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2. BAT CONSERVATION (2019 Update)

© W. Sutherland et al., CC BY 4.0 https://doi.org/10.11647/OBP.0179.02

Anna Berthinussen, Olivia C. Richardson & John D. Altringham

Expert assessors

Fabio Bontadina, SWILD — Urban Ecology & Wildlife Research, Switzerland

Jasja Dekker, Jasja Dekker Dierecologie, Netherlands

Brock Fenton, University of Western Ontario, Canada

Winifred Frick, Bat Conservation International, USA

Alice Hughes, Xishuangbanna Tropical Botanical Garden, UK/China

David Jacobs, University of Cape Town, South Africa

Johnny de Jong, Swedish University of Agricultural Sciences, Sweden

Bradley Law, Forest Science Centre, New South Wales Department of Primary Industries, Australia

Rodrigo Medellin, National Autonomous University of Mexico, Mexico

Kirsty Park, University of Stirling, UK

Silviu Petrovan, University of Cambridge, UK

Paul Racey, University of Exeter, UK

Orly Razgour, University of Southampton, UK

Guido Reiter, Austrian Coordination Centre for Bat Conservation and Research, Austria

Danilo Russo, Federico II University of Naples, Italy

Ricardo Rocha, University of Cambridge, UK

Emma Stone, African Bat Conservation, UK/Malawi

Scope of assessment: for native wild bat species across the world.

Assessed: 2019. For previous assessments and expert panels please check What Works in Conservation 2018.

Effectiveness measure is the median % score for effectiveness.

Certainty measure is the median % certainty of evidence for effectiveness, determined by the quantity and quality of the evidence in the synopsis.

Harm measure is the median % score for negative side-effects to the group of species of concern.

This book is meant as a guide to the evidence available for different conservation interventions and as a starting point in assessing their effectiveness. The assessments are based on the available evidence for the target group of species for each intervention. The assessment may therefore refer to different species or habitat to the one(s) you are considering. Before making any decisions about implementing interventions it is vital that you read the more detailed accounts of the evidence in order to assess their relevance for your study species or system.

Full details of the evidence are available at www.conservationevidence.com

There may also be significant negative side-effects on the target groups or other species or communities that have not been identified in this assessment.

A lack of evidence means that we have been unable to assess whether or not an intervention is effective or has any harmful impacts.

2.1 Threat: Residential and commercial development

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for residential and commercial development?

Likely to be beneficial

Unknown effectiveness (limited evidence)

No evidence found (no assessment)

Likely to be beneficial

Create alternative bat roosts within developments

Ten studies evaluated the effects of creating alternative bat roosts within developments on bat populations. Two studies were in the USA and eight studies were in Europe.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (10 STUDIES)

Use: (10 studies): Two replicated studies in the USA and UK found that bats did not use any of the alternative roosts provided in bat houses or a purpose-built bat wall after exclusion from buildings. One review in the USA and two studies (one replicated) in the UK found that bat boxes or bat lofts/barns were used by bats at 13–74% of development sites, and bat lofts/barns were used by maternity colonies at one of 19 development sites. Three of five before-and-after studies in Ireland, Portugal, Spain and the UK found that bat colonies used purpose-built roosts in higher or similar numbers after the original roosts were destroyed. The other two studies found that bats used purpose-built roosts in lower numbers than the original roost.

Assessment: likely to be beneficial (effectiveness 40%; certainty 40%; harms 10%).

http://www.conservationevidence.com/actions/949

Unknown effectiveness (limited evidence)

Retain existing bat roosts and access points within developments

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

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (2 STUDIES)

Use (2 studies): One before-and-after study in Ireland found similar numbers of brown long-eared bats roosting within an attic after existing access points were retained during renovations. One replicated, before-and-after study in the UK found that four of nine bat roosts retained within developments were used as maternity colonies, in two cases by similar or greater numbers of bats after development had taken place.

Assessment: unknown effectiveness (effectiveness 67%; certainty 27%; harms 0%).

http://www.conservationevidence.com/actions/947

Relocate access points to bat roosts within developments

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)

USAGE (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.

Assessment: unknown effectiveness (effectiveness 45%; certainty 32%; harms 10%).

http://www.conservationevidence.com/actions/946

Change timing of building work

One study evaluated the effects of changing the timing of building work on bat populations. The study was in Ireland.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One before-and-after study in Ireland found that carrying out roofing work outside of the bat maternity season, along with retaining bat access points, resulted in a similar number of brown long-eared bats continuing to use a roost within an attic.

Assessment: unknown effectiveness (effectiveness 50%; certainty 12%; harms 0%).

http://www.conservationevidence.com/actions/950

Exclude bats from roosts during building work

One study evaluated the effects of excluding bats from roosts during building work on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Behaviour change (1 study): One replicated, before-and-after study in the UK found that excluding bats from roosts within buildings did not change roost switching frequency, core foraging areas or foraging preferences of soprano pipistrelle colonies.

Assessment: unknown effectiveness (effectiveness 45%; certainty 23%; harms 17%).

http://www.conservationevidence.com/actions/1930

Create or restore bat foraging habitat in urban areas

Three studies evaluated the effects of creating or restoring bat foraging habitat in urban areas on bat populations. One study in the USA evaluated restored forest fragments, and two studies in the UK and the USA evaluated green roofs.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, controlled, site comparison study in the USA found no difference in species richness over green roofs and conventional unvegetated roofs.

POPULATION RESPONSE (3 STUDIES)

Abundance (3 studies): One site comparison study in the USA found higher bat activity (relative abundance) in two of seven restored forest fragments in urban areas than in two unrestored forest fragments. One replicated, controlled, site comparison study in the UK found significantly greater bat activity over ‘biodiverse’ green roofs than conventional unvegetated roofs, but not over ‘sedum’ green roofs. One replicated, controlled, site comparison study in the USA found greater bat activity for three of five bat species over green roofs than over conventional unvegetated roofs.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 60%; certainty 36%; harms 0%).

http://www.conservationevidence.com/actions/954

Protect brownfield or ex-industrial sites

One study evaluated the effects of protecting brownfield or ex-industrial sites on bat populations. The study was in the USA.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One study in the USA found that five bat species were recorded within a protected urban wildlife refuge on an abandoned manufacturing site.

POPULATION RESPONSE (0 STUDIES)

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 40%; certainty 20%; harms 0%).

http://www.conservationevidence.com/actions/953

Legally protect bats during development

Three studies evaluated the effects of legally protecting bats by issuing licences during development on bat populations. The three studies were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (0 STUDIES)

OTHER (3 STUDIES)

Impact on bat roost sites (2 studies): One review in the UK found that licenced activities during building developments had a negative impact on bat roosts, with 68% of roosts being destroyed. One replicated, before-and-after study in the UK found that five of 28 compensation roosts provided under licence were used, and two by similar or greater numbers of bats after development.

Change in human behaviour (2 studies): One review in the UK found that the number of development licences for bats more than doubled over three years in Scotland. One review in the UK found that 81% of licensees did not carry out post-development monitoring to assess whether bats used the roost structures installed.

Assessment: unknown effectiveness (effectiveness 18%; certainty 15%; harms 2%).

https://www.conservationevidence.com/actions/1935

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.2 Threat: Agriculture

2.2.1 All farming systems

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for all farming systems?

Likely to be beneficial

Unknown effectiveness (limited evidence)

No evidence found (no assessment)

Likely to be beneficial

Use organic farming instead of conventional farming

Seven studies evaluated the effects of using organic farming instead of conventional farming on bat populations. Six studies were in Europe and one in the USA.

COMMUNITY RESPONSE (4 STUDIES)

Richness/diversity (4 studies): Three of four replicated paired sites or site comparison studies in the UK, USA and France found that the number of bat species did not differ between organic and non-organic farms. The other study found more bat species on organic farms than non-organic farms.

POPULATION RESPONSE (7 STUDIES)

Abundance (7 studies): Four of five replicated, paired sites or site comparison studies in Europe and the USA found that total bat activity (relative abundance) and common pipistrelle activity did not differ between organic and non-organic farms. The other study found significantly higher total bat activity on organic farms than non-organic farms. Two replicated, paired sites and site comparison studies in the UK found significantly higher activity of Myotis species over water and rivers on organic farms than non-organic farms, but no differences were found for other species or habitats.

USAGE (0 STUDIES)

Assessment: likely to be beneficial (effectiveness 41%; certainty 45%; harms 0%).

http://www.conservationevidence.com/actions/961

Retain remnant forest or woodland on agricultural land

Six studies evaluated the effects of retaining forest or woodland on agricultural land on bat populations. Four studies were in Australia, one in the UK, and one in Brazil.

COMMUNITY RESPONSE (4 STUDIES)

Community composition (2 studies): One of two replicated, site comparison studies in Australia and Brazil found that remnant woodland had a different composition of bat species to plantations and treeless paddocks. The other study found that bat species composition was similar between remnant forest and plantations.

Richness/diversity (4 studies): Three of four replicated, site comparison studies in Australia and Brazil found more bat species in remnant forest and woodland than in plantations or treeless paddocks or pasture. The other study found a similar number of bat species in remnant forest, plantations and paddocks.

POPULATION RESPONSE (6 STUDIES)

Abundance (6 studies): Five replicated, site comparison studies in Australia, the UK and Brazil found higher bat activity (relative abundance) or more bats in remnant forest or woodland than in plantations, treeless paddocks or pasture, or on arable land. One replicated study in Australia found higher activity for three of 10 bat species in remnant woodland than in treeless paddocks.

USAGE (1 STUDY)

Use (1 study): One replicated, site comparison study in Australia found bats roosting in trees within remnant woodland but not in trees within plantations.

Assessment: likely to be beneficial (effectiveness 55%; certainty 52%; harms 0%).

http://www.conservationevidence.com/actions/1947

Retain or plant native trees and shrubs amongst crops (agroforestry)

Seven studies evaluated the effects of retaining or planting native trees and shrubs amongst crops on bat populations. Two studies were in South America, four were in Mexico, and one was in Tanzania.

COMMUNITY RESPONSE (7 STUDIES)

Community composition (1 study): One replicated, site comparison study in Tanzania found different compositions of bat species in coffee plantations with different amounts and types of shade cover.

Richness/diversity (7 studies): Four of six replicated, site comparison studies in Columbia, Mexico and Costa Rica found a similar number of bat species in shaded and unshaded coffee plantations, and in coffee plantations with different amounts and types of shade cover. The two other studies found more bat species and higher bat diversity in coffee, cacao and banana plantations with varied shade cover, than in plantations with a single shade species or no shade. One replicated, site comparison study in Tanzania found more bat species in shaded coffee plantations than in traditional mixed agroforestry systems with natural forest vegetation.

POPULATION RESPONSE (5 STUDIES)

Abundance (5 studies): Two replicated, site comparison studies in Mexico captured more bats in coffee plantations with varied shade cover than in plantations with a single shade species. One replicated, site comparison study in Mexico found higher activity (relative abundance) of forest bat species in plantations with a varied shade cover than in plantations with a single shade species, but the opposite was true for open habitat bat species. One replicated, site comparison study in Costa Rica found no difference in the number of bats captured between cacao and banana shade plantations and unshaded monocultures. One replicated, site comparison study in Tanzania found greater bat occurrence in shaded coffee plantations than in traditional mixed agroforestry systems with natural forest vegetation.

USAGE (0 STUDIES)

Assessment: likely to be beneficial (effectiveness 55%; certainty 50%; harms 0%).

http://www.conservationevidence.com/actions/963

Unknown effectiveness (limited evidence)

Introduce agri-environment schemes

Three studies evaluated the effects of agri-environment schemes on bat populations. The three studies were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (3 STUDIES)

Abundance (3 studies): Two of three replicated, paired sites study in the UK found that total bat activity (relative abundance) and the activity of six bat species did not differ significantly between farms managed under agri-environment schemes and those managed conventionally. The other study found significantly lower overall bat activity and activity of pipistrelle species on agri-environment scheme farms than conventional farms.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 35%; certainty 30%; harms 10%).

http://www.conservationevidence.com/actions/962

Engage farmers and landowners to manage land for bats

One study evaluated the effects of engaging farmers and landowners to manage land for bats on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One study in the UK found that during a five-year project to engage farmers and landowners to manage land for bats, the overall population of greater horseshoe bats at four maternity roosts in the area increased (but see summary below).

USAGE (0 STUDIES)

OTHER (1 STUDY)

Change in human behaviour (1 study): One study in the UK found that a landowner engagement project resulted in 77 bat-related management agreements covering approximately 6,536 ha of land.

Assessment: unknown effectiveness (effectiveness 55%; certainty 20%; harms 0%).

http://www.conservationevidence.com/actions/1936

Retain unmown field margins

One study evaluated the effects of retaining unmown field margins on bats populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ between unmown field margins managed for wildlife on agri-environment scheme farms and field margins on conventional farms.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 0%; certainty 10%; harms 0%).

http://www.conservationevidence.com/actions/1940

Manage hedges to benefit bats

One study evaluated the effects of managing hedges to benefit bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ between hedges managed for wildlife on agri-environment scheme farms and hedges on conventional farms.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 0%; certainty 20%; harms 0%).

http://www.conservationevidence.com/actions/1943

Retain existing in-field trees

Two studies evaluated the effects of retaining existing in-field trees on bat populations. Both studies were in Australia.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, site comparison study in Australia found that grazed pasture with scattered trees had more bat species than pasture without trees.

POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): Two replicated studies (one site comparison study) in Australia found that paddocks/pasture with scattered trees had greater overall bat activity (relative abundance) or greater activity for four of 10 bat species than treeless paddocks/pasture.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 50%; certainty 30%; harms 0%).

http://www.conservationevidence.com/actions/1945

Create tree plantations on agricultural land to provide roosting and foraging habitat for bats

Three studies evaluated the effects of creating tree plantations on agricultural land to provide roosting and foraging habitat for bats on bat populations. The three studies were in Australia.

COMMUNITY RESPONSE (3 STUDIES)

Richness/diversity (3 studies): Three replicated, site comparison studies in Australia found no difference in the number of bat species in agricultural areas with and without plantations of native trees.

POPULATION RESPONSE (3 STUDIES)

Abundance (3 studies): Two of three replicated, site comparison studies in Australia found no difference in bat activity (relative abundance) in agricultural areas with and without plantations of native trees. The other study found higher bat activity in plantations next to remnant native vegetation than in isolated plantations or over grazing land. In all three studies, bat activity was lower in plantations compared to original forest and woodland remnants.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 30%; certainty 30%; harms 0%).

http://www.conservationevidence.com/actions/958

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.2.2 Livestock farming

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for livestock farming?

Unknown effectiveness (limited evidence)

No evidence found (no assessment)

Unknown effectiveness (limited evidence)

Remove livestock modifications from water troughs

One study evaluated the effects of removing livestock modifications from water troughs on bat populations. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One replicated, paired sites study in the USA found that removing livestock modifications from water troughs resulted in bats drinking from them more frequently.

Behaviour change (1 study): One replicated, paired sites study in the USA found that when livestock modifications were removed from water troughs, bats approached troughs fewer times before successfully drinking from them.

Assessment: unknown effectiveness (effectiveness 60%; certainty 30%; harms 0%).

http://www.conservationevidence.com/actions/1951

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.2.3 Perennial, non-timber crops

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for perennial, non-timber crops?

No evidence found (no assessment)

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.3 Threat: Energy production — mining

2.3.1 Wind turbines

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for wind turbines?

Beneficial

Likely to be

beneficial

No evidence found (no assessment)

Beneficial

Increase the wind speed at which turbines become operational (‘cut-in speed’) to reduce bat fatalities

Four studies evaluated the effects of increasing the wind speed at which turbines become operational (cut-in speed) on bat populations. One study was in Canada and three studies were in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (4 STUDIES)

Survival (4 studies): Three randomized, replicated, controlled studies (including one before-and-after study) in Canada and the USA, and one review in the USA found that bat fatalities were significantly reduced when the wind speed at which turbines became operational (‘cut-in speed’) was increased.

USAGE (0 STUDIES)

Assessment: beneficial (effectiveness 80%; certainty 70%; harms 0%).

https://www.conservationevidence.com/actions/1960

Likely to be beneficial

Deter bats from turbines using ultrasound

Two studies evaluated the effects of deterring bats from wind turbines using ultrasound on bat populations. The two studies were in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Survival (1 study): One randomized, replicated, controlled study with a before-and-after trial in the second year in the USA found mixed results. In the first year of the study, 21-51% fewer bats were killed at turbines with an ultrasonic deterrent fitted than at control turbines, but in the second year, from 2% more to 64% fewer bats were killed at turbines with ultrasonic deterrents fitted.

USAGE (1 STUDY)

Behaviour change (1 study): One paired sites study in the USA found significantly fewer bats flying near one of two wind turbines with an ultrasonic deterrent compared to turbines without.

Assessment: likely to be beneficial (effectiveness 40%; certainty 45%; harms 7%).

http://www.conservationevidence.com/actions/968

Prevent turbine blades from turning at low wind speeds to reduce bat fatalities

Three studies evaluated the effects of preventing turbine blades from turning at low wind speeds on bat populations. Two studies were in Canada and one review was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (3 STUDIES)

Survival (3 studies): Two replicated, controlled before-and-after studies (including one randomized study) in Canada and one review in the USA found that bat fatalities were significantly reduced when turbine blades were prevented from turning at low wind speeds.

USAGE (0 STUDIES)

Assessment: likely to be beneficial (effectiveness 80%; certainty 50%; harms 0%).

http://www.conservationevidence.com/actions/970

Automatically reduce turbine blade rotation when bat activity is high

Two studies evaluated the effects of automatically reducing turbine blade rotation when bat activity is high on bat populations. One study was in Germany, and one in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Survival (2 studies): Two replicated studies (one randomized, controlled and one paired sites study) in Germany and the USA found that automatically reducing the rotation speed of wind turbine blades when bat activity is predicted to be high resulted in significantly fewer bat fatalities for all bat species combined and for little brown bats.

USAGE (0 STUDIES)

Assessment: likely to be beneficial (effectiveness 80%; certainty 55%; harms 0%).

http://www.conservationevidence.com/actions/971

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.3.2 Mining

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for mining?

Unknown effectiveness

(limited evidence)

No evidence found (no assessment)

Unknown effectiveness (limited evidence)

Install and maintain gates at mine entrances to restrict public access

Four studies evaluated the effects of installing gates at mine entrances on bat populations. Three studies were in the USA and one in Australia.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, before-and-after study in the USA found that significantly fewer bat species entered mines after gates were installed.

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, controlled, before-and-after study in Australia found fewer bats in mines after gates were installed.

USAGE (3 STUDIES)

Use (1 study): One before-and-after study in the USA found that 43 of 47 mines continued to be used 12 years after gates were installed, however bats abandoned four mines with ‘ladder’ design gates.

Behaviour change (2 studies): Two replicated, before-and-after or site comparison studies in the USA and Australia found that bats at mine entrances circled more and entered mines less after gates were installed.

Assessment: unknown effectiveness (effectiveness 25%; certainty 30%; harms 20%).

http://www.conservationevidence.com/actions/1963

Maintain microclimate in closed/abandoned mines

One study evaluated the effects of maintaining the microclimate in an abandoned mine on bat populations. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One before-and-after study in the USA found that modifying the microclimate of an abandoned mine by closing a man-made entrance resulted in a greater number of bats hibernating within the mine.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 45%; certainty 20%; harms 0%).

https://www.conservationevidence.com/actions/1964

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.4 Threat: Transportation and service corridors

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for roads?

Likely to be

beneficial

Unknown effectiveness (limited evidence)

Unlikely to be

beneficial

No evidence found (no assessment)

Likely to be beneficial

Install underpasses as road crossing structures for bats

Six studies evaluated the effects of installing underpasses or culverts as road crossing structures for bats. Five studies were in Europe and one in Australia.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (6 STUDIES)

Use (6 studies): Six studies (including four replicated studies) in Germany, Ireland the UK and Australia found that bats used underpasses below roads, and crossed over the roads above them, in varying proportions. One replicated, site comparison study in Australia found that bat species adapted to cluttered habitats used small culverts and underpasses more than bat species adapted to open or edge habitats.

Assessment: likely to be beneficial (effectiveness 52%; certainty 50%; harms 0%).

http://www.conservationevidence.com/actions/976

Install overpasses as road crossing structures for bats

Three studies evaluated the effects of installing overpasses as road crossing structures for bats. Two studies were in Europe and one in Australia.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One site comparison study in Australia found that the same number of bat species were recorded at an overpass and in nearby forest and bushland.

POPULATION RESPONSE (0 STUDIES)

USAGE (2 STUDIES)

Use (2 studies): One replicated, site comparison study in Ireland found that three bat species used overpasses but up to three-quarters of bats crossed the road below at traffic height. One study in the UK found that an overpass with planters was used by two-thirds of crossing bats, and an unvegetated overpass with a paved road over it was not used by crossing bats.

Assessment: likely to be beneficial (effectiveness 45%; certainty 42%; harms 0%).

http://www.conservationevidence.com/actions/977

Unknown effectiveness (limited evidence)

Install green bridges as road crossing structures for bats

One study evaluated the effects of installing green bridges as road crossing structures for bats. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One study in the UK found that a green bridge was used by 97% of bats crossing a road.

Assessment: unknown effectiveness (effectiveness 70%; certainty 27%; harms 0%).

http://www.conservationevidence.com/actions/979

Divert bats to safe crossing points with plantings or fencing

One study evaluated the effects of diverting bats using an artificial hedgerow on bat populations. The study was in Switzerland.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One controlled, before-and-after study in Switzerland found that up to one fifth of lesser horseshoe bats within a colony flew along an artificial hedgerow to commute.

Assessment: unknown effectiveness (effectiveness 10%; certainty 10%; harms 5%).

http://www.conservationevidence.com/actions/981

Maintain bat roosts in road bridges and culverts

One study evaluated the effects of maintaining bat roosts within a bridge on bat populations. The study was in Ireland.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One before-and-after study in Ireland found that a maternity colony of Daubenton’s bats continued to roost in a road bridge over a river in similar numbers after crevices were retained during repair work.

Assessment: unknown effectiveness (effectiveness 55%; certainty 20%; harms 0%).

http://www.conservationevidence.com/actions/1966

Unlikely to be beneficial

Install bat gantries or bat bridges as road crossing structures for bats

Two studies evaluated the effects of installing bat gantries as road crossing structures for bats. Both were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (2 STUDIES)

Use (2 studies): Two replicated studies (including one site comparison) in the UK found that fewer bats used bat gantries than crossed the road below at traffic height, and one bat gantry was not used at all.

Assessment: unlikely to be beneficial (effectiveness 2%; certainty 40%; harms 0%).

http://www.conservationevidence.com/actions/978

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.5 Threat: Biological resource use

2.5.1 Hunting

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for hunting?

No evidence found (no assessment)

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.5.2 Guano harvesting

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for guano harvesting?

No evidence found (no assessment)

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.5.3 Logging and wood harvesting

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for logging and wood harvesting?

Likely to be beneficial

Unknown effectiveness

(limited evidence)

No evidence found (no assessment)

Likely to be beneficial

Thin trees within forests

Six studies evaluated the effects of thinning trees within forest and woodland on bat populations. Four studies were in the USA, one study was in Canada, and one in Australia.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, site comparison study in Australia recorded the same bat species in thinned and unthinned forest, except for the chocolate wattled bat, which was not recorded in forests with unthinned regrowth.

POPULATION RESPONSE (6 STUDIES)

Abundance (6 studies): Four of five replicated, site comparison studies (including two paired sites studies and one controlled study) in the USA and Australia found greater total bat activity (relative abundance) in thinned than unthinned forest. The other study found similar total bat activity in thinned and unthinned stands. One replicated, controlled, site comparison study in Canada found greater activity of silver-haired bats in thinned than unthinned stands, but no difference for little brown bats or long-eared bats.

USAGE (0 STUDIES)

Assessment: likely to be beneficial (effectiveness 55%; certainty 45%; harms 1%).

http://www.conservationevidence.com/actions/991

Retain forested corridors in logged areas

Three studies evaluated the effects of retaining forested corridors in logged areas on bat populations. The three studies were in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 studies): One replicated, site comparison study in the USA found that bat activity (relative abundance) was significantly higher along the edges of forested corridors than in corridor interiors or in adjacent logged stands, which had similar activity levels.

USAGE (2 STUDIES)

Use (2 studies): One replicated, site comparison study in the USA found more Seminole bats roosting in forested corridors than logged stands or mature forest. One replicated, site comparison study in the USA found more male but fewer female evening bats roosting in forested corridors than logged stands.

Assessment: likely to be beneficial (effectiveness 55%; certainty 40%; harms 0%).

http://www.conservationevidence.com/actions/996

Unknown effectiveness (limited evidence)

Use selective or reduced impact logging instead of conventional logging

Three studies evaluated the effects of using selective or reduced impact logging instead of conventional logging on bat populations. Two studies were in the Neotropics and one study was in Italy.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, controlled, site comparison study in Trinidad found that the composition of bat species differed between selectively logged and conventionally logged forest.

POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): A review of 41 studies in the Neotropics found that reduced impact logging had a significantly smaller effect on bat abundance than conventional logging. One replicated, site comparison study in Italy found greater bat activity (relative abundance) at two of three sites that used selective logging techniques to open up the forest canopy rather than leaving the canopy intact.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 58%; certainty 30%; harms 2%).

http://www.conservationevidence.com/actions/989

Use shelterwood cutting instead of clearcutting

One study evaluated the effects of using shelterwood cutting instead of ‘gap release’ cutting on bat populations. The study was in Australia. We found no studies that evaluated the effects of shelterwood cutting instead of clearcutting.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One site comparison study in Australia found more Gould’s long-eared bats roosting in remnant trees within forests that had been shelterwood harvested than in forests.

Assessment: unknown effectiveness (effectiveness 15%; certainty 10%; harms 0%).

http://www.conservationevidence.com/actions/990

Retain residual tree patches in logged areas

Two studies evaluated the effects of retaining residual tree patches in logged areas on bat populations. The two studies were in Canada.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): Two replicated, site comparison studies in Canada found no difference in bat activity (relative abundance) along the edges of residual tree patches and the edges of clearcut blocks. One replicated, site comparison study in Canada found that the activity of smaller bat species was higher along the edge of residual tree patches than in the centre of clearcut blocks, but the activity of larger bat species did not differ.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 20%; certainty 25%; harms 0%).

http://www.conservationevidence.com/actions/995

Retain riparian buffers in logged areas

Two studies evaluated the effects of retaining riparian buffers in logged areas on bat populations. The two studies were in Australia.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, site comparison study in Australia found a similar number of bat species in riparian buffers within logged forest, regrowth forest and mature forest.

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in Australia found similar total bat activity (relative abundance) in riparian buffers within logged forest, regrowth forest and mature forest.

USAGE (1 STUDY)

Use (1 study): One replicated, site comparison study in Australia found that southern forest bats roosted less often in riparian buffers in logged forest than in unlogged forest, but Gould’s long-eared bats had a similar number of roosts in riparian buffers in logged forest, remnant trees in logged areas and unlogged forest.

Assessment: unknown effectiveness (effectiveness 35%; certainty 24%; harms 0%).

https://www.conservationevidence.com/actions/1985

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.6 Threat: Human disturbance — caving and tourism

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for caving and tourism?

Likely to be

beneficial

Trade-offs between

benefit and harms

Unknown effectiveness

(limited evidence)

No evidence found (no assessment)

Likely to be beneficial

Impose restrictions on cave visits

Three studies evaluated the effects of imposing restrictions on cave visits on bat populations. One study was in the USA, one in Canada and one in Turkey.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): Two before-and-after studies in Canada and Turkey found that bat populations within caves increased after restrictions on cave visitors were imposed.

USAGE (1 STUDY)

Behaviour change (1 study): One study in the USA found that reducing the number of people within cave tour groups did not have a significant effect on the number of take-offs, landings or overall activity (bat movements) of a cave myotis colony roosting within the cave.

Assessment: likely to be beneficial (effectiveness 64%; certainty 45%; harms 0%).

http://www.conservationevidence.com/actions/1002

Trade-off between benefit and harms

Install and maintain cave gates to restrict public access

Eleven studies evaluated the effects of installing cave gates on bat populations. Six studies were in the USA and five studies were in Europe.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (7 STUDIES)

Abundance (7 studies): Three of four before-and-after studies (including one replicated study and one controlled study) in the Netherlands, the USA, Spain and Turkey found more or similar numbers of bats in caves and a bunker after gates were installed to restrict public access. The other study found fewer bats in caves after gates were installed. Two before-and-after studies in the USA and Spain found more bats within two caves after the size of the gated entrances were increased. One replicated, before-and-after study in the USA found that installing cave gates resulted in population increases or decreased rates of decline for 13 of 20 colonies of Indiana bat. One replicated, site comparison study in Spain found no difference in the population growth rates of bats roosting in caves with and without cave gates.

Condition (1 study): One site comparison study in the USA found that bats hibernating in a cave with a wall and gate over the entrance lost more body mass than bats in a nearby unmodified cave.

USAGE (5 STUDIES)

Use (1 study): One replicated, site comparison study in Spain found no difference in the occupancy rates of bats roosting in caves with and without cave gates.

Behaviour change (4 studies): One replicated, controlled, before-and-after and site comparison study in the USA found that bats at cave entrances circled more and entered caves less after gates were installed. One replicated study in the USA found that bats flew through gates with a funnel design more frequently than gates with a round bar or angle iron design. One randomized, controlled, before-and-after study in the UK found that fewer bats flew through cave gates when the spacing between horizontal bars was reduced. One before-and-after study in the USA found that significantly fewer bats emerged from a cave with a gate installed compared with a cave with a fence.

Assessment: trade-offs between benefits and harms (effectiveness 70%; certainty 50%; harms 20%).

http://www.conservationevidence.com/actions/999

Unknown effectiveness (limited evidence)

Install fencing around cave entrances to restrict public access

Two studies evaluated the effects of installing fencing around cave entrances on bat populations. One study was in the USA and one study was in Spain.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in Spain found no difference in the population growth rates of bats roosting in caves with and without fencing or gates installed.

USAGE (2 STUDIES)

Use (1 study): One replicated, site comparison study in Spain found no difference in the occupancy rates of bats roosting in caves with and without fencing or gates installed.

Behaviour change (1 study): One controlled, before-and-after study in the USA found that significantly more southeastern myotis bats and gray myotis bats emerged from a cave after a steel gate was replaced with a fence.

Assessment: unknown effectiveness (effectiveness 40%; certainty 20%; harms 0%).

http://www.conservationevidence.com/actions/1991

Restrict artificial lighting in caves and around cave entrances

One study evaluated the effects of restricting artificial lighting in caves on bat populations. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Behaviour change (1 study): One controlled study in the USA found that using low intensity white lights or red lights in caves resulted in fewer bat flights than with full white lighting, but the number of bat movements was similar between all three light treatments.

Assessment: unknown effectiveness (effectiveness 15%; certainty 12%; harms 0%).

http://www.conservationevidence.com/actions/1994

Minimize noise levels within caves

One study evaluated the effects of minimizing noise levels within caves on bat populations. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Behaviour change (1 study): One controlled study in the USA found that experimental cave tours with groups that did not talk resulted in fewer bat flights than when groups did talk, but talking did not have an effect on the number of bat movements.

Assessment: unknown effectiveness (effectiveness 40%; certainty 21%; harms 0%).

http://www.conservationevidence.com/actions/1995

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.7 Threat: Natural system modification

2.7.1 Fire and fire suppression

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for fire and fire suppresion?

Likely to be

beneficial

Likely to be beneficial

Use prescribed burning

Nine studies evaluated the effects of prescribed burning on bat populations. Eight studies were in the USA and one study was in Australia.

COMMUNITY RESPONSE (1 STUDY)

Community composition (1 study): One replicated, controlled, before-and-after, paired sites study in Australia found that the composition of bat species differed between burned and unburned woodland sites.

POPULATION RESPONSE (4 STUDIES)

Abundance (4 studies): Two replicated, site comparison studies (including one controlled study) in the USA found that the activity (relative abundance) of open habitat bat species and evening bats increased with the number of prescribed fires, but there was no effect on other bat species, including cluttered habitat bat species. One replicated, controlled, before-and-after, paired sites study in Australia found that prescribed burning resulted in higher overall bat activity. One site comparison study in the USA found that two of seven sites that had been burned alongside other restoration practices had higher bat activity than unrestored sites.

USAGE (4 STUDIES)

Use (4 studies): One replicated, controlled before-and-after study in the USA found that more female northern myotis bats roosted in burned than unburned forest. Two replicated, controlled, before-and-after studies in the USA found that fewer female northern myotis bats and male Indiana bats roosted in burned than unburned forest. One replicated study in the USA found that evening bats roosted in burned but not unburned forest.

Behaviour change (2 studies): Two replicated, controlled, site comparison studies in the USA found no difference in roost switching frequency or the distance between roost trees for female northern myotis bats and male Indiana bats in burned and unburned forests. One replicated, controlled, before-and-after study in the USA found that female northern myotis home ranges and core areas did not differ in size between burned and unburned forests, but home ranges were closer to burned forest than unburned forest.

Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 10%).

https://www.conservationevidence.com/actions/1006

2.7.2 Dams and water management/use

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for dams and water management/use?

Unknown effectiveness

(limited evidence)

Unknown effectiveness (limited evidence)

Create or maintain small dams to provide foraging and drinking habitat for bats

One study evaluated the effects of maintaining small dams as foraging and drinking habitat for bats on bat populations. The study was in Portugal.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in Portugal found that reservoirs created using small dams had greater activity (relative abundance) of four bat species than the streams feeding into them.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 51%; certainty 20%; harms 0%).

http://www.conservationevidence.com/actions/1997

Relocate bat colonies roosting inside dams

One study evaluated the effects of relocating bat colonies inside dams on bat populations. The study was in Argentina.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One study in Argentina found that almost two-thirds of a large colony of Brazilian free-tailed bats relocated to a different dam compartment five months after being displaced from six compartments where the colony originally roosted.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 5%; certainty 5%; harms 5%).

http://www.conservationevidence.com/actions/1998

2.8 Threat: Invasive species and disease

2.8.1 Invasive species

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for invasive species?

Likely to be beneficial

Unknown effectiveness (limited evidence)

No evidence found (no assessment)

Likely to be beneficial

Control invasive predators

One study evaluated the effects of controlling invasive predators on bat populations. The study was in New Zealand.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Survival (1 study): One replicated, before-and-after study in New Zealand found that controlling ship rats resulted in increased survival probabilities for female long-tailed bats.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 80%; certainty 40%; harms 0%).

http://www.conservationevidence.com/actions/1007

Unknown effectiveness (limited evidence)

Control invasive plant species

One study evaluated the effects of controlling invasive plant species on bat populations. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One site comparison study in the USA found that two of seven forest fragments where invasive plant species had been removed alongside other restoration practices had significantly higher bat activity (relative abundance) than two unrestored forest fragments.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 20%; certainty 10%; harms 0%).

http://www.conservationevidence.com/actions/1008

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.8.2 Disease

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for disease?

No evidence found (no assessment)

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.8.3 White-nose syndrome

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for white-nose syndrome?

Unknown effectiveness

(limited evidence)

No evidence found (no assessment)

Unknown effectiveness (limited evidence)

Modify bat hibernacula environments to increase bat survival

One study evaluated the effects of modifying hibernacula environments to increase bat survival. The study was in the USA.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Survival (1 study): One randomized, replicated, controlled study in the USA found that a greater number of little brown bats infected with the white-nose syndrome fungus survived in hibernation chambers at 4°C than at 10°C.

USAGE (1 STUDY)

Behaviour change (1 study): One randomized, replicated, controlled study in the USA found that little brown bats infected with the white-nose syndrome fungus stayed in hibernation for longer in hibernation chambers at 4°C than at 10°C.

Assessment: unknown effectiveness (effectiveness 50%; certainty 30%; harms 10%).

https://www.conservationevidence.com/actions/1013

Treat bats for infection with white-nose syndrome

One study evaluated the effects of treating bats with a probiotic bacterium to reduce white-nose syndrome infection. The study was in Canada.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Survival (1 study): One randomized, replicated, controlled study in Canada found that treating little brown bats with a probiotic bacterium at the time of infection with white-nose syndrome increased survival, but treating bats 21 days prior to infection had no effect.

Condition (1 study): One randomized, replicated, controlled study in Canada found that treating little brown bats with a probiotic bacterium at the time of infection with white-nose syndrome reduced the symptoms of the disease, but treating bats 21 days prior to infection made symptoms worse.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 30%; certainty 25%; harms 10%).

http://www.conservationevidence.com/actions/2008

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.9 Threat: Pollution

2.9.1 Domestic and urban waste water

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for domestic and urban waste water?

Unknown effectiveness (limited evidence)

No evidence found (no assessment)

Unknown effectiveness (limited evidence)

Change effluent treatments of domestic and urban waste water

One study evaluated the effects of different sewage treatments on the activity of foraging bats. The study was in the UK. We found no studies that evaluated the effects of changing effluent treatments of domestic and urban waste water discharged into rivers on bat populations.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in the UK found higher activity (relative abundance) of foraging bats over filter bed sewage treatment works than over active sludge systems.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 25%; certainty 20%; harms 0%).

http://www.conservationevidence.com/actions/1014

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.9.2 Agricultural and forestry effluents

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for agricultural and forestry effluents?

Likely to be beneficial

Unknown effectiveness (limited evidence)

No evidence found (no assessment)

Likely to be beneficial

Reduce pesticide, herbicide or fertiliser use

Two studies evaluated the effects of reducing pesticide, herbicide and fertiliser use on bat populations. One study was in Mexico and one study was in Portugal.

COMMUNITY RESPONSE (2 STUDIES)

Community composition (1 study): One replicated, site comparison study in Portugal found that farms using few or no chemicals had different compositions of bat species to farms using high chemical inputs.

Richness/diversity (1 study): One site comparison study in Mexico found that coffee agroforestry plantations using few or no chemicals had a higher diversity of insect-eating bat species than plantations with high chemical inputs, but the diversity of fruit and nectar eating bat species did not differ.

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, site comparison study in Portugal found that farms using few or no chemicals had higher bat activity (relative abundance) than farms using high chemical inputs.

USAGE (0 STUDIES)

Assessment: likely to be beneficial (effectiveness 60%; certainty 40%; harms 0%).

https://www.conservationevidence.com/actions/2013

Unknown effectiveness (limited evidence)

Plant riparian buffer strips

One study evaluated the effects of planting riparian buffer strips on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ along waterways with buffer strips on agri-environment scheme farms and waterways on conventional farms.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 5%; certainty 10%; harms 0%).

http://www.conservationevidence.com/actions/2016

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.9.3 Light pollution

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for light and noise pollution?

Likely to be beneficial

Unknown effectiveness (limited evidence)

No evidence found (no assessment)

Likely to be beneficial

Leave bat roosts, roost entrances and commuting routes unlit

Three studies evaluated the effects of leaving bat roosts and roost entrances unlit on bat populations. One study was in the UK one in Hungary and one in Sweden.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Condition (1 study): One replicated, controlled study in Hungary found that juvenile bats had a higher body mass and greater forearm length at unlit roosts than at roosts with artificial lighting.

USAGE (3 STUDIES)

Use (1 study): One replicated, before-and-after study in Sweden found that all of 13 unlit churches continued to be used by brown long-eared bat colonies over 25 years, but bat colonies abandoned their roosts at 14 of 23 churches that were either partly or fully lit with floodlights.

Behaviour change (2 studies): Two replicated, controlled studies in the UK and Hungary found that more bats emerged and bats emerged earlier and foraged for shorter periods when roosts were left unlit than when they had artificial lighting.

Assessment: likely to be beneficial (effectiveness 80%; certainty 46%; harms 0%).

http://www.conservationevidence.com/actions/1017

Avoid illumination of bat commuting routes

Two studies evaluated the effects of avoiding the illumination of bat commuting routes on bat populations. One study was in the Netherlands and one in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): One replicated, before-and-after study in the Netherlands found similar numbers of pond bats flying along unlit canals and canals illuminated with lamps.

One replicated, controlled study in the UK found greater activity (relative abundance) of lesser horseshoe bats along unlit hedges than along hedges illuminated with streetlights.

USAGE (2 STUDIES)

Behaviour change (2 studies): One replicated, before-and-after study in the Netherlands found that 28–96% of pond bats changed their flight paths along canals to avoid light spill from lamps. One replicated, controlled study in the UK found that lesser horseshoe bats were active earlier along unlit hedges than along those illuminated with streetlights.

Assessment: unknown effectiveness (effectiveness 70%; certainty 49%; harms 0%).

https://www.conservationevidence.com/actions/2017

Use low intensity lighting

Two studies evaluated the effects of using low intensity lighting on bat populations. The two studies were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, randomized, controlled study in the UK found that activity (relative abundance) of lesser horseshoe bats, but not Myotis bats, was higher along hedges with medium or low intensity lighting than hedges with high intensity lighting.

USAGE (1 STUDY)

Behaviour change (1 study): One replicated, controlled study in the UK found that more soprano pipistrelles emerged from two roosts when the intensity of red lights was reduced by placing filters over them.

Assessment: unknown effectiveness (effectiveness 70%; certainty 50%; harms 0%).

http://www.conservationevidence.com/actions/1018

Unknown effectiveness (limited evidence)

Restrict timing of lighting

One study evaluated the effects of restricting the timing of lighting on bat populations. The study was in France.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in France found that turning off streetlights for part of the night resulted in mixed results for activity (relative abundance), depending on bat species, when compared with leaving streetlights switched on all night.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 38%; certainty 20%; harms 0%).

http://www.conservationevidence.com/actions/1019

Avoid illumination of key bat habitats

One study evaluated the effects of avoiding the illumination of key bat habitats on bat populations. The study was in Italy.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, randomized, before-and-after study in Italy found that unlit water troughs had greater activity (relative abundance) of five of six bat species/species groups than troughs illuminated with artificial light.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 72%; certainty 35%; harms 0%).

http://www.conservationevidence.com/actions/2018

Use UV filters on lights

One study evaluated the effects of using ultraviolet filters on lights on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One randomized, replicated, controlled study in the UK found that hedges lit with ultraviolet filtered lights had higher soprano pipistrelle, but not common pipistrelle activity (relative abundance) than hedges lit with unfiltered light.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 45%; certainty 22%; harms 0%).

http://www.conservationevidence.com/actions/1020

Use red lighting rather than other lighting colours

Two studies evaluated the effects of red lighting on bat populations. One study was in the UK and one study was in the Netherlands.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, controlled, site comparison study in the Netherlands found that red lighting resulted in higher activity (relative abundance) for one of three bat species groups than white or green lighting.

USAGE (1 STUDY)

Behaviour (1 study): One replicated, controlled study in the UK found that more soprano pipistrelles emerged from a roost when lit with red light than when lit with white light, but no difference was found between red and blue lights.

Assessment: unknown effectiveness (effectiveness 50%; certainty 30%; harms 0%).

http://www.conservationevidence.com/actions/2021

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.9.4 Noise pollution

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for light and noise pollution?

No evidence found (no assessment)

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.9.5 Timber treatments

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for timber treatments?

Likely to be ineffective or harmful

No evidence found (no assessment)

Likely to be ineffective or harmful

Restrict timing of treatment

One study evaluated the effects of restricting the timing of timber treatment application on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Survival (1 study): One replicated, controlled laboratory study in the UK found that treating timber with lindane and pentachlorophenol 14 months prior to exposure by bats increased survival but did not prevent death.

USAGE (0 STUDIES)

Assessment: likely to be ineffective or harmful (effectiveness 5%; certainty 55%; harms 50%).

http://www.conservationevidence.com/actions/1023

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.10 Climate change and severe weather

Based on the collated evidence, what is the current assessment of the effectiveness of actions related to climate change and severe weather?

No evidence found (no assessment)

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.11 Habitat protection

Based on the collated evidence, what is the current assessment of the effectiveness of habitat protection for bats?

Unknown effectiveness

(limited evidence)

No evidence found (no assessment)

Unknown effectiveness (limited evidence)

Legally protect bat habitats

Three studies evaluated the effects of legally protecting bat habitats on bat populations. One study was in the UK, one was in Spain, and one in Europe.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, paired sites study in Europe found that the number of bat species did not differ between protected and unprotected forests.

POPULATION RESPONSE (2 STUDIES)

Abundance (2 studies): One replicated, site comparison study in the UK found that the activity (relative abundance) of Daubenton’s bats was significantly higher over rivers on farms in protected areas than in unprotected areas. One replicated, paired sites study in Europe found that the activity of common noctule bats was higher in protected forests than unprotected forests, but bat activity overall did not differ.

USAGE (1 STUDY)

Use (1 study): One study in Spain found that the distributions of 10 of 11 bat species overlapped with areas designated to protect them significantly more than by chance.

Assessment: unknown effectiveness (effectiveness 50%; certainty 25%; harms 0%).

http://www.conservationevidence.com/actions/2045

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.

Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 0%).

http://www.conservationevidence.com/actions/2046

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.12 Habitat restoration and creation

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for habitat restoration and creation?

Likely to be beneficial

Unknown effectiveness

(limited evidence)

No evidence found (no assessment)

Likely to be beneficial

Create artificial water sources

Five studies evaluated the effects of creating artificial water sources for bat populations. One study was in Israel, one in the USA, one in Germany, one in South Africa and one in Mexico.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One replicated, paired sites study in South Africa found a similar number of bat species over farm ponds and in grassland/crops, trees, vineyards or orchards.

POPULATION RESPONSE (5 STUDIES)

Abundance (5 studies): Five replicated studies (including four site comparisons and one paired sites study) in Israel, the USA, Germany, South Africa and Mexico found that bat activity (relative abundance) was similar or higher over reservoirs and waste water treatment pools, heliponds and drainage ditches, retention ponds and farm/cattle ponds compared to over natural wetlands, nearby vineyards, surrounding forest or grassland/crops, trees and orchards.

USAGE (0 STUDIES)

Assessment: likely to be beneficial (effectiveness 70%; certainty 55%; harms 0%).

https://www.conservationevidence.com/actions/959

Unknown effectiveness (limited evidence)

Create artificial hollows and cracks in trees for roosting bats

One study evaluated the effects of creating artificial hollows and cracks in trees for roosting bats. The study was in Australia.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One replicated study in Australia found that eight of 16 artificial hollows cut into trees for bats, birds and marsupials with two different entrance designs were used by roosting long-eared bats.

Assessment: unknown effectiveness (effectiveness 50%; certainty 23%; harms 0%).

https://www.conservationevidence.com/actions/2047

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.

Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 0%).

https://www.conservationevidence.com/actions/2046

Reinstate bat roosts in felled tree trunks

One study evaluated the effects of reinstating a bat roost within a felled tree trunk on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (1 STUDY)

Use (1 study): One before-and-after study in the UK found that a roost reinstated by attaching the felled tree trunk to a nearby tree continued to be used by common noctule bats as a maternity roost.

Assessment: unknown effectiveness (effectiveness 35%; certainty 10%; harms 0%).

https://www.conservationevidence.com/actions/2048

Create artificial caves or hibernacula for bats

Two studies evaluated the effects of creating artificial caves or hibernacula for bats on bat populations. Both studies were in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (2 STUDIES)

Uptake (1 study): One study in the UK found that the number of bats using an artificial hibernaculum increased in each of nine years after it was built.

Use (2 studies): One study in the UK found that an artificial cave was used by a small number of brown long-eared bats. One study in the UK found that an artificial hibernaculum was used by four bat species.

Assessment: unknown effectiveness (effectiveness 55%; certainty 22%; harms 0%).

https://www.conservationevidence.com/actions/2049

Restore or create forest or woodland

Two studies evaluated the effects of restoring forests on bat populations. One study was in Brazil and one in Australia.

COMMUNITY RESPONSE (1 STUDY)

Richness/diversity (1 study): One site comparison study in Brazil found that a reforested area had significantly lower bat diversity than a native forest fragment.

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, controlled, site comparison study in Australia found that forests restored after mining had significantly higher or similar bat activity (relative abundance) as unmined forests for five of seven bat species.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 40%; certainty 15%; harms 0%).

http://www.conservationevidence.com/actions/2050

Restore or create grassland

One study evaluated the effects of creating grassland on bat populations. The study was in the UK.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One replicated, paired sites study in the UK found that pipistrelle activity (relative abundance) did not differ between species-rich grassland created on agri-environment scheme farms and improved pasture or crop fields on conventional farms.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 2%; certainty 10%; harms 0%).

http://www.conservationevidence.com/actions/2051

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.13 Species management

2.13.1 Species management

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for species management?

Likely to be beneficial

Unknown effectiveness (limited evidence)

No evidence found (no assessment)

Likely to be beneficial

Provide bat boxes for roosting bats

Thirty-nine studies evaluated the effects of providing bat boxes for roosting bats on bat populations. Twenty-five studies were in Europe, eight studies were in North America, three studies were in Australia, two studies were in South America, and one study was a worldwide review.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (0 STUDIES)

USAGE (39 STUDIES)

Uptake (9 studies): Nine replicated studies in Europe and the USA found that the number of bats using bat boxes increased by 2–10 times up to 10 years after installation.

Use (39 studies): Thirty-six of thirty-eight studies (including thirty-one replicated studies and one review) in Europe, the USA, South America, and Australia found that bats used bat boxes installed under bridges and in forest or woodland, forestry plantations, farmland, pasture, wetlands, urban areas or unknown habitats. The other two studies in the USA and UK found that bats displaced from buildings did not use any of 43 bat houses of four different designs or 12 heated bat boxes of one design. One review of 109 studies across Europe, North America and Asia found that 72 bat species used bat boxes, although only 18 species commonly used them, and 31 species used them as maternity roosts. Twenty studies (including sixteen replicated studies, one before-and-after study and one review) found bats occupying less than half of bat boxes provided (0–49%). Nine replicated studies found bats occupying more than half of bat boxes provided (54–100%).

OTHER (19 STUDIES)

Bat box design (14 studies): Two studies in Germany and Portugal found that bats used black bat boxes more than grey or white boxes. One of two studies in Spain and the USA found higher occupancy rates in larger bat boxes. One study in the USA found that bats used both resin and wood cylindrical bat boxes, but another study in the USA found that resin bat boxes became occupied more quickly than wood boxes. One study in the UK found higher occupancy rates in concrete than wooden bat boxes. One study in Spain found that more bats occupied bat boxes that had two compartments than one compartment in the breeding season. One study in Lithuania found that bat breeding colonies occupied standard and four/five chamber bat boxes and individuals occupied flat bat boxes. Three studies in the USA, UK and Spain found bats selecting four of nine, three of five and three of four bat box designs. One study in the UK found that different bat box designs were used by different species. One study in Costa Rica found that bat boxes simulating tree trunks were used by 100% of bats and in group sizes similar to natural roosts.

Bat box position (10 studies): Three studies in Germany, Spain and the USA found that bat box orientation and/or the amount of exposure to sunlight affected bat occupancy, and one study in Spain found that orientation did not have a significant effect on occupancy. Two studies in the UK and Italy found that bat box height affected occupancy, and two studies in Spain and the USA found no effect of height. Two studies in the USA and Spain found higher occupancy of bat boxes on buildings than on trees. One study in Australia found that bat boxes were occupied more often in farm forestry sites than in native forest, one study in Poland found higher occupancy in pine relative to mixed deciduous stands, and one study in Costa Rica found higher occupancy in forest fragments than in pasture. One study in the USA found higher occupancy rates in areas where bats were known to roost prior to installing bat boxes.

Assessment: likely to be beneficial (effectiveness 50%; certainty 45%; harms 0%).

http://www.conservationevidence.com/actions/1024

Unknown effectiveness (limited evidence)

Manage microclimate of artificial bat roosts

Three studies evaluated the effects of managing the microclimate of artificial bat roosts on bat populations. Two studies were in the UK and one in Spain.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (1 STUDY)

Abundance (1 study): One before-and-after study in Spain found more bats in two artificial roosts within buildings after they had been modified to reduce internal roost temperatures.

USAGE (2 STUDIES)

Use (2 studies): One replicated, before-and-after study in the UK found that heated bat boxes were used by common pipistrelle bats at one of seven sites, but none were used by maternity colonies. One replicated study in the UK found that none of the 12 heated bat boxes installed within churches were used by displaced Natterer’s bats.

Assessment: unknown effectiveness (effectiveness 40%; certainty 30%; harms 0%).

http://www.conservationevidence.com/actions/2052

Rehabilitate injured/orphaned bats to maintain wild bat populations

Four studies evaluated the effects of rehabilitating injured/orphaned bats on bat populations. One study was in Brazil, two studies were in the UK, and one in Italy.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (4 STUDIES)

Survival (4 studies): One study in Brazil found that two hand-reared orphaned greater spear-nosed bats survived for over three months in captivity. Two studies in the UK and Italy found that 70–90% of hand-reared pipistrelle bats survived for at least 4–14 days after release into the wild, and six of 21 bats joined wild bat colonies. One study in the UK found that pipistrelle bats that flew in a large flight cage for long periods before release survived for longer and were more active than bats that flew for short periods or in a small enclosure. One study in the UK found that 13% of ringed hand-reared pipstrelle bats were found alive in bat boxes 38 days to almost four years after release into the wild.

Condition (1 study): One study in Brazil found that two orphaned greater spear-nosed bats increased in body weight and size after being hand-reared, and reached a normal size for the species after 60 days.

USAGE (0 STUDIES)

Assessment: unknown effectiveness (effectiveness 47%; certainty 27%; harms 0%).

http://www.conservationevidence.com/actions/2054

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.13.2 Ex-situ conservation

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for ex-situ management?

Unlikely to be beneficial

No evidence found (no assessment)

Unlikely to be beneficial

Breed bats in captivity

Six studies evaluated the effects of breeding bats in captivity on bat populations. Three studies were in the USA, two in the UK and one in Brazil.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (6 STUDIES)

Reproductive success (5 studies): Five studies in the USA, UK and Brazil found that 6–100% of female bats captured in the wild successfully conceived, gave birth and reared young in captivity. Two studies in the UK and Brazil found that two of five and two of three bats born in captivity successfully gave birth to live young.

Survival (6 studies): Six studies in the USA, UK and Brazil found that 20–86% of bat pups born in captivity survived from between 10 days to adulthood.

USAGE (0 STUDIES)

Assessment: unlikely to be beneficial (effectiveness 30%; certainty 40%; harms 18%).

http://www.conservationevidence.com/actions/2053

No evidence found (no assessment)

We have captured no evidence for the following interventions:

2.13.3 Translocation

Based on the collated evidence, what is the current assessment of the

effectiveness of interventions for bat translocation?

Likely to be ineffective or harmful

Likely to be ineffective or harmful

Translocate bats

Two studies evaluated the effects of translocating bats on bat populations. One study was in New Zealand and one study was in Switzerland.

COMMUNITY RESPONSE (0 STUDIES)

POPULATION RESPONSE (2 STUDIES)

Reproductive success (1 study): One study in Switzerland found that a female greater horseshoe bat that settled at a release site after translocation had a failed pregnancy.

Survival (1 study): One study in Switzerland found that four of 18 bats died after translocation.

Condition (1 study): One study in New Zealand found that lesser short-tailed bats captured at release sites eight months after translocation were balding and had damaged, infected ears.

USAGE (2 STUDIES)

Uptake (2 studies): Two studies in New Zealand and Switzerland found that low numbers of bats remained at release sites after translocation.

Behaviour change (1 study): One study in Switzerland found that bats homed after release at translocation sites less than 20 km from their original roosts.

Assessment: likely to be ineffective or harmful (effectiveness 5%; certainty 40%; harms 80%).

https://www.conservationevidence.com/actions/1009

2.14 Education and awareness raising

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for education and awareness raising?

No evidence found (no assessment)

No evidence found (no assessment)

We have captured no evidence for the following interventions: