Herwig Leirs ( Global Change Ecology Centre, Research Group Evolutionary Ecology ): “ The recent nuisance is not surprising. It is not that there are suddenly more rats: if the sewers are filled with water due to sustained rain, the rats are forced to move to the surface.”
Chicken coops are very attractive for rats, where they can feed on the grains that are there.
Herwig: “But we should also be aware for in-house rats. Through a door, a badly closed drain or a broken water pipe: they can enter in multiple ways. A small opening of 2 cm is already enough. If you see a rat in your house, you should quickly find out how it entered.”
Once a rat is in your house, more are bound to come. Rats are real family animals. They learn from each other where food can be found.