There's only a couple of these Caltrans "Watch for Wild Animals" signs placed in the north/southbound directions of the State Route 23 between Thousand Oaks and Moorpark but many of you may have noticed them. According to this Caltrans District 7 article from 2009, the signs were placed as part of a mitigation plan after a road-kill study done prior to widening of the highway.
Caltrans counted 222 road-kill in a three year study and decided to do something about it, including setting up 12 one-way wildlife gates, cleaning out culverts to allow for animals to cross underneath the highway, increasing the height of fencing to prevent animals from hopping over, and placing these signs to alert motorists.
In other news, last night a black bear was struck and killed on the 101 freeway near Lindero Canyon, which according to the National Park Service was a bit unusual as there are no bears in the nearby Santa Monica Mountains. It must have come from the Santa Susana Mountains. In any case, perhaps we need some of these "Watch for Wild Animals" signs on the 101 too! Or at least provide some glow-in-the dark jackets for brave animals to wear who dare cross the 101 freeway at night!