It is common practice to install ‘turnarounds’ at fence ends and where barriers are unable to span across private road entries and easements. For this, road barriers end in a “U” shape and are designed to redirect animals back in the opposite direction at fence ends and keep them off the roadway. Although they are recommended in many countries and in guidance documents, there are no systematic studies to our knowledge that have addressed the relative effectiveness of turnarounds. We conducted studies at the Rancho Jamul Ecological Reserve in Jamul, California to test the effectiveness of turnarounds in changing the trajectory of movement for herpetofauna and small mammals. We installed three 28 m segments of barrier fencing within coastal sage scrub habitat adjacent to a dirt road. At the ends of each segment, we installed turn-arounds approximately 1.5 m long and 1 m wide. At the opening of each turnaround, we installed a HALT® active infrared trigger and camera system that allowed us to document animals going into and out of the turnarounds, as well as determine their trajectory upon leaving the turnaround. The cameras were placed 4.25 m from the end of the turnaround (2.25 m from trigger) with a frame of view that allowed us to follow the movement of animals for approximately 1 m in any direction and were set to record video for 25 seconds upon an animal activating the trigger. From March to September, 2019, we documented 264 lizard, 96 snake, 59 toad, one frog, and 370 small mammal turnaround encounters and exits. We documented that over 90% of herpetofauna (lizards, snakes and toads), as well as 69% of small mammals, changed course after leaving the turnaround. Of these, 67% of herpetofauna and 43% of small mammals moved back along the original fence line. Since we only documented animal movement for up to 1 m after leaving the turnaround. It is entirely possible that animals changed course again after they left the field of view of the video camera. However, other field studies where we have tracked amphibians over longer distances show a substantial proportion of individuals continuing to move back along the fence for 20-125m. Further studies are needed to test different designs and track individuals over longer distances and time periods. The results of these studies will help to inform transportation agencies on these important components of road barrier and crossing systems.
Terrestrial wildlife (vertebrate and/or invertebrate) and ecosystem interactions