Why is my unneutered outdoor cat suddenly aggressive and attacking us?

Hi and thank you for your post on Petco Pet Education Center, formerly Petcoach! These can be common behaviors in male cats that are not neutered. I would recommend neutering him soon to help decrease these behaviors a bit. In addition, neutering him will help lessen the risks of cancers later in life as well as help decrease the feral cat population.

Hi and thanks for using Petco Pet Education Center, formerly Petcoach! Sorry to hear about Snoopy. You only have a few choices here I believe. Neutering him would hopefully lessen his aggressive behavior. Another choice would be taking him to your vet and letting your vet screen him for a medical problem which could lead to abnormal behavior. Your vet can run tests (blood, urine, x-rays) to rule out medical disease. If a medical problem is ruled out, neutering and drug therapy could be used to try to lessen the aggression. Cat bites/scratches are very serious and this is a serious problem. Someone can get injured quite severely especially if they are immune compromised or have diabetes and suffer a cat bite. Another concern is rabies. Rabies causes aggression in animals along with other forms of nervous system diseases. It's important to get him evaluated as soon as possible. Good luck with Snoopy.

It may be a hormonal problem so the first thing you should do is have him neutered. Your cat may also be redirected his aggression on to you. Redirected aggression occurs when a cat experiences something that is over-stimulating or highly arousing or something that causes fear and the cat redirects their frustration, aggression onto whoever is closest. Sometimes it can be another cat or animal outside that is causing the problem. You could also try a Feliway diffuser/spray and/or Soliquin chews and see if that helps.

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.

Getting him sterilized may help. If you are not planning on breeding him then it would be best to go ahead and do it. I also recommend you put some Feliway diffusers in your house (if you can get them in your country) and do some environmental enrichment for him. Usually these two things help redirect this type of behavior. ( https://www.feliway.com/us/Products/FELIWAY-CLASSIC-Diffuser ) ( thedrakecenter.com/materials/environmental-enrichment-indoor-cats ) ( https://www.youtube.com/watch?v=AejmrLa_Cs4 )

I am sorry to hear about your concern for Tumbles! I would suspect he smelled another male cat's urine/marking which got him excited/worked up. If it becomes a routine issue you can consider using Feliway multicat products https://www.feliway.com/us/Products/FELIWAY-MultiCat-Diffuser

That must have been very scary for you! Yes, I would be very concerned about Boo Bear attacking you viciously, especially if this is out of character for him. I'm not sure what his vaccination status is, but (not to scare you but to put the fact out there), sudden aggressiveness can be a sign of rabies. If he isn't vaccinated against rabies and is allowed to go outdoors, then I would be concerned rabies is a possibility. I would take him into a vet immediately if he isn't vaccinated and allowed outdoors, and you should see a doctor as well as soon as possible. Cats have a lot of nasty bacteria in their mouth, and you can get a terrible infection from the bite. You need to be on antibiotics now to prevent this. Other causes of his sudden aggression could be hormone related (I see he isn't neutered and he could be acting territorially), or a medical illness such as pain, an injury, or systemic illness. If he is up to date on his rabies and isn't allowed outside, then I would take him to the vet first thing in the morning. He should be examined by a vet to make sure there isn't a medical cause behind this sudden aggressive behavior. If it is hormone related, then I would have him neutered to help with that.