Toad Tunnel Targets Adult Toads

A new toad tunnel installed under Highway 6 at Summit Lake south of Nakusp by the Ministry of Transportation and Infrastructure (MOTI) is already being used by young toadlets and, more importantly, adult toads.

The tunnel, constructed in summer 2014, will help reduce mortality of Western Toads – a species at risk – as they cross the road to and from Summit Lake.

While there are two smaller existing wildlife culverts running under the highway, the new box culvert, with concrete construction, is much larger at 1.8 metres wide. The tunnel floor is covered in soil so it feels as natural as possible.

The Fish and Wildlife Compensation Program and the Ministry of Forests, Lands and Natural Resources Operations, have also constructed temporary directional fencing to help guide the toads into each entrance.

There are three migrations – or road crossings – that occur at different times of the year for the Western Toads. First, when the ice comes off the lake in early spring, the adults that are ready to breed make their way to the lake; after breeding they return to their upland habitat; and then in late summer, millions of dime-sized toadlets that are the progeny of the spring breeding, leave the lake and head upland where they mature into adults.

While the timing for these movements is typical, researchers have observed some adults heading down to the lake well before winter – possibly to get a jumpstart or some competitive advantage for the breeding the following spring.

“We are extremely pleased that the new tunnel is being used by the migrating adults. In September we recorded two dozen adults over the course of just two nights using the tunnel, many of them females laden with eggs,” says Wildlife Biologist Jakob Dulisse. “The large structure also allows other animals to use the tunnel, and at least four species of mammals have already been recorded using it.”

The adult female Western Toads are especially important because each female ready to spawn is carrying an average of 12,000 eggs. To put that figure into perspective, during the annual Toadfest event organized by the FWCP, a similar number of toadlets, on average, are carried across the road each year.

It is anticipated that this is just the start of the positive results, and that in the years ahead the number of toads using the tunnel will increase.

In preparation to select the optimal site for the toad tunnel, MOTI utilized information collected during the Western Toad Research Project at Summit Lake. The project involves many partners including the Fish and Wildlife Compensation Program, Columbia Basin Trust, the Ministry of Forests, Lands and Natural Resource Operations, Nakusp and Area Community Forest, and BC Parks.