It might've been kids skulls they probably pulled a red riding hood but instead of like throwing them in the woods they just ate them(i think it was red hiding hood)...there was some kids in the credits concept art i think.
I reckon they don't give a crap what they eat as long as its food, i think they try to act civilized but they just fail at it really hard and also they can't cook for **** they put live chickens in the oven without plucking them.They could be cannibals though remember that guy who pops out the oven on fire?Didn't look like a nice simmer it was probably a prank lol.