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Critter Crossings: Linking Habitats and Reducing Roadkill

Amphibian-Reptile Wall and Culverts

Florida


[Photo: Green treefrog - Photo: Florida banded water snake - Photo: Spotted leopard frog - The green treefrog (above top), Florida banded water snake (above middle), and spotted leopard frog (above bottom) are three of the most frequently killed species on U.S. 441. The Florida banded water snake lives in gator holes. It's a fish-eater and harmless to humans. The tiny, brightly colored green treefrog is sometimes called the "rain frog" because it tends to call only during humid weather, and the chuckling calls of a chorus of spotted leopard frogs make it sound as if the whole swamp is laughing.]

A short stretch of U.S. 441 in central Florida has more documented roadkills than any other road segment in the state.

Thousands of animals from more than 80 species are killed every year on the nearly 2-mile (3.2-km) section that crosses Paynes Prairie State Preserve just outside Gainesville. Most are frogs, turtles, and snakes attempting to cross the road to mate and to forage for food.

In 1997 a multi-disciplinary "Paynes Prairie Working Group" representing state transportation and natural resource agencies, environmental groups, and the University of Florida met to brainstorm ways to curb the death toll and help animals resume their natural movement patterns.

[Photo: Wall and culvert - Amphibians and reptiles that manage to scale the vertical surface of this wall will be stopped by a "lip" at its top. - Photo: Wall]

The group came up with an innovative strategy: a 3 1/2-foot-high (1.1-meter-high) concrete wall that will divert animals to eight highway underpasses.

The wall's distinguishing feature - a 6-inch (15.2-cm) "lip" at the top - is characteristic of walls in zoo serpentariums. Snakes, frogs, alligators, and other animals that manage to scale the smooth vertical surface of the wall will be stopped by the lip. "At that point, the force of gravity will take over," says Jim Weimer, park biologist at the Paynes Prairie State Preserve. "It will force the animals to lean backwards. Their own body weight will then flip them upside down and off the wall."

"Even large alligators will be deterred," says Pete Southall, a Florida Department of Transportation (FDOT) biologist. Southall admits that rat snakes and other habituated climbers may occasionally scale the wall, but he says there are few such species in the area.

Southall thinks the new wall will not only benefit Paynes Prairie animals that climb but also those that jump - for example, bobcats. "When bobcats reach the wall, they'll most likely behave as they do when they encounter a similar barrier along the highway," he says. "Instead of trying to jump over the fence, they typically move along it to the culvert opening."

FDOT began construction in December 1999. The wall will extend along 1.8 miles (2.9 km) of highway and connect with four new pipe culverts which will be spaced between four existing culverts.

If the U.S. 441 project is successful, it will become the model for the rest of the state - and for the nation.

Update: In 2000, the project won the prestigious Globe Engineering Award. The wall, now called an ecopassage, was completed in December 2000.

For more information, contact Pete Southall at 386-961-7470 or peter.southall@dot.state.fl.us

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