Identifying Hot Moments in Road‐Mortality Risk for Freshwater Turtles

Abstract

ABSTRACT Risk assessments can be used to identify threats, which vary both in space and time, to declining species. Just as hot spots describe locations where threat processes operate at a higher rate than in surrounding areas, hot moments refer to periods when threat rates are highest. However, the identification of hot moments can be challenging because the temporal complexity of some threat processes makes their effects on population viability difficult to predict. Declining throughout much of their range, Blanding's turtle (Emydoidea blandingii) populations are potentially most vulnerable to road mortality where road densities and traffic volumes are high. The temporal variations in road‐mortality risk faced by these and other semiaquatic turtles at the population level are a consequence of several factors, including sex‐specific movement characteristics and seasonal changes in traffic volume. We examined these risk factors for Blanding's turtle populations in Maine, USA, by integrating temporally explicit roadkill probabilities with demographic parameters informed by local and range‐wide studies. Specifically, we used population simulations to estimate the relative risk for 14 2‐week periods during the turtles’ active season. Our analysis clearly identified early summer as a period of elevated risk, with June through mid‐July signaling a road‐mortality hot moment for Blanding's turtles (for both M and F). These findings provide guidance for the implementation of temporally explicit conservation measures such as cautionary road signage, traffic management, and public outreach that, if timed strategically, could help to mitigate population impacts from road mortality.