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    ​Wildlife Crossings 

    Pennsylvania has a large network of roads that crisscross the state connecting our cities and towns. These roads create an obstacle between one part of a habitat to another. This is called habitat fragmentation. Wildlife cross the roads because they are looking for food, water, or they are running from a predator (including humans). Unfortunately, wild animals don't understand the dangers associated with roads and road traffic. One of the most significant threats to wildlife and the motoring public are collisions with and avoiding collisions with wildlife. 

    One way to reduce wildlife-vehicle collisions are to install wildlife crossings that connect these habitats with safe passages across the roads. Wildlife crossings are tunnels and bridges built around highways and major traffic areas for animals to utilize. They provide a safe crossing over or under roads. Underpasses offer a way for wildlife that fear bridges to cross under the road safely. Smaller animals frequently use these types of crossings to avoid the dangers of the road above. Larger overpasses are vegetated crossings that blend into the surrounding area and where it is impractical to go under the roadway. 

    Safety

    Across the United States, wildlife-vehicle crashes are estimated to cause over 200 human deaths and 1 million large animal deaths each year.  The state of Pennsylvania consistently ranks in the top five states throughout the nation for the highest odds of drivers hitting a deer.  According to insurance statistics, PA reported the highest number of total animal collision claims across all states with over 156,000 animal collisions reported from July 2021 to June 2022.  The vast majority of these reported collisions are due to whitetail deer strikes.

    These collisions come at a high cost to society.  Medical bills, property damage, and clean-up are all factored into a $9,200 cost per deer-vehicle crash (estimated by researchers Huijser, et al. in 2007 and adjusted to 2022 dollars).    However, wildlife crossing structures and associated fences are a demonstrated way to mitigate wildlife-vehicle crashes.  Research published in 2020 (Ament, et al.) found that wildlife-vehicle crashes can be reduced by as much as 97% when a combination of crossings, fencing, and jump-out ramps are installed.  Crossing structures like intentionally designed culverts and bridges can accommodate a variety of animals including other large mammals capable of causing wildlife-vehicle collisions like black bears as well as smaller reptiles and amphibians that might otherwise suffer high roadway mortality.  With these interventions in place, roadways become safer for both drivers and wildlife.

    Sources:

    How bridges over highways make animals – and people – safer. National Geographic. Vartan, Starre. (April 16, 2019). 

    Cost-Benefit Analyses of Mitigation Measures Aimed at Reducing Collisions with Large Ungulates in the United States and Canada:  Hiujser, et al. (2009) A Decision Support Tool. Ecology and Society Vol. 14, No. 2, Art. 15. 

    CPI Inflation. Bureau of Labor Statistics (2022).

    State Farm Newsroom statistics:
    State Farm auto claims data reveals drivers struck less animals than previous year

    Wildlife-Vehicle Conflict, Crossing Structures, and Cost Estimates.  Center for Large Landscape Conservation. Ament, et al. (2020).

    Wildlife Crossing Types

    Wildlife crossings come in all shapes and sizes. These range from small amphibian tunnels to box culverts for larger mammals and deer to large overpass structures designed for all wildlife to use. Below are brief descriptions of these structures and their use:

    Designed exclusively for wildlife use. Due to their large size, they are used by the greatest diversity of wildlife and can be adapted for amphibian and reptile passage.

    Smaller than landscape bridges, these overpass structures are designed exclusively to meet needs of a wide range of wildlife from small to large. 

    Generally, the smallest of the wildlife overpasses. Designed for mixed wildlife and human use. This wildlife crossing type is best adapted in human disturbed environments and will benefit generalist type species adapted to regular amounts of human activity and disturbance. 

    This wildlife passage design is the largest of underpass structures. The large span and vertical clearance of viaducts allow for use by a wide range of wildlife. Structures can be adapted for amphibian and reptiles, semi-aquatic and semiarboreal species. These work well because of the large open natural areas. 

    Not as large as most viaducts, but the largest of underpass structures designed specifically for wildlife use. Designed for large mammals but small and medium-sized mammals use readily as well. 

     Designed similar to large mammal underpass; however, management objective is co-use between wildlife and humans. Design is generally smaller than a large mammal underpass because of type of wildlife using the structures along with human use. These structures usually result in use by generalist species common in human-dominated environments (e.g., urban or suburban habitats).

    An underpass structure designed to accommodate the needs of moving water and wildlife. These underpass structures are frequently used by some large mammal species, but their use depends largely on how it is adapted for their specific crossing needs. Small- and medium-sized mammals generally utilize these structures, particularly if riparian habitat or cover is retained within the underpass.

    One of the smaller wildlife crossing structures. Primarily designed for small- and medium-sized mammals, but species use will depend largely on how it may be adapted for their specific crossing needs. 

    Crossing designed specifically for passage by amphibians and reptiles such as turtles, frogs, and snakes, although other small-and medium-sized vertebrates may use as well. Many different amphibian and reptile designs have been used to meet the specific requirements of each species or taxonomic group. 

    Wildlife Crossing Story Map