Hmmm, if your boy's urine reeks that much I would question how successful his neuter was. Normal cat pee (Savannah or otherwise) is not horribly smelly, but an intact male's urine is about the stinkiest thing you can smell. There is a possibility that he had an undescended testicle they didn't find, or even left a piece of his testicle behind when resecting it. If so, the outside cat could be triggering his hormones, leading him to urinate inappropriately. I believe you can run a blood test to check hormone levels to confirm this one way or the other -- ask your vet when you see him tomorrow.
As the others have said, you need to thoroughly clean the spots that were peed on - that means soaking that mattress and chair pad all the way through (believe me, the urine soaked all the way through). Follow the directions on whichever product you purchase (both products that Pam mentioned work quite well) and repeat if needed.
Of course none of this will accomplish anything in the long run unless you remove the trigger(s), which sounds like it means removing the cats outside. If these cats don't belong to anyone consider trapping and altering them - check with your vet or local animal shelter to see if they have a TNR program so that it doesn't cost a fortune. Use the Fabuloso or other cat deterrent to try to keep the other cats away. Hopefully the behavior will resolve on its own in time - believe me, I know how frustrating this can be for you!
As the others have said, you need to thoroughly clean the spots that were peed on - that means soaking that mattress and chair pad all the way through (believe me, the urine soaked all the way through). Follow the directions on whichever product you purchase (both products that Pam mentioned work quite well) and repeat if needed.
Of course none of this will accomplish anything in the long run unless you remove the trigger(s), which sounds like it means removing the cats outside. If these cats don't belong to anyone consider trapping and altering them - check with your vet or local animal shelter to see if they have a TNR program so that it doesn't cost a fortune. Use the Fabuloso or other cat deterrent to try to keep the other cats away. Hopefully the behavior will resolve on its own in time - believe me, I know how frustrating this can be for you!
on the floor so I thought I would try this new litter from Blue Buffalo called Herbal Attraction...it's all natural. It really worked! Nothing on the floor!
It will probably work with cat urine too!