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Design, installation, and monitoring of safe crossing points for bats on a new highway scheme in Wales

  • Author(s): Wray, Stephanie
  • Reason, Paola
  • Wells, David
  • Cresswell, Warren
  • Walker, Hannah
  • et al.
Abstract

The greater horseshoe bat (Rhinolophus Ferrumequinum) is strictly protected under European Union (EU) and United Kingdom (UK) legislation. This serves to ensure that the species (as well as its roosting sites and feeding habitat) receives strict protection and that appropriate monitoring of populations will be undertaken. The Milton-Carew-Sageston area of West Wales (UK) has been shown to be utilized by much of the Welsh population of greater horseshoe bats. Potentially, therefore, anything which significantly affects this area could have an important impact upon the survival of this population. A proposed road scheme, the A477 Sageston to Redberth Bypass, was to pass through a mosaic of pasture, hedgerows, marshy stream courses, and small woodlands, which constitutes near optimal foraging habitat and dispersal routes for bats. Greater horseshoe bats had been shown to cross the existing road in several locations, and there were known to be nine principal greater horseshoe bat roosts within 2.5 km of the study area. In order to reduce the likelihood of the bats being killed on the new road, it was necessary to discourage the bats from foraging along the road verge, while simultaneously providing safe and attractive crossing points, at locations where the bats were already known to cross the route of the proposed road. This involved: (i) the maintenance of attractive linear features (lines of trees, hedgerows, etc.) perpendicular to the route to lure the bats away from the road; (ii) a relatively wide verge of poor quality habitat (e.g., amenity grassland, hard standing, etc.) directly adjacent to the carriageway (and for some distance along it) to discourage the bats from foraging along the road; (iii) safe crossing points at culverts underneath the road on the alignment of existing flight lines; and (iv) the omission or alteration of street lighting at crossing points to be retained so that these areas remain in relative darkness. The exact location of the tunnels, the planting leading to them, and the engineering design of the tunnel approaches were developed by an integrated team of ecologists and engineers. The measures were installed in 2002, and the road opened to traffic in 2003. The success of the mitigation measures have been monitored through bat activity surveys in 2003 and 2004, and the tunnels are proving to be extremely effective in allowing bats to cross the road safely. No records of bat/vehicle collisions have been recorded. Information is also provided on other schemes in Wales which have involved the provision of safe crossing points and mitigation for horseshoe bats

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