Bat overpasses: An insufficient solution to restore habitat connectivity across roads

Published source details Claireau F., Bas Y., Puechmaille S.J., Julien J.-F., Allegrini B. & Kerbiriou C. (2019) Bat overpasses: An insufficient solution to restore habitat connectivity across roads. Journal of Applied Ecology, 56, 573-584.
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This study is summarised as evidence for the following.

	Action	Category
	Install bat gantries or bat bridges as road/railway crossing structures for bats Action Link
	Install overpasses as road/railway crossing structures for bats Action Link

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

A study in 2016 of a bat gantry (or bat bridge) at a road construction site near Beauvais, France (Claireau et al 2019) found that the temporary wire bat gantry was used by three bat species or species groups, although 46% of bats crossed the road at other locations. The gantry, installed within a bat commuting corridor, was used by 54% (97 of 180) of crossing bats, whereas 43% (77 of 180) crossed the road at other locations within the corridor and 3% (6 of 180) crossed at other locations outside the corridor. Crossing heights were not reported. Three bat species/species groups used the gantry (nearly all Pipistrellus spp.) and five bat species/species groups crossed at other locations (see original paper for details). The gantry (80 m long, <2 m high) was temporarily installed within a bat commuting corridor during the construction of a four-lane highway in 2015–2016. Two parallel wires (1.2 m apart) were strung across the road, each with 29 reflective polystyrene spheres (23-cm diameter) attached. Six pairs of bat detectors on opposite sides of the road (one pair at the gantry, five pairs within the commuting corridor or adjacent habitats) simultaneously recorded crossing bats over four consecutive nights in May 2016.

(Summarised by: Anna Berthinussen)
Install overpasses as road/railway crossing structures for bats

A replicated study in 2016 of two overpasses over a road near Lyon, France (Claireau et al 2019) found that both ‘U-shaped’ metal overpasses were used by two bat species or species groups, although 51–65% of bats crossed the road at other locations. One overpass, installed within a bat commuting corridor, was used by 39% (26 of 67) of crossing bats, whereas 51% (34 of 67) crossed the road at other locations within the corridor. The other overpass, installed 325 m from a bat commuting corridor, was used by 19% (7 of 37) of crossing bats, whereas 65% (24 of 37) crossed the road within the original commuting corridor. Crossing heights were not reported. Two bat species/species groups (all Pipistrellus spp.) used the overpasses and 4–6 bat species/species groups crossed at other locations (see original paper for details). Both overpasses (40 m long x 4.8 m wide, <10 m high) were installed (2.5 km apart) over a new four-lane highway in November 2012. At each site, six pairs of bat detectors on opposite sides of the road (one pair at the overpass, five pairs within the commuting corridor or adjacent habitats) simultaneously recorded crossing bats over five consecutive nights in July or September 2016.

(Summarised by: Anna Berthinussen)