I cracked open a pork rib with a hammer lengthwise, and put it in the 'tat yesterday evening. Just went to take a look...and found it sticking straight up but pulled down into the substrate an inch and a half. I pulled it back up, and found the bone marrow just gone from the lower half inch and a bunch of scratches on the bone - and a tunnel away from where it was pulled under.
I know they drag food and bury it for later - I didn't think they'd try to do it with a bone, though. Maybe I should have named one of them Fido!
