Install fencing around cave entrances to restrict public access

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

Effectiveness

40%
Certainty

20%
Harms

0%

Calculating overall effectiveness category

Background information and definitions

Fencing may be installed around cave entrances to restrict public access and reduce disturbance to cave-dwelling bats.

Study locations

Key messages

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.

BEHAVIOUR (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.

About key messages

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

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

Supporting evidence from individual studies

A controlled, before-and-after study in 1994–1996 at one cave on a forested limestone ridge in north Florida, USA (Ludlow et al 2000) found that replacing a steel bar gate with a fence resulted in more southeastern myotis bats Myotis austroriparius and gray myotis bats Myotis grisescens emerging from the cave entrance. More bats emerged from the cave entrance when a fence was installed (average 1,517 bats/month, 48% of total bats emerging) instead of a steel bar gate (306 bats/month, 8%). The number of bats emerging from a second ungated open entrance to the cave decreased after the gate was replaced with a fence (from 3,609 to 1,651 bats/month). The cave gate consisted of steel bars 13 mm in diameter spaced 100 mm apart in one direction and 465 mm in the other. Before removal of the gate a 2.2 m high chain-link fence was erected 6–8 m from the cave entrance. Emerging bats were counted monthly at the gated entrance and the open entrance for one year before and one year after the cave gate was removed and replaced with a fence (August 1994 to July 1996).
Study and other actions tested
Referenced paper
Ludlow M.E. & Gore J.A. (2000) Effects of a cave gate on emergence patterns of colonial bats. Wildlife Society Bulletin, 28, 191-196.
A replicated, site comparison study in 1997–2014 of 34 caves in eastern Spain (Machado et al 2017) found that installing fencing or cave gates did not have a significant effect on the occupancy or population growth rates of nine bat species. Average occupancy rates were similar in caves with (11 of 20, 57% of caves occupied) and without (8 of 14, 60% of caves occupied) gates or fencing (separate results for cave gates and fencing not reported). Population growth rates also did not differ significantly between caves with or without fencing or gates (data reported as statistical model results). Fourteen caves had fencing installed (2.5 m high gridded metal fences in a 20 m radius around the cave entrance), two caves had rigid panels installed (filling three-quarters of the cave entrance), two caves had iron bars installed (filling the entire cave entrance), and two caves had cave gates installed (with 2 x 1 m² openings for bats). Fourteen caves did not have fencing or gates installed. Bats were counted annually using infrared video cameras and bat detectors at cave entrances between May and July in 1997–2014.
Study and other actions tested
Referenced paper
Machado M.C., Monsalve M.A., Castello A., Almenar D., Alcocer A. & Monros J.S. (2017) Population trends of cave-dwelling bats in the eastern Iberian Peninsula and the effect of protecting their roosts. Acta Chiropterologica, 19, 107-118.

Please cite as:

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

Where has this evidence come from?

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This Action forms part of the Action Synopsis:

Bat Conservation

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Minimize alterations to caves for tourism Action Link	No evidence found (no assessment)	0	Synopsis Link
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Impose restrictions on cave visits Action Link	Likely to be beneficial	4	Synopsis Link