I have my predators of all sorts (foxes, hawks, owls, raccoons, opossums, snakes etc.) very much under control. This has come at a cost where the number of rats and mice has greatly increased and they are causing damage. Most of my birds are in small pens that can be moved. The rodents are so abundant and aggressive with their burrowing that they are making it difficult for me to walk and to place pens on level ground as I move them. They also create numerous mounds that make mowing real fun (sarcasm). They also consume of the feed when it is out after dark but cost of that is not known. The rodent abundance picks up where dogs maintain the exclusion zone for predators but even outside I can find lots of activity by the rodents. The high grass which benefits the chickens as cover and food source may also be promoting the rodent problem. Species ID of rodents is not known but I do not think they are the standard house mice or black / Norway rats. I suspect the rats are cotton rats. Early in year they were a source of entertainment as they harassed an unpleasant neighbor enough that he resorted to shooting them as they visited his front porch. I am not keen on using poisons and traps do not look like they will be able to get job. Using a rat terrier dog would possibly cause more damage to ground with all the holes dug. I may simply move all pens and plow ground up and manage ground differently where pens are located and I walk.