Positive effects of roads on small mammals: a test of the predation release hypothesis

Abstract

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.

Roads do not increase carrion use by a vertebrate scavenging community

“…The risk of predation in open areas along roads may discourage scavenging by less dominant species and favor carcass consumption by larger and more dominant carnivores. Conversely, some animals may face reduced predation risk near roads due to predator release 38 .…”

Nowhere to hide: Effects of linear features on predator–prey dynamics in a large mammal system

“…Such features include roads, railways, power lines, pipelines and seismic lines. LFs have been implicated in altering predator-prey dynamics with the direction of outcomes being contextspecific (DeGregorio, Weatherhead, & Sperry, 2014;Downing, Rytwinski, & Fahrig, 2015;Fahrig & Rytwinski, 2009). Perhaps, the most well-known example is their hypothesized influence on interactions between woodland caribou and wolves (Ehlers, Johnson, & Seip, 2014;James & Stuart-Smith, 2000;Latham, Latham, Boyce, & Boutin, 2011;Whittington et al, 2011).…”

Positive roadside edge effects on artificial nest survival in a lowland Atlantic Forest

“…However, the predation release hypothesis also predicts that prey are more abundant near the roads (Downing et al, ; Fahrig & Rytwinski, ; Rytwinski & Fahrig, ). A previous study conducted at the same edge‐interior gradient at Sooretama Biological Reserve found no evidence of edge effects on abundance of bird species (Silva, ).…”

“…Our results confirmed a key prediction of predation release hypothesis that suggests a decrease in nest predation attempts near the roads (DeGregorio et al, 2014;Dziadzio et al, 2016;Fahrig & Rytwinski, 2009). Therefore, road mortality or mortality risk, and/ or road disturbance (e.g., noise) may be negatively affecting predator abundance near the road (Downing et al, 2015;Fahrig & Rytwinski, 2009;Rytwinski & Fahrig, 2013). Some studies in open habitat types have shown that the densities of many species decrease next to roads (Benítez-López et al, 2010;Clark & Karr, 1979;Fahrig & Rytwinski, 2009;Illner, 1992), which can be a response to noise (Pescador & Peris, 2007).…”

“…The predation release hypothesis states that prey are favoured near roads because roads negatively affect the predators' abundance and/or foraging activity due to road mortality and traffic disturbance (Downing, Rytwinski, & Fahrig, 2015;Fahrig & Rytwinski, 2009;Rytwinski & Fahrig, 2013). Although it is well known the negative impacts of roads on bird predators (Trombulak & Frissel, 2000;Zabala et al, 2006), studies failed to support the prediction of lower adult and nest predation near roads (DeGregorio, Weatherhead, & Sperry, 2014;Dziadzio, Smith, Chandler, & Castleberry, 2016), probably because some predators can be favoured by roads (DeGregorio et al, 2014).…”