Effects of Road Mortality and Mitigation Measures on Amphibian Populations

Abstract

Road mortality is a widely recognized but rarely quantified threat to the viability of amphibian populations. The global extent of the problem is substantial and factors affecting the number of animals killed on highways include life-history traits and landscape features. Secondary effects include genetic isolation due to roads acting as barriers to migration. Long-term effects of roads on population dynamics are often severe and mitigation methods include volunteer rescues and under-road tunnels. Despite the development of methods that reduce road kill in specific locations, especially under-road tunnels and culverts, there is scant evidence that such measures will protect populations over the long term. There also seems little likelihood that funding will be forthcoming to ameliorate the problem at the scale necessary to prevent further population declines.

Roadside Abundance of Anurans within a Community Correlates with Reproductive Investment

“…Amphibians in general appear to be highly susceptible to traffic mortality (Fahrig and Rytwinski, 2009;Rytwinski and Fahrig, 2012;Beebee, 2013), and anurans have been identified as highly vulnerable to road effects (Fahrig and Rytwinski, 2009;Rytwinski and Fahrig, 2012;Smith, 2012;Beebee, 2013), which could select for road avoidance behavior. There is growing consensus that risktaking behavior and other aspects of animal "personality" have a genetic component (Stamps and Groothuis, 2010), which could allow selection for road avoidance.…”

“…However, if roads elicit behavioral avoidance in some species, ecopassages will not be enough to mitigate their impact. In such cases it may be necessary to create new breeding ponds that can be reached without crossing roads (Beebee, 2013), or even to seasonally close roads to traffic (Jackson et al, 2015). Considering the rapid extinction of many amphibian species worldwide (e.g., Houlahan et al, 2000;Stuart et al, 2004), identifying threats to vulnerable species and the best way to mitigate those threats will be critical for maintaining amphibian biodiversity into the future.…”

“…Amphibians in general appear to be highly susceptible to traffic mortality and anurans have been identified as highly vulnerable to road effects (Fahrig and Rytwinski, 2009;Rytwinski and Fahrig, 2012;Smith, 2012;Beebee, 2013). We predicted that populations of species that produce larger numbers of offspring would be better able to compensate for these negative effects and would be found in higher abundances near roads.…”

Current Knowledge on Wildlife Mortality in Railways

“…Thus, there is still an important difference between the abundance of amphibian and reptile mortality in roads and in railways. While there are plenty of data on mortality of these taxa on roads (Beebee 2013;Hels and Buchwald 2001;Carvalho and Mira 2011), records for railways are much rarer (van der Grift and Kuijsters 1998). Unfortunately, there are no studies that compare detectability and persistence rates of carcasses between road and railway surveys, so the difference in numbers remains an open question.…”

Citizen science reveals widespread negative effects of roads on amphibian distributions

“…Roads directly replace wetland and upland habitat, and they can lower the quality of adjacent habitat by creating edge effects (Marsh and Beckman, 2004) and causing run-off of deicing salts (Karraker et al, 2008). Because amphibians move slowly, individuals are also susceptible to direct mortality when moving across roads (Fahrig et al, 1995;Mazerolle, 2004;Beebee, 2013). For species with biphasic life cycles, roads can increase mortality risk during breeding migrations, ultimately increasing the probability of local extinction (Gibbs and Shriver, 2005).…”