In a recent post about my experience of deer running into my truck, I mentioned several mitigation techniques to potentially reduce such unfortunate encounters. One of which is influencing how and where deer cross roadways. While leafing through the latest issue of the Wildlife Professional, I came across a blurb about pronghorns and mule deer and their use of under- and overpasses along Highway 191 in Wyoming.
There are numerous examples of species using under- and overpasses. In Montana, US 93 wildlife crossings reduced large wild mammal collisions by 71%. In Colorado, the newly constructed wildlife crossing is readily being used on US 9. Perhaps the most famous wildlife crossing structures are those on the Trans-Canada Highway through Banff National Park. Work began in 1996 and it is the longest on-going wildlife crossing research and monitoring program in the world.
These wildlife crossings are now being incorporated into highway planning to mitigate wildlife conflicts before they happen. Smart! Check out this Florida panther using a brand-spanking new wildlife pathway under I-75 on January 26!
There are many different varieties of wildlife crossing structures – narrow, wide, over, under, etc. And it turns out that species have a preference for which they like best. Enter pronghorn and mule deer. Unlike Pennsylvania deer, western ungulates need to migrate seasonally. When a large and busy highway stands between them and summer/winter grazing lands…well…you know what happens.
Wildlife underpasses are cheaper to construct. 
Wildlife overpasses can cost five to six times as much. YIKES! When you are looking to stretch your infrastructure dollars, this is a big deal. Here’s the thing – Pronghorn don’t like to go under the road. They prefer wide open spaces. Mule deer, on the other hand, are fine with underpasses.
We already knew antelope steal gallbladders. Now we find out they need a special bridge to cross the road. Antelope are nothing but trouble. It turns out that elk and moose don’t like underpasses either but they don’t pilfer internal organs.
The next time PennDOT restructures or widens a highway, it may be in their (and drivers’) best interest to include some wildlife crossings. Given deer are the number one issue, we can stick to the cheap underpass option. No need for fancy pronghorn passes in PA.
Biologist
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