Cat Suddenly Aggressive Towards Sister After Move - Please Help

[agorman1000]

I was having some issues with family that resulted in an emergency relocation of both myself and my cats to a friends place. I have one boy and one girl, presumably from the same litter (they were found in a dumpster inside a box together), but as soon as we let them out of their crates, the boy displayed immediate aggression towards his sister. His sister is hiding in a crevice under a dresser and her brother keeps walking over and sticking his head in to hiss and growl at her. She isn’t reacting at all as far as I can tell, aside from being very stressed, but he is actively trying to initiate a fight with her.
They have never had any problems before this except once when she smacked him too hard and he stayed mad at her for a couple days. I’m going through a lot right now and this behavior is just worrying me more. Is there anything I should do? Because I’m not sure whether I should wait it out and let him figure out it’s her, or if I should try to find a way to separate them so he leaves her alone while she adjusts, and so on. I’m very worried about them, I had no time to prepare them for the move and I don’t have a lot of familiar things here aside from my suitcase and backpack.

 

[abyeb]

I think a lot of this could be caused by stress from the move. Cats usually do better if they’re introduced to a new environment slowly; one room at a time. A Feliway diffuser could also help. Feliway mimics feline pheromones, which helps cats to relax. You could also try separating the cats, and then reintroducing them when they calm down a bit.

 

[agorman1000]

Yeah, I’d been hearing about the diffuser so I did order one, but that can only become a solution in a couple days when it shows up. They’re pretty much trapped in one room until then though, unfortunately there aren’t other places for them to wait since there are other pets in the house as well as other people...
I’m just worried that the situation might escalate. The girl is getting more comfortable here and she seems to recognize her brother (she keeps approaching him in a non-threatening way), but now he’s resulted to batting at her, hissing, spitting, and growling. I think he’s reading her comfort as her threatening him? I just don’t know if it’ll be okay to keep them in a room together overnight like this or if I should just force one of them into another room.

 

[rubysmama]

Hello and welcome to TCS. How are things today?

You may have to separate them and do an "introduction". Here are some TCS articles that may be helpful. Good luck.

How To Deal With Non-recognition Aggression In Cats
How To Fix An Unsuccessful Cat Introduction
How To Move With Your Cat To A New Home In A Safe Way