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Paw Print Wildlife and Highways: An Overview Tortoise Underpasses Badger Tunnels Four Tools to Assess Wildlife Linkage Areas Programs to Remove Fish Passage Barriers Bear Underpasses Salamander Tunnels Passages for Large Mammals Goat Underpasses Computer Model Highway-Wildlife Relationships Amphibian-Reptile Wall and Culverts An Overpass for Animals and Humans
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Bear Underpasses

Photo: America black bear This sub-species of the American black bear is black with a brown muzzle. Males weigh about 350 pounds; females, approximately 150. They live in forests and eat mostly vegetable matter. A female's home range averages 11 square miles (28.5 km2); a male's can reach 66 square miles (171 km2), making male bears particularly vulnerable to roadkill. Florida black bears have been on the state's list of threatened species since 1974. There used to be 12,000 in the state; now there are 1,500 or fewer. More than 50 bears are killed on Florida roads each year.

When biologists and engineers from the Florida Department of Transportation (FDOT) and the Florida Fish and Wildlife Conservation Commission (FWC) designed the state's first underpass for black bears on a stretch of State Route 46 in Lake County, they had done their homework.

They knew bears had been using similar crossings built for Florida panthers on Alligator Alley (now I-75). They had also observed that bears routinely traveled across the targeted section of SR 46 near County Road 433 to get to habitat within central Florida's Wekiva River Basin. And they had learned bears were being hit by vehicles more often at this spot on SR 46 than at almost any other spot on the highway.

To ensure bears could easily access the underpass from the south, the FWC purchased a 40-acre (16-ha) tract of land in the bears' travel corridor - a private "inholding" within Rock Springs Run State Park.

The SR 46 underpass built by FDOT is a bear-friendly, dirt-floor box culvert, 47 feet- (14.3 m-) long by 24 feet- (7.3 m-) wide by 8 feet- (2.4 m-) high. Work crews elevated the two-lane road over the crossing to give skittish animals a clear view across to the other side. They also planted rows of pines in the open pasture on one side of the road to guide bears to the culvert entrance.

Bears did indeed use the SR 46 crossing. In fact, post-project research revealed that bears plus 12 other species, including bobcats, gray foxes, and whitetail deer, crossed through it.

Laurie MacDonald, field coordinator of Defenders of Wildlife and director of Defenders' Habitat for Bears Campaign, sees the SR 46 crossing as an important step in connecting bear habitat. "The Florida black bear needs a half million acres of connected habitats to survive," she says. "The SR 46 underpass helps meet that challenge."

"Underpasses like this one, together with land acquisition and habitat protection, are tools we can use to minimize the impacts of highways on wide-ranging mammals," adds Terry Gilbert, an FWC biologist and member of the SR 46 design team.

Photo: State Route 46 underpass State Route 46 was elevated over this bear underpass so crossing animals could clearly see from one side of the road to the other.

Gilbert and his colleagues have analyzed more than 20 years of collected black bear roadkill data. They've identified and prioritized 15 bearkill "hot spots" - problem areas within seven counties which represent at least 39 percent of Florida's bear roadkills. "Their research will help in the planning, project development, construction, and maintenance of existing and future highways in Florida," says FDOT ecologist Gary Evink.

For more information, contact Terry Gilbert, 850-488-6661 or

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Updated: 7/18/2012
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