When toads meet roads, it’s often the end of the road for the amphibians.
Road crossings are a perilous, yet unavoidable obstacle in the journey of migrating Western toads on Vancouver Island, but a new transportation project aims to provide safe passage thanks to an underground tunnel.
B.C.’s Ministry of Transportation is constructing a series of cross-culverts tunnelling under the road network west of Duncan so that toads can safely migrate to breeding grounds at Wake Lake.
“[Roads are] dangerous for the animals themselves because they’re on the move to get to their breeding grounds and basically anything in their path, they’ll try and cross to get to the lake,” explained Sean Wong, senior biologist with the ministry.
“That’s the main area where we’re doing some mitigation to help reduce the mortality from vehicle traffic with the toads or other amphibians that end up potentially on the road vulnerable to vehicles,” he told All Points West host Kathryn Marlowe.
Wong says the construction project consists of upgrading two existing culverts with bigger ones and building two additional culverts in areas with high mortality rates.
One of the most important additions, he says, is directive fencing to make sure the toads end up in the tunnels and don’t continue to hop up onto the dangerous road.
“We end up with about 400 metres of this directive fencing, or guide fencing, that is intended to funnel the critters into the culverts rather than having them more exposed by still attempting to climb up and end up on the road itself.”
The tunnels themselves are made of plastic drainage culverts with a diameter of approximately 450 millimetres. The fencing consists of the same culverts that have been cut in half.
Wong says that after successful breeding and the emergence of juvenile toadlets, the population of Western toads will out-migrate away from Wake Lake, back to their feeding areas.
The migration usually begins in late spring or summer, but the biologist says construction crews have already noticed some adult toads on the move.
“It was pretty much the first day that we didn’t have hard frost and then with a little bit of light drizzle, rain, that probably was a stimulus to get them moving,” said Wong.
He says construction will be mostly complete by Wednesday and expects that since migration occurs mostly during the evening and nighttime, the remaining work won’t be disruptive to the toads.