A wildlife crossing bridge built for local bighorn sheep over Interstate 11 between Boulder City and the Hoover Dam. Tuesday, March 14, 2023.
Monday, March 20, 2023 | 2 a.m.
Nevada bills on deck
While driving down Interstate 11 toward the Hoover Dam, travelers get the treat of watching a herd of bighorn sheep leisurely making their way along the dirt overpass across the highway.
The local sheep, which can be observed in places like Hemenway Park in Boulder City, can pose a road hazard during their treks through the mountains. Other animals, like the threatened desert tortoises, have been caught under cars while trying to graze.
Wildlife crossings — bridges or tunnels dedicated to help wildlife cross roads — are one of Nevada’s solutions to reducing animal-involved collisions and preserving some of the animals that call this state home.
“Wildlife crossings in my mind are some of the single biggest improvements that can be done to landscapes to help improve the status of our wildlife populations,” said Cody McKee, elk and moose staff biologist at the Nevada Department of Wildlife (NDOW).
Nevada has more than 20 wildlife crossings throughout the state, including under- and overpasses. And out of the 22 bridges in the United States for animals, Nevada has six of them, said Nova Simpson, a biological supervisor at the Nevada Department of Transportation (NDOT). Nevada has been considered a pioneer in bringing these wildlife crossings to life, she added.
More could be in the works.
State lawmakers are considering Assembly Bill 112, which calls for identifying areas where wildlife bridges should be erected and asks for the state to match federal funds from the Bipartisan Infrastructure Law designated for wildlife crossings.
The Bipartisan Infrastructure Law includes $60 million for the Wildlife Crossings Pilot, a grant program providing financial assistance to projects that reduce animal-vehicle collisions through solutions like wildlife crossings.
Proving successful
These wildlife passages are built above or beneath roadways and have been used in places like Canada’s Banff National Park and throughout Europe for years, according to National Geographic.
The first wildlife overpass here was built in the early 2010s in northeast Nevada to help protect migrating mule deer, said Mike Cox, bighorn sheep and mountain goat staff biologist at NDOW. Arizona, Montana and Wyoming had already been constructing underpasses in the 1990s, he said.
Simpson helped study the effectiveness of these crossings in Wells — even amidst initial skepticism from Nevadans on whether they were worth the money spent.
Within the first few years of the wildlife crossings being opened, Simpson and her cohorts “documented a 50% decrease in mortalities with each subsequent migration (of deer).”
“A lot of people didn’t think they were going to work, but once we started to get results and once the local people saw the actual improvements, the lack of (deer) carcasses and the lack of hitting animals on the road, they then realized how successful (the wildlife crossings) were being,” Simpson said.
With Nevada finding a way to “practically eliminate these animal-vehicle collisions,” NDOT and NDOW began creating heat maps to find spots they believed a wildlife crossing was most needed.
A majority of the overpasses are located outside of the Las Vegas area.
The only wildlife bridge in Southern Nevada is the Boulder City Bypass, a $1.6 million project which was built in 2018 alongside the completion of I-11, Simpson said. Concerned for the bighorn sheep population in the area, NDOT incorporated the wildlife bridge into the bypass’s master plan.
Simpson said there have been zero reported collisions with the local bighorn sheep since the bridge was completed.
Although these structures are similar to a pedestrian bridge you’d see on the Strip, wildlife crossings are typically designed to emulate the surrounding environment, Simpson said.
“So, animals don’t necessarily understand the human environment, so what we try to do is reduce the impact that we’re making by making these structures as natural as possible,” Simpson said.
Bridges are often covered with grass, dirt and shrubs while many underpasses are carved out of existing washes or other caverns underneath roads. It helps provide cover for big and small species while reducing stress on the animals.
Fencing is also erected in the areas surrounding the bridges to encourage animals to use them instead of attempting a frightening dash across the road.
Animals eventually learn to cross them and pass that knowledge down to their offspring, McKee said.
An acute need
From wild mustangs in Reno to the mule deer in Elko and bighorn sheep in Boulder City, every area of Nevada has a species that locals have seen one too many vehicles hit.
“Why did the chicken cross the road?” Cox said jokingly about the need for animals to migrate. “Some of these roadways are smack dab in the middle of (the animals’) home range, (and) they need to get across to survive, to find the food they need.”
Nevada sees more than 500 car crashes involving wild and domestic animals each year, according to the Nevada Department of Transportation. This results in crash costs of over $19 million and kills an estimated 5,032 animals
But that is just what is being reported.
Officials at NDOT believe the number could be much higher, especially considering wildlife-involved crashes cause $5 billion to $8 billion in damage each year nationally.
The state spends about $20 million a year on these crashes — much of it going toward infrastructure damages, human injuries, losses of human and animal life, emergency response, traffic control and travel delays.
Previous wildlife crossings have been funded through the state, Simpson said. There’s no average cost for these projects, but they can be upwards of millions of dollars. Trying to get that funding amidst some of the other priorities NDOT has can be difficult.
“Funding has been a challenge,” Simpson said. “We, as a department, have so many different needs … when it comes to animal-vehicle collisions, that is fairly low on the list of NDOT needs, and so we’re competing with all these other needs.”
There are no plans for more wildlife crossings in Southern Nevada, but the passing of Assembly Bill 112 and continued development of the region might change that, officials said.
“We are a desert environment, (and) do not have dense populations of wildlife so we do try to protect and do the right thing for the wildlife we have here because it’s important to the citizens, and that’s important to us as well,” Simpson said.
