On the other hand, rats (especially of the size you're talking about, barely larger than field mice) are not nearly so dangerous as wild dogs, and much more common, so if you prefer to live-trap them and take them across town, hey, whatever. Somebody will probably call an exterminator on their offspring sooner or later, but it's not like you're introducing something that wasn't around in fair quantity already. Once you've got rats on a given continent, you're pretty much always going to have rats. That is to say, a "conservation status" of "least concern" is generally another way of saying, "we probably couldn't cause the extinction of these things even if every human on the planet agreed on it as a goal."

Our current cats are kept indoors & in our screened courtyard (for their safety and that of the local wildlife), so they only get to hunt the occasional lizard or grasshopper that foolishly blunders into their lair.

The problem with most house cats is that they're too soft, they've had such an easy life that they lack the killer instinct of, say, a real working farm cat. But then, you'd not really want a mean old farm cat as a pet.

One of my cats brought in an immature brown rat once, and had no idea what to do with it once it was indoors. We spent a day chasing it about under the fitted kitchen cabinets before we could get rid of it. They're completely different from the more usual mice, shrews and voles, fearless and aggressive, and incredibly fast. Really hard to catch.

I have to say that I do think that you should really get the rats destroyed rather than releasing them. I don't know about your area, but in some places it's illegal to do otherwise. For all that I think rats are amazing animals, and domesticated ones make great pets, they are destructive vermin, not to mention the fact that they are host to all sorts of entertaining pathogens that you really don't want to expose yourself or anyone else to.

Dan, you want to be rid of those creatures.

You're most unlikely to have caught a native rat (Rattus fuscipes) - they are extremely shy and prefer dense bush to suburbia. Feral cats and competition from black rats (Rattus rattus) and Brown Rats (Rattus norvegicus) have made them moderately rare anyway. So your rats are almost certainly another gift from Europe to the Australian environment.

Exterminate the brutes, I say.

Rat terriers do indeed seem to be good for killing small vermin. Some friends of ours have 3 that kill more than their 4 cats. terriers also have a tendency to be less. . . generous. . . than the cats. Which is good, because you don't have to worry about small, cold bodies in the sheets.

Every now and then, though, you get a dud. Our rat terrier, Jake, is absolutely terrified of mice and gophers.

Oh yeah.. rats... rats... Yeah, I suppose see what they think of the litter pan! Sharp idea!