Provide alternative bat roosts during maintenance work at road/railway bridges and culverts

Overall effectiveness category Unknown effectiveness (limited evidence)
Number of studies: 1
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How is the evidence assessed?

Effectiveness

20%
Certainty

22%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Bats may be temporarily excluded from their roosts in bridges or culverts during maintenance work to prevent injury or death. Alternative structures, such as bat houses, may be provided as temporary roosts until the work is complete.

For the effects of excluding bats, see ‘Exclude bats from roosts during maintenance work at road/railway bridges and culverts’.

Study locations

Key messages

One study evaluated the effects of providing alternative bat roosts during maintenance work at road bridges. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

BEHAVIOUR (1 STUDY)

Use (1 study): One review in the USA found that bat houses provided as alternative roosts during bridge replacement works were used by fewer Mexican free-tailed bats than the original roost at one site and were not used by bats at all at three sites.

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 review in 2017–2018 of case studies at four road bridges in California, USA (Harvey & Associates 2019) found that bat houses provided as alternative roosts during bridge replacement works were used by fewer bats than the original roost or were not used at all. At one site, seven bat houses built to replace a roost for four years during bridge replacement works were used by fewer Mexican free-tailed bats Tadarida brasiliensis (2,000 bats) than the original roost (40,000 bats). At three other sites, bat houses built to replace roosts used by pallid bats Antrozous pallidus (18 bats), Yuma myotis bats Myotis yumanensis (40–100 bats), and/or Mexican free-tailed bats (994 bats) during bridge replacement works were not used at all. At all four sites, bat houses (or ‘condominiums’) were built as temporary roosts while bats were excluded from their original roosts during bridge replacement works (dates not reported). Counts of bats before and after the works were taken from questionnaires completed by the California Department of Transportation.
Study and other actions tested
Referenced paper
Harvey & Associates H.T. (2019) Caltrans bat mitigation: A guide to developing feasible and effective solutions. California Department of Transportation (Caltrans) report.

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?

List of journals searched by synopsis

All the journals searched for all synopses

This Action forms part of the Action Synopsis:

Bat Conservation

Related Actions

Actions	Effectiveness	Studies	Category
Minimize road lighting to reduce insect attraction Action Link	No evidence found (no assessment)	0	Synopsis Link
Install green bridges as road/railway crossing structures for bats Action Link	Unknown effectiveness (limited evidence)	1	Synopsis Link
Replace or improve habitat for bats around roads/railways Action Link	No evidence found (no assessment)	0	Synopsis Link