Last winter, a single crash killed 11 pronghorn near Timmerman Hill in Blaine County.
Now, the county commissioners are teaming up with the Idaho Department Fish and Game to minimize the risk of those roadside incidents in the future—and, to prioritize protection for the charismatic quadrupeds along their migration routes through southern Idaho.
On Tuesday, the board unanimously agreed to commit just over $90,000 from the Land, Water and Wildlife Levy fund to partner with the department in a five-year tracking study of local herds in the hope of identifying common crossings along U.S. Highway 20 in Blaine and Camas counties.
That allocation, previously recommended by the Levy Advisory Board, unlocks another $270,000 in grant money to capture, collar and track animals, mapping how they move through the area en route to their northerly summer ranges. If the data present a clear picture, Fish and Game can work with the Idaho Transportation Department to construct safe highway crossings at hot spots along migration paths, which, studies elsewhere suggest, are ingrained in herds over hundreds if not thousands of years.
While Fish and Game has migration data on elk and mule deer, information on pronghorn—a smaller, antelope-like animal unique to the North American West—is spotty at best in Idaho.
“We are starting from scratch with pronghorn,” said Frank Edelmann, environmental staff biologist for Fish and Game’s Magic Valley Region. “This is a real issue we’re trying to address. We have documented that mortality occurs [along the highway], but we don’t have an estimate of the total number killed. …We don’t know what’s going on.”
They do have a prediction: As both Boise and Blaine County continue to grow, collisions on the road between will increase.
The plan involves capturing 40 pronghorn by helicopter using netguns or tranquilizer darts, fitting them with GPS collars and mapping where they go from there. Researchers will collar another 10 each year; since they don’t have mortality estimates, those annual additions should either maintain or grow the study population. If all goes well, Fish and Game would publish a final report in 2023.
Elsewhere, the department has already gotten started. Biologists recently captured and tagged some specimens wintering in Gooding and Jerome counties. On Monday, the first of those was tracked crossing Highway 20 near Magic Reservoir, Fish and Game Regional Population Biologist Sierra Robatcek told the commissioners.
“In the old days, we had to fly around and find them,” Edelmann said. “Now, we can just sit at our desk and see where these critters are going.”
The collars, which have battery life of three or four years, ping back a location every six hours to paint a fine-grain picture of animal movements.
Mule deer have been tracked by GPS and radio transmitters for years, and supporters of the study can simply point down the road to see results. At sites near Rock Creek and Willow Creek on Highway 20, ITD is replacing culverts with bridges that will act as underpasses for the deer in “concentrated crossing areas,” Edelmann said.
Pronghorn prefer overpasses, he added, and are unlikely to use the underpasses. And, they don’t jump fences, making their migration patterns more likely to be affected by human development.
“We are always surprised, because they go farther, and they go crazy places that we cannot predict,” Edelmann said. “Until we put the collars on, we won’t know what the answers are—that’s what makes it interesting.”
Once compiled, the data will be available to private landowners and to the BLM, which manages much of the range. And it could provide a model for harmony between traffic and wildlife for Blaine County’s other conflict zone, along state Highway 75.
With development lining that road, it could take “decades” to get there, Edelmann said.
“From what I’ve seen, [Highway 75] is going to be a lot more difficult,” he said. “But if we create a culture of wildlife coexistence starting with Highway 20, it could make 75 easier.
“This is not a short game. It may take the rest of my career. We’re in this for the long haul.”