The only bits my cats leave are pieces of the digestive tract - I don't know the...

The only bits my cats leave are pieces of the digestive tract - I don't know the first thing about anatomy but it looks like kidneys and intestines. They've only caught a few things big enough that they can't eat it in one sitting (or they try anyway and throw it all back up)

"Fortunately" squirrel screams are the worst so I can usually rescue them before the meal begins. Literally just happened 20 minutes ago...