Great thought grayjay, I had actually wondered about some sort of biological explanation for this nut job. CJD (Creutzfeldt-Jakob Disease) is a HORRIBLE disease that is essentially 100% fatal and has a very rapid onset with symptoms of gait imbalances, mental confusion, etc. It is a prion disease sort of like Mad Cow disease, but not exactly the same. Anyways, MH was a monster years ago because of the fires he started in Colorado. Therefore, I think his consumption of squirrels is related to some sort of fetish he had with squirrels, trees, leaves, and harming other beings.
I wonder if he wasn't working on his insanity defense by collecting leaves. He appears to be a planner.