Movement of California Tiger Salamanders along barrier fencing and underpasses in Stanford, CA.

There is recent evidence that road mitigation systems with inadequate underpass spacing between uplands and breeding ponds may result in population declines in pond breeding amphibians. The common toad, Bufo bufo, in the Netherlands were shown to turn around or "give-up" after an average of 50m if they did not reach an underpass. We were interested if this behavior is exhibited pond breeding amphibians in California to inform underpass spacing for the California DOT (Caltrans). We were also interested if the opacity (solid vs. transparent) of barrier fencing affects animals' movement speed or give-up distances, and if 'turn-arounds' at fence ends are effective in altering the trajectory of movement.
We studied the movement of California tiger salamanders (CTS: (Ambystoma Californians) adjacent to three existing underpasses along Junipero Serra Blvd in Stanford, CA (Stanford University) in the winter breeding seasons of 2017 and 2018. The road bisects a historic CTS breeding pond (Lake Lagunita) and upland CTS habitat. Approximately 125m of exclusion fencing was installed on each side of the underpass entrance with 1.5mx 3m turn-arounds at the fence ends. On the same side of the road, one side of the fencing installed was semi-transparent and the other side was solid. HALT active trigger cameras were set along the fence lines every 25m to capture photos of animals moving along the fence line. Photos were then analyzed using pattern recognition software to identify individuals by their unique spot patterns. Location, time and direction of movement were recorded for each individual. In the second year, we also monitored movement through the underpasses with HALT cams installed in both sides of each underpass. We present preliminary results from this study that include average distances, speed, and direction changes of CTS along the different fences and through the underpass structures.
This study is part of a larger research program in collaboration with the Western Transportation Institute (WTI; Montana State University) for the California Department of Transportation (Caltrans) to inform best management practices for barrier and crossing systems for sensitive amphibians and reptiles in California.