EFFECTIVE CULVERT PLACEMENT AND DESIGN TO FACILITATE PASSAGE OF
AMPHIBIANS ACROSS ROADS
Journal of Herpetology 44(4): 618-626
David A. Patrick, Christopher M. Schalk, James P. Gibbs & Hara W. Woltz
Abstract: Efficient deployment of culverts to mitigate mortality of amphibians on roadways requires identification of locations within road networks where animals cross (hotspots), points within identified hotspots for culvert placement, and attributes of culverts that make them behaviorally palatable to migrating individuals. In this study, we assessed road crossing frequency of Spotted Salamanders,
Ambystoma maculatum, and American Toads,
Anaxyrus americanus, along a 700-m transect within a known crossing hotspot, and related these distributions to habitat variables within the hotspot including the presence of existing culverts. We also placed experimental arrays of culverts of varying attributes in the path of migrating Spotted Salamanders to examine culvert preference by salamanders under typical movement environments and appropriate animal behavioral states. Our studies of patterns of road occurrence demonstrated that both species avoided crossing where there was a wetl!
and within 15 m of the downslope of the road and that neither species showed a strong preference for crossing near existing culverts. When considering the choice for experimental culverts by Spotted Salamanders, we found no preference for culverts of varying aperture size, length, or substrate. Our results indicate that patterns of occurrences of the two species of amphibian within a crossing hotspot may be linked to the physical attributes at the site. For Spotted Salamanders in particular, predicting where they will cross within a hotspot may not be easy. Spotted Salamanders showed little preference for culverts of different design, indicating that a variety of culvert designs can suffice for mitigation if placed in appropriate locations.
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