Relocate access points to bat roosts within developments

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 2
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How is the evidence assessed?

Effectiveness

45%
Certainty

32%
Harms

10%

Calculating overall effectiveness category

Background information and definitions

This intervention involves relocating the access points to a bat roost within a building development when the original access has been removed or altered. This could involve leaving gaps in brickwork, lead flashing or sofits, or the use of purpose-made ridge and roof tiles, bat bricks, tubes or chutes. For an intervention that involves retaining existing access points, see ‘Retain existing bat roosts and access points within developments’.

Study locations

Key messages

Two studies evaluated the effects of relocating access points to bat roosts within building developments on bat populations. One study was in Ireland and one in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (2 STUDIES)

Use (2 studies): One before-and-after study in Ireland found that fewer brown long-eared bats used a roost after the access points were relocated, and no bats were observed flying through them. One before-and-after study in the UK found that few lesser horseshoe bats used an alternative access point with a ‘bend’ design to re-enter a roost in a building development, but the number of bats using the roost increased after an access point with a ‘straight’ design was installed.

About key messages

Key messages provide a descriptive index to studies we have found that test this intervention.

Studies are not directly comparable or of equal value. When making decisions based on this evidence, you should consider factors such as study size, study design, reported metrics and relevance of the study to your situation, rather than simply counting the number of studies that support a particular interpretation.

Supporting evidence from individual studies

A before-and-after study in 2004–2008 of one building renovation in Ireland (Aughney 2008) found that after relocating the access points to a bat roost within an attic during renovations, fewer brown long-eared bats Plecotus auritus used the roost and no bats were observed flying through the new access points. Before the renovations, 19 and eight brown long-eared bats were recorded exiting the roost through two original access points. After the renovations, no bats were observed exiting through two relocated access points and the number of droppings found inside the attic (<100) indicated that fewer bats were using the roost than before the renovations (number not reported). The building was a 19^th century brick house. During renovation work, two bat access points consisting of angled slats (‘louvres’) were installed in the roof in different locations to the original bat access points. Renovations were completed in early 2007. Emergence counts were carried out once in June 2004 before the renovations, and once in August 2008 after the renovations. An internal inspection was carried out in October 2008.
Study and other actions tested
Referenced paper
Aughney T (2008) An investigation of the impact of development projects on bat populations: Comparing pre- and post-development bat faunas. Bat Conservation Ireland report.
A before-and-after study in 1993–2016 of one building development in the UK (Reason 2017) found that an alternative access point with a ‘straight’ design resulted in an increase in lesser horseshoe bats Rhinolophus hipposideros using the basement of the building as a roost, but an access point with a ‘bend’ resulted in a decrease in bats re-entering the roost. Up to 35 bats were counted emerging from the roost prior to the installation of an alternative access point. After installation of the access point with a ‘bend’ in 2000, a similar number of bats exited the roost (data not reported), but only two were observed re-entering. In 2001, the access point was modified to a ‘straight’ design and the number of bats using the roost increased over a 15-year period (2002: 27 bats; 2016: 416 bats). The ‘bend’ design consisted of a 90° turn at the base of a short vertical shaft and was in place for 11 months. The ‘straight’ design consisted of a sloped chute enclosing the original flight route with a clear flight line into the roost. The building was a large manor house converted into a hotel in 2000–2001. Counts of emerging bats were carried out at least once/year between May and July in 1993–2000. Emergence and re-entry counts were carried out three times/year in 2000–2001. Biennial counts were carried out in July in 2002–2016.
Study and other actions tested
Referenced paper
Reason P.F. (2017) Designing a new access point for lesser horseshoe bats, Gloucestershire, UK. Conservation Evidence, 14, 52-57.

Please cite as:

Berthinussen, A., Richardson O.C. and Altringham J.D. (2021) Bat Conservation: Global Evidence for the Effects of Interventions. Conservation Evidence Series Synopses. University of Cambridge, Cambridge, UK.

Where has this evidence come from?

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This Action forms part of the Action Synopsis:

Bat Conservation

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Create alternative bat roosts within developments Action Link	Unknown effectiveness (limited evidence)	11	Synopsis Link