Chavs, I think you did take the title too literally. Like the way you think, though.
This sign seems a little unnecessary. I mean, who doesn't know to beware of poisonous snakes? It could just as easily have said "beware of running with scissors" or "beware of live electricity."
Perhaps, though, it is referring to possible rattlesnakes on the trail to the Missouri River in central South Dakota where I took the picture.