DAN HOLDSWORTH: Cat Matters

Recently I experienced a bit of a problem with one or two neighbourhood cats which were engaged in a literal pissing match, partly involving my back yard. A new, pure white[1] cat had recently arrived, and was trying to establish territory by scent marking; the residents were resisting by similar methods.

Faced with a back yard reeking of cat pee, I at first tried scent deterrents, making my back yard at first reek of Jeyes Fluid, then of garlic essence. Neither worked for long, and nor did lemongrass oil, or citrus oil (though the yard smelled quite nice). Then I tried putting one of these devices out, a couple of feet away from where a cat jumping down into the yard would land.

http://www.amazon.co.uk/Innotek-Ssscat-Cat-Spray-Deterrent/dp/B000RIA95G

The yard is monitored by a CCTV camera, so I was able to see the result. A couple of close encounters with a horrible hissing monster in the dark was enough; the pissing match has been postponed indefinitely.
So, might I suggest deploying one of these things near where you'd prefer the cat not to go? All it does is hisses loudly and unexpectedly close to the cat, which is apparently a hell of a shock for a feline, though it is otherwise harmless. They soon learn to avoid it, though, and it is less intrusive than scent deterrents.

[1] Cats in my neighbourhood have a sadly limited lifespan, mostly due to traffic. A pure white individual, even a widely ranging one, would likely live longer due to being more visible to traffic.