First do a forum search for rats and chickens, there are hundreds of threads with this subject beat to death. Find Howard E's Rat 101 post from a few years back. You can find hundreds of posts with all sorts of advice.
The advice tends to go poison, rat proof the coop, traps, then on to the useless advice like plaster of paris, scents, the usual old wives tales. The problem with poisons and traps is that you are dong things backward. Howard E said it best several years back, sanitation, exclusion, extermination, in that order.
Sanitation, clean up around the coop so any rodent traveling has to be in the open where predators can reach them. Eliminate hiding places and runways. Doesn't help much once they have tunneled under the coop. Get your bulk feed in metal barrels or metal trash cans with lids. I have seen mice jump out of a 55 gallon barrel. Next get a treadle feeder, a proper treadle feeder with good reviews, anything over ten percent negative reviews is useless in a rodent situation. No plastic parts, no wooden parts, narrow and distant treadle, spring loaded door and a counterweight. Avoid the wide steps that rats can use to reach the feed. Avoid the guillotine style feeders that have a lid opening overhead because you have to block them open to train the birds and leave them open for weeks which means the rodents learn where the feed is and now know to push the lid open. This style of feeder is also not rat proof, the lid is easily pushed open. Again, check the negative reviews, those will be the folks with a rodent problem and while a poorly designed feeder might prevent rats from ever colonizing a coop they rarely are able to stop an established colony.
Make sure the treadle feeder has a wide and deep feed tray, not a narrow slit like the plastic ones, the birds will quickly learn to rake feed out. Make sure the feeder has a feeder lip extender, few need them but there are hens that will rake feed and the usual 1/2" feeder lip protruding into the feed tray won't stop them.
Once you are no longer providing free food the rats will either leave or starve to death or become a meal themselves out foraging for natural food. This works every time assuming you have some full sized birds to operate the feeder and not a flock of silkies and bantams. It if doesn't work, you haven't assembled the feeder correctly, haven't installed it correctly, or you have dozens and dozens of rats that will begin to get caught in the feeder and suffocate. One way or the other, a proper treadle feeder stops rodents.
Exclusion is a lot harder and more expensive which is why Howard E. put it second. Metal, metal, metal. Wood and concrete can be chewed through. Metal cannot.
Once all this has failed, and it won't, you can poison. The problem with poison is that it never ends as newer populations move into the territory. The rodents get smart quickly and learn to leave the poison alone, ditto on traps. However, once the feed is cut off and if you already have a massive population that poison becomes very effective as they are starving. But you are also poisoning the natural predators which is a bad thing so use poison sparingly and only if you have chicks around that the rats will kill when they get desperate.
The advice tends to go poison, rat proof the coop, traps, then on to the useless advice like plaster of paris, scents, the usual old wives tales. The problem with poisons and traps is that you are dong things backward. Howard E said it best several years back, sanitation, exclusion, extermination, in that order.
Sanitation, clean up around the coop so any rodent traveling has to be in the open where predators can reach them. Eliminate hiding places and runways. Doesn't help much once they have tunneled under the coop. Get your bulk feed in metal barrels or metal trash cans with lids. I have seen mice jump out of a 55 gallon barrel. Next get a treadle feeder, a proper treadle feeder with good reviews, anything over ten percent negative reviews is useless in a rodent situation. No plastic parts, no wooden parts, narrow and distant treadle, spring loaded door and a counterweight. Avoid the wide steps that rats can use to reach the feed. Avoid the guillotine style feeders that have a lid opening overhead because you have to block them open to train the birds and leave them open for weeks which means the rodents learn where the feed is and now know to push the lid open. This style of feeder is also not rat proof, the lid is easily pushed open. Again, check the negative reviews, those will be the folks with a rodent problem and while a poorly designed feeder might prevent rats from ever colonizing a coop they rarely are able to stop an established colony.
Make sure the treadle feeder has a wide and deep feed tray, not a narrow slit like the plastic ones, the birds will quickly learn to rake feed out. Make sure the feeder has a feeder lip extender, few need them but there are hens that will rake feed and the usual 1/2" feeder lip protruding into the feed tray won't stop them.
Once you are no longer providing free food the rats will either leave or starve to death or become a meal themselves out foraging for natural food. This works every time assuming you have some full sized birds to operate the feeder and not a flock of silkies and bantams. It if doesn't work, you haven't assembled the feeder correctly, haven't installed it correctly, or you have dozens and dozens of rats that will begin to get caught in the feeder and suffocate. One way or the other, a proper treadle feeder stops rodents.
Exclusion is a lot harder and more expensive which is why Howard E. put it second. Metal, metal, metal. Wood and concrete can be chewed through. Metal cannot.
Once all this has failed, and it won't, you can poison. The problem with poison is that it never ends as newer populations move into the territory. The rodents get smart quickly and learn to leave the poison alone, ditto on traps. However, once the feed is cut off and if you already have a massive population that poison becomes very effective as they are starving. But you are also poisoning the natural predators which is a bad thing so use poison sparingly and only if you have chicks around that the rats will kill when they get desperate.
