Humans are the reason why rats are a problem in cities – because urban development displaces natural predators (owls, hawks, cayotes, foxes, wild felines) that would otherwise keep rats in check. Many dogs, however, if allowed and encouraged to follow their instincts, could be effective rat hunters. Warning: parts of this video are not appetizing, but it’s Nature at work.
(8) The Vigilante Group Of New Yorkers Who Hunt Rats At Night - YouTube