Along an 18-mile strip of land between the Canadian province of Alberta and its neighbor Saskatchewan, the rat patrol keeps guard. An eight-person team, armed with poison and shotguns, hunts daily for any sign of the rodent invaders.

The Alberta rat patrol checks more than 3,000 farms a year, but it rarely sees an actual rat. Alberta has 4.3 million people, 255,000 square miles, and no rats—bar the stray handful that make it into the killing zone each year. Ever since 1950, a sternly enforced program of exclusion and extermination has kept the province rat-free. Nowhere else in the world comes close; the only other rat-free areas are isolated islands such as the remote British territory of South Georgia.

Public support and education have been key to Alberta’s success. Locals use hotlines (310-RATS or 310-ARM) to report any sign of rodents, though false alarms are common. School programs educate kids about the telltale signs of the invaders. Keeping pet rats is banned and can earn you a fine of almost $4,000.