Volunteers like retired veterinarian Ron Ringen, 69, are taking photographs of killed animals and using GPS devices to record the precise location for the study, The New York Times reported.
"I'm almost a fanatic with it," Ringen said. "You get hooked."
He's among hundreds of volunteers collecting and uploading roadkill data to the California Roadkill Observation System, a mapping Web site built by researchers at the University of California, Davis.
The aim is to better understand where and why cars strike animals.
"For some people the only contact they have with wild animals is when they run them over," Fraser M. Shilling, lead researcher on the project, said. "This is the first time people have been able to record roadkill online and I think it will change our understanding of what our road system is really doing to wildlife."
Researchers say they will use the data to build statistical models to predict roadkill hot spots and suggest where animal road crossings, culverts and warning signs would be most effective on current and future roadways, the Times said.