I know some folks who feed a lot of squirrels from the UK and their ferts do well on them. If you are worried about parasites then freeze for two weeks or longer. I agree with everyone else; a conversation with a local wildlife authority will set your mind at ease.
If I had access to them [no squirrels in this country] I would feed the same way I feed rabbits; guts out, fur left on. The ferrets will easily be able to deal with a squirrel; mine eat predominantly wild caught rabbits, which have pretty dense bones. They leave the bones from the back legs and the thickest part of the spine; everything else gets consumed, including the head.
I just cut mine in half and pop out the stomach and intestines (they stink if left around ), but I leave their fur on. I find that they have no interest in eating them (dragging them around maybe but not eating them) if I leave them in their altogether. I know, my brats are spoiled. ciao
It would be nice wouldn't it. My guys have funny quirks about size too. It's like they can't be bothered. Maybe, they know deep down inside their sneaky little hearts that we would never in a million years let them go really hungry. Spoiled ciao