Mitigating reptile road mortality: Fence failures compromise ecopassage effectiveness

Published source details Baxter-Gilbert J.H., Riley J.L., Lesbarrères D. & Litzgus J.D. (2015) Mitigating reptile road mortality: Fence failures compromise ecopassage effectiveness. PLoS ONE, 10, e0120537.
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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 barriers and crossing structures along roads/railways Action Link

Install tunnels/culverts/underpasses under roads/railways

A replicated study in 2013 along a section of highway through wetlands, rocky outcrops and mixed forest in Ontario, Canada (Baxter-Gilbert et al. 2015) found that few painted turtles Chrysemys picta entered a culvert under the highway. In a choice experiment, only 9% (5 of 54) of painted turtles Chrysemys picta entered the culvert, whereas 22% (12 of 54) moved away from the culvert and 69% (37 of 54) remained at the entrance. Authors reported that the percentage of turtles entering the culvert was lower than that recorded in a previous arena study away from the highway (47% crossed). In 2013, adult painted turtles (30 females; 24 males) were caught in the wild and brought to a culvert that had been constructed under a highway (2.5 km from capture location). The culvert (and highway) was located between the individuals and their home range. Turtles were allowed to acclimate for 10 minutes in an open box near the entrance to the culvert. The box was then removed and movements were monitored to see if they used the culvert, moved away from it, or did not move.

(Summarised by: William Morgan)
Install barriers and crossing structures along roads/railways

A controlled, before-and-after study in 2012–2013 along a section of highway through wetlands, rocky outcrops and mixed forest in Ontario, Canada (Baxter-Gilbert 2015) found that installing fencing and culverts prevented an increase in road use by snakes, but may have increased the percentage of snakes and turtles that died on the road. The number of snakes and turtles (both dead and alive) discovered on roads stayed similar in areas with fencing and culverts (snakes: 0.6–0.7/day; turtles: 0.5/day), but without fencing and culverts snake numbers increased (before: 1.4/day; after: 2.4/day), but turtle numbers stayed the same (1.0–1.1/day). However, the percentage of dead reptiles may have increased with fencing and culverts (before: 68% of turtles, 68% of snakes; after: 86% of turtles, 90% of snakes), but stayed similar in the area without (before: 86% of turtles, 76% of snakes; after: 88% of turtles, 88% of snakes), but this result was not tested statistically. In 2012, three crossing structures (culverts) were installed along a 13 km section of highway and connected with fencing (plastic sheeting and a chain-link fence). A similar 13 km section of highway with no fencing or culverts was also selected. In May–August in 2012 (before installation) and 2013 (after installation), both sections of highway were surveyed by car (13 km section; 3 surveys/day) or by foot (2 km section; 1 survey/day) to count the number of live and dead reptiles on the road.

(Summarised by: William Morgan)