"Yes - the Thing can only turn into living creatures. The way it works is that it absorbs animals and uses their mass to make a copy out of...whatever it's made of. I don't know if it can assimilate plants. It's not a chance I'd take." Not that Antarctica has much in the way of growing plants, anyway, or maybe animals just suited the Thing's purposes better.

If the Thing could turn into seemingly innocuous household objects to approach its targets, that would have made it even worse. Kinner thanks his lucky stars, whichever they may be, that's not what he's dealing with now.