Action: Conserve roosting sites for bats in old structures or buildings
- Two studies evaluated the effects of conserving roosting sites for bats in old structures or buildings on bat populations. Both studies were in the UK.
COMMUNITY RESPONSE (0 STUDIES)
POPULATION RESPONSE (1 STUDY)
- Abundance (1 study): One before-and-after study in the UK found that a greater number of bats hibernated in a railway tunnel after walls with access grilles were installed at the tunnel entrances and wood was attached to the tunnel walls.
USAGE (1 STUDY)
- Use (1 study): One before-and-after study in the UK found that Natterer’s bats used a roost that was ‘boxed-in’ within a church, but the number of bats using the roost was reduced by half.
Old structures or buildings and the roosting spaces within them may be conserved as roosting sites for bats. Conflict may arise when old buildings are also used by humans, and solutions may be sought to both conserve bat roosts and reduce any negative impacts on human inhabitants or visitors.
Supporting evidence from individual studies
A before-and-after study in 1993–1997 of a disused railway tunnel in Wiltshire, UK (Mitchell-Jones et al 2007) found that conserving a roosting site by constructing walls with access grilles at the ends of the tunnel, along with attaching wood to the tunnel walls, resulted in an increase in the number of hibernating bats. More bats were counted hibernating in the tunnel after the end walls were constructed and wood attached (before: 117 bats; two years after: 190 bats). During fourteen subsequent surveys (dates not reported), the number of hibernating bats increased to 678, with 30% of bats roosting behind the wood on the tunnel walls. The majority (94%) were Natterer’s bats Myotis nattereri. Brown long-eared bats Plecotus auritus, Daubenton’s bats Myotis daubentonii, whiskered/Brandt’s bats Myotis mystacinus/brandtii and barbastelle bats Barbastella barbastellus were also recorded. The end walls with access grilles were constructed in 1994, and wood was attached to the tunnel walls in 1994 and 1995. The temperature was reported to be more stable after the end walls were constructed (before: not reported; after: 8˚C) and humidity inside the tunnel increased (before: 80%; after 95%). Hibernating bats were counted in the winters of 1993 and 1996/1997.
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 radiotracking were carried out at each site between July and September in 2012 or 2013.
- Mitchell-Jones A.J., Bihari Z., Masing M. & Rodrigues L. (2007) Protecting and managing underground sites for bats. EUROBATS report.
- 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