Bats underneath: assessing neotropical bat use of highway underpasses using photo-trapping

Abstract Roads impact bats through roadkill, roost and habitat degradation and destruction, as well as fragmentation of habitats when roads act as barriers to movement. Bats are usually not focal species when designing highway mitigation unless a known refuge might be affected. Wildlife underpasses are generally designed for medium to big-size mammals. Research on the effectiveness of crossing structures in highways for bats needs to be expanded and consistent despite knowing that they use wildlife underpasses. After a year of monitoring underpasses at the Nuevo Xcan-Playa del Carmen highway in Quintana Roo, Mexico, with a total trapping effort of 5,531 camera trap/nights, we got 916 independent bat records in 26 of the 28 surveyed structures. We recorded 716 in concrete box culverts, 156 in concrete pipes, and 44 in wildlife underpasses. We found daily activity from dusk till dawn concentrated from 1 to 5 AM, and the annual cycle had activity during the rainy season (July to February) and no activity during the dry season (March to June). We selected 143 photos for species identification and found 15 species using those structures—11 belonging to Phyllostomidae, 3 to Moormopidae, and 1 to Natalidae. These species are cluttered space flyers, mostly gleaners with different diets. We found that local variables within the right of way are relevant for predicting bat use of the underpasses. We found that partial flooding inside culverts is the most important variable in predicting bat use of the structures, together with an interaction between vegetation cover at the entrance and its cross-sectional area. Photo-trapping could become a helpful tool, especially when combined with acoustic surveys for long-term monitoring of bats if conditions and equipment are appropriately chosen.