Culverts and connectivity: Measuring the success of culverts in mitigating herpetological road mortality

Schmidt, Kelly
Tom Wessels, MA
Department of Environmental Studies
2008
Road mortality is a major threat to the sustainability of wildlife populations, especially for amphibian and reptiles. The key to providing connectivity between road-fragmented habitats lies in answering how to get wildlife across or under roadways. It is critical to understand how culverts function as passageways, particularly for groups such as freshwater turtles and other herpetological species that are at risk to road mortality effects. Relative abundance estimates of painted (Chrysemys picta) and snapping turtles (Chelydra serpentina) were made via mark and recapture work from June through October 2007. Road kill surveys of reptiles and amphibians took place during the turtle nesting season from May through July. Infrared cameras were used to provide evidence of culvert use by turtles and other small animal species. 23 reptiles and 53 amphibians were found dead on the road (DOR). Significantly more turtles were observed DOR than expected at large culvert sites (observed= 13, expected= 5.7, X²= 9.35, p=.05) and there was a significant difference in the number of turtles found DOR among all sites (large and small culverts and sites without passable culverts) (X²= 13.45, p=.05) suggesting that culverts may not have an effect on passage or that animals are not using them for some reason. Presence of animals documented with infrared cameras suggests that culverts work as functional passageways for some mammal species but it is still unknown if they support herpetological passage. The camera in the second smallest culvert, approximately 2 ft. in diameter, recorded two small mammals, wood ducks and mallards. This study has found that culverts appear to be successful as passageways for mammals but the relationship between culvert passage, traffic volumes, culverts as prey traps and why herpetofauna are using or not using culverts is unclear.

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