I keep both of my cats indoors for this very reason - they might be cute and cuddly, but they are also animals of predation and the many and varied wildlife of Australia are their favourite food. I don't want to see them collected by the front end of some a$$hole's ute, but I also don't want to see them chowing down on a tiny sugar glider or a bird or a native mouse or anything.
Anyone who says "but it's unnatural to keep cats indoors you're a monster" can feel free to take a sugar-frosted...screw... off the end of my sizable crotch implement. It's RESPONSIBLE CAT OWNERSHIP to have them spayed/neutered, registed with the local council, and kept indoors where they're safe from harm but also away from being able to cause environmental damage. If it's "natural" for a cat to be forced to scavenge to survive, and have a short unhappy pain-filled lifespan filled with injuries, infections and accidents, not to mention the constant threat of starvation, then I guess I want my cats to have as unnatural a life as I can possibly create for them.