There's a really good book about the history of the relationship between urban environments and rats by journalist Robert Sullivan. My favorite anecdote was an interview with an exterminator that worked in New York. He was dealing with a rat infestation in a building in Queens. The landlady had insisted over and over that she wanted to get cats to control the infestation. The exterminator said absolutely do not do that. Against his advice, she gets two cats for the building. Two weeks later, the exterminator returns to the building the rats are still there and there's two cat skeletons in the basement. City rats do not fuck around.