Anuran carcass persistence on roads: causes and implications for conservation

Abstract

Roads are pervasive and ubiquitous landscape features that have substantial and predominantly negative effects on wildlife. Conducting road surveys to count animals that have been struck and killed by vehicles is a common method for estimating the impact of roads on wildlife, especially for species at risk and animals with low road avoidance (i.e., herpetofauna). For road surveys to provide accurate animal mortality data, information about carcass persistence in different environmental contexts and in relation to survey frequency is necessary, but few studies have implemented these data into evaluations of road effects. Using road survey data collected in Ontario, Canada, in 2015 and survival analysis, we quantified anuran carcass (n = 91) persistence and determined the effects of carcass characteristics (size, species, condition), road characteristics (lane position, traffic volume), and environmental characteristics (precipitation, temperature) on carcass persistence on the road. Contrary to previous findings, we found that anuran carcasses persisted on roads longer than expected (5.5 ± 4.4 days, mean ± SD), with some carcasses persisting for up to 30 days. Temperature and precipitation had the greatest influence on the duration of anuran carcass persistence. Carcass condition, (i.e., intact versus partially intact carcasses), species, location on the road, and traffic volume had little to no effect on persistence. We recommend incorporating carcass persistence into road ecology studies, especially in the context of evaluating population-level impacts of road mortality. Failure to do so could alter estimates of population viability and misinform management decisions.