Mitigating the impact of bats in historic churches: the response of Natterer’s bats Myotis nattereri to artificial roosts and deterrence

Published source details Zeale M.R.K, Bennitt E., Newson S.E, Packman C., Browne W.J, Harris S., Jones G. & Stone E. (2016) Mitigating the impact of bats in historic churches: the response of Natterer’s bats Myotis nattereri to artificial roosts and deterrence. PLoS ONE, 11, e0146782.
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This study is summarised as evidence for the following.

	Action	Category
	Manage microclimate of artificial bat roosts Action Link
	Conserve roosting sites for bats in old structures or buildings Action Link
	Leave bat roosts and roost entrances unlit Action Link
	Provide bat boxes for roosting bats Action Link

Manage microclimate of artificial bat roosts

A replicated study in 2012–2013 at six churches in Norfolk, UK (Zeale et al 2016) found that Natterer’s bats Myotis nattereri did not use any of the 12 internal and external heated bat boxes provided after being displaced from roosts inside the churches. Two bat boxes (Bat Conservation International design) containing heat mats and thermostats were installed at each of six churches, one inside the church and one outside at roof height. Acoustic deterrents and artificial lighting were used to deter bats from their existing roost locations inside the churches where droppings and urine were causing problems. Emergence surveys and radio-tracking were carried out at each site between July and September in 2012 or 2013.

(Summarised by: Anna Berthinussen)
Conserve roosting sites for bats in old structures or buildings

A before-and-after study in 2012–2013 at one church in Norfolk, UK (Zeale et al 2016) found that two sections of an existing roost within the church that were ‘boxed-in’ continued to be used by Natterer’s bats Myotis nattereri, but the number of bats using the roost after it had been ‘boxed-in’ was reduced by half. The ‘boxed-in’ areas continued to be used by up to 52% of bats (46 of 88) that originally roosted in the church. Up to 28 of the bats that originally roosted in the church used an external roost location in the church porch as a new roost site. The ‘boxed-in’ areas (5 m long) were accessible to bats via existing entry points and were sealed off from the internal spaces of the church. They included roof timbers and mortise joints that had previously been used by the bats. The roosts were ‘boxed-in’ after the build-up of droppings and urine within the church interior caused problems for human visitors. Emergence surveys and radio-tracking were carried out at each site between July and September in 2012 or 2013.

(Summarised by: Anna Berthinussen)
Leave bat roosts and roost entrances unlit

A controlled study in 2012 at a church in Norfolk, UK (Zeale et al 2016) found that when bat roost entrances were left unlit more Natterer’s bats Myotis nattereri emerged than when entrances were illuminated with artificial light. Eleven bats emerged from the roost when the entrances were left unlit, whereas no bats emerged on the first night entrances were illuminated, and two bats emerged on the second night. On the third night, after the light was switched off, all 11 bats emerged. However, emergence times were reported to be earlier than those recorded prior to lighting (data not provided). A 400-W halogen lamp was placed 7.5 m below the roost and directed upwards to illuminate the roost entrances. In July–August 2012, the movements of 11 radio-tagged adult female Natterer’s bats were monitored during four nights with the roost left unlit, four nights with the light switched on and four nights after the light was switched off.

(Summarised by: Anna Berthinussen)
Provide bat boxes for roosting bats

A replicated study in 2012–2013 at six churches in Norfolk, UK (Zeale et al 2016) found that Natterer’s bats Myotis nattereri did not use any of the 12 heated bat boxes provided after being displaced from roosts inside the churches. Two bat boxes (Bat Conservation International design) containing heat mats and thermostats were installed at each of six churches, one inside the church and one outside at roof height. Acoustic deterrents and artificial lighting were used to deter bats from their existing roost locations inside the churches where droppings and urine were causing problems. Emergence surveys and radio-tracking were carried out at each site between July and September in 2012 or 2013.

(Summarised by: Anna Berthinussen)