Wildlife fences in Western Colorado: are they keeping out or letting out the elk?

The fencing that line both sides of Interstate 70 in western Colorado may lack the iconic character of those creosote-lined barriers that flank the highways surrounding Lexington, Kentucky’s horse country.  The green of those rolling Appalachian hillsides offers a critical backdrop to the black-as-pitch (literally!) wood that lends structure to the fences in the Bluegrass State.  But in Colorado, where the fencing consists of a nondescript dark brown against a straw-brown landscape, the justification for their presence may be a bit more impressive.  Extending the analogy, in Kentucky they tend to demarcate the outer edges of privately-owned horse pastures, keeping the prized fillies, colts, mares, geldings, and especially those stallions from escaping, whereas in the Rocky Mountain West they are a deterrent for wild, free-roaming populations.  And, unlike Kentucky, much of the land in Colorado (more than one-third of it) is federal, a high percentage that characterizes all the Western states.  In short, the public sector—either the State of Colorado or (most likely along I-70) the US Department of Interior or USDA—has financed wildlife fences to protect against vehicle-animal collisions.

It’s great that these two non-adjacent states have these fences; they undoubtedly prevent many animal-vehicle collisions, sometimes lethal for the motorist, nearly always lethal for the animal.  I recall reading in one book—potentially Urban Ecology: Science of Cities by Richard T. T. Forman—that approximately one million animals perish due to vehicles every day in the US. So why is it that we don’t encounter these fences everywhere?  The explanation in Kentucky is simple: if a horse farmer owns land that directly abuts a busy thoroughfare, it is in his or her best interest to protect them from escaping while maximizing their grazing potential.  In Colorado, the justification for protecting wildlife from cars (and vise versa) may seem straightforward, but why are these wildlife fences prevalent here but not elsewhere?  The high plains of eastern Colorado, filled with farms and ranches, don’t have them.  Federal land ownership characterizes western Colorado specifically, making it far easier to construct large civil works initiatives without dealing with the requisite negotiations of numerous landowners—a huge contrast from neighboring states like Kansas and Oklahoma, where federal land ownership is extremely low (less than 2%).

So that’s one explanation.  But still…why don’t we see wildlife fences throughout eastern Utah, less than a hundred miles away from the photo above?  It has an even higher percentage of federal land than Colorado—at over 60%, it’s one of the highest in the country.  My answer: the lush, arboreal forests of the Colorado Rockies support more wildlife than the arid Colorado Plateau to the west (which, despite its name, comprises significantly more land in Utah than Colorado; the name comes from the Colorado River that wends its way throughout the American Southwest).  The wildlife of eastern Utah’s harsh, almost waterless ecosystems is mostly drought tolerant and tiny: mammals include various rabbits, chipmunks, and kangaroo rats that are no great threat to motorists.  Conversely, the evergreens and aspens of central and western Colorado support mule deer, coyotes, bobcats, and gray foxes.  These mammals are certainly larger than the aforementioned rodents, but various subspecies of coyotes and deer are equally visible throughout the Great Plains and Midwestern states, where few if any of such wildlife fences exist.  The absence of federal lands might again explain why wildlife fences are rare in Ohio and Indiana (where coyotes and deer are abundant), but is that enough explanation?  Ohio and Indiana have a higher density of federal highways than Colorado or most other western states (or Kentucky for that matter), so the odds of vehicle/animal collision could be greater.

The explanation why central and western Colorado host all these fences, from what I can determine, comes one large mammal most characteristic of Colorado: the Rocky Mountain elk.  Though not endangered any longer—the subspecie of elk (wapiti) has recovered after approaching extinction a century ago—it remains an icon throughout the region, notable for its size; males can easily weigh from 600 to 1,000 pounds, and while the local bear population might prey on elk calves, no record exists of of an adult bull elk succumbing to a bear attack.  Due to their size, speed (up to 45 mph), and capacity for aggression, adult elk tend to avoid predation by bears.  Such an encounter is likely to be fatal for the bears of the Colorado Rockies.  Elk are tough.

More importantly, elk are versatile throughout the region: their territory is often large and they are unafraid of dense human development within the mountains.

The photo above shows a herd of Rocky Mountain elk (mostly cows) meandering its way through a community in the western suburbs of Denver, nestled right within the Front Range.  Less than thirty miles west of Colorado’s largest city, elk will graze (unapologetically!) in people’s back yards.  It’s not a novel appearance.  The scores of people moving to the Colorado Rockies each day have no choice but to grow accustomed to the male’s unusually high-pitched bugle, prevalent during rutting period—autumn in the Northern Hemisphere.  The second half of the video below offers a quintessential bull elk’s Miles Davis impression:

The heightened aggression during the rut makes the males particularly bold and unafraid to assert their presence in the middle of a Colorado town.

Much like their smaller deer cousins, Rocky Mountain and Roosevelt’s elk (the two most common subspecies in the region) have no problem browsing along major highways.  It logically follows that vehicle collisions with elk are very dangerous, with a higher fatality rate for humans than collisions with smaller deer or wolves.  In Colorado, they may pose a greater threat than the mighty moose, which are equally large but less prevalent in the region and whose habitat encompasses more remote areas.  (Elk and moose are among the few animals large enough to survive many collisions with cars.) Throughout central and western Colorado,  the elk crossing signs look very different from the more ubiquitous deer crossing signs that most Americans recognize.  Therefore, these wildlife fences are most essential for restricting the movement of elk.

At this point, I’ve exhausted all deductive reasoning necessary to explain why it’s particularly important that western Colorado should feature wildlife fencing.  It’s fundamentally about saving human lives where animal collisions are a greater threat. But I haven’t yet explored one other remarkable little feature: access points.

From the angle in the above photo, it looks a weird mound of soil aligned with a breach in the fence.  If we had been able to get an oblique angle, it might have been more obvious: it’s an escape ramp.  Here’s a clearer view.  The earthen ramp is only on one side of the wildlife fence—the side facing the interstate—and it intends to offer an easier means of surmounting the fence for the hapless elk (or deer, or coyotes) who are stuck in the narrow ribbon of land between I-70 (with all its speeding cars) and the fence.  These escape ramps aren’t frequent, but they’re a potential lifesaver for antelopes that somehow manage to surmount other fences and have navigated their way across the busy highway.  This represents true strategy in pursuing a compromise between protecting motorists and tapping into animal psychology that might allow it to coexist humanely with technology.  It’s the best example I’ve witnessed in years—certainly at least since the wildlife overpass I discovered over a busy interstate in Northern New Jersey.  And for those asking the reasonable question: “If these elk are so fast and huge, why can’t they jump over a plain old fence?”  I was wondering the same thing.  But we must remember, animals achieve higher verticality when they can get a good run, and when they can confront the object head-on, at a 90-degree angle.  Since the elk are running along a highway, it may be hard for them to achieve the velocity, and it’s probably difficult to time the jump at an oblique angle.

Let this horrifying video serve as the lesson learned on exactly how wildlife fences can work—and their unintended consequences.  Makes me appreciate those Colorado escape ramps so much more.

All photos and videos courtesy of Sarah and Jonathan McAfee.