I've got a suspicion!

The beast doesn't actually exist as a biological, magical or any other physical entity. It is there mere fact that all believe there is a beast that drives people crazy enough to behave in quite unusual ways, causing other people to think 'there's something really wrong here! Maybe he or she is posessed ?' and explaining it with your typical default approach: 'There must be some kind of evil in these woods!'. This in turn leads back to square one.

Proof ? None. Slight indications that would be in accordance with said theory ? Hell yes!

[sub]Please don't take it seriously![/sub]