Roadkill risk map for the endangered Ryukyu long-furred rat Diplothrix legata along Prefectural Route 2 on northern Okinawa-jima Island, Japan

Abstract

A part of Prefectural Route 2 and 70 on northern Okinawa Island, Japan, crosses forested areas containing several endangered species. The prevention of roadkill of endangered species has become an important issue in island species conservation. We conducted a census of the Ryukyu long-furred rat (Diplothrix legata), a species endemic to the Nansei Islands, counting live individuals and roadkill nearly every day for 6 years between May 2011 and April 2017. A total of 122 records (75 live individuals and 47 roadkill) were obtained along the road in the census. Based on these records, we created a roadkill risk map for this species along Route 2, and compared the risk map to priority areas for the prevention of roadkill set along Route 2. We also evaluated the effectiveness of the priority area using roadkill rate per individuals. We found that only part of the high-risk area had been targeted, leaving some high-risk areas without protection. Road kill rate did not decrease at the priority area. Our study may contribute to improving actions for the prevention of roadkill by illustrating the actual risk distribution and evaluating effectiveness of current actions.