I don't know......there was an article on FR a few months ago that claimed that when cats bring you dead animals, they are actually trying to teach you how to hunt. Or, to put it another way, they are commenting on what a terrible hunter you are.
LOL! I'd have to disagree with that article then, as Spooky was hanging out with me in the garden shed today while I was skinning a buck that I bagged last week. She regularly accompanies me while I skin and butcher, so maybe she is simply trying to keep up with me when she leaves her mice. ;-)