From this story in the New York Times:
To Ron Ringen, a retired veterinarian, roadkill is a calling. Nearly every week for the last seven months, Mr. Ringen, 69, has driven the roads north of this college town near Sacramento, scanning the pavement for telltale bits of fur and feathers. Pulling over, Mr. Ringen gets out, snaps photographs and uses his GPS device to record the precise location where creatures met their end. He has logged more than 1,400 animals, from the miniature (one-ounce song sparrows) to the gargantuan (a 1,500-pound black Angus bull). "Most people don't realize how many animals die on the road every day -- they just don't see it," he said. _While Mr. Ringen's friends goad him with nicknames like "Doctor Roadkill," he is not alone in his peculiar pursuit. Hundreds of volunteers collect and upload roadkill data to the California Roadkill Observation System, a mapping Web site built by researchers at the University of California, Davis, to better understand where and why cars strike animals.