Animal Vehicle Collision Reduction and Habitat Connectivity Pooled Fund Study – Literature Review

Abstract

This report contains a summary of past research and new knowledge about the effectiveness of mitigation measures aimed at reducing animal-vehicle collisions and at providing safe crossing opportunities for wildlife. The measures are aimed at terrestrial large bodied wild mammal species, free roaming large livestock species (e.g. cattle, horses), free roaming large feral species (e.g. “wild” horses and burros), and small animal species (amphibians, reptiles, and small mammals). While mitigation is common, it is best to follow a three-step approach: avoidance, mitigation, and compensation or “off-site” mitigation. If reducing collisions with large wild mammals is the only objective, the most effective measures include roadside animal detection systems, wildlife culling, wildlife relocation, anti-fertility treatments, wildlife barriers (fences),and wildlife fences in combination with wildlife crossing structures. If the objectives also include maintaining or improving connectivity for large wild mammals, then wildlife barriers (fences) in combination with wildlife crossing structures are most effective. Measures for large domestic mammal species are largely similar, though for free roaming livestock there are legal, moral and ethical issues. For small animal species, temporary or permanent road closure and road removal are sometimes implemented, but barriers in combination with crossing structures are the most common.

Impact of Wildlife Crossing Structures on Wildlife–Vehicle Collisions

“…Fencing is a popular method, but can be costly to install and maintain, and cannot be used everywhere. On U.S. Highway 93 on the Flathead Reservation in Montana, the cost of wildlife fencing is $7.9, $11.6, or $12.5/ft, depending on the road section ( 1 ). Huijser et al also mention that fencing is impractical in dense vegetation areas where there is little public roadside right of way ( 1 ).…”

“…On U.S. Highway 93 on the Flathead Reservation in Montana, the cost of wildlife fencing is $7.9, $11.6, or $12.5/ft, depending on the road section ( 1 ). Huijser et al also mention that fencing is impractical in dense vegetation areas where there is little public roadside right of way ( 1 ). Highly motivated wildlife can find their way around the ends of a fenced highway segment, and fencing does not connect wildlife habitats from one side of a highway to another.…”

“…The number of wildlife–vehicle collisions in the United States poses a safety concern, as 1 to 2 million collisions between vehicles and large animals occur every year ( 1 ). In the state of Washington, highway U.S. 97 in Okanogan Valley alone has to deal with more than 350 deer carcasses each year on a 12.5-mi stretch of the highway ( 2 ).…”

“…They found that wildlife underpasses and fencing improve road safety. Nonetheless, in a report to Congress, Huijser et al stated a need to address knowledge gaps, insufficient information, and statistical methods to analyze the data associated with the study of wildlife–vehicle collision reduction ( 1 ). There are no standards for collecting wildlife–vehicle collision data, and methods vary between states and agencies.…”

Vehicular traffic effects on elk and white-tailed deer behavior near wildlife underpasses

“…Roads and highways threaten species population viability as well as overall biodiversity by destroying habitat and fragmenting populations [ 1 ]. Wildlife-vehicle collisions have increasingly been an issue of concern for many state and provincial transportation agencies [ 2 , 3 ]. Mitigation efforts, such as the construction of underpasses and overpasses, are measures to reduce some of the negative effects of roads [ 4 – 6 ].…”