Response of carnivores to existing highway culverts and underpasses: implications for road planning and mitigation

Published source details Grilo C., Bissonette J.A. & Santos-Reis M. (2008) Response of carnivores to existing highway culverts and underpasses: implications for road planning and mitigation. Biodiversity and Conservation, 17, 1685-1699.
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This study is summarised as evidence for the following.

	Action	Category
	Install barrier fencing and underpasses along roads Action Link

Install barrier fencing and underpasses along roads

A replicated study in 2004 along two roads in southern Portugal (Grilo et al. 2008) found that underpasses and culverts along roads bounded by livestock fencing were used by carnivore species to cross highways. Crossing rates of underpasses were similar to those of culverts for red fox Vulpes vulpes (underpasses: 0.25 crossings/day; culverts: 0.11), badger Meles meles (underpasses: 0.30; culverts: 0.15), genet Genetta genetta (underpasses: 0.15; culverts: 0.9) and Egyptian mongoose Herpestes ichneumon (underpasses: 0.29; culverts: 0.22). Stone marten Martes foina used underpasses more (0.22 crossings/day) than they used culverts (0.05 crossings/day). Fifty-seven passages under 252 km of two major roads were monitored. They comprised 1.2 circular culverts/km (1 and 1.5 m diameters), 0.3 box culverts/km (2 × 2 m to 5 × 5 m), and 0.5 underpasses/km (5 m high and 8 m wide). Crossing structures were 5–1,566 m apart. Livestock fencing, 1.5 m high, ran along both sides of both roads. A 1-m² plot of marble dust was placed at each end and in the middle of each passage. This was checked for tracks every five days, over 20 consecutive days of monitoring, in both spring and summer 2004.

(Summarised by: Lauren Vorhees )