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What is a Preliminary Roost Assessment - 'PRA'

The aim of a Preliminary Roost Assessment is to establish whether buildings have the potential to support roosting bats.


In the UK, bat populations have been declining considerably over recent years. Bats are a protected species as are their resting and breeding sites. Bats are under threat from building and development work that affects roosts, loss of habitat, the severing of commuting routes, chemical treatments of building materials, wind turbines and certain lighting.




On a 'PRA' an enims ecologist will make a thorough inspection of all outbuildings, main dwellings and the surrounding area on which the proposed development is due to take place. We will look at the structure of the building and determine any features that may have potential for bats to roost. This assessment will be carried out both from outside the buildings and inside the buildings. We will look at the surroundings - perhaps certain trees local to the proposed development may have the potential for bats to roost which can also have an impact on proposed plans.



We will then look for material evidence of bats being present; especially bat droppings which can easily be distinguished from mice or rat droppings because of the bats diet of insects.


We also do some desk study work to look at local records to determine whether the property is near a known commuting site for bats or whether certain breeds of bats have been noted to be seen in the local vicinity.


This enables us to get a broad view and understanding of the potential that the site may have to support roosting bats.


We will collate all of the information into a detailed report, and categorise different points of the site that may have the potential of roosting bats as low, moderate or high.


A PRA can be conducted throughout the year however, If the ecologist deems the site to have potential for roosting bats then further survey works will need to be completed to establish the the presence or likely absence of bats. Depending on the category of risk of potential for roosting bats will determine how many surveys will need to be completed as a rule high risk developments will need x3 separate surveys x2 conducted at dusk and one at dawn. These surveys can only be completed from May - September when the bats are active. Find out more about further surveys here.



If bats are found on your proposed development it will mean that we will have to look into obtaining a licence from Natural England if the development will disturb or damage their habitat. This may mean looking at restrictions on the times of year you may be able to start and complete works, creating additional habitat or keeping certain features to retain their habitat or enhancing the area around the development to enable the bats to continue to roost.


Further Blog posts will be published on how enims conduct their surveys, and why bats are so important shortly.




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