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Bat Surveys

We are fortunate in Great Britain to have 17 breeding species of bat. However urban development, loss of roosts, popularity of building conversions such as old barns, use of agricultural pesticides and loss of natural habitats for example hedges and trees have contributed to the decline in our bat population over the last 100 years. To try and help reverse this decline bats have been protected for over 35 years by the 1981 Wildlife and Countryside Act and more recently the Conservation of Habitats and Species Regulations in 2010.

This legislation can be a little confusing at times and open to interpretation but essentially the key themes are;

  • It is an offence to sell or advertise for sale dead or live bats or any parts of bats.
  • It is an offence to obstruct access to or intentionally or recklessly disturb bats where they are living.
  • It is an offence to deliberately capture, injure, kill or keep a bat.
  • It is an offence to control bats.
  • It is an offence to transport dead or live bats.
  • It is an offence to damage or destroy breeding sites even it is accidental.
Bat report
Bat Report

Where do bats roost?

Some species of bats like to live in buildings often in roof spaces, crevices or under roof tiles, particularly old buildings can provide a number of roosting sites, other species prefer natural roosting sites including hedges and trees

How can I spot if bats are present?

At dawn or dusk you may see them flying around as they hunt for insects to eat but probably the easiest evidence of their presence is their droppings. A lot of people confuse bat droppings with those of rodents because they are a similar shape and size but a bat dropping will crumble if you rub it between your fingers whereas rodent droppings just squash without crumbling. Rodent droppings tend to be smooth but those produced by a bat tend to have rough edges and can also look segmented though the size and appearance does vary between bat species. Droppings may be scattered in a circular pile or along a line according to the species of bat and where they are roosting. Common places to find droppings are in roof spaces, under a porch or facia boards, on window sills, on top of bins or other containers and near potential access points. Bats like to use exiting small openings to get into spaces so can be found where buildings are in disrepair such as a missing roof tile or one that has been dislodged, a damaged facia or soffit board 

When to have a bat survey

If you think there may be bats in the building where work is to be carried out or in the area where a new development is proposed you must commission a bat survey. Often planners will insist that bat surveys are carried out before a new building development or alterations to existing buildings to rule out the presence of bats. Initially this is just a visual inspection carried out by an ecologist. If the ecologist finds evidence that there may be bats using the area for a roost then a more detailed survey is required. This could take the form of a survey on particular section of a building or a transect survey of a large area such as a field.

A survey aims to identify if bats are present, which species  and how many there are, also the type of roost for example winter hibernation or maternity, along with the roost access points  and where exactly the roost is. This will help to establish any likely impacts of the proposed schedule of works or new build on the bats and roost sites. Sometimes a survey will not find any evidence.

Surveys inside buildings can be carried out any time of year but if an ecologist believes there may be a maternity roost then the bats must be left undisturbed and cannot be surveyed inside. Outside surveys are carried out between April and September.

Bats use echolocation to find food and navigate, they are nocturnal so to detect bats moving about in the dark specialist electronic bat detectors are used which pick up echolocation noises inaudible to the human ear. These amazing pieces of equipment convert the bats’ echolocation calls into sounds humans can hear. In addition some detectors display the data in visual form. Bat species have different calls so an experienced ecologist trained to use detectors can tell if bats are present, which species and how many but it can be confusing because the immediate environment of the bats’ surroundings can change the sound, shape and pattern of the call. Surveys are usually carried out  from 15 minutes before dusk into the night and before dawn until 15 minutes after  typically surveys take between 1  ¾ and 4 hours. In the half-light ecologist can also use flight patterns, behaviour and the mammal’s appearance to determine which species of bat it is.

Licences are required from Natural England or Natural Resources Wales if you wish to disturb a bat roost (any removal must be carried out by a professional with a Bat Disturbance Licence). Sometimes it is possible to carry out the repairs / maintenance or development by altering the proposals, changing the method or avoiding certain times of year then a licence is not required. However you will need to seek the advice of a licenced ecologist.