Architect Robert Rock is facing a Herculean task: Design a bridge that will allow mountain lions to cross safely over a stretch of the 101 Freeway that roars with the traffic of 300,000 vehicles each day.

On a recent morning, he stood on a hilltop and gazed at a vista of steep fire-stripped slopes, rocky arroyos, weedy humps and 125-degree grade shifts on both sides of the freeway at Liberty Canyon in the city of Agoura Hills.

The terrain was as challenging as could be. But Rock could see the future — cougars who would otherwise become roadkill crossing a proposed $87-million bridge so that they could roam, find prey and mate.

“Mountain lions are prone to wander,” said Rock, 40, raising his voice to be heard over the din of freeway traffic. “A wildlife crossing here is our best hope for keeping them from wandering into extinction.”

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