Effects of Roads on Predation

Forest roads create corridors by which predators, especially people, can enter the forest environment and affect wildlife populations.

There is strong evidence that human predation, either legally in game management programs or illegally, is greatly facilitated by roads and can significantly affect populations of animals. High road densities are associated with a variety of negative human effects on several wildlife species (Brocke and others 1988). People directly affect snakes by collecting, harassing, and killing them (Wisdom and others 2000). Increases in illegal hunting pressure, facilitated by roads, also negatively affect populations. Moose, wolves, caribou, pronghorn antelop, mountain goat, and bighorn sheep are particularly vulnerable to this kind of predation (Lyon and Marzluff 1985, Wisdom and others 2000).

Roads may increase nest depredation of song-birds by predators attracted to edges. Evidence for edge effects, however, is highly variable (Paton 1994). Although evidence has been found for local edge effects in cowbird parasitism and nest depredation, their effects on bird populations are not documented. Geographic location and large-scale patterns in the amount of forest and nonforest habitats may be more important in determining the reproductive success of forest songbirds (Donovan and others 1997, Robinson and others 1995).

Forest carnivores apparently travel on roads in winter when snow is deep, and thus the road system alters and enhances their ability to move (Paquet and Callaghan 1996). Wolves and grizzly bears are two key species that have chronic, negative interactions with people, and roads are a key facilitator. Repeated, negative interactions of these two species with people increase mortality of both species and often cause high-quality habitats near roads to be population sinks (Wisdom and others 2000).

See also: Fragmentation, Roadkill, Recreation.