You could get some really sexy, well trained lab rats (from Monkeyface), insert them into your dry walls and wait until the remaining rat shags itself to death. Then collect the sexy lab rats and get rid of them, since they might have been impregnated by a super rat that survived poison.
Alternatively, you could play the most annoying music you can find and wait until the rat commits suicide.
Here's a contender (put it on loop):
Have you politely explained to the rat(s) that this is your property and that you'd like for them to go elsewhere? You can post signs for them. We have a faux-officious "NO GEESE ALLOWED" sign to keep the Canada gooses away at work.
Singaporean chick at the sauna caught a rat today too, she drove across the river and let it out. Then two other girls started talking about a children's rat book which caused me to lose my breath, my face is still red, and had to leave the sauna earlier than I wanted to.
Our rats are not as big as the monstrosities you see here. Probably because everything here is full of chemicals. I once was waiting for the bus in Miami and I saw a rat that instead of running was fucking jumping. Put food with a poisonous chemical in it, should do the trick. Also a cat, nothing beats a cat to keep your house clear of rats.
I think this is The Noodles Good Natured Advice thread of DW. Leland asks for advice on rats. Us knowledgeable people give advice. Leland ignores it. Ask for more advice. We give. He ignores it.
I don't know how many times we have told him that harnessing these rats for fun and profit is the way to go. Yet time and time again he insists on ignoring this advice. Just watch him reject Leitmotif's sensible advice on Crunchy Rat Meals.