Effects of roads on survival of San Clemente Island foxes

Roads generate a variety of influences on wildlife populations; however, little is known about the effects of roads on endemic wildlife on islands. Specifically, road‐kills of island foxes (Urocyon littoralis) on San Clemente Island (SCI), Channel Islands, California, USA are a concern for resource managers. To determine the effects of roads on island foxes, we radiocollared foxes using a 3‐tiered sampling design to represent the entire population in the study area, a sub‐population near roads, and a sub‐population away from roads on SCI. We examined annual survival rates using nest‐survival models, causes of mortalities, and movements for each sample. We found the population had high annual survival (0.90), although survival declined with use of road habitat, particularly for intermediate‐aged foxes. Foxes living near roads suffered lower annual survival (0.76), resulting from high frequencies of road‐kills (7 of 11 mortalities). Foxes living away from roads had the highest annual survival (0.97). Road‐kill was the most prominent cause of mortality detected on SCI, which we estimated as killing 3–8% of the population in the study area annually. Based on movements, we were unable to detect any responses by foxes that minimized their risks from roads. The probabilities of road‐kills increased with use of the road habitat, volume of traffic, and decreasing road sinuosity. We recommend that managers should attempt to reduce road‐kills by deterring or excluding foxes from entering roads, and attempting to modify behaviors of motorists to be vigilant for foxes.