Effect of traffic volume on American black bears in central Florida, USA

Abstract

Of American black bears (Ursus americanus) killed by vehicles in Florida from 1976 to 2003, 45% were from the population in central Florida centered in Ocala National Forest (ONF). This area contains 8 of the state's 15 most severe roadkill areas. More bears were killed along State Road 40 (SR-40), which bisects this population, than along any other road in the state. Interest in widening this road provided an opportunity to document bear movements and the frequency with which they crossed SR-40 when average annual daily traffic (AADT) volume was at each of two levels: 5,100 vehicles per day (vpd) in ONF and 15,700 vpd in the adjacent community of Lynne. We analyzed the locations of 86 radiocollared bears (33 F∶40 M in ONF and 13 F in Lynne) and monitored them 1–3 times/week from May 1999 through May 2003. Forty-eight bears crossed SR-40 a minimum of 388 times. ONF female bears were 2.9 times more likely than Lynne females to cross SR-40, but this rate was only marginally significant. ONF male bears were 4.3 times more likely to cross SR-40 than ONF females and 12.3 times more likely to cross than were Lynne females. We documented the mortality of 7 radiocollared bears by vehicles, 4 males in ONF and 3 females in Lynne. There were no deaths of ONF females due to vehicular collisions, but female bears in Lynne died from vehicle collisions at near the rate of ONF male bears. We recommend that a minimum of 6 crossing structures be incorporated along this highway to reduce the effect of highway expansion on the Ocala population of Florida black bears.