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Planning any building work? Then make sure you check for the presence of bats first.

PUBLISHED: 11:47 17 September 2018 | UPDATED: 11:47 17 September 2018

Brown long eared bats in a summer roost in loft  Pic: David Hosking / Alamy Stock Photo

Brown long eared bats in a summer roost in loft Pic: David Hosking / Alamy Stock Photo

Credit: David Hosking / Alamy Stock Photo

With bat numbers declining in the UK it is important habitats are preserved including in buildings where they dwell and roost.

Daubentons bats hibernating   Pic: Arthur RivettDaubentons bats hibernating Pic: Arthur Rivett

If you are searching for the presence of bats in a property, there are a couple of giveaway clues that they are in residence.

Firstly, if you find droppings that resemble mouse droppings but which easily crumble when rubbed between your fingers, the chances are they are bat droppings. This is because bats feed on insects, so unlike mice have little moisture in their excrement. Bats droppings also sparkle slightly in the light.

The second tell-tale sign that bats are in the vicinity is a build-up of moth and butterfly wings on the floor that bats, having eaten the rest of the insect, find indigestible and have discarded.

These are just two of the many useful pieces of information I picked up (along with some bat droppings) last week whilst attending a Bats and Buildings course put on by Essex County Council’s Place Services division. The four-hour event, held at the Cressing Temple Barns complex near Braintree, was aimed at building managers, architects and developers to learn how to carry out preliminary bat roost assessments before they launch into building work.

Protected species

Natterer's and Daubenton's bat in bat brickNatterer's and Daubenton's bat in bat brick

Knowledge of this kind is important because all UK bats are protected species and any human activity that disturbs or destroys the living quarters of these fascinating and diminutive flying mammals could result in a substantial fine and even a prison sentence.

Built environment officer for the Bat Conservation Trust, Jo Ferguson, took us through some key information, telling us that some species of bats, including common and soprano pipistrelles, dwell in crevices such as under tiles and wall cavities; while other species, like the brown long-eared bat, prefer to group together in roof voids.

And it’s not just old buildings where bats roost. “I’ve found bats roosting in modern developments only eighteen months old - the buildings were close up to greenbelt and had gaps under the roof big enough for bats to enter,” said Jo.

Understanding the yearly cycle of bats is also important as bats may live in several different roosts over twelve months. Bats usually only have one young a year, mating in the autumn before hibernation - the females incredibly storing the sperm during this time before taking the pregnancy on in the spring. As summer approaches mother bats gather together and find somewhere warm to rear their young in what is known as a maternity roost - where temperatures can reach 40°C.

As winter comes around, the bats’ main food source, insects, diminishes, forcing them to hibernate between November and March/April in hibernation roosts, which are often cool spaces, generally between 0 and 6°C. Ever versatile, bats lower their body temperature during this time to conserve energy.

Temperature, it became clear, is very important to bats and any building work - whether it be demolition, re-wiring, or installing insulation - that changes the temperature of a roost can drive bats out and is therefore illegal.

Delegates on a bats and historic buildings course at Cressing Temple BarnsDelegates on a bats and historic buildings course at Cressing Temple Barns

Plan around bats

Jo’s main piece of advice to anyone undertaking building work is to have a bat ecological survey undertaken right at the beginning before any work begins, at the same time as a survey for asbestos might take place. If the expert identifies the presence of bats - say for instance in a maternity roost - it is known from the outset that any work that might disturb that location can’t happen in the summer, for example. Unfortunately, says Jo, many developers only find out they are dealing with bats in the course of their work and then become frustrated when this discovery holds a project up.

“Delays occur when you don’t have the information at the start - if you know what you’ve got, you can always plan around it,” Jo added.

Other building-related work can also have an indirect impact on bats, I learnt: installing artificial lighting can prevent some bats feeding at the right times while the removal of hedges and other vegetation near a roost can rob them of feeding spots, cover from predators and navigations lines.

Later as dusk fell, Sue Hooton, principal ecologist at Place Services, took us on a tour of the magnificent medieval Cressing Temple Barns where we put our new found bat detection skills to the test - examining every crevice and void with Sherlock Holmes-like intensity.

Bats over waterBats over water

A smattering of wing parts from unfortunate peacock butterflies were a sign that Natterer’s bats had feasted in one building while the discovery of sparkling droppings in the main barn signalled the presence of brown long-eared bats.

All that glitters, it would appear, is not gold.

Place Services’ next bat course: Preliminary Bat Surveys of Trees and Woodland - takes place on October 31st at Danbury Country Park. Visit: www.placeservices.co.uk/courses

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