Some dogs exhibit the unusual behavior of walking or digging in a cat's litter box. Other dogs actually seek out the litter box and eat any available cat feces (Coprophagia). The smell of the litter box initially alerts the dog to its presence but when he develops an appetite for cat feces, he will return to the box to see if he can find a treat. A few techniques might just help keep your dog out of the litter box.
Instructions
VetInfo.com suggests removing cat feces from the litter box as soon as your cat eliminates. Keep a litter scoop handy and remove the cat feces, flushing it or placing it in a small zip-type plastic bag to eliminate the smell before disposing of it in the trashcan.
Visit your veterinarian to rule out an underlying disorder. Although eating cat feces is a common behavior in many dogs, malabsorption can result in excessive hunger in a dog. Dogs receiving corticosteroid medications or those with intestinal parasites can become unusually hungry, leading them to seek out the litter box.
Trick your dog's sense of smell. Cats often eat foods high in protein and meat products and some of it doesn't digest, resulting in cat feces that attract the dog. Some dog owners have luck by sprinkling a small amount of meat tenderizer (monosodium glutamate) on their cat's food, making the smell of their feces disagreeable to dogs. In addition, pet food additives made with alfalfa can alter the smell of your cat's feces. (See Resources)
Raise the litter box or put it in a separate room, accessible only through a small cat door. Cats can easily jump up to a litter box that sits on a shelf out of reach of the dog --- but it is more difficult to keep clean.
Keep your pooch occupied with dog chew toys or frequent walks if he gets into the cat's litter box just to dig and watch the litter fly. Some dogs relieve anxiety and boredom by digging --- a litter box provides an attractive spot.