Yep, we have a Good Nature A24 – https://goodnature.co.nz – which is an automatic, CO2-powered rodent-killing machine. Basically they stick their heads up inside a tube in search of food – there’s chocolate-flavoured rat-nip (lure) up the top. They nudge a wire trigger and the gas-powered ram smacks them in the head like a bolt gun. Resets automatically and repeat. Works brilliantly.
Ours has now done for 28 assorted rodents since May, so while the initial investment is steep, the price per dead rodent is falling. The crawl space will be shelter, but they have to find food elsewhere. Unless your floorspace has a concrete slab base, they can simply dig in under the foundations, but yeah, block the obvious existing access. Remove any food sources – bird feeders included, or at least minimise any spill from them – then kill the little bastards.
I wouldn’t use poison, apart from the risk of them dying somewhere inaccessible and stinking while they decompose, you’re putting a toxic chemical into the environment and potentially other local wildlife and pets. Rats are too big to dry out quickly apparently, though that’ll work with mice.
Traditional traps are a bit messy – we have a few lying about if you want to try them, just shout – which is why we got the A24. It’s very effective and kills them instantly, which is relatively humane and something that most conventional traps fall short on sometimes.
Shout if there’s anything else I can tell you. We have coffee too.