Roadkill as sentinels for parasite detection in a wild squirrel population

Jonah Giermann, a student at College of St. Scholastica, worked in the lab of Dr. Sonia Altizer

Abstract Disease surveillance of wild populations is difficult, as capture and release techniques can be time-iRoadkill is an excellent display of human-wildlife conflict. Carcasses can inform ecologists about population trends, species distribution, and behavior. Carcasses can be inspected for parasitic infection, but data obtained is subject to bias from a variety of factors. We chose rock squirrels as our study system because their behavior makes them host to a variety of parasitic species. I asked questions regarding the factors influencing measures of infection (richness, abundance, diversity) in roadkill, and how those measures compare in live-trapped samples.Samples were collected in Zion National Park from 2020-2022. Roadkill intestines were dissected, and whole worms were counted. Fecal samples were obtained from live trapped squirrels. Fecal flotation using sodium solution was conducted and any resulting eggs were counted. We found that squirrels collected in autumn host more parasites than the other two seasons. Male squirrels are collected as roadkill more frequently than females. Males display exploratory and dispersal behavior, likely causing more vehicle collisions. Parasite richness was higher in the roadkill population than it was in the livetrap population.  We used the Shannon diversity index to get a parasite diversity value for each sample type. The diversity index factors in both richness and abundance to analyze diversity. Roadkill had higher diversity, but livetrap had a similar value. Microparasites were found in live-trapped samples but could not be seen using our roadkill sampling method. Based on these results, roadkill seems to be an effective indicator of parasitic infection in wild populations, provided biases are accounted for.