11 years old - you did not mention if this is a new behavior or if it has been happening all along. If it has been happeneing all along, the cat was never trained to use the box, and it may be too late now, if it is a new behavior, it is possible the cats brain is having trouble communicating with its spine. This happened wth my cat. She had degenerative spinal issues, and had trouble only in old age. The thing about letting the cat is out, is one, will it return to a feral state? Will it have a negative impact on the native animal community by hunting? Will it be safe from vehicle traffic?? If the situation is the same as my old cats, this will not get better on its own.

Mazer, timing was mentioned: This has been going on for at least a year

onecatonedog: Is your small child by any chance about a year old?

I have no doubt that an 11 year old 20# cat has arthritis and/or degenerative spinal problems and chronic pain associated with it. He may be painful getting into position and now associates pain with pooping in the box. He probably doesn't experience the same pain to pee, which is why he stills pees in the box and uses it sometimes.

As far as safety with the child, I'd deworm the cat every 3 months to make sure nothing can be transmitted to the baby. Also keep kitty on monthly year round flea control.

If this is strictly a behavior problem, which I strongly doubt, then you are stuck retraining the cat or rehoming him or throwing him out of the house. Retraining usually involves confining to one room or even a large dog kennel. But I think given the weight and age of the cat, his primary problem is chronic pain. For that he needs a serious weight loss diet and pain medication.

Good luck with everything.

My first thought is what weed30 brought up. Small children can be confusing and threatening to cats. They mistake a crawling child for an animal and not a human. He may just be trying to mark his territory before this other "pet" does. I've read that once children start to walk, the behavior will often abate. Make sure your child isn't making the kitty feel harassed. Maybe even set up a kitty bedroom on a closet shelf, or some other high up area where the cat feels like it can get away from the child.

My other thought was about litter box placement. Did you move it or change anything about it at the time the behavior started? Of my last 3 cats, 2 have been extremely picky about the litter box. My new little guy will just go ahead and poop outside the box if he doesn't like the conditions. My old girl will hold everything if one little thing is out of order. A few years ago we had the litter box in a closet where we stored other utility items. DH set a very small wooden shelf against one wall, and out of the way. That one change was enough to disturb her and deter her from using the box. So make sure he is comfortable with the box situation- peeing is faster and less vulnerable than pooping. Is it possible that the box is located somewhere where the cat has felt threatened by the presence of the child while he is in it? Like in a second bathroom where the child's bath belongings are? Just a thought... He may feel threatened by the kid (or something else) in an area that he use to consider his sacred turf.

It probably wouldn't be a bad idea to have a vet check the cat out to make sure that everything is in order. It would be a shame to chalk the problem up to behavior if it was based on a physical issue.

Thanks for your advice and input. A couple comments/responses:

My son is almost four years old. He doesn't have a whole lot of interest in the cat, and doesn't chase or harass him. I think my son thinks the cat is quite boring actually. The litter box has been in the same place since before my son was born, so no changes there.

He is a big cat, and has been big since he was a kitten. He's got an overall big structure - big head, long body, big legs. The vet has told us that he's just a big guy, and doesn't seem to have much excess fat on him that could be lost to reduce his weight. However, all of this said, I would also be inclined to believe that there may be some kind of spine or pain issue going on. Hopefully my husband will find a job soon and we can give that the attention it deserves.

We do have a dog in the house - a 7 year old lab who is as sweet as she can be. The cat & dog get along great, they always have, though the cat is extremely dominant over the dog. The dog is OK with that and has never challenged him.

Thanks again for your suggestions.