Here’s what you need to know about the Liberty Canyon Wildlife Crossing

A proposed bridge over the 101 would allow mountain lions and other wildlife to cross safely over the freeway and improve their access to food and mates. But can humans and predatory animals coexist in the city?

As part of our series Bridges and Walls, DnA looks at the design of a bridge to resolve a problem created by a wall – a freeway – so as to give wildlife connected terrain to roam.

DnA spoke with advocates and a staunch opponent of a proposed wildlife crossing; transit engineers and architects who are using scent and plantings to design a wildlife crossing; and conservationists – and children – who have turned P22 into a poster lion for animal-wildlife coexistence.

Here are answers to questions you may have about the bridge:

Where will it be?

It’ll be in Agoura Hills, just west of Liberty Canyon Road. It would connect the Santa Monica Mountains to the south with Simi Hills to the north. It crosses 10 lanes of freeway and a parallel collector road, Agoura Road.

What will it look like?

It will look like a regular overpass, but it will be covered in plants – most likely a scrub oak landscape. It’s being designed to resemble an extension of the mountainside, and will be made of concrete and the soil that had been removed from that site to build the freeway. Last year Caltrans released an environmental assessment for the project.

A rendering of the proposed wildlife bridge at Liberty Canyon.

Why would we need this?

Wild animals need to roam, but our freeways are in the way. The proposed bridge over the 101 would allow mountain lions and other wildlife to cross safely over the freeway, and ensure the safety of motorists as well. Bobcats, coyote and deer will use it, as well as wren tits, fence lizards and all sorts of other fauna.

“Freeways are unique in that they can kind of divide up habitat and territory in a way that other infrastructure cannot, and I think that Caltrans wants to play a role in rectifying that problem in the future,” said Caltrans structural engineer Ulysses Smpardos.

Being confined to a small geographic area has led to animals fighting and inbreeding, leading to reduced genetic diversity and a risk that the mountain lions could become extinct in as little as 50 years.

“There was one litter of kittens, P36 and 37, where P12 was the father and the grandfather and the great grandfather. That’s what happens when you have all these animals basically stuck in this small area and they’re not able to get back and forth,” said Seth Riley, wildlife ecologist with the National Park Service.

How much will it cost, and who’s paying for it?

It’s estimated to cost $60 million, and is expected to be built by 2022. That money would come largely from private donations. A Caltrans engineer told DnA that taxpayers would not be on the hook, at least “not yet.” About $3.7 million has been collected so far. The National Wildlife Federation and Santa Monica Mountains Fund are fundraising for the project. In November, conservationists purchased the land where the animal overpass will be built.

They’re enlisting Hollywood celebrities like, Rainn Wilson, to get the word out:

Can I hike there?

It’s still being studied, but the designers of the bridge believe humans will be allowed to access it.

Will I see mountain lions on it?

It’s unlikely. There will be plenty of vegetation blocking your view from the freeway. Plus the mountain lions will most likely use the bridge between midnight and 5 am. There will also be visual and sound barriers on the edges of the structure to block noise and headlights from scaring away wildlife.

Will P22 use it?

P22 is the poster lion for the bridge, but sadly he won’t be able to benefit from it because he’s trapped in Griffith Park by the 101 and 405 freeways. But some of his relatives could use it.

How did P22 become the face of a movement?

P22 became a worldwide celebrity after a National Geographic photographer captured this heartwarming picture of the lonely lion and Los Angeles Times reporter Martha Groves broke his story. Nat Geo photographer Steve Winter had been alerted by the National Park Service after a Natural History Museum wildlife biologist named Miguel Ordeñana captured an image on a motion-activated camera. Ordeñana was seeking to find out if “wide ranging animals” like bobcats, coyotes or deer were in the park; he told DnA that discovering a mountain lion in Griffith Park was beyond his wildest expectations, “like finding Bigfoot.” It took 14 months of waiting for Winter to get this shot. Now this “Brad Pitt” of lions “is inspiring a new conservation movement,” says the National Wildlife Federation’s Beth Pratt Bergstrom.

Mountain lion P22 is seen prowling Griffith Park in a remote photo. Photo courtesy National Park Service.

How will animals find it?

Designers of the bridge plan to use wildlife fencing to help direct wildlife in the area to the crossing. There will also be native vegetation planted in and around the crossing.

Clark Stevens, an architect working on the wildlife crossing with the Resource Conservation District of the Santa Monica Mountains, suggested to DnA that “certain vegetation species have a scent trail” such as riparian mule, and those will be used “so that wildlife has multiple ways to get across here.”

However, in response to concerns expressed by residents of Agoura Hills, National Park Service spokesperson Kate Kuykendall wrote to DnA asking that the statement be corrected: “Although we will have native vegetation in and around the crossing, we will not be using plant or animal scent to lure mountain lions. Mountain lions, and most other larger wildlife species (bobcats, coyotes, deer, etc.) do not respond to specific plant species.” And Seth Riley, wildlife ecologist with the National Park Service, told DnA in an e-mail that “we have never planned to use scent lures on the overpass or any other crossing.”

Riley went on to add: “Clark is certainly right that we will use native vegetation for the crossing,” but that “there is no evidence that I know of that mammals are attracted to particular plants, or particular areas because of the plants, because of their smell. It is certainly true that animals use various senses, including smell, much more so than us, and in ways that we don’t understand. But there aren’t particular plants that we know will attract particular wildlife species, certainly for things like mountain lions. It has never been the plan that we are going to select particular plants for the overpass that are going to attract wildlife such as mountain lions by their scent. We are indeed going to plant native vegetation, and we hope to make the overpass feel as much like native habitat as possible, mostly visually, but we hope, eventually, in every way, including olfactorily.”

Are there other crossings like this?

Yes, there are many all over the world, built to rectify problems caused by the infrastructure building of the late 20th century. You’re more likely to find them in Western Europe and Canada, but the one at Liberty Canyon is expected to be the biggest in the world and the first of its kind in California. Check out this video from Vox about the usefulness of wildlife crossings:

Louie the Mountain Lion

Are the animals excited about it?

They haven’t told us, and Beth Schaefer, general curator at the Los Angeles Zoo, warns against treating these apex predators like cartoons.

“I think it’s very easy for us to anthropomorphize animals, especially here in Hollywood,” Schaefer said. “So we do get a very distorted view of their true nature. I think it is very possible to respect these animals and to love them for what they are.”

However, we have a feeling these inbred mountain lions will be eager to find new mates and fresh food.