Enlarge / Ariel and Caliban learned as kittens that scratching posts were fair game for their natural claw-sharpening instincts. (credit: Sean Carroll) Ah, cats. We love our furry feline overlords despite the occasional hairball and their propensity to scratch the furniture to sharpen their claws. The latter is perfectly natural kitty behavior, but overly aggressive scratching is usually perceived as a behavioral problem.