Creating an amphibian-friendly pathway over the rip rap beneath the Lost Shoe Bridge has continued since our earlier post this summer. We had always planned to add soil and plants over the mixture of sand and small stones, called "pit run", used to fill cracks in the rip rap. The importance of doing so was reinforced when we watched a Wandering Salamander struggle to get purchase on the "pit run" as it climbed up the slope at one of the bridge corners.
Then, from the corners where the fencing meets the bridge abutments to as far as the light can reach beneath the bridge, we planted dozens of sword ferns and lady ferns, sedges, rushes, false lily of the valley, coastal strawberry, twinflower and mosses. The final step was to spread fallen alder leaves over the soil and around the plants.
The following photos show the transformation from rip rap to pit run to a vegetated path in the southeast corner of the bridge.
More dramatic results happened in the southwest corner where the log placement reduced a steep drop across the rocks where the amphibian fencing joined the bridge abutment.
We were very pleased to find a Rough-skinned Newt on the path at this corner last week. It camouflaged well with the layer of dead alder leaves.
Our ongoing task is to monitor amphibian movements beneath the bridge. We installed cameras and search for frogs and salamanders along the highway and fences during warm rainy nights. The survey data will give us a relative measure of how many amphibians are moving across the road and being intercepted by the fencing. This will provide an index of how many we should expect to photograph moving under the bridge if our path is working!
Stay tuned for the results later this winter after we go through our camera images!
The Central Westcoast Forest Society, B.C. Ministry of Transportation and Infrastructure and Habitat Conservation Trust Foundation support this project. We are grateful to them and a dozen community volunteers who have helped with the night surveys.