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Florida was one of the first states to recognize and react to the detrimental impact that roads have on wildlife. Florida’s human population has increased rapidly, from 9.7 million in 1980, to 12.9 million in 1990 to almost 16 million in 2000.³ Unfortunately, the human population grows at the expense of wildlife populations. This human increase has led to the development and expansion of roads, greater traffic density, faster highways, and increased habitat fragmentation. According to the Florida Department of Transportation (FDOT), for the past 50 years, the state has built an average of 4.5 miles of high-speed paved road per day.

Increased traffic and habitat fragmentation has pushed the endangered Florida panther — one of the rarest mammals in the world — ever closer to extinction. With approximately 80 cats in existence, each individual killed on Florida’s highways is a devastating loss. Between 1978 and 1994, 20 panther deaths (12 males and 8 females) and six injuries were documented from collisions with cars and trucks. Spring 2001 was especially deadly. Seven cats were killed on Florida highways in three months — as many as in all of 2000.⁴

When Alligator Alley, which crosses South Florida, was converted to I-75, 24 underpasses were installed to aid the crossing of panthers and other wildlife. Roadkill and radio telemetry data were assessed to find the best locations for the new underpasses. In addition to the underpasses, an 11-foot-high chain link fence topped with three strands of outrigger barbed wire was added to prevent panthers and other species from crossing the busy highway. Although primarily constructed for the panther, the crossing structures have benefited a wide range of species such as the bobcat, deer, great blue heron, wild turkey, and alligators.

The Florida black bear is another of the state’s imperiled species that has suffered great losses on roads and highways. More than 800 bears were documented to have been killed by vehicles between 1976 and 2002. State wildlife officials said increasing human encroachment on bear habitat resulted in at least 120 black bears killed by motor vehicles in 2002 alone, up from 104 in 2001.

FDOT and the Florida Fish and Wildlife Conservation Commission teamed up to build the state’s first underpass for black bear in 1994. The underpass on State Road 46 is a dirtfloor box culvert, 47 feet long by 24 feet wide by 8 feet high. The two-lane road was elevated above the crossing to give skittish animals a clear view across to the other side. The state also planted rows of pines in the open pasture on one side of the road to guide bears to the culvert entrance. To ensure that bears could easily access the underpass from the south, the FWC purchased a 40-acre tract of land in the bears’ travel corridor — a private “inholding” within Rock Springs Run State Park.

Post-project research revealed that bears and at least 12 other species, including bobcats, gray foxes, and whitetail deer had used the culvert. “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,” says Terry Gilbert, an FWC biologist and member of the SR 46 crossing design team.

Endnotes

3. US Census, http://quickfacts.census.gov/qfd/states/12000.html

4. Defenders of Wildlife, Habitat & Highways Campaign http://www.defenders.org/habitat/highways