I had some West Highland White Terriers that were superb ratters...also had a doxy cross that was awesome. Gracie, my English Shepherd is just as good, but she's bigger so she can't fit in all the little paces they could get in.
Mine didn't stay in the house - but I did have a nice secure pen for them. They did justify their existence by meeting/exceeding their weight in dead rats, lol!
sandy soil with drought and heat can make for a very tough environment for either an earth worm or a compost type worm (which lives in organic matter up top).
i have a similar problem here in some gardens because they are almost all clay (with just a little sand). it is not the best habitat for worms, but what i've been doing which eventually does establish a worm population is dig fairly deep holes and put organic materials down deeper so the worms have a place to go when it gets either too hot or too cold up top.
in a primary sand garden soil i will always add a small amount of clay to help hold nutrients, water and this also makes the organic materials stretch further.
gardens and areas here that used to have no worms at all are now showing signs of worm life and i can find worms when i did in gardens i've been working on, but it takes a few years before you may see results.
remember when you transplant worms from one location to another that the adult worms will not often survive such a move. the tiny worms and worm cocoons may eventually take and you will then see them after they've grown up a bit and have adapted to your soil/conditions. but still you won't have worms if it gets too dry or too cold because they'll want to go down deeper or may not survive.
transplanting compost worms into sandy soil. not likely to go that well. make sure you have some logs and piles of organic matter on the surface for them to inhabit and make sure those are kept wet during dry spells. also like someone mentioned add the compost worms to under your rabbit hutch. they'll take off if that is moist and kept from the animals getting all the worms.
i keep worms in buckets indoors to avoid the predator issues.