Effectiveness of amphibian mitigation measures along a new highway

Published source details Merrow J. (2007) Effectiveness of amphibian mitigation measures along a new highway. Proceedings of the 2007 International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, 370-376.
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This study is summarised as evidence for the following.

	Action	Category
	Install barrier fencing along roads Action Link
	Create ponds for amphibians Action Link
	Install culverts or tunnels as road crossings Action Link

Install barrier fencing along roads

A study in 2004–2008 of a barrier wall leading to a culvert under a new highway through upland forest in New Hampshire, USA (Merrow 2007) found that the wall only diverted small numbers of amphibians towards the culvert. Small numbers of spotted salamanders Ambystoma maculatum and wood frogs Rana sylvatica were found moving along the wall. However, small numbers were also found crossing the road in areas without a wall or culvert. There was no evidence that amphibians used the tunnel during the first three years. The diversion wall was at least 0.3 m high and extended from the culvert to a stone-lined stream channel on one side and a larger pedestrian culvert on the other. Spring amphibian migrations were monitored for three years after construction.
Create ponds for amphibians

A small replicated study in 1998–2007 of two constructed temporary ponds along a new highway bypass in New Hampshire, USA (Merrow 2007) found that during the first two years, a relatively diverse community of amphibians used the ponds. Spotted salamanders Ambystoma maculatum were found in one of the two ponds. In existing ponds, spotted salamander breeding was similar in the six years before and two years after highway construction (14–73 vs 28–77 egg masses/pond). However, the highway had not yet opened for traffic. Created ponds were designed to mimic existing ponds and a 60 m upland buffer was preserved around each. Egg mass counts were undertaken.
Install culverts or tunnels as road crossings

A study in 2004–2008 of a culvert with barrier wall along a new highway through upland forest in New Hampshire, USA (Merrow 2007) found no evidence that it had been used by amphibians during the first three years. A ‘wildlife diversion wall’ preventing access to the road and funnelling animals to the culvert did divert amphibians. Small numbers of spotted salamanders Ambystoma maculatum and wood frogs Rana sylvatica were found moving along the wall. However, small numbers of these species were found crossing the road in areas without a wall or culvert. The culvert was constructed near to the most productive pond for amphibians. It was 17 m long with an opening 1.2 x 1.2 m. Loamy soil material was used and was sloped across the width of the culvert to confine stream flow to one side. The diversion wall (0.3 m high) extended from the culvert to a stone-lined stream channel on one side and a larger pedestrian culvert on the other. Spring amphibian migrations were monitored for three years after construction.