Besides what
@Tesumph said, this is one of my tricks.
Rats and mice can go thru any hole big enough for its head to pass through.
Cut a hole in the lid of a cottage cheese container or a lid for a plastic coffee can. The hole is smaller than your chickens head.
Put a chunk of rat poison in the container, snap on the lid and put the container in places you know are infested. Check it daily to see if anything is eating the bait and replenish as necessary.
The critters take the bait back to their tunnels for babies too.
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We can get Tomcat at our feed stores. I get the economy size because we have several barns with storage.
I do not set these containers where my barn cats are because I've been told that cats eating mice that are poisoned might make the cat sick.
Once you see a rat, chances are there is a colony. Act quickly because they multiply faster than rabbits.