answer:It’s extremely unlikely that we would not know about a large land mammal at the top of the food chain. When we find undiscovered species, it’s usually of humble things like bladderworts or fruit flies. Occasionally, you’ll hear about small lizards, mammals, or birds. The Bigfoot legend almost certainly relates to sighting of ordinary bears, or perhaps moose or other large mammals. If you’ve hiked in the woods, you know that your spatial orientation can get screwed up. Things can look more distant than they are, or closer than they are, or can appear to be something they’re not. I once encountered what I first thought to be a horse while singletracking in the woods – it turned out to be a big dog. Fortunately, it was just lost and very friendly.