Bat behavior around double-track electrified railways

Abstract

Animals’ mortality due to transportation infrastructure is a significant problem for some species. Scale of mortality in part depends on their behavior near railways and other transport routes. We studied the mortality and flight activity of bats in 7 double-track electrified (i.e., leading the catenary, a railway overhead electric line) railway sites in Poland. We aimed to measure the likelihood that bats use areas which pose a potential risk of collision with trains. During acoustic (ultrasound detectors) and visual (thermal imaging cameras) observations, we identified bats’ positions near the railway (A — high above catenary; B — close (< 1 m) but not under catenary; C — the space destined for passing trains between tracks, traction poles, and the top of the catenary; D — at the side of the railway and next to vegetation without crossing the railway area; and E — under bridges) in different habitats (forest, water, open, urbanized). Bat activity was significantly lower (4%) in high-risk impact zone (C) than that in other zones (96%). However, bats were more prone to occur in high-risk impact zones in urbanized and open habitats, whereas, in water and forest habitats, bats occurred much less frequently. In forest sections of the railways, flights along the railway typically took place between the line and vegetation (zone D), or close to the catenary (zone B). We detected significant differences between species activity in and outside the high-impact zone (C) and other zones (A, B, D, E). Open-spaced and high-flying common noctule Nyctalus noctula usually flew or foraged above the railway area. Daubenton’s bat Myotis daubentonii almost exclusively sought food above lakes or rivers and under the railway bridges. In serotines Eptesicus and pipistrelles Pipistrellus group, there was a higher tendency to use a high-risk impact zone. The search for bat casualties conducted by the researchers and a trained dog revealed one dead bat under the 50-m overpass of the two-track railway immediately following the simultaneous passage of two trains. We assumed that there is a lower chance of bat collisions with trains than with cars because of the low level of nighttime traffic on railways, when bats are active, and the specific arrangement of electrified railways. Such railways provide bats with additional open space between tracks with electrification system and the forest edge, or above the catenary for foraging and commuting. Bats utilize this space and avoid flying in the area over the track that is cluttered by the catenary; this may reduce their exposure to passing trains and the likelihood of collisions.