Evaluation of deer-exclusion grates in urban areas
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abstract
The extensive and growing road network in the United States has substantial ecological, economic, and social impacts. Under- and overpasses in combination with fencing can reduce ecological impacts of the expanding road network. In urban areas, however, wildlife can trap themselves inside fenced roadways by entering via access roads. Wildlife-exclusion guards can ameliorate this problem but must be safe for pedestrians and cyclists. For the endangered Florida Key deer (Odocoileus virgin/anus clavium), nearly 50% of mortality is attributed to deer-vehicle collisions. An underpass, fencing, and exclusion-grate system was chosen by the Florida Department of Transportation (FDOT) to address this problem. Traditional exclusion guards were deemed unsafe for pedestrians and cyclists, so we evaluated 3 types of bridge grating for deer-exclusion efficiency. All grates were 6.1 m x 6.1 m; only the openings differed: 1) 10.1 x 12.7-cm rectangular opening, diagonal cross member, 2) 7.6 x 10.1-cm rectangular opening, no diagonal cross member, 3) 10.1 x 7.6-cm rectangular opening, no diagonal cross member. Grate 1 was 99.5% efficient for Key deer exclusion, while grates 2 and 3 were 75% efficient. Grate 1 also may be the safest for pedestrians and cyclists since it has the smallest opening size. It should be an effective tool for reducing economic and social costs associated with deer-vehicle collisions on urban highways.
