A sprawling cattle ranch along Highway 101 near the border of Santa Clara and San Benito County could become home to a unique overpass. Not for cars, but for wildlife.

In December, the nonprofit Land Trust of Santa Cruz County spent $17 million to buy Rocks Ranch, a 2,600-acre property near San Juan Bautista that developers have eyed in recent years for subdivisions, hotels and other projects.

Instead, the group is working on a plan with Caltrans to build a wildlife crossing so that mountain lions, deer, bobcats, badgers, foxes and other animals can traverse four lanes of speeding traffic on Highway 101 without being hit by cars.

That area is a hotspot for wildlife-vehicle collisions that not only rack up roadkill but can injure or kill motorists. The freeway also can block animals from roaming to breed, find food and settle into new habitat areas.

“The Santa Cruz Mountains are essentially an island with an ocean to the west and the Bay Area to the east and farmland to the south,” said Bryan Largay, conservation director for the Land Trust of Santa Cruz County. “And what happens on islands is that species can go extinct. We’re trying to build land bridges to connect the Santa Cruz Mountains to the rest of California.”

Planning is still in the early stages for the crossing, which would be the first such natural bridge built over any freeway in Northern California.

The idea is to connect two places that are still relatively wild: the Gabilan Range — which runs roughly from Pinnacles National Park to Fremont Peak near Hollister — and the Santa Cruz Mountains.

At the head of the plan is Rocks Ranch, which has 2.5 miles of frontage on Highway 101, just south of Highway 156. Caltrans planners are studying several spots along the property where under crossings could be built below the freeway. But an overpass would work well in several of them, said Morgan Robertson, a biologist and senior environmental scientist for Caltrans District 5.

“This is a key linkage point,” she said. “It’s a really important piece of the puzzle.”

Caltrans should be finished with a feasibility study by the end of this year, she said. The agency is applying for several grants to fund engineering and environmental studies over the next three years, with construction planned for 2028 if funding can be secured.

An overcrossing would probably be 120- to 160-feet wide. It would be constructed of concrete and covered with grass, brush, rocks, logs and possibly even trees. Fencing would be built along parts of the freeway to help keep animals off the road and direct them to the overpass, Robertson added.

“They are habitat,” she said of wildlife overpasses. “From the highway they look a lot like standard overpasses. But they are just for animals.”

Statewide, at least 302 mountain lions, 502 black bears, 144 elk, 42 bighorn sheep and about 29,000 other large wild animals, most of them deer, were hit and killed by vehicles in California between 2016 and 2020, according to an annual study by scientists at UC-Davis. Dozens of people are killed every year in collisions with wildlife on highways.

Animal crossings are part of a growing trend in California and the West — and are already making a difference.

Last year, Caltrans and the Land Trust of Santa Cruz County finished a $12 million project to build a tunnel under Highway 17 at Laurel Curve near Scotts Valley.

Ten years in the making, the land trust pieced together about 700 forested acres near the curve. Caltrans contributed $3 million, $5 million came from county transportation funds, and the rest came from private donations.

There already are several large wildlife crossings operating in Canada. Six overpasses and 38 underpasses for wildlife exist between the east gate of Banff National Park and the British Columbia-Alberta border.

In Wyoming, state fish and game officials built two wildlife bridges in 2012 for pronghorn antelope to cross over Highway 191 near Pinedale, along with six underpasses. Wildlife-vehicle crashes have dropped by 85% in the area since then.

The most high-profile project in California is near Los Angeles.

Construction began last spring on an $87 million wildlife bridge with vegetation over the 10-lane 101 freeway at Liberty Canyon in Agoura Hills. That project, designed to keep mountain lions from going extinct in the Santa Monica Mountains area, is expected to open in 2025 and will be the largest of its kind in the world. Sixty percent of the funding comes from private donations and the rest from state wildlife and environmental grants.

Planners are also studying a proposal to build a similar wildlife overpass at Highway 152 east of Gilroy, near Pacheco Pass.

Mountain lion experts say that as California’s population has grown, freeways have blocked lions from their natural roaming.

“Animals need to be able to move back and forth among mountain ranges and breed with each other,” said Chris Wilmers, a professor of environmental studies at UC Santa Cruz. “This creates a larger gene pool that is more resilient to inbreeding and ultimately extinction.”

Rocks Ranch has been grazed by cattle for more than 150 years. In the 1800s, a stagecoach route ran through the property. Tiburcio Vasquez, a famous bandit during the Gold Rush, was said to have roamed its rocky outcroppings.

“Legend has it that he would wait to see the dust trail from the stage coach, then rob the stage and dive down into the box canyons to get away with the gold,” said Ben Bingaman, whose family had owned the property since 1947 before selling to the land trust.

Bingaman, who worked on the ranch as a child starting at age 6, said he’s pleased the property will be kept in its natural state, adding that he supports the wildlife crossing projects.

“We were talking with developers and got right to the point of signing an agreement in 2015,” he said. “Honestly, I just looked at it one day and said this isn’t for me. I’m not going to be the guy that levels this place. It just didn’t feel right.”