Nick Redfern has a new Mysterious Universe article on the possibility of Bigfoots that live in caves and/or underground. Here's how it starts:
You can see the full thing here.
"One of the most thought-provoking theories for Bigfoot's overwhelming elusiveness suggests that the creatures spend a great deal of time living in natural caves and caverns, as well as abandoned, old mines. In the early 1900s, a number of stories surfaced in the Oregon press that, upon careful reflection, just might offer a degree of support for this particularly intriguing theory that Bigfoot is very much a creature of the underworld."
You can see the full thing here.