Mitigation of barrier effect on linear infrastructures on wildlife

Published source details Rosell C., Parpal J., Campeny R., Jove S., Pasquina A. & Velasco J.M. (1997) Mitigation of barrier effect on linear infrastructures on wildlife. Pages 367-372 in: Habitat Fragmentation & Infrastructure. Ministry of Transport, Public Works and Water Management, Delft, Netherlands.
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This study is summarised as evidence for the following.

	Action	Category
	Install tunnels/culverts/underpasses under roads/railways Action Link
	Install tunnels/culverts/underpass under roads Action Link
	Install culverts or tunnels as road crossings Action Link

Install tunnels/culverts/underpasses under roads/railways

A replicated study in 1993–1994 in four motorway roadside verges in Catalonia, Spain (Rosell et al. 1997) found that road underpasses (‘culverts’) were used by reptiles and that reptiles were recorded more often in circular than rectangular underpasses. Results were not statistically tested. Reptiles used four of 17 rectangle-shaped underpasses and 23 of 39 circle-shaped underpasses. The authors reported that reptiles were only recorded crossing shorter-length underpasses and were more likely to be recorded when there was natural substrate on the floor of the underpass and the opening of the structure was at ground level. In November 1993–September 1994, fifty-six underpasses (including drainage channels) along four 10 km-long stretches of motorway were surveyed for use by reptiles. Thirty-nine underpasses were circular in cross section (1–3 m diameter) and 17 were rectangular (4–12 m wide). Each underpass was monitored four times for four days/season (16 days in total/underpass) using a 50 cm long strip of powder substrate across each underpass and infra-red and photographic cameras.

(Summarised by: Katie Sainsbury)
Install tunnels/culverts/underpass under roads

A replicated study in 1993–1994 along four roads in Catalonia, Spain (Rosell et al. 1997) found that underpasses were used by several mammal species. Small mammals used all rectangular culverts and 94% of circular culverts. Hares Lepus spp. and rabbits Oryctolagos cuniculus used 83% and 23% of rectangular and circular culverts respectively whilst carnivores used 88% and 75% respectively. Carnivores recorded were weasel Mustela nivalis, beech marten Martes foina, badger Meles meles, genet Genetta genetta and fox Vulpes vulpes. Wild boar Sus scrofa and roe deer Capreolus capreolus also used underpasses. Use was greater by small mammals for underpasses at the same level as the surroundings and those with natural substrate on the floor. Those with water were used less frequently. Rabbits did not use narrow structures (<1.5 m), whereas wild boar used underpasses >7 m wide. A total of 39 circular (1–3 m diameter) and 17 rectangular drains (4–12 m wide) and other underpasses were surveyed along four 10-km sections of road. Underpasses were monitored for four days/season over a year, in 1993–1994. Animal tracks were monitored using marble power (50 cm wide) across the centre of each structure. Infra-red and photographic cameras were used at entrances.

(Summarised by: Rebecca K. Smith)
Install culverts or tunnels as road crossings

A replicated, site comparison study in 1993–1994 of 56 tunnels under roads in Catalonia, Spain (Rosell et al. 1997) found that amphibians used 23% of circular and 59% of rectangular tunnels. Use was greater for wider tunnels with water within or at entrances. Tunnels with steps or wells at the entrances or within large embankments were used less frequently. A total of 39 circular (1–3 m diameter) and 17 rectangular cross-section (4–12 m diameter) drains/underpasses were surveyed along four 10 km stretches of roads. Tunnels were monitored for four days each season over a year in 1993–1994. Tracks were obtained using marble power across the centre of each structure. Infra-red and photographic cameras were used at entrances.