In my experience there are areas where conditions are similar to known active areas, one could call them 'squatchy', but just like Maine looks like Oregon, they are very different with respect to flora and fauna. But repeat trips to these "squatchy" areas have not produced any evidence they are active. I pretty much have discounted wood sign: crossed poles, snqp off, tepee looking constructs etc. Not that they could not be sign but simply because when I had an active area going, nothing of that nature was evident in the area. I can only conclude that such things are regional in nature or perhaps creations of a tribe of BF into making things. Human presence may be the difference also. A reclusive tribe of sentient beings may be full aware that if they built a tepee structure, for whatever reason, that is evidence they are around. My former active area was fairly active with humans recreating with some seasonal human presence. Perhaps my BF tribe decided that they could not risk such construction because it gave them away. Where as deep in Skamania County, and human presence is rare, BF may well do things with wood structures. I cannot shake the gut feeling that deep in the National Forest in some of the designated Wilderness areas, there are literally villages of BF, back in some remote canyons. There are tantalizing, signs of trails visible from the air in remote forested areas, that are not on any map. Close looks from the air, do not reveal any sign they were made by man. But it is hard to tell from the air. Log roads 75 years ago were not what they are now. It takes boots on the ground to really know. That would be a good project for a young active researcher. Take satellite images, compare known trails and roads on USGS charts to the images, and go boots on the ground to find out what is really there if the USGS does not know something is there. Satellite images have reaped many discoveries in the last few years. Unknown ancient villages, unknown pyramids in Egypt, and lost cities in the Amazon. Why not bigfoot trails or villages?
Vocalizations are very rare. Otherwise we would have hundreds of recordings. Tree knocks cannot be counted on as evidence of presence. Some of both are us, thanks to BFRO. Some are natural. Several knocks I have heard turn out to be a tree knocking against another now and then when a the wind gust moved it. Now and then a spastic woodpecker will get me going. Oh I check them out, but they have never led to anything.
But my experience with active areas; there are a few things in common:. Running water, year round, or nearly year round. Lots of cover. Presence of deer and/ or elk. At or near the snow line in the winter. Footprint finds are the gold standard of active. An active area will reveal footprints finds if you get into the field enough when the ground is soft enough for them to be left. If a BF left a footprint, it was there, at least that time of year.