during works and that the colony of bats is ensured roosting provision. So, although there maybe some delays and additional cost, the development almost always goes ahead even if bats are present – the key to making sure you reduce the delays is to get the initial bat survey done as early as possible!

3 – Bat myth busting!  Contrary to some stories you may hear, bats wont get tangled in your hair or attack you! Bats are actually very beneficial animals to have around. Being nocturnal hunters of flying insects, during the summer months when bats are at their most active, they can catch thousands of midges and mosquitoes in one night. Some farmers in the USA even encourage bats to roost close to their crops so that they can control the number of moth pests that damage their plants.

To learn more about bats – check out the Bat Conservation Trusts website.