How Alberta eradicated rats - Works in Progress Magazine

Rats have conquered nearly every place on earth where humans live. Only Alberta soldiers on.

Most of us accept rats as a fact of life. They live in tunnels and sewers, gnaw through walls, contaminate food, and resist nearly every attempt to push them back. A 2023 estimate put New York City’s rat population at about three million animals, roughly one rat for every three human residents. Almost nowhere do authorities try to get rid of rats altogether. The goal is usually to reduce sightings of them, limit the damage they cause, and coexist as painlessly as possible.<br>That makes one place stand out. Alberta, a Canadian province, is rat free, and has been for more than seventy years. On a map of global rat distribution, Alberta is a blank spot in an otherwise unbroken sea of rodents.

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Other places have eliminated rats too: South Georgia and a handful of New Zealand islands have done so to protect endangered birds. But these are tiny, uninhabited landmasses surrounded by ocean, with no permanent human population to speak of. Alberta, by contrast, has almost five million people and two cities of over a million each. It shares land borders on all sides with provinces and states that rats colonized in the 1950s, and its farmland and trade links make it an obvious target. Yet it stopped them. After Antarctica, Alberta is the largest rat-free area on Earth.<br>This half a million square kilometres of rat-free land exists because Alberta acted fast. Rats could only enter the province through a narrow corridor along its eastern border, which the government sealed before they could establish themselves. Had it waited, the opportunity would have been gone for good – like its neighbors, Alberta would now be spending millions a year managing a permanent infestation. It’s also an example of the day-to-day maintenance that civilization is built of: Alberta’s rat control program is in a never-ending fight against new incursions. If it were to lapse, the province’s rat-free status would be lost forever.<br>An invasive species<br>Rats are not native to the Americas. The first rat, the black rat, travelled across the Atlantic with the conquistadors, and slowly spread through Central America and the Caribbean, and into the port cities of North America’s eastern seaboard. But around 1775, a stronger competitor showed up: the Norway rat, Rattus norvegicus, also known as the brown rat or sewer rat, carried across the Atlantic on European ships. Bigger, stronger, and better adapted to colder climates, it rapidly displaced the black rat as the dominant rodent in North America.<br>Once Norway rats move in alongside people, they are very hard to get rid of. They live in our buildings, eat what we throw away, and can have 50 to 80 surviving young a year. Rats can overrun an area in months, and once they have, controlling them becomes a permanent, expensive job. New York City, for instance, has a dedicated ‘rat czar’ and spends $4.7 million per year directly on rat mitigation, but this is not enough to prevent rat populations from growing.<br>In the decades after their arrival, Norway rats entrenched themselves in major Atlantic ports like New York, Boston, and Philadelphia, where they lived in dense housing, warehouses, and wharves. As cities grew during the industrial revolution, the animals moved along railroads, and settled across North America. By the end of the nineteenth century, the Norway rat was endemic in most large cities.<br>Norway rats reached the countryside more slowly, but just as surely. Beginning in the 1920s, Norway rats moved steadily westward across the North American prairie, advancing roughly 24 kilometers per year through the Canadian province of Saskatchewan by hitchhiking between towns with human travelers on cars, trucks, and trains.

After crossing Saskatchewan, the rats would reach Alberta, whose farms were close to a perfect home: warm, full of grain, and almost free of predators. Once settled in Alberta, rat populations would have exploded and destroyed crops, gnawed through infrastructure, contaminated food, and spread disease.<br>So when field crews from Alberta’s Department of Health studying sylvatic plague (caused by the same bacterium responsible for bubonic plague in humans) in local gopher populations discovered Norway rats on a farm near the eastern border in 1950, the Alberta government declared an emergency and decided to try to stop the rats’ westward march.<br>The Rat Control Zone<br>Rather than attempting to manage rats everywhere, the Albertans concentrated their efforts where the rat invasion was most likely to originate. Rats could enter the province only from Saskatchewan, as Montana was too sparsely populated, the Northwest Territories were too cold, and the border with British Columbia was too mountainous.<br>William Lobay, a crop protection supervisor at the...