Natterer’s Bats and Churches Research 
Latest Developments: March 2014 

Our objective has been to investigate new methods that can be used to reduce the problems caused by the presence of bats in some churches, while maintaining the favourable conservation status of bats. A series of experiments has been designed to show whether encouraging Natterer’s bats away from sensitive areas in churches can be achieved in a practicable and ecologically sound manner. Our studies rely on altering where bats roost and changing their activity within churches, without adversely impacting on the welfare and conservation of bats. It should be stressed that all research has taken place under licence, as the use of such techniques to disturb bats would otherwise be illegal. 

What has been happening? 
In 2011 and 2012 we held meetings with people who use and care for church buildings to learn about their experiences with bats, the issues that gave most concern and what solutions they would like to see. 
 
Field studies began in 2011 by examining the roosting and foraging behaviour of Natterer’s bats that inhabit churches. In total, 48 bats from eight churches were radio-tracked all night for up to five nights between July and September 2011-12. The results from this study, combined with a review of peer-reviewed literature and the discussions with church communities, informed the development of bat deterrents (‘sticks’) and alternative roosts in the form of bat boxes (‘carrots’) that were used subsequently in trials aimed at limiting the impact of bats within churches. 
 
After surveying more than 25 churches for the presence of Natterer’s bats, ten with sufficiently high numbers were selected for the research project’s manipulative trials which are described below. The condition of bats was examined prior to each trial to avoid disturbance to heavily pregnant bats or dependant young. Throughout the trials, and at all sites, we monitored both the use of roosts that were affected directly by deterrents and the overall level of bat habitation inside the churches. Bats were radio-tagged at each site to monitor the use of roosts inside and outside of churches and to estimate the availability of alternative roosts away from churches in the local area. 
 
Trials of acoustic deterrents 
Pilot investigations of different deterrent types revealed that sound had the greatest potential as a safe, effective deterrent and so an acoustic deterrent was used in short-term trials at six sites in 2012. Each trial lasted for 13 days during which the deterrent was in use for four days. The acoustic deterrent that was trialled in 2012, the Deaton deterrent, was a model used at wind turbines in the USA and emitted a loud continuous signal that was largely ultrasonic but with some frequencies within the audible range of humans. It was therefore switched off during the day to avoid disturbing visitors to churches. 
 
In 2013 we evaluated the effectiveness of the Deaton acoustic deterrent over sustained periods of use to see if ultrasound permanently relocates bats away from sensitive areas in churches. The Deaton acoustic deterrent was installed in three churches for trials that lasted 25 days during which the deterrent was in use for 15 days. These longer-term trials investigated: i) whether Natterer’s bats habituated to acoustic deterrence, ii) whether under longer-term use bats remained within the original roost in the church building, relocated to alternative roosts within the church or were excluded from the building, and iii) whether bats were adversely affected by the long-term use of deterrents. 
 
A prototype of a newly developed acoustic deterrent designed for use in churches was also trialled in 2013. The specification for the new acoustic deterrent was to be smaller, lighter, cheaper and more practical for churches than the original industrial-type units. The prototype deterrent did not produce sound audible to humans, so was left on continuously for four days and nights during the short-term (13 day) trials. 
 
Investigating artificial lighting 
The trials in 2012 also revealed a strong effect from lighting. A deterrent using high intensity lighting directed at the roost was used at a single church. The bats were found to be highly sensitive to the presence of light and they were unwilling to leave the roost. Due to concerns about the welfare of the bats, this trial was stopped and not repeated. 
 
Investigations were modified in 2013 to examine whether artificial lighting could be used safely, away from the roost, to create ‘no-fly zones’ within churches to reduce the area affected by bat droppings without impacting on bat welfare. At separate churches from those where acoustic trials took place, artificial lighting was used for short periods (four nights of an overall 13 day trial) to determine the impact on bat activity of raising ambient light levels. We examined whether artificial lighting has the potential to exclude bats from large areas within churches without adversely affecting bat welfare or conservation (by leaving parts of the church in darkness). This was important in evaluating whether lights could be used appropriately in the future to contain bats (and associated problems caused by droppings and urine) to localised zones within churches where they can be tolerated. At each site one area of the church was illuminated while leaving the remaining area half unlit. The overall levels of bat flight activity in lit and unlit areas, and roosting behaviour were monitored. 
 
Provision of bat boxes 
The type of bat box provided was chosen based on a literature review. Initially a single heated bat box was installed at each church at ceiling height. The specific location of boxes varied between churches depending on accessibility and negotiations with church wardens. In 2012, over the 13-day trials at each church, no bats were recorded using the bat boxes. In 2013, at each church where a bat box had been installed in 2012, an additional box was installed outside the church to try to improve the chances of bats using the boxes. The use of the boxes was monitored throughout the field season. 
What has been learned from the research? 
The radio-tracking studies of Natterer’s bats that were undertaken throughout the research project have shown that the colonies studied were highly dependent on their church roosts, with little use of alternative external roosts (i.e. other roosts in the local area) observed. This demonstrates the importance of understanding how an individual bat colony uses a church, when attempting to manipulate its behaviour to reduce negative impacts on a church community. 
 
In the short-term trials in 2012, the Deaton deterrent appeared to be effective at preventing bats from using their original roost within the church, during the four days of deterrent use. Bat droppings collected below affected roosts typically reduced to zero, or near to zero, by the third or fourth day of deterrent use. We found no evidence that use of this acoustic deterrent affected the foraging behaviour of Natterer’s bats. 
 
At the churches which operated the extended trials of the acoustic deterrents designed for use at wind-farms, the bats quickly relocated to alternative roosting locations within the church when the deterrents were operated. There was no evidence that the bats habituated to the deterrents during their 15-days of operation. The use of the deterrents did not appear to result in the exclusion of bats from the churches over the period, with similar numbers of bats present throughout the trial, but they roosted in different locations. There were no discernible changes to foraging behaviour. 
 
The prototype UK model acoustic deterrents were considered to show promise but further development would be required. 
 
The use of directed artificial lighting substantially reduced bat flight activity in lit areas of churches. The flight activity of all species present in the churches where this approach was trialled was reduced. The response of Natterer’s bats was particularly strong, but common and soprano pipistrelle species were less affected. The response of bats to the lighting varied among the churches, most likely to do with how reflected light impacted the remaining “dark” areas within each church. As well as changes to flight activity within the church, however, the lighting was also observed to change the emergence and nocturnal activity of Natterer’s bats. Time of emergence became more variable and the length of time the bats spent foraging outside the church was reduced. The use of lighting over extended periods may potentially be detrimental to bat welfare and conservation. 
 
There was little evidence that bat boxes installed inside and outside the churches had been used by bats during the study’s experimental periods but droppings underneath the boxes suggest some have been used subsequently. It has been observed in other mitigation studies that it may take a number of years before artificial enhancements such as boxes are used. Within churches bats may choose to use other alternative known roosting locations in preference to these newly installed features. 
 
Tailored use of deterrents to change the behaviour of bats inside churches, to reduce their impact on congregations, may be an option for some churches that have difficult problems with bats that cannot be resolved by other means. The techniques tested were successful in changing bat behaviour to reduce impact of the bats on church communities, but some approaches also have tangible risks to the welfare or status of the colonies which are not fully understood and merit further investigation. 
 
With judicious use of deterrents, problems caused by bats in churches can be mitigated. Deterrents can be used to move roosting sites within churches and limit where bats leave their droppings and urine so that problems to congregations and to artefacts of historic and cultural significance can be much reduced. In order to protect Favourable Conservation Status, these deterrents will need to be used under licence from Natural England or the relevant Statutory Nature Conservation Organisation (SNCO). 
 
What will happen next? 
The results of the research will inform pilot use in 2014 at a small number of churches where church communities experience severe problems. The pilot project will be funded by English Heritage. It will aim to refine the use of the techniques and equipment that were trialled in the research, to optimise their effectiveness in reducing safely the impacts caused by bats in these churches and to learn more about how they can be adapted to individual church situations. It is expected that the pilot project in 2014 will aim to address a current knowledge gap by investigating the effects of deterrents on bats in spring and early summer. The bats will be monitored to ensure that the deterrents can be used without impacting adversely on bat welfare or conservation. A toolkit to develop a framework for licensing the management of bats in churches will be developed during the pilot project. Churches experiencing problems with bats should continue to seek advice from the National Bat Helpline or relevant SNCO as well as from their Diocesan Advisory Committee for the Care of Churches (or equivalent in other denominations), and consider all the options appropriate for their situation. 
 
Further information 
The final report of this study was published on the Defra website in March 2014 and is available to DOWNLOAD FROM HERE  
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