Bear Underpasses in Florida

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

To ensure that bears could easily access the underpass from the south, FWC purchased a 16-hectare (40-acre) tract of land in the bears' travel corridor.

The SR 46 underpass built by FDOT is a bear-friendly, dirt-floor box culvert, 14.3 meters (47 feet) long by 7.3 meters (24 feet) wide by 2.4 meters (8 feet) 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 habitats. "The Florida black bear needs a half million acres of connected habitats to survive," she said. "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," said Terry Gilbert, an FWC biologist and member of the SR 46 design team.

Gilbert and his colleagues have analyzed more than 20 years of data about black bears killed by motor vehicles. They identified and prioritized 15 "bearkill" problem areas within seven counties, in which at least 39 percent of Florida's bear roadkills occurred.

"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 at (850) 488-6661 or gilberd@gfc.state.fl.us.

Biologists and engineers from the Florida Department of Transportation and the Florida Fish and Wildlife Conservation Commission knew that black bears were using underpasses designed for endangered Florida panthers along Alligator Alley (I-75). So, when they discovered that black bears were being hit by vehicles more often at one spot on state Route 46 in Lake County than at any other place along the highway, they designed and built the state's first underpass for black bears at that spot. Photo Credit: William J. Weber

The Northwest Forest Plan calls the Snoqualmie Pass/Interstate 90 corridor east of Seattle "a critical connective link in the north-south movement of organisms in the Cascade Range." The corridor, which passes through old-growth forests, is a critical link because it separates the unique plant and animal species that live in the forests.

Early in 1998, the Washington State Department of Transportation (WSDOT) and the U.S. Forest Service (USFS) launched a cooperative research effort to study the effects of I-90 on wildlife movement. The researchers chose a 48-kilometer (30-mile) study area along I-90 from Snoqualmie Pass (and its popular ski resort) east to the town of Cle Elum on the edge of the Wenatchee National Forest. In many places, I-90 is eight lanes wide. Traffic averages 24,400 vehicles a day and is expected to grow to 41,400 vehicles a day by 2018.

Along the study section of I-90, dramatic changes in elevation and precipitation - snow depth can reach 10 meters at the pass but rarely exceeds 1 meter at Cle Elum - have created a variety of vegetation zones and associated wildlife communities. Wide-ranging, large carnivores, such as lynx and wolverines, have been reported, as well as little-known, old-forest species, such as the red-backed vole and the papillose tail-dropper.

"Many of our old-forest species hardly move at all," says USFS biologist Peter Singleton. "In fact, some spend their whole life on one log."

To learn about the wildlife in the study area, the researchers used a multiscale approach. They looked not only at where animals cross the highway, but how they get there in the first place. They analyzed habitats to determine where animals are likely to live and raise their young and which other habitats they may travel through. They looked at wildlife distribution both along and near the highway.

"It's like buying a house," says Singleton. "You look at everything - the city, the neighborhood, the street, even the color of the carpet."

Fish passage structures help salmon and trout negotiate barriers on their journey to upstream spawning habitats. Photo Credit: Washington Department of Fish and Wildlife

The research team used Geographical Information System (GIS) technology to evaluate habitat connectivity and to analyze the distribution of roadkill of deer and elk. The team used snow-tracking to document highway crossings and animal distribution along the highway. They used off-road, automatic cameras to identify wildlife found near the highway; and they monitored bridges and culverts to find out which species use these structures to cross the highway.
The team discovered that:

• Small mammals - but not medium and large carnivores - use I-90 drainage culverts.
• Three locations in the corridor - Easton Hill and the north and south ends of Keechelus Lake - are important habitat connectivity areas.
• No substantial differences were detected between species found more than a mile from I-90 and those found within a mile of the highway.

Both the research results and methodology are valuable to transportation planners.
"This work has major implications for how we adapt existing crossing structures and how we build new ones," says Marion Carey, a biologist at WSDOT. "It will be a vital resource for us as we try to make highways safer for animals and humans."

For more information, contact Peter Singleton at (509) 662-4315 extension 226 or phsingle/r6pnw_wenatchee@fs.fed.us.