Roadkill reimagined: a review of innovative scientific use and value of animals killed by vehicular traffic

Millions of animals are killed by vehicles on roads yearly, left mostly to rot, but these unfortunate mortalities may have a benefit to society that is not widely appreciated: they represent a valuable source of animals for study that does not require and could even replace the use of live wildlife. Here, we provide the first literature review to uncover validated uses for roadkill and, in doing so, encourage uptake of this valuable resource. We located 312 studies using roadkill whose aim included purposes other than enumerating or mitigating roadkill. We identified 26 broad-use and 91 specific-use categories of roadkill carcasses. Most common uses included assessing species presence or distribution, assessing parasite, disease or pathogen presence, assessing roadkill as an index of species abundance, describing species diet and lodging specimens in museums. The studies included at least 650 species; mammals dominated the studies, followed sequentially by reptiles, birds, amphibians and invertebrates. We discuss how we might better take advantage of this source of animals for study and highlight limitations and cautions in their use. Given the proven and diverse uses demonstrated in our review, we encourage the scientific community to now (re-)consider roadkill as an ethical alternative to live animal sampling.