San Diego Union-Tribune (Sunday)
IT’S CARS VS. SHEEP — AND CARS ARE WINNING
Endangered Peninsular bighorns are being struck and killed while crossing I-8 where S.D. and Imperial counties meet; effort to build wildlife bridge under way
The curving, winding lines in the desert sand were a dead give away — a pack of coyotes had feasted on the body of this Peninsular bighorn ram. Though the coyotes clearly ate well off the ram, leaving little behind along the circuitous drag trail except for bare ribs and the tough hind legs, they were the lucky benefactors of its death, not the killers. The culprit was also not a mountain lion, nor disease, nor any of the endangered Peninsular bighorn sheep’s other naturally occurring threats.
It was a human behind the wheel of a vehicle on Interstate 8 approaching San Diego County.
Over the past decade, more than two dozen Peninsular bighorn sheep have been struck and killed while trying to cross I-8 in the rocky, mountainous region where San Diego and Imperial counties meet, though for various reasons that number is likely an undercount of the actual death toll. In recent years, state wildlife officials identified that 13-mile stretch of freeway where the eastbound and westbound lanes split through a steep grade as one of the state’s most problematic barriers to wildlife movement.
An effort is now under way, with a key first step completed earlier this year, to build one of the state’s first wildlife bridges along that stretch of I-8. The envisioned overpass, now in the planning stages after securing grant funding, would facilitate the natural movements of the estimated 790 or so members of the federally protected Peninsular bighorn species, which live between the U.s.-mexico border and Palm Springs in the California desert.
“In the case of these bighorn sheep, we can lose populations forever because of roads,” Mari Galloway, the California project director for Wildlands Network, a nonprofit focused on protecting wildlife movement, said recently. “If they’re unable to travel back and forth to necessary
resources — the mortality rate can be so high it can extinguish them.”
Don Crocker, a senior environmental scientist with the California Wildlife Conservation Board, said a big part of conservation efforts going forward will be focused on wilderness connectivity and roadway permeability. Crossing projects like the one being planned along I-8 are one of the keys to linking protected land across whatever barriers exist, most notably roads, but also railroads, canals and other human-made infrastructure.
“Reconnecting is going to be huge,” said Crocker, who specializes in wildlife crossings and habitat restoration. “It’s a new twist on what we’ve been doing.”
While there are several dozen wildlife underpasses below California roads, there is just one wildlife overpass at the moment — the Clinton Keith Wildlife Crossing in Riverside County. The bridge was designed primarily for the endangered Quino checkerspot butterfly, which typically flies low to the ground and only short distances from one shrub to another, and thus is susceptible to being hit by vehicles. The overpass also serves bobcats, coyotes and other animals.
But more wildlife overpasses — which utilize natural migration patterns, existing landscapes and fencing to funnel animals to them — are in the works. According to data compiled by Wildlands Network, five such overpasses, including the I-8 bridge for bighorn sheep, are in various stages of planning, and one other is under construction. That one, the Wallis-annenberg Wildlife Crossing in the Santa Monica Mountains of Los Angeles County, is designed primarily to protect mountain lions, though many other species will also use it. Once complete, likely in 2025, it will be the largest wildlife bridge in the world as it spans 10 lanes of Highway 101 and an adjacent road.
“The situation in five years is going to be vastly different,” Crocker said.
Additionally, state lawmakers passed a bill last year requiring that Caltrans identify barriers to wildlife movement and prioritize crossings when building or improving roadways. Numerous studies have shown that crossings of all types, and overpasses in particular, are effective at reducing animal collisions and deaths. Crossings have also been found to be economically worthwhile, in the long run, by reducing vehicle damage and potential injuries and death.
But the I-8 overpass is unique as it would be the first such wildlife bridge in the state designed for bighorn sheep. Most other crossings, whether overpasses or underpasses, are built with mountain lions, deer or elk in mind.
“Sheep are very picky” about where they cross roads, Devin O’dea, western policy and conservation manager with the group Backcountry Hunters & Anglers, said. He explained they will not cross below a road through a tunnel, culvert or any other narrowly enclosed underpass, but will cross below tall bridges with wide berths.
Two such crossings already exist below the westbound lanes of I-8 in the Peninsular bighorn sheep’s territory. But no such crossings exist under the eastbound lanes.
And so, in December 2022, Galloway, O’dea and others gathered up local stakeholders and began to put together a proposal for an overpass project. By August, Crocker presented it to the Wildlife Conservation Board, which approved a $5.8 million grant for the planning and design phase of the project, which will be carried out by the University of California, Davis, Road Ecology Center.
Now, the work has begun to determine where, exactly, to build the bridge to ensure the best outcome for the sheep and drivers.
‘Giving the land a voice’
Bruce Gordon took off Dec. 12 from the Borrego Valley Airport to make a pass over the project area in his Cessna 210, giving the other five people on board the cramped, single-engine aircraft a bird’s-eye-view of the stretch of freeway and surrounding desert.
Gordon is the founder and chief pilot of Ecoflight, a Colorado-based nonprofit
that uses such flights to help better visualize conservation projects. Just before takeoff that morning, near the small airstrip that makes up the entirety of the Borrego Springs airport, Gordon explained how the aerial perspective helps in “giving the land a voice.”
The elevated view helps stakeholders “see how it all fits together,” Gordon said.
From the co-pilot’s chair, O’dea used his headset to tell the group more about the desert landscape passing below and the crossing project. During the application phase, those involved identified four potential locations for the bridge along different points of the freeway where sheep have been hit in higher numbers.
Though the crossing will be built in Imperial County, a majority portion of the Peninsular bighorn sheep’s habitat is in San Diego County. It also stretches north into Riverside County.
O’dea speaks passionately about the Peninsular bighorn species and the conservation work that has gone into more than doubling its population since 1998, when the population dropped to about 300 and it was listed as endangered.
“Every sheep lost is a significant event,” O’dea said.
As Gordon piloted the plane south from Borrego Springs over the I-8 project area, O’dea pointed out the “island” of wilderness between where the freeway’s westbound and eastbound lanes split apart. For humans, this area appears to be a wasteland of steep, rocky hills.
For Peninsular bighorn ewes, it’s protected from predators and is “critical habitat” for birthing their lambs, O’dea explained to those on board, who included Crocker from the Wildlife Conservation Board and Jonathan Jones, a tribal liaison from the Campo Band of Mission Indians.
“The island is their main nursery and lambing area during the spring,” Janene Colby, a wildlife biologist with the California Department of Fish and Wildlife, explained a week later from the side of eastbound I-8 near one of the proposed bridge locations. “They will cross the road a lot to forage with their lambs. Some of these ewes might cross the road two or three times a day.”
And traffic volume in the area, where the speed limit drops to 65 mph because of the steep grade, is increasing. On average, about 17,200 vehicles passed through that area each day in 2021,
according to the most recent data available from Caltrans. That’s up from a daily average of about 13,600 vehicles in 2013.
Colby has logged at least 28 sheep deaths along I-8 dating back to 2012, including at least three in 2023. But the actual death toll is likely significantly higher.
Roadkill deaths are typically only counted when the collision is bad enough that the driver reports it to the California Highway Patrol, whose officers then alert Colby. But for a variety of reasons — such as when a semi hits a sheep and is able to continue on with little damage to the truck — those collisions are not always reported.
Data compiled by Colby, who affixes radio collars to some ewes to track their movement patterns, indicated that one-third of radio-collared ewes that were struck and killed by vehicles were not reported to the CHP.
Colby sometimes finds out about unreported deaths anyway, such as the ram eaten by the coyotes, which was mentioned to her by a Caltrans crew after they spotted ravens circling and feeding off the carcass. In another case, a driver’s
dashboard camera recorded footage of his vehicle clipping the back end of a young sheep at high speed. Colby searched for the animal, knowing it couldn’t survive long after being hit, without luck. She was unable to record it as an official roadkill death without the body.
“With traffic loads increasing, at some point they’re not going to be able to cross the road anymore,” Colby said. “And not to mention that anytime (a sheep is hit by a vehicle), it’s going to risk people getting injured or killed, as well.”
Project approval
In 2020, the California Department of Fish and Wildlife compiled a report identifying the state’s 62 most problematic barriers to wildlife movement. As part of the report, which was updated in 2022, the state chose two barriers from each of its six land regions as top priorities for connectivity projects.
Among the 62 identified barriers, six were in or on the edges of San Diego County.
They include state Route 67 between Lakeside and Ramona, a barrier for mule deer, bobcats, mountain lions, western toads and badgers; Campo Road southeast of Jamul, which bisects the San Diego National Wildlife Refuge and is a barrier for mountain lions, badgers, mule deer and bobcats; I-8 between El Cajon and Alpine, a barrier for mountain lions, mule deer and the California gnatcatcher bird; and county Highway S22 near Borrego Springs, a barrier for Peninsular bighorn sheep.
The two that made the top-12 priority list were the I-8 project and a 6.7-mile stretch of Interstate 15 between East Mission Road in San Diego County and Temecula in Riverside County.
The report provided the first clear accounting of the most significant connectivity issues across California. It stated previous efforts to identify problematic corridors were limited and “executed in a piecemeal fashion.”
It also gave those like Crocker from the Wildlife Conservation Board and Galloway from Wildlands Network a quick and easy way to communicate to stakeholders why certain crossing projects were important and should move forward quickly.
And so in December 2022, Galloway and O’dea convened a meeting with representatives from government agencies and conservation organizations with a potential interest in the I-8 bighorn sheep crossing project. Galloway had put together similar proposals in the past, while O’dea knew many of the local stakeholders.
It was important to move quickly — there was grant funding available from the Wildlife Conservation Board that wouldn’t be available forever.
“We had to ask them to trust us,” Galloway said.
Representatives from the various agencies and organizations indicated their support, so Galloway got to work, enlisting UC Davis as the grant applicant. O’dea created an interactive website, largely using Colby’s data, to help explain the need for a crossing. One heart-wrenching segment features footage of an injured ewe and her lamb after the mother’s front legs were struck by a vehicle. Footage shot a short time later shows the lamb checking on its now dead mother, then trying and failing to cross the freeway on its own, being repeatedly spooked by oncoming traffic.
In August, Crocker took the application to the Wildlife Conservation Board and secured the $5.8 million grant.
Next steps
Over the next several years, the UC Davis Road Ecology Center, its subcontractors and others who are involved in the project will set about studying the project area to determine which of the four potential locations for the overpass is best. There must be environmental analyses, two different project documents involving Caltrans, the nailing down of designs and cost estimates.
Kumeyaay representatives will also be involved over the next several years.
Jones, the liaison from the Campo Band of Mission Indians, said that Native American monitors will conduct surveys to ensure the project does not disturb any historic burial grounds or human remains. Otherwise, other artifacts found in the area can be moved, Jones said. The Kumeyaay people “appreciate and admire” the Peninsular bighorn sheep, which used to be a significant and respected food source.
“Food is life ... (and) the bighorn used to help get our people through those rough areas,” Jones said.
He said the tribe is “100 percent behind” the crossing project’s effort to conserve the Peninsular bighorn.
The planning and feasibility portion of the project is expected to be completed sometime by mid-2027, Galloway said. At that point, more funding will be needed for the actual construction.
But that’s not expected to be a problem, as greater awareness of the need for these types of crossings have led to more funding in recent years from both the state and federal governments.
And as more such crossings are studied, planned and built, researchers will gain even better insight into what works and how to make human infrastructure more permeable for wildlife.
“Take the top 60 barriers — even if we finish them all, the next 60 are almost as important,” Crocker said. “There are no shortage of barriers that need to be worked on.”