I think bone may be too hard for a shredder
, bit too much like stone. Wood remember is fibrous.
Probably better to burn them in a wood fire.
Perhaps save for a while in a fox-proof container where the ants can clean them and then when you have a good load, have a proper wood fire in the open and when the first load becomes a barbeque, add the bones and cover with a fresh layer of wood, repeat the fresh layer until the bones are no longer visible amoungst the coals.
Hopefully whats left will be wood plus bone ash.