Abstract
An extensive and expanding infrastructural network destroys and fragments natural habitat and has detrimental effect on abundance and population viability of many amphibian species. Roads function as barriers in the landscape. They separate local populations from each other or prevent access to necessary resources. Therefore, road density and traffic intensity in a region may have severe impact on regional as well as local connectivity. Amphibians may be able to detect and avoid unsuitable habitat. Individuals’ ability to avoid roads can reduce road mortality but at the same time road avoidance behaviour, can increase the barrier effect of the road and reduce connectivity. We use an individual based model to explore how changes in road mortality and road avoidance behaviour affect local and regional connectivity in a population of Moor frogs (Rana arvalis). The results indicate that road mortality has a strong negative effect on regional connectivity, but only a small effect on local connectivity. Regional connectivity is positively affected by road avoidance and the effect becomes more pronounced as road mortality decreases. Road avoidance also has a positive effect on local connectivity. When road avoidance is total and the road functions as a 100% barrier regional connectivity is close to zero, while local connectivity exhibit very elevated values. The results suggest that roads may affect not only regional or metapopulation dynamics but also have a direct effect on local population dynamics.
Highlights
All over the world, amphibian populations are declining and many amphibian species are listed in the IUCN as threatened or vulnerable (IUCN 2012)
As hypothesized road mortality has a negative effect on between-cluster connectivity
An explanation could be that roads functions as traps if road avoidance is low
Summary
Amphibian populations are declining and many amphibian species are listed in the IUCN as threatened or vulnerable (IUCN 2012). The negative effect of urbanisation is due to changes in land use and destruction of habitat. Road density in an area as well as traffic density on individual roads have been shown to have a negative effect on amphibian populations (Eigenbrod et al 2009; Fahrig and Rytwinski 2009; Hels and Buchwald 2001; Reh and Seitz 1990; Vos and Chardon 1998). Veysey et al (2011) even found road density to have a stronger effect on population size than habitat availability, while Carr and Fahrig (2001) found more vagile species to be more vulnerable to road mortality Road density in an area as well as traffic density on individual roads have been shown to have a negative effect on amphibian populations (Eigenbrod et al 2009; Fahrig and Rytwinski 2009; Hels and Buchwald 2001; Reh and Seitz 1990; Vos and Chardon 1998). Veysey et al (2011) even found road density to have a stronger effect on population size than habitat availability, while Carr and Fahrig (2001) found more vagile species to be more vulnerable to road mortality
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