madurobob
Philosopher
The Bigfoot stay invisible, because the United States in particular, is filled with morons who own guns and go out into the woods on weekends to look for something to shoot.
Actually, those morons who go out into the woods? Yeah, they're sitting very quietly in the forest listening to every sound. They remove all UV brighteners from their camo clothes and they bathe in soap that is free from all perfumes and removes their natural human scent. They do all they can to be "invisible" to the eyes, ears and noses of everything else in the forest and they sit perfectly still and listen for hours at a time.
I can't really expect any intelligent comments here. Reason being is that you guys appear to have absolutely no field experience in listening for invisible people in the forest. I do.
I actually have quite a bit... see above.
Please be very careful wandering around on private property searching for invisible bigfoot ninjas during hunting season. I would not be surprised if some of your "encounters" were simply disgusted hunters making their way to another location since you spoiled the one they were in.