Animal activists call it a huge setback during efforts to rebuild the mountain lion population in the area.
The 150-pound mountain lion was found dead on the shoulder of the eastbound side of the freeway near the Liberty Canyon Road exit.
The fact that it was found near Liberty Canyon is significant.
Dan Cooper is a biologist with a Griffith Park project that studies mountain lions. He says the Liberty Canyon area is a popular crossing for the animals.
"Liberty Canyon is in an area of the Western Santa Monicas where there is a lot of open space on either side. You've got Palo Comado Canyon here, Las Virgenes, Chesebro Canyon, and then south of here you've got the huge open space of Malibu Creek State Park. And animals want to move back and forth," said Cooper.
Cooper says it's hard to gauge how significant the loss is. According to the National Park Service, there are approximately 10 mountain lions that live in the Santa Monica Mountains.
"We're talking about an area from Point Mugu on the coast near Oxnard, all the way through Calabasas, Topanga, all the way to Griffith Park near Glendale, so it's just a massive area that we drive by all the time. And we can count the number of animals on two hands," said Cooper. "So yes, losing one is significant. How significant? I don't think that's known right now."
If you happen to come across a mountain lion, Cooper says just leave them alone.
"They have every interest in staying out of your way. They seem to be largely nocturnal when they're foraging. They seem to stay toward areas that are away from people. The animal in Griffith Park spends most of its time in the farthest Western reaches of the park, and they've done a lot of tracking surveys in the Santa Monica Mountains, and they use the whole area but they seem to be where the people aren't, and where the roads aren't."
The California Highway Patrol says that if a motorist hits a wild animal on the freeway, like a mountain lion or a deer for example, notify the CHP, who will issue paperwork for reporting damage to the auto-insurance company.