Road Ecology Center

We examined spatial patterns of carnivore casualties by counting the number of animals killed on 574 km of national roads and highways in southern Portugal. We surveyed six national roads twice a month from July 2003 to December 2006. Highway casualty data were collected by Brisa Auto-Estradas de Portugal, S. A., a private concession. A total of 801 carnivores representing eight carnivore species were killed. We found an average of 47 vehicle-killed individuals/100km/year; foxes were most numerous with the 20 individuals killed/100km/year. The distribution of carnivore vehicle-kills was clustered except fox. We calculate the mean road kill rate on different classes of variables that may influence road mortality and compare among them to identify the level of risk posed by each class of variable. Casualties were more likely to occur near to suitable habitats preferred by carnivores, in high traffic volume areas, and close to streams. Livestock exclusion fences, the type of road, and the number of passages did not influence mortality. To improve the cost-effectiveness of mitigation measures for new and existing roads, the priority should be given to the road segments crossed by streams in a cork oak woodlands matrix. Short sections of buried fences near culvert openings (100m on each side) should reduce the number of casualties considerably. Habitats connectivity is a serious issue where high volume traffic discourages carnivores from crossing roads at-grade. Connectivity is enabled by appropriately-designed passages.