Why is my neutered cat suddenly aggressive and hissing outdoors?

Thanks for using Petco Pet Education Center, formerly Petcoach! On the whole, I’m not worried about this yet. It can take a couple weeks to feel completely normal after a neuter, especially in adult males. If you have pain medication still, go ahead and give it as even mild pain can cause some cats to be a little crankier than usual. Sometimes, a long trip to the vet or anesthesia seems to disturb cat relations and anxiety is more of a problem. If this behavior is not improving with pain medication, or persists for another week or more, consider these anxiety-reducing home helps. -Feliway- calming cat pheromone- comes in many forms from pet stores or online. 

- Adding a litter box. Studies show that the ideal number of litter boxes for a home is #of cats +1 . This is regardless of how clean you keep his current litter box.

 -making sure he has plenty of “high space”. The safest (and therefore least anxiety-inducing) place for a cat is up. If you don’t already, get a cat tree or put up a shelf or two that he can go perch on. Best wishes to you and Gus!

That is unusual behavior so he may be irritable from being in pain. Outdoor unneutered male cats often fight and he may have an injury you can’t see which is painful. I recommend confining him to another room until he calms down so no one else gets injured, and see if he is eating normally. If this behavior continues please take him in for an exam to check for a wound or area of pain. In addition I would consider neutering him also. Neutered male cats seldom fight, they are more docile and less aggressive. Thanks for using Petco Pet Education Center, formerly Petcoach to help you care for Timmy.

It can take several weeks for testosterone levels to decrease after neutering. Until then, consider using a pheromone product, such as Feliway spray or plug in diffuser, to decrease any anxiety or aggression in the home. Provide extra litter boxes, bowls, toys and bedding to prevent food aggression or resource protection.

You should have him checked, or rechecked, by your veterinarian. Neutering typically does not result in more aggressive behavior. Additionally, any sudden behavioral change can be due to illness or injury. Once medical causes have been ruled out, you can focus on behavioral issues. Consider a pheromone product, such as Feliway Spray or plug in diffusers, to help decrease anxiety or aggression. Provide additional litterboxes, bowls, toys and bedding to prevent resource protection. You may have to separate them for a week or two then gradually reintroduce them while employing the measures described above.

I'm sorry to hear this! I know how frustrating behavioral issues can be! This sounds like Tatty is behaving this way out of stress. Stress can result from a underlying medical issue among other things. Inappropriate elimination (peeing or pooping outside the litter box) in cats can be frustrating and difficult to treat. The first step you should take is scheduling an appointment for your cat to see a veterinarian. A lot of times a cat will start going outside of the litter box due to health problems like urinating tract infections, pain, urinary tract inflammation and digestive problems. Once you have established that there aren't any medical reasons for inappropriate elimination the following may be helpful: 1. Cats will urinate or defecate outside of the litter box for stress related reasons. Therefore it is best to keep the litter boxes in several different, quiet areas of the household. This may also help reduce Tatty's stress level. 2. A pheromone diffuser like Feliway can be quite helpful. This can be very useful when a cat is showing agression like Tatty. 3. Ensure you have at least one litter box in the household per cat plus one. For example, if you have 3 cats, then 4 litter boxes are recommended. 4. Feeding an all canned food diet can help if there is inflammation in the bladder. There are also prescription diets available to help with bladder inflammation or digestive issues. Your veterinarian can help you choose the best one for your cat. 5. The litter boxes should be cleaned once to twice daily and completely emptied and washed weekly. Most cats prefer litter to be the clumping type that is kept a few inches deep. Certain litter types like Dr. Elsey's Cat Attract litter may be helpful. 6. If you are still having problems after taking the above steps you may want to talk to your veterinarian about behavioral medication. Thanks for using Petco Pet Education Center, formerly Petcoach and good luck to you and Tatty!

It is not likely because of a female in heat. What you describe sounds more like he is running away from an itch or pain. Some cats act like that when they have fleas. If you are not doing flea prevention, it may be a good idea to do so. You may also want to check if there are any painful areas on his body (especially where he licks himself). Also check for flea poop (part the hair in the area near the base of the tail on his back and abdomen for little black specs). If you find little black specs of poop, flea prevention is in order. If you find an area that hurts him, you should take him to a veterinarian for an exam.

I'm sorry you're having this situation!  It increases the stress for everyone when inter-cat relationships are aggressive.   While uncommon in neutered males, sexual aggression is still possible. Here is an interesting article from Tufts university regarding this issue.     I haven't personally run into this in my practice, but I have heard of Boar Mate spray being recommended.  Sometimes anti-anxiety medication such as fluoxetine can also be helpful when given to the aggressive cat.   Talk to your veterinarian about specific recommendations for use. http://www.tuftscatnip.com/issues/22_1/feature/Understanding-Feline-Sexual-Aggression-222-1.html