JACKSON HOLE — In fall 2011, Jeff Burrell was sitting with his spotting scope at Trappers Point, a 6,000-year-old antelope migration corridor in Sublette County, watching the fleet-footed ungulates nervously approaching busy U.S. Highway 191.

The antelope clearly looked flummoxed and scared when faced with the obstacle on their path from Grand Teton National Park to winter range in south central Wyoming.

“They’d be about a mile away and you could see that they were on high alert,” Burrell said, standing near the same vantage point this October.

The timid antelope would approach the road slowly, in groups, often being spooked into retreat.

“Sometimes, for the better part of the day, they’d go back and forth and back and forth and back and forth,” said Burrell, a wildlife management specialist who works for the Wildlife Conservation Society.

Their intuition wasn’t misguided. Combining antelope and mule deer, 702 animals were recorded killed on a 27-mile stretch of U.S. Highway 189/191 during a recent five-year period.

This year, Burrell said, the antelope are changing their behavior. The sharp-eyed animals still show some trepidation, but they now have a safe passage when they arrive at the barrier.

Aiding animals in crossing the deadly flow of traffic is now a $2.5 million, 150-foot-wide overpass.

To funnel 2,000 to 3,000 antelope and about 2,000 mule deer onto the Trappers Point overpass, plus another overpass and six underpasses, the Wyoming Department of Transportation installed about 31 miles of 8-foot-high fencing. October marked the start of the first migration since the project was completed.

After two years of construction, the $9.7 million wildlife crossing project is complete. Paid for and designed by WYDOT, it’s the first overpass system in the world designed specifically for antelope.

Before it was built, the animals would have to crawl under three strands of barbed wire before playing Frogger with traffic, often losing.

For about 400 Antilocapra americana making the 100-mile-plus journey from their birthing and summer grounds in Jackson Hole, the overpass is a critical piece of protection. Their migration is the second longest by mammals in the Western Hemisphere.

Halfway through this year’s migration, it’s working great, said Renee Seidler, a Wildlife Conservation Society field biologist.

“There’s hesitancy, nervousness, and you can definitely see the animals react to the structure,” Seidler said, observing with Burrell from an overlook near Trappers Point. “There is that negative piece to it, but there’s a huge positive piece. Best we know, 100 percent of the animals that are coming down here are crossing.”

For individual animals, there’s been a mixed bag of behavioral reactions to the new structure, located about 5 miles east of Daniel Junction.

“They’re generally moving at a good pace headed for Trappers Point,” Seidler said. “They go right to the fence on the west side, maybe a half-mile from the crossing.”

After hitting the 8-foot fence, the antelope shift into a trot headed eastward toward the overpass, Seidler said.

“Almost always, they blow right by the old underpass,” she said. “I have seen hundreds of pronghorn, and five of them have used the underpass. Everybody else is using the overpass.”

Beginning mid-October, the first trickle of animals from Jackson Hole made it across the highway.

That’s known because the Wildlife Conservation Society, Grand Teton National Park and the Wyoming Game and Fish Department embarked on a telemetry study of antelope in Jackson Hole in 2010, outfitting 28 specimens with radio collars.

“Last night, we had our very first radio-collared animal from the park move through,” Seidler said last month. “Today we had three more. That’s exciting.”

Completion of the overpasses, underpasses and fencing network will be a boon for the antelope, deer, occasional elk and moose, coyotes and other critters that frequent the sage fields and riparian areas paralleling the highway, said Scott Smith, Game and Fish’s Pinedale wildlife management coordinator.

“I think from a wildlife perspective, it’ll be a great success story,” Smith said. “I think we’ve already seen how the pronghorn are figuring out how to take to those overpasses. And the mule deer will take to the underpasses.

“When WYDOT designed the crossing structures,” Smith said, “the primary species that was both endangering motorists and dying was mule deer.”

A look at the raw data corroborates Smith’s point, and illustrates that the crossing system is every bit as important for that species. Of 274 ungulate fatalities tallied within the project area between 2006 and 2008, 257 were mule deer.

“I’m cautiously optimistic this’ll work great,” Smith said. “It’s the Department of Transportation that should receive all the accolades here.”

Cost-benefit analysis

The large number of animals being hit — and causing damage and potentially death for humans — underscores how this project is clearly both an economic and also human health and safety issue.

For John Eddins, WYDOT’s district engineer, there was a “pretty good cost-benefit analysis” that went into the Trappers Point wildlife crossing project.

Just the cost of the killed wildlife averaged about $450,000 a year, Eddins said, based on the formula used to charge poachers for restitution.

For collisions, factoring in vehicle damage, tows, hospital bills and other expenses, the average crash came to $11,000, Eddins said. On the year, the total bill for drivers was $375,000, he said.

“You put those numbers together, that’s approaching $800,000 a year,” Eddins said. “Over 50 years, that’s $40 million of saving. Theoretically, that $9.5 million will pay for itself soon.”

Back at Trappers Point, Burrell is fielding a question about what work remains to be done in securing the so-called “path of the pronghorn” migration.

“It’s better each year,” he said. “It’s only been since 2000 that we even knew that was a migration corridor. It’s amazing how much has happened.”

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