Dogs have the EXACT OPPOSITE instinct, than cats = they DO NOT want to eliminate over and over in the *same location* they want to use DIFFERENT locations and both make & female may have a tendency to MARK.. Aside from the foolishness of this “IDEA” is the fact, that the high sides (to help HOLD the litter of any cat pan) will make the dog be forced to jump, over and over & over, all day long, every day, 365.
NEWS FLASH: Chihuahua are not BUILT for jumping and are prone to slipped patella (kneecaps) and torn ACL. so asking the dog to do something NOT NATURAL to its behavior will also end up costing you $$$$ in vet bills you do not need to pay…. if you will just housebreak it to eliminate it OUTSIDE the home.
Pee pads are only going to TEACH the dog it is okay to GO inside the home and they will… anywhere and EVERYWHERE – not just on the pads (since dogs do not see ANY DIFFERENCE between the pad – on the floor, and the plain floor). BTW, the absorbent material in the pads is TOXIC to dogs – if chewed/ingested.