I’ve been trying to think what predators might do that. I assume it is happening at night when they are locked in the coop. Predators don’t always act the way their species is supposed to. Many will normally go for the head and kill but may on occasion go for another body part. The wounds you are describing sounds strange to me, both where it is and that it would be that consistent. A wound that size is huge too. Are you sure something is not wounding them and the other chickens then peck that area?
Is there any way to set up a game camera to see what is happening? It really helps a lot to know for sure what you are dealing with.
Are you seeing any rat droppings or droppings of any other kind? Droppings can be valuable in identifying the critter. With larger predators outside you can sometimes see footprints which can help but inside a coop and with smaller things like rats that’s usually not real easy.
Rats are certainly a possibility, especially since rat poison disappeared. But other animals will eat rat poison too. And one bite doesn’t kill rats or mice either for that matter. They normally have to eat it for a few days to get a lethal dose. Did you ever see or smell any corpses?
Since they breed so fast, it’s difficult to eradicate rats or especially mice with poison once they are established. You can get a lot of them but it seems you always miss a few. Then they come roaring back. Traps are less effective at eradicating them. I have traps set right now for mice. I know I will never totally eradicate them with traps but it does help keep the numbers under control.
So what can you do? I don’t know what your coop looks like but rats can get through some pretty small holes. They can chew or dig their way in too if they really want in. If you can identify where they are getting in maybe block that access with hardware cloth or something else.
They are probably attracted to the feed. Store feed in containers where they can’t get to it and remove and safely store any feed at night. Don’t leave it out where rats can get to it. Rats and mice will feed during the day and chickens usually spill enough feed in the bedding to still attract them, but don’t make it easy for them to find plenty to eat.
A large cat or a dog, especially a terrier, can be pretty effective in keeping the numbers down or keeping them away. Not everybody is set up to keep a dog or cat at their coop. I’m not.
One thing that can help a lot is to eliminate their hiding places. Don’t let grass or weeds grow up around the coop. Keep trash and debris cleaned up. That’s a lot easier said than done. Rats are really good at finding a place to nest. Often that nest in in the coop walls if they are enclosed or if you coop has a floor, right under the floor.
I like the idea of traps, either live traps or snap traps. Be careful with snap traps or you might kill something you don’t want to, maybe a wild bird or a chicken. It may not totally eliminate them but it does help keep the numbers down. Plus if you are catching them, it tells you that you have more around.
My problem is mice not rats, but when the numbers get out of hand even with traps set, I will use poison. There is obviously a lot of risk with poison. You have to take great care that things you don’t want eating it can’t get to it. If you go that route use a lot. Spread it out and don’t let it run out. They have to consistently eat it for a few days for it to get to a lethal dose.
Good luck. Sounds like you are taking the right steps.
