Evaluating Exclusion Barriers for Treefrogs in Agricultural Landscapes

Agricultural co-management aims to promote environmental sustainability while maintaining food-safety standards. Amphibians, especially treefrogs, are known to enter fields of fresh produce intended for human consumption, which raises concerns for food safety and quality. We evaluated the effects of modifications to reduce the scalability of exclusion barriers on the fence-crossing behavior of Pacific treefrogs (Hyliola regilla) from lettuce fields in the Salinas Valley of California during January to May 2019. From small-scale field experiments, we found that fences modified with a horizontal lip at the top prevented all treefrogs from successfully crossing over. Fences incorporating sandpaper were also effective at deterring treefrog crossings compared to fences made of fiberglass square mesh (window screen) and polypropylene fabric (silt fence). The fence design that inhibited the most treefrog crossings—aluminum flashing with a horizontal lip—was a modification to commercially available material that is feasible to install at large scales, is durable over long periods of time, and can help to exclude additional nuisance wildlife, such as small mammals and lizards. Our findings provide quantitative evidence on the efficacy of an exclusion barrier constructed with off-the-shelf material that can be easily modified to improve the co-management of amphibians and agriculture.