I too discovered tunnels everywhere this year.. I'm a newbie w 2022 my 2nd winter tending chickens and I only have 3 hens. I've seen the tunnels under/into my garage, outside chicken pen, garden beds and compost! Then I saw several rats in my garage (where my smaller, Fort Knox nighttime coop is located, but not penetrable by rats - so far, gratefully!)
I keep food away, having all surplus in metal cans, I don't spread feed in the outside enclosure, plus clean up any inside spillage nightly.
In my garage I started hearing squeaking along w/ rustling - in numerous areas simultaneously - at night. I personally love and respect all animals and don't want to kill any living creature. I've tried numerous live-trapping, repeaters traps, etc., I trapped 14 rats (eeks def not for the faint of heart!!!) but all to no avail. Still hearing LOTS of activity at night.
And multiple sized rats captured indicating multiple litters. Rats multiply VERY fast, reaching sexual maturity at 5-6 weeks, females come into heat all year-round, every 4 to 5 days, and have large litters - average of 10 to 12!
The rats are super smart and started avoiding the live traps, (even when changing types) regardless of what tasty, smelly baits I used, and leaving them not set for days to increase rats not fearing apparatus, etc. I considered buying the Uhlik trap for $200 + along w/ expensive release chambers, but geez...
So when they started infesting my garage and everywhere else, jeopardizing my girls health & safety, (and likely mine, since my garage wreaks of rat excrement now) they've got to go! Plus THEY CAN MIGRATE into YOUR HOUSE!
I don't want to use poison, (so cruel) but I learned online baking soda is effective for rodents if they eat enough. Rodents (like chickens) are unable to belch or pass gas, so the B soda causes rodents to have internal eruptions, (same w insects.) Tho it is ultimately fatal for the rats, I pray the eruptions are a quicker demise than the slow, commercial poison that kill thru internal bleeding. As well as hopefully not be harmful to other animals that could eat them.
There are several recipes online mixing equal amounts of B soda w corn meal (or jiffy mix) w a little sugar. I saw signs the rats were going after it every night, (footprints in the substance) but I was still hearing lots of noise and activity every night.
Very recently, the best I've discovered online so far is mixing B soda half & half w peanut butter, and I roll it into little balls. I've used that 2 nights, they seem to ingest more and I think it made a difference already, as the noise has reduced!
Yesterday I saw another recipe of popcorn (broken down smaller) then sprinkled w soap shavings (or even liquid detergent) then add baking soda. I saw video somewhere here on rat / chicken forums that changing up the baits can be most effective.
Perhaps the rats can be cats in their next life, or something else not so dangerous to humans and chicken health.
I hadn't heard about the contraception approach, and I'll add it in. I guess measures it will be an ongoing maintenance upkeep to prevent re-infestation.
