16
BCD SPECIAL REPORT ON
HISTORIC CHURCHES
21ST ANNUAL EDITION
balances ongoing building use, the protection
of historic or culturally significant fabric, and
the future management of bat colonisation.
The aim of the University of Bristol
research project was to examine the impact
of current licensable activities and investigate
new mitigation activities that could be used
to reduce conflict between humans and
bats while maintaining the conservation
status of bats. The research focussed on two
major areas of conflict: situations where
large maternity roosts exist in a domestic
setting, and churches. This article focusses
on the second aspect of the report.
The research team conducted extensive
research across a series of church buildings in
Norfolk, and in particular examined whether
acoustic or light deterrents were effective
in encouraging bats to move away from
sensitive areas of churches where conflict
with human activity or the presence of
important artefacts was considered greatest.
The findings regarding acoustic deterrence
were particularly interesting and useful.
Speakers emitting continuous broadband
ultrasound were carefully positioned so as
to deter bats from entering particular parts
of each building. The study found that the
observed response of bats to the presence of
an acoustic deterrent was strong. Within a
matter of days, most bats had either moved
to alternative roosts within the church or had
found roosts outside the church. Importantly
from a species conservation point of view,
the presence of an acoustic deterrent did not
affect the home ranges, habitat preferences
or nocturnal behaviour of foraging bats. The
report suggests that a prototype acoustic
deterrent, developed during the project as a
practical and affordable option that could be
licensed for use by churches in the future, was
effective at deterring many bats from roosts
but will benefit from further development
to improve long-term performance.
The use of lighting deterrence was much
less encouraging. While the costs involved
for lighting are lower than for acoustic
deterrence, the impact on the welfare of
bat populations can be severe because
lighting can have a detrimental effect on the
emergence and foraging time of bats. Care
needs to be taken when positioning lighting
as lights shone at roosts can have the effect
of entombing bats, and evidence suggests
that sustained use of lights in this way may
result in the deaths of many bats. Owing
to welfare concerns, one of the studies was
terminated early and the report authors
concluded that the use of lighting to manage
bats in churches has the potential to cause
serious harm and should be strictly regulated.
While it can help to deter vandals and lead
thieves, the sustained use of nocturnal lighting
in churches is also potentially expensive,
increases the church’s carbon footprint
and can have a negative aesthetic impact.
Lighting distorts the foraging opportunities
available for bats and this may even
encourage them to prefer specific locations
and deter them from roosting in others.
The research project looked to a limited
degree at the provision of artificial roosts to
Technical drawing of a bat hotel at the Canons’ Cloister, St George’s Chapel, Windsor Castle and, below,
construction in progress before the roof decking was re-laid
