cat suddenly starts biting stuff and growling (at other cat?)

[LeChat]

Houston, I have a problem.
Hi all. So I have two cats a 2y old boy and a 6y old girl. I got them in that order. They usually get along very well. They are both spayed.
Since a month or so ago, the boy has started behaving a weird, he'd sometimes bite into sth strongly (usually one of the toys or a blanket) and start growling and even hissing. He often seems to provoke the girl, he'd look at her or even take the toy closer to her. If I try to take him away he keeps growling and biting hard like a mad dog...
He is usually a very friendly and curious cat, but seems to be turning into Jeckyl and Hyde.. what's happening

[lilynmitz]

For sudden changes in behaviour like this I would recommend a vet visit. This can be an indicator of pain or ill health, and he's just taking it out on your other cat. (Imagine how grumpy we can get when we've got a head ache).

Otherwise, are there any changes in your household that might be troubling him? Try to see his world from his view point and address any changes. Getting a Feliway diffuser in might help.

Also, are there any new cats on the block, resulting in a re-ordering of territory? Cats can find this very stressful too.

But, vet visit first - if there is a physical issue waiting to sort out household/territory issues first could lead to unnecessary delays and further suffering if he does in fact need vet attention. With these issues, soonest caught, soonest mended.

[LeChat]

Thanks for the reply. I will consult a vet. But I doubt he has any physical problems, but yeah, maybe I can't see it.
I also wonder if it's not a hormonal issue, even though he's neutered..
There are no changes in the environment, and they are indoor cats (4th floor of an apartment house)

[fjm]

If you are in an apartment block, have there been changes amongst the neighbours, perhaps another cat or a dog moving in? Cats have much better hearing than we do, and he could be picking up noises or scents that are not apparent to you. But in the absence of any obvious source of upset I would start by ruling out a physical problem - animals hide pain well, and often the only sign is grumpiness or hiding away.

[LeChat]

Hello, no, I haven't noticed any changes.. (we seem to be the only ones with pets)

[lilynmitz]

I agree, given absence of changes in their environment it's most likely a health issue. As fjm says, cats are very good at hiding ill health and pain, and changes in their behaviour are often the first indicators. Let us know how you get on.

[LeChat]

I see.
Another issue I have with him is that he sometimes gnaws stuff like rubber mat (put it away by now), and recently even his toys like plush mice. In the morning I sometimes find that he did that and puked it all over the place...

[fjm]

Have you checked his mouth and teeth? Chewing and biting can be an attempt to soothe sore gums.

[LeChat]

Mouth seems fine, he actually hasn't done any of the things the past few days, hopefully things are getting better.
Except, he has diarrhea now I was thinking it might have been caused by sth he swallowed, but not sure, he had it last year for a few months as well (maybe the season change affects him?)..

[LAR]

Has he had a rabies vaccine recently? I have heard from many pet parents that soon after a rabies vaccine their pet became extremely aggressive. If not, I would say that kitty is in pain. Can you check his mouth/gums? Is he going to the bathroom and eating okay?
Does he chew on plastic or string or try to eat odd items? (besides the litter mat haha)

[LeChat]

Has he had a rabies vaccine recently? I have heard from many pet parents that soon after a rabies vaccine their pet became extremely aggressive. If not, I would say that kitty is in pain. Can you check his mouth/gums? Is he going to the bathroom and eating okay?
Does he chew on plastic or string or try to eat odd items? (besides the litter mat haha)

Hello, nah, no vaccine recently. He does chew on his fluffy toys, but his stool and eating are fine and he really doesn't seem to have any pain. It's become more rare recently, though every now and then he still does it.