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2. BAT CONSERVATION

Anna Berthinussen, Olivia C. Richardson, Rebecca K. Smith, John D. Altringham & William J. Sutherland

Expert assessors

John Altringham, University of Leeds, UK

James Aegerter, Animal and Plant Health Agency, UK

Kate Barlow, Bat Conservation Trust, UK

Anna Berthinussen, University of Leeds, UK

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

David Bullock, National Trust, UK

Paul Cryan, Fort Collins Science Center, US Geological Survey

Brock Fenton, University of Western Ontario, Canada

Anita Glover, University of Leeds, UK

Joanne Hodgkins, National Trust, UK

David Jacobs, University of Cape Town, South Africa

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

Christoph Meyer, Centre for Environmental Biology, Portugal

Kirsty Park, University of Stirling, UK

Guido Reiter, Co-ordination Centre for Bat Conservation and Research in Austria

Danilo Russo, Federico II University of Naples, Italy

Rebecca K. Smith, University of Cambridge, UK

Matt Struebig, University of Kent, UK

Christian Voigt, Freie Universität Berlin, Germany

Michael Willig, University of Connecticut, USA

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

Assessed: 2015.

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?

Unknown effectiveness (limited evidence)

● Protect brownfield sites

● Provide foraging habitat in urban areas

No evidence found (no assessment)

● Change timing of building works

● Conserve existing roosts within developments

● Conserve old buildings or structures as roosting sites for bats within developments

● Create alternative roosts within buildings

● Maintain bridges and retain crevices for roosting

● Retain or relocate access points to bat roosts

● Retain or replace existing bat commuting routes within development

Protect brownfield sites

One study in the USA found bat activity within an urban wildlife refuge on an abandoned manufacturing site to be consistent with predictions across North America based on the availability of potential roosts. Assessment: unknown effectiveness (effectiveness 40%; certainty 20%; harms 0%).

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

Provide foraging habitat in urban areas

One site comparison study in the USA found higher bat activity in restored forest preserves in urban areas than in an unrestored forest preserve. One replicated, controlled, site comparison study in the UK found higher bat activity over green roofs in urban areas than conventional unvegetated roofs. Assessment: unknown effectiveness (effectiveness 50%; certainty 30%; harms 0%).

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

We have captured no evidence for the following interventions:

2.2 Threat: Agriculture

2.2.1 Land use change

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for land use change?
Likely to be beneficial	● Protect or create wetlands as foraging habitat for bats
Unknown effectiveness (limited evidence)	● Retain or plant trees on agricultural land to replace foraging habitat for bats
No evidence found (no assessment)	● Conserve old buildings or structures on agricultural land as roosting sites for bats ● Retain old or dead trees with hollows and cracks as roosting sites for bats on agricultural land ● Retain or replace existing bat commuting routes on agricultural land

Protect or create wetlands as foraging habitat for bats

We found no evidence for the effects of protecting existing wetlands. One replicated, controlled, site comparison study in the USA found higher bat activity over heliponds and drainage ditches within a pine plantation than over natural wetlands. A replicated study in Germany found high levels of bat activity over constructed retention ponds compared to nearby vineyard sites, but comparisons were not made with natural pond sites. Assessment: likely to be beneficial (effectiveness 60%; certainty 48%; harms 0%).

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

Retain or plant trees on agricultural land to replace foraging habitat for bats

We found no evidence for the effects of retaining trees as foraging habitat for bats. Two site comparison studies (one replicated) in Australia found no difference in bat activity and the number of bat species in agricultural areas revegetated with native plantings and over grazing land without trees. In both studies, bat activity was lower in plantings than in original forest and woodland remnants. Assessment: unknown effectiveness (effectiveness 20%; certainty 20%; harms 0%).

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

We have captured no evidence for the following interventions:

2.2.2 Intensive farming

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

Likely to be beneficial

● Convert to organic farming

● Encourage agroforestry

Unknown effectiveness (limited evidence)

● Introduce agri-environment schemes

Convert to organic farming

Four replicated, paired, site comparison studies on farms in the UK had inconsistent results. Two studies found higher bat abundance and activity on organic farms than conventional farms, and two studies showed no difference in bat abundance between organic and non-organic farms. Assessment: likely to be beneficial (effectiveness 40%; certainty 40%; harms 0%).

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

Encourage agroforestry

Four replicated, site comparison studies (three in Mexico and one in Costa Rica) found no difference in bat diversity, the number of bat species and/ or bat abundance between cacao, coffee or banana agroforestry plantations and native rainforest. One replicated, site comparison study in Mexico found higher bat diversity in native forest fragments than in coffee agroforestry plantations. One replicated, randomized, site comparison study in Costa Rica found lower bat diversity in native rainforest than in cacao agroforestry plantations. A replicated, site comparison study in Mexico found that bat diversity in coffee agroforestry plantations and native rainforest was affected by the proportion of each habitat type within the landscape. Three studies found that increasing management intensity on agroforestry plantations had a negative effect on some bat species, and a positive effect on others. Assessment: likely to be beneficial (effectiveness 50%; certainty 50%; harms 10%).

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

Introduce agri-environment schemes

One replicated, paired study in Scotland, UK found lower bat activity on farms participating in agri-environment schemes than on non-participating conventional farms. Assessment: unknown effectiveness (effectiveness 0%; certainty 18%; harms 13%).

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

2.3 Threat: Energy production – wind turbines

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for wind turbines?
Beneficial	● Switch off turbines at low wind speeds to reduce bat fatalities
Likely to be beneficial	● Deter bats from turbines using ultrasound
Unknown effectiveness (limited evidence)	● Deter bats from turbines using radar
No evidence found (no assessment)	● Automatically switch off wind turbines when bat activity is high ● Close off nacelles on wind turbines to prevent roosting bats ● Leave a minimum distance between turbines and habitat features used by bats ● Modify turbine design to reduce bat fatalities ● Modify turbine placement to reduce bat fatalities ● Remove turbine lighting to avoid attracting bats

Switch off turbines at low wind speeds to reduce bat fatalities

Three replicated, controlled studies in Canada and the USA have shown that reducing the operation of wind turbines at low wind speeds causes a reduction in bat fatalities. Assessment: beneficial (effectiveness 80%; certainty 70%; harms 0%).

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

Deter bats from turbines using ultrasound

Five field studies at wind farms or pond sites (including one replicated, randomized, before-and-after trial), and one laboratory study, have all found lower bat activity or fewer bat deaths with ultrasonic deterrents than without. Assessment: likely to be beneficial (effectiveness 50%; certainty 40%; harms 10%).

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

Deter bats from turbines using radar

A replicated, site comparison study in the UK found reduced bat activity in natural habitats in proximity to electromagnetic fields produced by radars. We found no evidence for the effects of installing radars on wind turbines on bats. Assessment: unknown effectiveness (effectiveness 20%; certainty 10%; harms 0%).

http://www.conservationevidence.com/actions/967

We have captured no evidence for the following interventions:

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

No evidence found (no assessment)

● Legally protect bat hibernation sites in mines from reclamation

● Provide artificial hibernacula to replace roosts lost in reclaimed mines

● Relocate bats from reclaimed mines to new hibernation sites

We have captured no evidence for the following interventions:

2.5 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	● Install underpasses as road crossing structures for bats
Unknown effectiveness (limited evidence)	● Divert bats to safe crossing points with plantings or fencing ● Install bat gantries or bat bridges as road crossing structures for bats ● Install overpasses as road crossing structures for bats
No evidence found (no assessment)	● Deter bats with lighting ● Install green bridges as road crossing structures for bats ● Install hop-overs as road crossing structures for bats ● Replace or improve habitat for bats around roads

Install underpasses as road crossing structures for bats

Four studies (two replicated) in Germany, Ireland and the UK found varying proportions of bats to be using existing underpasses below roads and crossing over the road above. Assessment: likely to be beneficial (effectiveness 60%; certainty 50%; harms 0%).

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

Divert bats to safe crossing points with plantings or fencing

We found no evidence for the effects of diverting bats to safe road crossing points. One controlled, before-and-after study in Switzerland found that a small proportion 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

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

One replicated, site comparison study in the UK found fewer bats using bat gantries than crossing the road below at traffic height. Assessment: unknown effectiveness (effectiveness 0%; certainty 35%; harms 0%).

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

Install overpasses as road crossing structures for bats

One replicated, site comparison study in Ireland did not find more bats using over-motorway routes than crossing over the road below. Assessment: unknown effectiveness (effectiveness 0%; certainty 20%; harms 0%).

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

We have captured no evidence for the following interventions:

2.6.1 Hunting

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

No evidence found (no assessment)

● Educate local communities about bats and hunting

● Introduce and enforce legislation to control hunting of bats

● Introduce sustainable harvesting of bats

We have captured no evidence for the following interventions:

2.6.2 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)

● Introduce and enforce legislation to regulate the harvesting of bat guano

● Introduce sustainable harvesting of bat guano

We have captured no evidence for the following interventions:

2.6.3 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	● Incorporate forested corridors or buffers into logged areas ● Use selective harvesting/reduced impact logging instead of clearcutting ● Use shelterwood cutting instead of clearcutting
Unknown effectiveness (limited evidence)	● Retain residual tree patches in logged areas ● Thin trees within forests
No evidence found (no assessment)	● Manage woodland or forest edges for bats ● Replant native trees ● Retain deadwood/snags within forests for roosting bats

Incorporate forested corridors or buffers into logged areas

One replicated, site comparison study in Australia found no difference in the activity and number of bat species between riparian buffers in logged, regrowth or mature forest. One replicated, site comparison study in North America found higher bat activity along the edges of forested corridors than in corridor interiors or adjacent logged stands. Three replicated, site comparison studies in Australia and North America found four bat species roosting in forested corridors and riparian buffers. Assessment: likely to be beneficial (effectiveness 50%; certainty 50%; harms 0%).

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

Use selective harvesting/reduced impact logging instead of clearcutting

Nine replicated, controlled, site comparison studies provide evidence for the effects of selective or reduced impact logging on bats with mixed results. One study in the USA found that bat activity was higher in selectively logged forest than in unharvested forest. One study in Italy caught fewer barbastelle bats in selectively logged forest than in unmanaged forest. Three studies in Brazil and two in Trinidad found no difference in bat abundance or species diversity between undisturbed control forest and selectively logged or reduced impact logged forest, but found differences in species composition. Two studies in Brazil found no effect of reduced impact logging on the activity of the majority of bat species, but mixed effects on the activity of four species. Assessment: likely to be beneficial (effectiveness 60%; certainty 50%; harms 10%).

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

Use shelterwood cutting instead of clearcutting

One site comparison study in North America found higher or equal activity of at least five bat species in shelterwood harvests compared to unharvested control sites. One replicated, site comparison study in Australia found Gould’s long eared bats selectively roosting in shelterwood harvests, but southern forest bats roosting more often in mature unlogged forest. A replicated, site comparison study in Italy found barbastelle bats favoured unmanaged woodland for roosting and used shelterwood harvested woodland in proportion to availability. Assessment: likely to be beneficial (effectiveness 50%; certainty 48%; harms 18%).

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

Retain residual tree patches in logged areas

Two replicated, site comparison studies in Canada found no difference in bat activity between residual tree patch edges in clearcut blocks and edges of the remaining forest. One of the studies found higher activity of smaller bat species at residual tree patch edges than in the centre of open clearcut blocks. Bat activity was not compared to unlogged areas. Assessment: unknown effectiveness (effectiveness 20%; certainty 25%; harms 0%).

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

Thin trees within forests

Two replicated, site comparison studies (one paired) in North America found that bat activity was higher in thinned forest stands than in unthinned stands, and similar to that in mature forest. One replicated, site comparison study in North America found higher bat activity in thinned than in unthinned forest stands in one of the two years of the study. One replicated, site comparison study in Canada found the silver-haired bat more often in clearcut patches than unthinned forest, but found no difference in the activity of Myotis species. Assessment: unknown effectiveness (effectiveness 45%; certainty 38%; harms 10%).

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

We have captured no evidence for the following interventions:

2.7 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	● Impose restrictions on cave visits
Trade-offs between benefit and harms	● Use cave gates to restrict public access
No evidence found (no assessment)	● Educate the public to reduce disturbance to hibernating bats ● Legally protect bat hibernation sites ● Maintain microclimate at underground hibernation/roost sites ● Provide artificial hibernacula for bats to replace disturbed sites

Impose restrictions on cave visits

Two before-and-after studies from Canada and Turkey found that bat populations within caves increased after restrictions on cave visitors were imposed. Assessment: likely to be beneficial (effectiveness 70%; certainty 50%; harms 0%).

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

Use cave gates to restrict public access

Ten studies in Europe, North America and Australia provide evidence for the effects of cave gating on bats, with mixed results. Four of the studies (one replicated) found more or equal numbers of bats in underground systems after gating. Two of the studies (one replicated) found reduced bat populations or incidences of cave abandonment after gating. Five studies (two replicated) provide evidence for changes in flight behaviour at cave gates. Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 60%; harms 50%).

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

We have captured no evidence for the following interventions:

2.8 Threat: Natural system modification – natural fire and fire suppression

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for natural system modification?
Trade-offs between benefit and harms	● Use prescribed burning

Use prescribed burning

Four studies in North America looked at bat activity and prescribed burning. One replicated, controlled, site comparison study found no difference in bat activity between burned and unburned forest. One replicated, site comparison study found higher activity of bat species that forage in the open in burned than unburned stands. One site comparison study found higher bat activity in forest preserves when prescribed burning was used with other restoration practices. One controlled, replicated, before-and-after study found that the home ranges of bats were closer to burned stands following fires. Four studies in North America (three replicated and one controlled) found bats roosting more often in burned areas, or equally in burned and unburned forest. Assessment: trade-offs between benefits and harms (effectiveness 65%; certainty 50%; harms 20%).

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

2.9 Threat: Invasive species

2.9.1 Invasive species

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for invasive species?
Unknown effectiveness (limited evidence)	● Remove invasive plant species
Likely to be ineffective or harmful	● Translocate to predator or disease free areas
No evidence found (no assessment)	● Control invasive predators

Remove invasive plant species

One site comparison study in North America found higher bat activity in forest preserves where invasive plant species had been removed alongside other restoration practices. Assessment: unknown effectiveness (effectiveness 20%; certainty 10%; harms 0%).

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

Translocate to predator or disease free areas

Two small unreplicated studies in New Zealand and Switzerland found low numbers of bats remaining at release sites after translocation, and observed homing tendencies, disease and death. Assessment: Likely to be ineffective or harmful (effectiveness 5%; certainty 40%; harms 80%).

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

We have captured no evidence for the following interventions:

Control invasive predators

2.9.2 White-nose syndrome

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

No evidence found (no assessment)

● Control anthropogenic spread

● Cull infected bats

● Increase population resistance

● Modify cave environments to increase bat survival

We have captured no evidence for the following interventions:

2.10 Threat: Pollution

2.10.1 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)	● Change effluent treatments of domestic and urban waste water

Change effluent treatments of domestic and urban waste water

We found no evidence for the effects on bats of changing effluent treatments of domestic and urban waste water discharged into rivers. One replicated, site comparison study in the UK found that foraging activity over filter bed sewage treatment works was higher than activity over active sludge systems. Assessment: unknown effectiveness (effectiveness 40%; certainty 30%; harms 30%).

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

2.10.2 Agricultural and forestry effluents

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for agricultural and forestry effluents?

No evidence found (no assessment)

● Introduce legislation to control use of fertilizers, insecticides and pesticides

● Change effluent treatments used in agriculture and forestry

We have captured no evidence for the following interventions:

2.10.3 Light and noise 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

● Leave bat roosts, roost entrances and commuting routes unlit

● Minimize excess light pollution

No evidence found (no assessment)

● Restrict timing of lighting

● Use low pressure sodium lamps or use UV filters

● Impose noise limits in proximity to roosts and bat habitats

Leave bat roosts, roost entrances and commuting routes unlit

Two replicated studies in the UK found more bats emerging from roosts or flying along hedgerows when left unlit than when illuminated with white lights or streetlamps. Assessment: likely to be beneficial (effectiveness 80%; certainty 50%; harms 0%).

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

Minimize excess light pollution

One replicated, randomized, controlled study in the UK found that bats avoided flying along hedgerows with dimmed lighting, and activity levels were lower than along unlit hedges. We found no evidence for the effects of reducing light spill using directional lighting or hoods on bats. Assessment: likely to be beneficial (effectiveness 65%; certainty 50%; harms 0%).

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

We have captured no evidence for the following interventions:

2.10.4 Timber treatments

Based on the collated evidence, what is the current assessment of the effectiveness of interventions for timber treatments?
Beneficial	● Use mammal safe timber treatments in roof spaces
Likely to be ineffective or harmful	● Restrict timing of treatment

Use mammal safe timber treatments in roof spaces

Two controlled laboratory studies in the UK found commercial timber treatments (containing lindane and pentachlorophenol) to be lethal to bats, but found alternative artificial insecticides (including permethrin) and three other fungicides did not increase bat mortality. Sealants over timber treatments had varying success. Assessment: likely to be beneficial (effectiveness 90%; certainty 80%; harms 0%).

http://www.conservationevidence.com/actions/1022

Restrict timing of treatment

One controlled laboratory experiment in the UK found that treating timber with lindane and pentachlorophenol 14 months prior to exposure by bats increased survival time but did not prevent death. Bats in cages treated with permethrin survived just as long when treatments were applied two months or 14 months prior to exposure. Assessment: Likely to be ineffective or harmful (effectiveness 5%; certainty 55%; harms 50%).

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

2.11 Providing artificial roost structures for bats

Based on the collated evidence, what is the current assessment of the effectiveness of providing artificial roost structures for bats?
Likely to be beneficial	● Provide artificial roost structures for bats

Provide artificial roost structures for bats

We found 22 replicated studies of artificial roost structures from across the world. Twenty-one studies show use of artificial roosts by bats. One study in the USA found that bats did not use the bat houses provided. Fifteen studies show varying occupancy rates of bats in artificial roost structures (3–100%). Two studies in Europe found an increase in bat populations using bat boxes in forest and woodland. Eight studies looked at bat box position. Three of four studies found that box orientation and exposure to sunlight are important for occupancy. Two studies found more bats occupying bat boxes on buildings than trees. Two studies found more bats occupying bat boxes in farm forestry or pine stands than in native or deciduous forest. Eleven studies looked at bat box design, including size, number of compartments and temperature, and found varying results. Assessment: likely to be beneficial (effectiveness 60%; certainty 60%; harms 0%)

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

2.12 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)

● Provide training to professionals

● Educate homeowners about building and planning laws

● Educate to improve public perception and raise awareness

We have captured no evidence for the following interventions: