Life in the fast lane: roadkill risk along an urban–rural gradient

Sarah E Perkins,Amy L W Schwartz,Eleri Kent

doi:10.1093/jue/juaa039

Abstract

Abstract Wildlife-vehicle collisions are a major cause of mortality in animal populations and can cause significant population-level effects. Urban areas are typically associated with higher road densities and unique wildlife communities in comparison to rural areas, and therefore have the potential to be associated with high numbers of collisions, and roadkill risk. Here, we use a citizen science database of wildlife roadkill and species distribution models to assess how roadkill risk (probability of roadkill observation per km2) varied along an urban–rural gradient for British wildlife. Roadkill risk was positively associated with road density, until around 5000 m/km2, a value representing villages or the outskirts of towns and cities. Beyond 5000 m/km2, risk remained high for some species (hedgehog, fox, pigeons and gulls) but reduced for other species (badger, rabbit, pheasant). Roadkill risk was a function of live species distribution for badger, hedgehog and rabbit, with significant overlap between spatial patterns of roadkill risk and the species’ live distribution. This was not the case for fox, pheasant, pigeons and gulls. Fox roadkill risk was underrepresented in rural areas, possibly due to low road density, while pheasant risk was overrepresented. For pigeons and gulls—well-known urban exploiters—roadkill risk was overrepresented in urban areas given their live distributions, possibly due to risks associated with foraging, particularly roadkill scavenging by gulls. Our results highlight the dangers of the UK’s dense road networks to wildlife, even to species considered adapted to urban environments and human disturbance.

Highlights

IntroductionA fifth of the Earth’s terrestrial surface is located within 1 km of a road (Ibisch et al 2016), and their effects can permeate far into the surrounding habitat (Forman 2000; Jaeger et al 2005; Ibisch et al 2016)
Roads make an important contribution to the global human footprint
Across an urban–rural gradient, road density was the most important variable for predicting roadkill risk for all focal species (Table 1), with risk increasing with increasing density of roads, rising sharply for all species up to a peak road density of c. 5000 m/km2 (Fig. 1A and B)

Summary

Introduction

A fifth of the Earth’s terrestrial surface is located within 1 km of a road (Ibisch et al 2016), and their effects can permeate far into the surrounding habitat (Forman 2000; Jaeger et al 2005; Ibisch et al 2016). As a universal characteristic of human development, roads are found across many habitat types, including along the entire urban–rural gradient (Forman 2000; Lawton 2018). The population-level effects of this anthropogenic mortality are significant for some species and can lead to major population declines (Coffin 2007; Fahrig and Rytwinski 2009; Lawton 2018). Roads have been described as a significant contributor to current widespread biodiversity declines (Yue et al 2019). Urban infrastructure has profound effects on habitat quality, with knock-on effects for population sizes, community structures

Methods

Results

Conclusion