Reptile and Amphibian Responses to Directional Fencing
Wildlife & Ecosystems
Directional fencing is an important component of wildlife crossing designs. When successful, fencing can guide animals to a safe crossing location and significantly reduce road mortality. Most current research is focused on large mammals. Large mammals are readily surveyed using GPS collars and passive infrared (PIR) camera trapping protocols. However, reptiles and amphibians are not readily surveyed using either of these methods. Reptiles and amphibians generally also have differing movement and dispersal methods between taxa and when compared to large mammals in general. A recently published innovation in camera trapping, the Hobbs Active Light Trigger (HALT), has documented dramatically improved detection rates for small reptiles and amphibians. This innovation may dramatically improve research and knowledge of reptile and amphibian use of crossing structures. The cameras, coupled with fencing designs, could experimentally investigate behavioral responses to fencing materials (e.g. mesh vs opaque); fencing lengths between crossings (e.g. total travel distances, directionality, turn around distances, persistence, etc.); crossing structure designs (e.g. width, length, substrate). The ideal research project would experimentally investigate a few representative threatened or endangered species that are commonly impacted from road mortality. It is anticipated that species will respond differently to fencing and crossing structures. Knowledge of their behavioral responses are essential to determine appropriate crossing designs. Improper designs may affect species negatively despite the best intentions (e.g. desiccation, exhaustion, barrier effects, reduced overall road permeability). Knowledge of species responses will lead to better designs and appropriate evaluations of transportation mitigation solutions that could be built into funded transportation projects. As more data are collected, generalities may emerge to develop best management practices.
Effective crossing designs supported by science may lead to acceptable onsite mitigation that can be incorporated into transportation project designs.
California Department of Fish and Wildlife
June 4, 2019
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