Board Thread:Speculation House/@comment-3257939-20150601205621/@comment-25396609-20151109225139

VedranTheII wrote: Minus that one stomach they have so they can digest human carcasses, like the nevermore in WOR; also a brain/cortex since decapitation qualifies as instant death, despite the fact it’s only occupied a 6th of it’s body; oh and let’s not forget taste buds that let the Ursa in volume 1 recognize sap from water. They have no stomach or they would leave behind desecated human remains when they die.

We have not seen a grimm be dismembered without death following from other causes so i don't think we can rule out all dismemberment being a kill just yet. taste buds? maybe. I'll give you that one.