CHILLIWACK, British Columbia, July 23 (UPI) -- Canadian volunteers in British Columbia were scooping up thousands of western toads Wednesday to prevent them from being killed by cars.

The toads, listed as a federal "species of special concern," are late in their migratory move from wetlands in the south-central city of Chilliwack to forested uplands, and thousands have been killed crossing the road that separates the two habitats, The Province newspaper in Vancouver reported.

Biologist Zoey Slater told the newspaper gloved volunteers began scooping the dime-sized toads into buckets and boxes Tuesday night and ferrying them across the road.

"Residents told us that in the past, the road would be covered with squished toads, like a huge oil slick," she said.

She said the death of one female toad has a huge impact, as female western toads only reproduce twice in their lifetime, laying up to 20,000 eggs.

Slater said the toads' numbers are shrinking from the Fraser Valley lowlands because of development.