I adopted a pregnant stray, who couldn't prey on anything to save her life. I've seen a mouse run circles around her while she watched complacently.

Her kittens, however, have been predators since birth. They caught that mouse (at 3 months old) and are forever leaving dismembered crickets and moths lying around. Once they even ripped apart a wasp. They seem to have some sort of instinct about which critters are bad, though, because every once in a while they find a spider they won't touch. Instead, they scream at the top of their lungs until I find a shoe to smash it with.