Decent people need no sign.
The sign is meant for indecent people, but fails because it tries to perpetuate people that shouldn’t be on the trails in the first place.

For example:
Normal people know you do not disturb 1200 pound horses, and you stay out of their way. No sign is necessary.

If you are intellectually challenged and you try to engage a large animal it may stomp a mud hole in your ass and commence to walk it dry. Thus, darwin is the great emancipator of humanity and the problem is solved.

For millennia nature has been a perfect teacher.

(let them eat pye)