Well, having been gone from the forums for a while, I took some time over the last hour or so, and read much of this thread.
I've got a few points to make, that may or may not have been glossed over.
1) There's alot of talk about trackways not being observed in the winter, and how if they were moving around, "it'd be easy to spot some sign of them". That's ridiculous ! Let me ask you a question... Of all the members here, how many or what percentage of us go traipsing around far off the beaten path in Winter? I take walks regularly where I'm at in upstate NY, and while I'm no woodsman, I consider myself fairly knowledgeable after doing so for most of my now 45 years. I could walk out the door now, head out across a large field that's right next to the house, and regardless of whether i walked up the left, center, or right of the field, there's a nearly certain chance I'd miss any tracks (bigfoot or otherwise), if they weren't within 40 or so yards from where i was walking. You could walk through any wooded area and miss trackways. Unless you and/or a group of people where criss crossing back and forth, or walking a spread out line, you could easily miss what you didnt see. It's not like your going to find them driving down the highway, or even on dirt back roads.
2) I dont have a theory on how they survive in Winter months. Winters are tough, especially as other have mentioned in regions where all the vegetation and trees are dormant, and there is typically snow pack for the entire winter (5-6 months).
Here in NY Ive seen winters where wary country deer (not the tamer suburban variety) came right up to our yard and ate the tops off Arbor Vitae trees because it was green, and wasnt tree twigs. Cold, windy, and some winters several feet of snow on the ground thats present for most of the winter. It takes hardy creatures to survive these winters, and sadly many times deer and other critters dont make it. They starve or freeze to death because they cant keep their calorie count high enough. So in order to be surviving during northern winters especially, its for certain that some form of shelter and an abundant food supply would be necessary.
3) As far as trackways go, the first experience I ever had with anything possibly bigfoot related, was again here in upstate NY, and no further than five or six miles from where I sit at this moment looking out a window at the woods and fields. My entire lengthy report was at one point in the premium members section, although I have no idea if it survived the server upgrade or my account being disabled and eventually terminated due to my disappearance from the forums.
Long story short- in the dead of Winter, my brother and I found a trackway one morning that to us as children appeared to be as if a large person had walked barefoot down the trail during the night. On a 135+ acre piece of land, bordered on 3 sides by thousands of acres of state forest land. My brother, myself, and my uncle, who was a deputy sheriff at the time, followed that track way for nearly a mile. Through several large fields, over a stone wall, and eventually leading up to a dark pine forest, into which none of the three of us wished to continue pursuit.
There is so much wilderness out there, whether its Alaska, or somewhere in the lower 48, and the vast majority of it sees very little human activity, even in the summer months.
To say that not understanding how, or where these creatures survive during Winter months, is reason to question their existence, is being somewhat short sighted, and based on the assumption that like most things, we know better than nature or the rugged creatures that inhabit it. We do not.