for National Geographic News
Later this month, when the next warm, wet rain soaks the northeastern U.S., it will signal thousands of American toads to hop to their breeding ponds. To get there, many of the toads will cross roads that slice through their habitat.
John Serrao, a naturalist in Pennsylvania's Pocono Mountains, says that unless Buffo americanus and other amphibians get help crossing the road, their local populations will disappear.
Entire populations of American toads breed within the same few days at the same time each year, usually late April or early May.
According to Serrao, the toads hop to their breeding ponds after the ground has warmed, the air temperature stays above 65° Fahrenheit (18° Celsius), and the first hard spring rain falls.
"To get to their ancestral breeding ponds, a lot [of toads] have to cross roads," Serrao said. "And they're slow moving at that time of yearit's still cool, they've been inactiveand they get squashed."
Serrao recalls an April night five years ago when he went out to a backcountry road near his home to watch the breeding migration. He counted 100 toads; 95 were hit by cars.
A similar story can be told for several other species of toads, frogs, salamanders, alligators, and turtles around the world.
Roadkill is just one factor behind the dramatic decline of the world's amphibians. By one count, 1 in 3 of the 5,743 known species of frog, toad, salamander, and other amphibians are dwindling.
Better-known suspected culprits for the decline include global warming, insecticides, and paved-over wetlands.
Scott Jackson, a biologist at the University of Massachusetts in Amherst, said one way to help amphibians survive road crossings is to construct so-called amphibian tunnels beneath the pavement.
European countries have constructed these amphibian tunnels for decades. Jackson led a team that installed the first such tunnel in the U.S., which was built in Amherst in 1987.
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