Road Ecology: Measuring the Wildlife Death Toll along California Roads

September 2010

Roadkill is sometimes the subject of jokes. But it is no laughing matter to UC Davis researcher Fraser Shilling. Shilling is co-director of the UC Davis Road Ecology Center, which has just completed the first year of the largest-ever citizen-science survey of roadkill. The California Roadkill Observation System (CROS) is a website mapping database that allows anyone to quickly record roadkill observations. It presents grim statistics.

“Thousands of animals are killed on California’s roads every day, including endangered species,” says Shilling.

In August, the CROS reported that more than 250 observers recorded over 6,000 observations of roadkill around the state in the last year. As of mid-September, those numbers had climbed to 340 observers reporting 6,968 observations. According to the August report, 196 species are identified. The most common roadkill victims are raccoons.

The most active roadkill reporters are UC Davis alumni Ron Ringen, a retired veterinarian, and his wife, Sara, a retired family nurse practitioner. They have logged more than 1,000 records. A few times each month, they spend about three hours driving 100-mile-loops. Sara Ringen records GPS locations of each find while her husband identifies the animal, photographs it and removes the carcass from the road. They recently set a one-day personal record: 127 animals, including birds from 17 species.

Shilling has launched a similar effort for the state of Maine with Maine Audubon, and plans to expand the project to include focused studies on particular types of roads, roadkill website development in other states, and analyses of the causes of wildlife-vehicle collisions.

The Road Ecology Center aims to improve transportation systems by better understanding the impact of roads on natural ecosystems and human communities. Information about where wildlife vehicle collisions occur, what animals are involved, on what kinds of roads collisions are frequent, and other data can help inform policy, management, and financial investment in reducing roadkill. For example, data from the CROS can help researchers pinpoint roadkill hot spots, thus identifying locations along the road where animal crossing signs can alert drivers, or where structures such as culverts or wildlife overpasses may be considered.

The CROS and associated research is a joint effort of the Road Ecology Center and the Information Center for the Environment. The Information Center for the Environment hosts databases of natural-resource and environmental information, and helps the public use that data to make better decisions about resource management and policy. Both the Road Ecology Center and the Information Center for the Environment are affiliated research centers with the UC Davis Institute of Transportation Studies.