2.13.1 Species management

Likely to be beneficial

●Provide bat boxes for roosting bats

1Forty-four studies evaluated the effects of providing bat boxes for roosting bats on bat populations. Twenty-seven studies were in Europe, nine studies were in North America, four studies were in Australia, two studies were in South America, and one study was a worldwide review.

2COMMUNITY RESPONSE (0 STUDIES)

3POPULATION RESPONSE (0 STUDIES)

4BEHAVIOUR (44 STUDIES)

5Uptake (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.

6Use (43 studies): Forty-one of 43 studies (including 34 replicated studies and two reviews) in Europe, the USA, South America, and Australia found that bats used bat boxes installed in forest or woodland, forestry plantations, farmland, pasture, wetlands, urban areas and buildings, bridges, underpasses 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-two studies (including 17 replicated studies, one before-and-after study and two reviews) 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 %).

7OTHER (23 STUDIES)

8Bat box design (16 studies): Three studies in Germany, Portugal and Australia found that bats used black bat boxes more than grey, white or wooden 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 the USA found that Indiana bats used rocket boxes more than wooden bat boxes or bark-mimic roosts. 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. Four studies in the USA, UK, Spain and Australia found bats selecting four of nine, three of five, three of four and one of five 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.

9Bat box position (11 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. One review in the UK found that bat boxes were more likely to be occupied when a greater number of bat boxes were installed across a site.

10Assessment: likely to be beneficial (effectiveness 70 %; certainty 60 %; harms 0 %).

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

Unknown effectiveness

●Manage microclimate of artificial bat roosts

11Three 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)

12POPULATION RESPONSE (1 STUDY)

13Abundance (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.

14BEHAVIOUR (2 STUDIES)

15Use (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.

16Assessment: unknown effectiveness (effectiveness 40 %; certainty 30 %; harms 0 %).

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

No evidence found (no assessment)

17We have captured no evidence for the following interventions:

• Legally protect bat species
• Regularly clean bat boxes to increase occupancy
• Release captive-bred bats.

2.13.2 Ex-situ conservation

Unknown effectiveness

●Breed bats in captivity

18Eight 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 each of Italy, Brazil and New Zealand.

19COMMUNITY RESPONSE (0 STUDIES)

20POPULATION RESPONSE (8 STUDIES)

21Reproductive success (6 studies): Six studies in the USA, UK, Italy 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.

22Survival (8 studies): Seven studies in the USA, UK, Italy and Brazil found that 20–100 % of bat pups born in captivity survived from between 10 days to adulthood. One study in New Zealand found that two of five New Zealand lesser short-tailed bat pups born in captivity survived, both of which were hand-reared.

23BEHAVIOUR (0 STUDIES)

24Assessment: unknown effectiveness (effectiveness 50 %; certainty 30 %; harms 10 %).

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

●Rehabilitate injured/orphaned bats to maintain wild bat populations

25Four studies evaluated the effects of rehabilitating injured/orphaned bats on bat populations. Two studies were in the UK, one was in Italy and one in Brazil.

26COMMUNITY RESPONSE (0 STUDIES)

27POPULATION RESPONSE (4 STUDIES)

28Survival (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.

29Condition (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.

30BEHAVIOUR (0 STUDIES)

31Assessment: unknown effectiveness (effectiveness 47 %; certainty 27 %; harms 0 %).

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

2.13.3 Translocation

Likely to be ineffective or harmful

●Translocate bats

32Two studies evaluated the effects of translocating bats on bat populations. One study was in New Zealand and one study was in Switzerland.

33COMMUNITY RESPONSE (0 STUDIES)

34POPULATION RESPONSE (2 STUDIES)

35Reproductive 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.

36Survival (1 study): One study in Switzerland found that four of 18 bats died after translocation.

37Condition (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.

38BEHAVIOUR (2 STUDIES)

39Uptake (2 studies): Two studies in New Zealand and Switzerland found that low numbers of bats remained at release sites after translocation.

40Behaviour 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