Tell me where you go, and I'll tell you where you die: landscape connectivity as a tool to predict amphibian roadkill risk

Abstract

Human overpopulation, development, and consequent activities such as land conversion and linear infrastructure expansion, are currently some of the main threats to biodiversity. Amphibians are especially affected because they depend on both aquatic and terrestrial habitats to complete their life cycles, which can be negatively impacted by roads, due to reduced landscape connectivity. Understanding animal movement across the landscape may improve the prioritisation of sites to implementing mitigation measures. We assessed landscape connectivity using circuit theory, for two amphibian species (the Iberian spadefoot toad and the Iberian ribbed newt) on a Mediterranean landscape in Southern Portugal. We addressed the following question: Can landscape connectivity predict amphibian roadkill risk? Our connectivity models assigned higher current movement corridors to heterogeneous habitats composed of sparse forests combined with low-management agricultural areas and good networks of higher-density water bodies. We found a positive correlation between high-connectivity road segments and roadkill for both species, proving that landscape connectivity can be a valuable tool to predict locations with higher roadkill probability.

We acknowledge that maintaining a heterogeneous landscape, with a higher density of short-distance water bodies that connect highly suitable habitats is important for amphibians. The identification of corridors with increased amphibian movement probability provides useful insights for road agencies to implement amphibian-oriented roadkill mitigation measures.