Some authors have hypothesized that observed increases in small mammal populations with increasing road density (after controlling for habitat effects) are due to predation release. Predation could be reduced in areas with high road density because of negative effects of roads on predator numbers and/or hunting activity. However, there are no studies testing the relationship between road density and predation rate on small mammals. Based on the predation release hypothesis, we predicted that white-footed mouse (Peromyscus leucopus) individuals placed in sites with higher surrounding paved road density and/or closer to a paved road would experience fewer predation attempts than P. leucopus individuals placed in sites with lower surrounding paved road density and/or farther from a paved road. We recorded predation attempts on P. leucopus placed in wire mesh enclosures, using motion-triggered cameras, at 28 sites ranging widely in surrounding road density. There was no overall decline in predation attempts with increasing paved road density, or increase in predation attempts with increasing distance to the nearest paved roads. However, we cannot rule out the predation release hypothesis for larger mammalian predators, as they were not well sampled in our study. For predatory birds, we found weak evidence in support of the predation release hypothesis, but this conclusion is very tentative, as we only recorded three predation attempts by birds. We suggest that the predation release hypothesis for positive road effects on small mammals merits further investigation, using methods tailored to the particular predators most likely to impact small mammal populations.

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Keywords Landscape fragmentation, Predator–prey, Raptor, Road mortality, Traffic disturbance
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Journal Ecological Research
Downing, R.J. (Richard J.), Rytwinski, T. (Trina), & Fahrig, L. (2015). Positive effects of roads on small mammals: a test of the predation release hypothesis. Ecological Research, 30(4), 651–662. doi:10.1007/s11284-015-1264-4