L.A.'s P22 mountain lion was made famous by a National Geographic photo that captured him standing in the hills with the Hollywood sign and the illuminated city behind him.

P22 made headlines again Monday when he holed up in a crawl space under a Los Feliz home. As of Tuesday morning, he had apparently moved on, but it's not yet known where he's ended up. 

Seth Riley, a mountain lion expert with the National Park Service who teaches at UCLA, explained why keeping track of P22 and L.A.'s other mountain lions is no easy task.

"Well, the truth is, these animals -- all kinds of wildlife -- are very elusive. We know a lot about them, a lot more than if we weren't tracking them, but we still know relatively little in terms of their actual second-to-second movement," he said.

While the GPS collars provide great information, only nine locations are tracked each day, Riley said.

You can listen to the rest of the interview by clicking the blue audio player above.