Why animals are getting their own freeway overpasses in California, the West; more planned

Forget those dangerous dashes across busy highways: If animals had their own Waze app directing them to the nearest wildlife bridge or underpass, fewer would end up dead on the side of the road and a lot more would be bonding with their mates and sharing a healthy meal.

While no such app exists, the proliferation of animal-friendly passages in car-choked Southern California is becoming a new reality, prompting humans to direct creatures to take animal-only highways and to build more of them, enabling smarter animal transportation just like those app-monitoring motorists who find new side-street shortcuts.

Roadways for animals

Call it a different kind of alternative transportation. Not for humans, not for automobiles but for the wild things that live among us. Once thought of as ridiculous or too expensive, these wildlife overpasses and undercrossings allow animals to get where they’re going and curtail inbreeding, genetic demise, roadway collisions and the chance of being eliminated from the planet forever.

The Nature Conservancy and UC Davis have suggested a wildlife overpass at the Liberty Canyon Road exit of the 101 Freeway in Agoura Hills that would connect stranded mountain lions in the Santa Monica Mountains with a wider population in the Simi Hills and Santa Susana Mountains. It’s a concept that is decades in the making.

Likewise, an overpass and two underpasses are being considered to help stranded mountain lions in the Santa Ana Mountains cross the 15 Freeway and connect with a larger population in the Palomar Mountains south of the Temecula Creek Bridge in Riverside County.

The Santa Monica Mountains overpass would carry animals over 10 lanes of the 101 Freeway and would cost a whopping $60 million. Of that, $8.4 million has been raised by the #SaveLACougars campaign. The group hopes to have the massive animal bridge completed by 2023.

The Temecula crossings would be much less costly. One underpass exists but is blocked by homeless encampments. The people would be moved and fencing would guide lions and other critters to cross, said Michelle Mariscal, ecologist with the Puente Hills Habitat Preservation Authority, who has studied animal land bridges at University of California, Riverside.

Cougars face extinction

If nothing is done, the Santa Ana lion subpopulation, which roams north through Chino Hills State Park, Carbon Canyon and even through an underpass between Orange and Los Angeles counties — into the Puente Hills in La Habra Heights, Rowland Heights and Hacienda Heights — will be extinct within 12 years, according to a new study. The Santa Monica mountain lions population could die out in 15 years.

“The mortality rates are high,” said Winston Vickers, an associate veterinarian from UC Davis who studies mountain lions. “We are just good at killing them in Southern California with cars, poaching and permitted killings,” he said.

On a recent sunny morning, along the eastern edge of the Puente-Chino Hills, Mariscal and Andrea Gullo, executive director of the Puente Hills Habitat Preservation Authority, checked for wildlife tracks within the tubular Harbor Boulevard Wildlife Underpass.

The undercrossing was built in 2006 beneath busy Harbor Boulevard and stretches 160 feet long, stands 17 feet high and 20 feet wide. It links 4,600 acres of publicly protected land to the west with 14,000 acres to the east, strengthening the biodiversity of animals that use it, according to a 2008 study by David Elliott and Paul Stapp of the Department of Biological Science at Cal State Fullerton.

Gullo said rangers have reported seeing a mountain lion this past winter. Mariscal postulates the female lion comes from the Santa Ana Mountains cohort and is looking for food or a mate. She’s part of that isolated population hemmed in on the west by the 605 Freeway and the 15 on the southeast.

“We never thought we could support a female mountain lion,” Gullo said during an interview from the authority’s Whittier offices on Monday. “But it doesn’t mean she can’t stop by and use the area. The deer at Rose Hills (cemetery) have always attracted them.”

First underpass in LA County

Camera studies and tracks show the underpass beneath Harbor Boulevard is used by an ecosystem of vertebrates: ground squirrels, possums, raccoons, jackrabbits, mule deer, coyotes and even the elusive bobcat.

On Monday, Mariscal was thrilled to identify bobcat tracks halfway in the underpass. Bending over to examine the muddy paw prints, she concluded the small cat with the tufted ears had been there. “That looks like a bobcat. It looks like it stepped in its own print,” she said.

The San Gabriel Valley’s most famous bobcat, named ZEK by the U.S. Geological Survey, was part of a study of bobcats in the area in 2013. When he became ill with mange, most likely caused by rodenticide poisoning, he was captured and sent to an Orange County veterinarian for treatment.

He recovered and was released back into the Puente-Chino Hills, and mapping shows his movements ranged the width of the preserve and beyond, from the 605, through the Harbor Boulevard underpass to points south into Chino Hills and the Cleveland National Forest.

“We don’t know where ZEK is or if he is still alive,” Gullo said. “But we know there are a lot more bobcats out there.”

With no more money for collar studies, it’s unclear exactly how many bobcats roam the protected corridor. However, through camera data, bobcat sightings and new track data, Gullo said evidence is mounting that bobcats are using the 13-year-old underpass.

“This proves through the photos and the tracks that bobcats are moving from one side of the road to the other. They can stop inbreeding,” Gullo said.

The first and possibly only animal underpass in Los Angeles County was built in 2005-2006 for $1.4 million with money from the county, the California Department of Parks and the authority, Gullo said.

“It  has been 13 years and it is still doing its job. Hopefully, it will be here decades to come,” Gullo said.

New overpass/underpass in Murietta for butterflies

In September, an overpass with an underpass component was built for animal crossings on top and alongside an extension of the Clinton Keith Road in Murrieta from Vista Murrieta High School to Winchester Road. In April, teams finished blanketing the overpass with soil and natural scrub grasses, said Tricia Campbell, director of reserve management and monitoring at the Western Riverside County Regional Conservation Authority.

The $6 million overpass was built by the Riverside County Transportation Commission and is the most recent animal overpass constructed in Southern California.

This project is unique because its target users are butterflies, birds and insects, in particular, the Quino checkerspot butterfly, a federally listed endangered species.

“It was intended to support mammals as well as avian species and insects,” Campbell said. The orange-and-black butterfly was once seen in abundance from Baja, Mexico to the Santa Monica Mountains. A sharp drop in habitat has caused its numbers to decline to near-extinct territory.

Why do butterflies and birds need an overpass? Why can’t they just fly across traffic?

The Quino checkerspot is a low-flying flutterer, which means it usually ends up splattered on car windshields. Some birds, such as the California gnatcatcher, also extremely rare and endangered, will be helped by the Clinton Keith Road overpass, as will the greater roadrunner, a notorious low flier.

Meanwhile, the soil and vegetation on the bridge will raise the flying levels of these birds and insects over the cars and into tree level, Campbell said.

“Nonmigratory animals do not fly high. They fly low. They end up about level with a car. The overpass will get them to go higher than a road, to align them with the topography,” Campbell said.

Nearby, an undercrossing, about 500 feet left of the roadway, will be used by coyotes, skunks and mountain lions, she predicted. The group is stationing movement-triggered cameras this summer to begin a five-year study to determine what animals use the overpass and underpass.

The purpose is to get the animals to cross the road safely, and increase their gene pool by stopping inbreeding. “Roads are infamous for breaking connections of habitat in larger areas,” she said.

Animals bridges have been built in Colorado, Washington and Canada. Recently, scientists Hall Sawyer, Patrick Rodgers and Tom Hart said in three years, underpasses and an overpass above U.S. 191 in Wyoming has been crossed 60,000 times by mule deer and pronghorn elk.

Teaching animals new tricks

Back in La Habra Heights, Mariscal spotted a dead coyote on the north side of Harbor Boulevard, just yards from the underpass. As she bent to examine the carcass, a stench wafted across the canyon.

The CSUF study counted 175 vertebrate animals dead on the nearby roadways from July 2004 to July 2007, including Colima Road, Fullerton Road and Harbor Boulevard. While roadkill numbers dropped slightly in the year after the Harbor Boulevard underpass was completed, the number of animals killed by cars remained high.

“Our study underscores the substantial amount of movement that occurs across roads that bisect natural areas of the western Puente Hills, which often result in considerable wildlife mortality,” Elliott and Stapp concluded.

Mariscal surmised this coyote may not have been aware of the underpass.

“Maybe he crossed successfully at-grade before. He just might have attempted it again,” she said, adding it takes time to redirect animals to an overpass or undercrossing, even one in existence for 13 years.

“Yeah, they need to know that this is here,” she said.