The Legend of Bigfoot (1976)

Wikipedia calls this a "pseudo-documentary".  Other sites don't bother to gild the lily and call it what it is: a hoax.

Back in the 70s (and even into the 80s) the reality of Bigfoot was something people genuinely debated.  Earnest research teams set out to find it, as well as the Loch Ness Monster.  Without success, of course, since they don't exist.

Or at least, so you might believe until you saw the overwhelming evidence for Bigfoot that is presented here by Ivan Marx.

BWAHAHAHAHAHAHA.

Sorry, couldn't keep a straight face.

Marx presents himself as an experienced tracker and trapper who initially scoffed at the idea of Bogfoot, but began to believe otherwise when he found a bear with its neck snapped, and strange footprints in the mud nearby.

Looking into the matter, which apparently mostly consists of ranting about Bigfoot while showing footage of real animals, Marx discovered that there were tales of this creature in many areas.  Surely such tales could not have become so widespread without some truth to them?  Well actually, Mr Marx, tales of dragons are found all over the world, and yet I am not in any danger of having my house burned down by a giant flying lizard.

Eventually Marx gets some footage of a guy in a fur suit -- uh, I mean "Bigfoot" -- and his quest truly begins.  By which I mean he shows us yet more footage of other animals while spinning ever more outlandish theories.

Why are there no reputable sightings of Bigfoot (other than his own unimpeachable footage of course)?  Because that's how Bigfoot survives, man!  By hiding from humans!

Why are there almost never any sightings of young Bigfoots (Bigfeet?)?  Because they migrate thousands of miles a year to breed high above the Arctic Circle!

Why have no remains ever been found?  Because they carry their dead with them as they migrate thousands of miles a year and bury them in crevices in the glaciers where they breed, high above the Arctic Circle!

Good news though: Marx's "research" has established that Bigfoot is vegetarian.  Except when it eats fish.  Presumably it snaps the necks of bears for fun, rather than food, then.

You'll see better nature footage in a David Attenborough documentary, and Sir Dave won't subject you to chains of logic like:

1. A native told me the Bigfoot breed where the moose mate
2. I went where he said, and saw moose
3. Therefore, Bigfoot is real

Avoid.