Mountain Lions Push US to Build World's Largest Bridge for Animals

A mountain lion unable to find a mate after getting stuck in the middle of a Los Angeles freeway has inspired officials to build the world's largest wildlife overpass.

Perspective drawing of the completed Wallis Annenberg Overpass. Photo: National Wildlife Federation — Perspective drawing of the completed Wallis Annenberg Overpass. Photo: *National Wildlife Federation*

Mountain lion P-22 is well known to Hollywood stars, who sometimes see him roaming the neighborhoods near Griffith Park in Los Angeles. According to Beth Pratt, director of the National Wildlife Federation in California, P-22 survives in a much smaller space than any other male mountain lion, just 8.5 square miles (20.7 square kilometers). Mountain lions typically have a territory of 150 square miles (241 square kilometers).

Because P-22 was so beloved, people wanted to help the mountain lion and others like it cross the six-lane 101 Freeway in Los Angeles. The idea of building a wildlife overpass attracted a lot of interest, but funding was a major issue, so Pratt knocked on doors in the area asking for donations. Donations from celebrities including Leonardo DiCaprio, Rainn Wilson, Barbra Streisand and David Crosby, as well as support from South Los Angeles residents helped make the project a reality, CNN reported on October 8.

Some 300,000 to 400,000 cars will pass under the Wallis Annenberg Overpass a day when it opens in two years. The bridge includes specially designed sound barriers, along with natural sound barriers from tall trees and roadside vegetation. Everything is designed to filter out highway noise, as most animals are spooked and turn away if the environment is too noisy. Engineers also took into account animals' fear of bright lights. "All the headlights are a deterrent to wildlife. We designed light barriers not only on the overpass but also at the entrance so that animals don't get spooked and run away," Pratt said.

The Wildlife Overpass is a public-private project led by the National Wildlife Federation in partnership with the California Department of Transportation. About half of the $100 million cost came from private donations, including $26 million from philanthropist Wallis Annenberg. The National Park Service spent 20 years studying the exact location for the bridge. Ultimately, they chose to build the overpass over the Ventura Freeway and Agoura Road in Liberty Canyon in Agoura Hills, California.

Wildlife overpasses were first built in France in the 1950s and have been used across Europe, with the Netherlands being particularly popular. In Canada, a series of bridges and underpasses in Banff National Park have been a success. The wildlife corridors run above and below the massive Trans-Canada Highway that bisects the park. Many large animals use the system, including grizzly bears, black bears, moose, and mountain lions. The system helps grizzly bears maintain their populations by providing access to mates on both sides of the park.

Puma P-22 when alive. Photo: National Wildlife Federation — Puma P-22 when alive. Photo: *National Wildlife Federation*

That’s what needs to happen at the Wallis Annenberg Overpass, where the highway bisects the local mountain lion habitat. About 1 to 2 million large animals die on U.S. roads each year from vehicle crashes, according to the Federal Highway Administration. Pratt says the numbers are incomplete because they only include reported collisions.

In addition to its vast expanse, the 61-meter-long, 50-meter-wide Wallis Annenberg Overpass differs from other wildlife bridge systems in that it contains an ecosystem above it. A nearby plant nursery grows native fire-resistant plants that will cover the bridge’s surface. Invasive, flammable plants such as black mustard will be removed from the area.

P-22 didn’t live to use the overpass he inspired. In December 2022, just months after the National Wildlife Federation and the California Department of Transportation broke ground on the bridge, the cougar died. But Pratt said he had lived long enough for a mountain lion. His story will ensure a future for other cougars in the area.

An Khang (According to CNN )

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