Document: WIL-3-612-210
Highway impacts on animal populations and a way to reduce mortality and fragmentation.
BOARMAN, W.I.* 1,2 and M.SAZAKI 1,2
U. S. Geological Survey 1
University of California, Riverside., Riverside, CA 92521 USA 2
Abstract:
Roads and highways are a cause of mortality for many animals and may affect population viability by fragmenting populations. We investigated the effect highway traffic has on vertebrate populations in the Mojave Desert in California in two ways. We counted the number of vertebrate carcasses along 28.8 km of unfenced high-ways. We sampled for signs of desert tortoises (Gopherus agassizii) a threatened species, at different distances from the highway edge. We evaluated the effectiveness of a specially-designed barrier fence at reducing mortality along a 24-km long section of highway. We investigated how tortoises used habitat near the highway edge to determine if they increased their use of habitat near the highway following construction of the fence. Finally, using state-of-the-art technology, we monitored tortoise use of metal culverts to cross beneath the highway. We found the remains of 1078 vertebrates (8 species), including 37 desert tortoises, along two unfenced, paved highways. This level of mortality has probably resulted in a significant reduction in the density of one species, the desert tortoise, within 0.8 km or more of the highway. We found 93% fewer vertebrate carcasses and 88% fewer tortoise remains along 24 km of fenced highway compared with 24 km of unfenced highway. There was little significant change in the distribution of tortoises during the eight years following fence construction. Finally, tortoises occasionally used culverts to cross beneath the highway. Barrier fences are effective at reducing highway mortality in Mojave Desert vertebrates and culverts may help to reduce the fragmenting effect of fenced highways.
Keywords: n/a
This abstract is being presented at: 1:30 PM in session:
Oral Session #51: Disturbance Ecology: Harvesting, Grazing and Roads.