Paulides and the 411 crew have been coy to the point of secrecy in refusing to offer their own theories on what is causing the disappearances in national parks.
They seem quite sure of some causation, going so far as to broadly hint at the involvement of a furry hominid race, a giant bird and other cryptids in some cases, whilst steadfastly refusing to put money down on a particular culprit in a particular case.
There is however a list of common elements by type of unexplained disappearance. and one of these elements is the disappearance of experienced wilderness explorers in areas near a lake where there are large boulders – and the presence of a “bigfoot” type (TYPE – but in other ways NOT typical of the gentle wood ape) entity.
Here is something from 1956, from the long lost JADOO work by John Keel:
“Following the hot and cold Yeti trail, I arrived at last in the northern village of Lachen, 8,800 feet above sea level, where the natives grabbed me excitedly and led me through the tortuous passes to the marsh. …
Cautiously I moved forward, staggering up an inclined path strewn with giant boulders. Finally, I emerged onto the edge of a sweeping cavity filled with water, where broken trees and decayed bushes poked up like skeletons.
That was there I saw it!”
The Keel encounter with Yeti matches many of the details of the Missing 411 “sasquatch” cases.
Keel also notes in his usual scattershot way the connection between sightings of glowing balls of light and Yeti, “crazy bears” in North American Indian folk stories, and so on.
Personally I still think some of the furry strangers are surviving “Neanderthals” who are neither primitive – nor benevolent. They don’t “come out of” UFOs dropped off by aliens – they’re the pilots. But anyway.