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Hopovers as road crossings for bats

In Europe, the construction of roads is one of the most important causes of habitat fragmentation. Beside the impact on terrestrial animals, bats are vulnerable to habitat fragmentation. Bats use a network of daily roosts interconnected by commuting routes. Bat movements are strongly linked to landscape features as water ways (Myotis dasycneme and Myotis daubentonii) and hedges, belts, wooded banks and forested ridges (other species).

In Europe bats are strongly protected by international law. In many road construction schemes therefore, mitigation for bats is a hot topic. One of the mitigation measures frequently proposed in European countries (for example in UK, Germany, The Netherlands) are hop-overs. Hop-overs consist of tree lines or artificial ‘bridges’ which facilitate Bats to cross open space across roads, while using their traditional commuting routs or hunting movements. For juridical reasons and ecological motives it is essential to know the effectiveness of taken mitigation measures. In many cases however, such information is not available.

For this reason, A&W initiated in 2010 an experimental study on the effectiveness of overpasses (hop-overs) as a measure for preserving landscape connectivity for bats. The aim of the study is to provide scientific data on the use of these overpasses and the factors which influence the utilization by Bats. We visited existing overpasses on several sites in Wales (UK) and The Netherlands, to quantify the number of bats using them. In the Netherlands we compared the number of bats using man-made structures over roads (e.g. viaducts) with situations where such structures are lacking. Preliminary results show, that overpasses can aid bats crossing roads safely, but there may be differences between species and local situation. The results also give clues on the design of overpasses and can be used to improve their effectiveness. The study is due to continue in 2011 amongst others by a telemetry study. The results will be used in designing and locating several planned overpasses in a Dutch road scheme project.

For more information please contact  dr. ir. Daan Bos.