Taking a key step toward preserving the cougars of the Santa Ana Mountains, wildlife experts have completed a blueprint for connecting those severely inbred animals with the much larger, genetically-diverse population of mountain lions east of Interstate 15.
The estimated population of 16 adult cougars in the 600-acre Santa Ana range has moderate to near-certain odds of extinction over the next 50 years without wildlife-friendly changes to the roadways, according to a 2019 study on the animals called cougars, mountain lions and pumas.
Two recommendations in the connectivity study, completed in April, are already in motion. Both involve the I-15 bridge over Temecula Creek in Temecula and making that underpass more inviting to lions for use as a crossing.
First, The Nature Conservancy won a $400,000 grant last month to draw up shovel-ready underpass plans that includes habitat restoration, sound baffling and fencing to keep people out. That money also is being used by the organization to obtain permits for the work.
Second, Caltrans this month began construction of $1.5 million of wildlife fencing along 3 miles of I-15 south of Temecula Creek, where at least four cougars have been killed trying to cross since 2015. That fencing, part of a larger freeway improvement project, would not only deter lions from the roadway but would help steer them toward the underpass.
But the connectivity study, produced by UC Davis and The Nature Conservancy, looks well beyond those efforts.
It calls for an additional I-15 crossing south of Temecula Creek as well as a host of crossing improvements on highways east of the freeway, which would make it easier for lions on the east side to get to the I-15 underpass without getting hit by cars. A 2019 engineering study by Cal Poly Pomona, included in the connectivity study, provides designs for I-15 crossing alternatives south of Temecula Creek as well as an outline for work on the underpass.
“What we have now is a plan informed by data and we know where we need to go,” said The Nature Conservancy’s Trish Smith, who contributed to the study. “Of course, we have to implement it, but we have a plan.”
Likely the biggest hurdle ahead will be raising money, estimated to be in the millions of dollars, to build a second I-15 crossing. But after 20 years of growing concerns for the range’s lions, those studying the issue say there is more momentum than ever toward ensuring the animals’ longevity.
They point to the accumulation of research on the population, a growing understanding of the threats faced by the lions, and a decision by the state in April to give the lions of the Santa Ana Mountains and five other areas temporary protective status while considering making that standing permanent. They also note that roadway planners have increasingly embraced a role in establishing and maintaining passage for the animals.
It was Caltrans, in fact, that recommended Cal Poly for the I-15 crossing engineering study. Additionally, the agency is now in the pre-application process for a Wildlife Conservation Board grant to further develop Cal Poly’s proposals. Caltrans has been in regular contact with wildlife experts, participating in ongoing conversations and sometimes taking action before reports recommending them are even published.
“There’s more emphasis and awareness at Caltrans,” said Winston Vickers, a UC Davis reseracher who is lead author of the new report. The former Orange County veterinarian has been studying the Santa Ana Mountains cougars since 2001.
“I’m a lot more hopeful than I’ve ever been that these things can happen,” he said.
Roads vs. cats
The short, heroic life of the mountain lion known as M86 is a dramatic example of the big cats’ desire to roam freely on either side of the I-15, the way their ancestors did before there was a freeway.
Around 2011, M86 managed to cross the interstate from the east, bringing fresh genes into the area by fathering 11 kittens. However, six are now known to be dead and one is in captivity. It’s unknown if any are still alive or if they had offspring.
M86 was among several dozen lions that Vickers took genetic samples from and outfitted with radio collars from 2001 to 2016. Six other lions successfully crossed the freeway during that period, two males from the east with no known offspring and four males from the west.
Others continue to be killed trying and the four hit by cars on the I-15 since 2015 are just a hint of the threat roadways pose.
M86’s decomposed corpse was found near Santiago Canyon Road in 2015 — it was presumed he was hit by a car. Roadkill is a primary cause of death for lions on both sides of the interstate, with at least 57 killed by vehicles on the west side of I-15 since 1990 and 64 on the east side, Vickers said.
“It’s struck me how many times these lions have to cross highways just to live their lives,” he said.
Vickers’ latest study identified 185 current and potential crossing sites — a handful on I-15 and the rest on roadways east of the freeway. Of those, 33 bridges and 20 culverts were determined to be suitable for cougar crossing. And those 53 were further whittled down to 39 that had a likelihood for use by the lions because of the animals’ traffic patterns.
Part of the goal in identifying the crossings is to prioritize which should be made most attractive to the animals, including fencing to funnel them toward safe crossing areas.
The effectiveness of fencing can be seen in the $10 million, 6-mile stretch of such barriers erected in 2015 along the 241 toll road on the Orange County side of the Santa Ana Mountains. From 1998 to 2015, six lions and hundreds of deer, coyote and bobcats were killed on the stretch of road. In the first three years after the fence went up, the only animals killed by cars on that stretch were two coyotes, while the number of successful wildlife crossings increased.
Another goal in identifying prime crossing areas east of the I-15 is to help ensure that those locations can continue to be attractive to wildlife as the area becomes more developed, maintaining clear and relatively safe paths for the animals to traverse on their way to and from the envisioned freeway crossings.
“The idea was to provide a long-term guide to which crossings need to be retained,” Vickers said.
‘A step forward’
With the plans for the Temecula Creek underpass to be fleshed out over the next three years, and the price tag for the actual work expected to come in at $1 million or less, The Nature Conservancy is optimistic the project will get done. The work is expected to include landscaping of the vegetation and stream, sound baffles to quiet freeway noise in the underpass and fencing to keep people out of the area, a chronic deterrent to approaching wildlife.
A bigger challenge will be funding the second crossing south of Temecula Creek. That more southerly area has more open conservation space and more documented cougar activity. Cal Poly design options include both a culvert under the freeway and a wildlife bridge over it.
“The Cal Poly Pomona study was a big step,” Vickers said. “People have always been asking, ‘Where do you put a crossing?’ Now we know that it’s clearly buildable.”
Caltrans’ interest in refining that study is contributing to the building optimism, Smith said.
“Caltrans is a great partner in this,” she said.
Caltrans senior environmental planner Scott Quinnell, in turn, acknowledged the role Vickers and Smith are playing with their work.
“All of these studies are important, as they further justify our ability to receive grants and funding … and ultimately move a wildlife overcrossing-undercrossing forward,” Quinnell said. “The main obstacle to all of this is funding.”
Cal Poly ‘s preliminary cost estimates for that southern crossing range from $9 million to $26 million, although some say those price tags are low and point to the proposed wildlife crossing proposed for the 101 Freeway in Agoura Hills. That project recently had its price tag raised to $85 million, with $15 million in contributions received so far. No fundraising is yet underway for a new I-15 wildlife crossing.
But efforts are moving in that direction, with experts and environmentalists heartened to see years of talk evolving into action. And with the latest study, there is a map for action decades into the future.
“Nobody has done this before, looking at all these sites,” Vickers said. “And this pulls it all into one place for transportation and land-use planners. That’s a step forward. It will allow better prioritization.
“I’m hopeful this is something of a landmark.”