We have a young male (neutered) cat who likes being outside a lot. He’s what I think is appropriately territorial in our garden. He likes to be on top of the shed keeping an eye out and staring at other cats, puffing up if they get too close and hissing etc. He’s absent from the garden a lot too but no idea where he goes.
Recently another cat (who looks a lot like him weirdly) has been taking up his spot on the shed and our cat doesn’t seem at all bothered. He’s just slinking around - no puffing and happy to have his back to him. It’s very out of character, which is concerning me a bit. But what’s also very annoying is that this other cat keeps coming in our house, eating our cats food, heading upstairs etc. I’m worried that this isn’t a great situation for our cat. Plus cat food is expensive. We don’t have a cat flap - we have the back doors open because of the weather. I’m reluctant to get a cat flap and keep the doors closed because I like fresh air and we have no obvious place for a cat flap so would have get one installed in the wall. I could probably suck up the cost of that but not straight away.
I guess I’m asking if there is a way I haven’t thought of to keep this cat away? (Currently using a water pistol but I’m not on look out 24/7).
Is another cat coming in likely to be stressful for my cat?
And, why is he behaving differently with this cat?