Low_res_June 2022 - New homes overlooking Swale1

Like a Bat out of Hill ... ecology success story comes out of Graven Hill development

A long-term project to relocate bats on an Oxfordshire housing development has been hailed a success after newly installed roosts in the form of bat boxes have been taken over by several of the endangered species.

Back in 2015, plans were developed for a new 1900+ strong village community by the newly-formed Graven Hill Village Development Company (GHVDC). This was to take place on the abandoned 188-hectare former MoD site at Bicester.

GHVDC appointed specialist ecologists at Waterman Infrastructure & Environment, the abandoned buildings, hangars and woodlands were all carefully surveyed for any signs of bats roosting, breeding, feeding or using habitats as commuter routes to other grounds.

Evidence including active bat roosts were found for ten different species including the Common Pipistrelle and the Brown Long-Eared Bat. There are currently 17 varieties of bats native to the UK and over half of these species are found on Site.

As legally protected species, Waterman I&E had to apply for European Protected Species licences to Natural England for permission to demolish any affected buildings or sites and detail what mitigation and enhancement measures would be introduced to further protect the bat colonies.

Simon Dowell, principal ecologist at Waterman, explained: “As part of the licence granted by Natural England we had to provide alternative roosting options for the local bat populations and so bat boxes have been provided as part of a long-term ecology project to support the bats at Graven Hill.

“We’re now delighted to have discovered that several of the boxes we put up in the last couple of years have been colonised by the bats. Most bats are crevice dwelling so they like trees and buildings with rough interiors and edges to hang onto.

“Our bat boxes range in size. A hibernation box might be 50cm high x 38cm wide and that can hold hundreds of bats, a smaller one of maybe 36cm x 16cm can potentially hold 50-100. Ours are made out of woodcrete which has a rough surface they can hang on to, but we also include wooden baffles which they hold onto and they are also designed to stop drafts getting in.”

Some bat boxes are naturally damaged or lost in bad weather but they can be attached to almost anything. Some are round to mimic trees and they are placed deliberately at different heights and directions so the bats can choose their own “des res”. Bats are also transitional and might relocate if one box gets too hot, for example.

Waterman Infrastructure & Environment has static bat detectors placed at Graven Hill to pick up the calls and echo locations of bats in situ. Exact numbers are hard to define due to the bats’ nocturnal and roosting habits but signs are it is a substantial presence. 

Said Simon: “It is great news that the bats have taken to their new roosts and we want to make sure they continue to thrive at Graven Hill. The bats originally were mostly using the old MoD buildings rather than woodland on site to roost, but they have now found the boxes in the trees and seem to really like those.”

“Graven Hill Residents may well see the bats come out to feed at dusk but the bat boxes have been deliberately sited away from residential areas so they won’t be disturbed. We will also be providing a plan for new roosts but, again, these will be well away from any future developments so the bats can continue to enjoy their new homes at Graven Hill.” added Simon.