Cat has started being aggressive - multi cat household

[AnnieSaxophone]

All advice and thoughts welcome!

We had 2 cats (not siblings) that we rescued at 5 weeks old. They’re now 5 years old.

Last October, 4 kittens were dumped and rescued by a neighbour but she didn’t have the space for them - so as we have a large house and a garden and love cats, I took them in and kept them separate from our existing 2 cats and spent 6 weeks integrating all the cats. By Christmas all cats were fine with each other and sharing a bed etc.

All cats have separate microchip feeders as one of the 5 year old has a condition where she ends up needing oral steroids for a few weeks in the first half of the year. She’s on them now. No previous issues with her behaviour except she’s always ravenous! I control her portions as she turns into a hippo left to her own devices.

We went away over Easter for 10 days and a lovely friend house sat for us and looked after all the cats. The night we got back, one of the 5 year old cats for the first time ever, chased / attacked one of the other cats until he escaped under a bed. This happened about 4 times in a couple of hours so I separated her off with her own resources. My friend said it happened a couple of times while we were away but nothing major. She seems to go for 2 particular cats completely unprovoked.

We’re now in the 4th week of this behaviour and it isn’t fair on the other cats so we’ve separated her for now while we try and sort out what to do.

Is there anything we can do? Is this likely to be temporary or permanent?

Six cats sharing a space is a lot, even with separate food bowls.

You say you have a garden so I assume the cats are allowed outside too? If not, I would say that outdoor access may help so that they're not all confined inside together.

Did your friend see what set the cat off?

Are they all neutered?

I have 3 cats and they have a cat flap, multiple litter trays, food and water points.

My male cat will still chase and attack one girl cat, usually because he wants wet food or attention. I usually catch him and stick him straight outside. I’ve no solutions I’m afraid but he doesn’t use his claws, it’s all posturing and noise. Interestingly it only really started after I’d been in hospital for 2 weeks. Watching the thread for ideas!

Thank you so much for your replies - yes they’re all neutered and yes they can all go outside. My friend didn’t see what set they off.

@Biscuitandacuppa - that’s interesting. I did wonder if it’s because the Top Cat (me) was away and hence the dynamics and hierarchy shifted.

Or maybe it’s food related as the aggressive cat has monitored portions and the others have more in their bowls as they self-regulate and are much more active than she is and hence need more.