They protect their own.When I was at UT we lived in a house adjacent to Cumberland Ave and the dumpsters for several restaurants and bars. We had a rat problem.
Our first solution was to gather barn cats and bring them to town. We kept turning loose cats. The Animal Control people kept catching the cats and hauling them off. We finally talked to the cat catcher and explained we'd brought them there to kill the rats. He said, "We can't allow them to roam free." But had no solution for the rats.
We bought pellet guns and spotlights and had a rat killin by the dumpsters. We got in more trouble from the city. Can't shoot a pellet gun in town.
We tried putting out massive amounts of Decon and again got in more trouble from the city. Can't put out loose poison in the city.
We tried traps and caught the crap out of them. Sometimes 5 or 6 a night. But we could only trap them inside the house or around it.
It seems the Government had an answer to every plan we had to get rid of the rats but no answer as to how to actually get rid of them. You'd think rats were a protected species.