Not only do freeways and construction pose risks, but widespread use of chemicals, like rat poison, can also harm California's pumas.
The good news is state officials are taking note of the way human developments impact wildlife. A proposed $10 million overpass, for example, would connect cougars in the Santa Monica Mountains with those in the San Fernando Valley.
But not all changes would have to be so expensive, according to the authors of this study, like setting aside land as wildlife corridors rather than developing it. "I think there could be hope for this population," Ernest says. "They're at a point where they can be monitored and protected. They don't have to end up like Florida panthers. With early interventions, we wouldn't have to spend millions and millions of dollars later."