Stopped Dead in Their Tracks: The Impact of Railways on Gopher Tortoise (Gopherus polyphemus) Movement and Behavior

Habitat fragmentation is one of the leading causes of biodiversity decline and most commonly results from urbanization and construction of transportation infrastructure. Roads are known to negatively impact species, but railways can often cause similar effects. Certain taxa, such as turtles and tortoises, are more vulnerable to railways than others due to limitations in mobility. We studied the impact of rails on the movement and behavior of Gopher Tortoises (Gopherus polyphemus), a threatened, highly terrestrial species likely in frequent contact with railways. First, we used radio-telemetry to determine the frequency of railway crossings and compared this to correlated random walk (CRW) simulations to assess if tortoises were crossing the rails less frequently than is expected by unconstrained movement. Second, we placed tortoises into the railway and measured behavior for one hour to assess crossing ability. Lastly, we tested whether trenches dug underneath the rails could allow safe passage for tortoises. We found that railways impacted the movement of Gopher Tortoises. Gopher Tortoises crossed the railway less often than what would be expected by unhindered movement for five of our ten tortoises tracked. During behavioral trials, 0 of 24 tortoises placed within the railways were capable of escaping from the rails. Using game cameras, we detected tortoises using trenches dug underneath the rails and between the ties 68 times over the course of a single summer. For minimal financial cost, the trenches facilitated tortoise movement across the railway, maintained full rail functionality, and created an escape route for individuals that were trapped between the rails, and thus should be implemented as a mitigation strategy. Given the thousands of km of railways around the world, we recommend future studies focus on the new field of rail ecology.