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No. 61: Investigation of animal use of fauna/human passages at the Give-Billund express way and the Kolding-Esbjerg motorway

Madsen, A.B., Christensen, P.K., Møller, J.D. & Haugaard, L. 2013. Undersøgelse af faunaens brug af fauna/menneske passager på Give-Billund motortrafikvejen og Kolding-Esbjerg motorvejen. En biologisk vurdering af brugen og anbefalinger til forbedringer. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 36 s. - Videnskabelig rapport fra DCE - Nationalt Center for Miljø og Energi nr. 61. http://www.dmu.dk/Pub/SR61.pdf

Summary

Large transport infrastructures have a great impact on the possibility of the fauna to exploit all habitats in the landscape. To minimise the barrier function and fragmentation of the landscape caused by such infrastructures, passages over or under these are constructed. Passages for animals/ humans serve two purposes: (i) to facilitate passage of wild fauna and (ii) ensure local landowners passage in connection with, for instance, field work or tending of animals. The use of four passages for fauna/humans by mammals and amphibians at, respectively, the Give-Billund dual carriageway (an overpass) and the Kolding-Esbjerg motorway (a valley bridge and two underpasses) was investigated from late August to mid-December 2012 by Aarhus University for the Danish Road Directorate.

The use of the fauna of the four passages was recorded by means of direct observations and sound monitoring of amphibians, capture of small mammals in traps and by setting up game cameras for recording large and medium-sized mammals. On the basis of these investigations and earlier Danish and international studies it is evaluated whether the dimension and placement of the passages encourage the animals to use the passages.

During the investigation period amphibians (common frog, common toad and moor frog) were registered in the middle of or on three of four passages. At one of the passages only one common toad was observed at the southern entrance to the fauna passage.

Harvest mouse, bank vole, common field vole and common shrew mouse were frequently observed on/in the investigated passages. Moreover, individuals of yellow-necked mouse, common vole, pygmy shrew, wood mouse and water shrew were recorded. Weasel was caught a total of five times at one of the passages.

Roe deer, brown hare and red fox were the most commonly observed large and medium-sized mammals. Next, humans including vehicles were the most frequent users of the passages. Among domestic animals cats were the most frequently observed species. Particularly, and perhaps not surprising, the valley bridge at Åkær Å dominated in number of passes of medium-sized and large mammals. Only one observation of stone marten/pine marten was made. Badger, polecat, mink, stoat, weasel and hedgehog were not observed using the passages.

The dimensions of the four passages, plantation etc. are described and compared with the surrounding landscape on both sides of the road, for instance forest, guidelines, uncultivated fields and nature types. Deer fences have been established along all road sections between Give-Billund and Kolding-Esbjerg, including all four passages. There is no significant disturbance from other infrastructures or buildings within a 200 m buffer zone around all the fauna and human passages.

Due to the limited dimensions of the three passages at Porshusvej, Stilde Å and Vejen Mose it can be difficult to create favourable passing conditions for a broad range of species. However, simple initiatives may be taken to increase the diversity of guidelines and habitats within the passages and at the entrance areas to improve the efficiency of the passages.

At the localities Porshusvej, Stilde Å and Vejen Mose establishment of fences for amphibians along the road will improve the guiding of animals towards the passages. In the passage at Stilde Å and Vejen Mose stone heaps will be erected to improve the possibilities of refuge for both amphibians and small mammals. In the passage at Åkær Å establishment of several small thickets and heaps of brushwood in the grass field below the bridge east of the stream will provide better protection, primarily for amphibians passing through the fauna passage and for other small mammals as well.

Based on the present investigation, AU concludes that the combined use of passages for both animals and humans cannot always explain the limited level of activity of selected species. AU also concludes that a potential extra cost to improve the possibility of animals to pass will be well worth it for passages established for the purpose of allowing local landowners to continue activities on both sides of a road system.