Two important secrets are geography and recent occupation of the land. Rats (like sparrows) need to be around human garbage to thrive.<p>Alberta's population is highly concentrated in a central corridor that goes from Edmonton to Calgary. Around that there is very little population: the Rockies on the West, the Saskatchewan prairies on the East, the uninhabited Northwest Territories on the North and Montana on the South.<p>Besides that, the province was established in 1905 and had very few people until the oil boom in the 70s.<p>These 2 factors made it easy to start early and expand the extermination gradually. These days the wars are mostly outside of the province, to prevent the rats from coming back.<p>The only rats I've seen here are lab rats, grown under special license. I've had also the tiny field mice (actually it is a vole) in my backyard but they're very easy to catch: just keep the place clean and use a cheap trap once every 4 years.<p>So our big cities don't have rats but we have lots of sparrows, crows, hares, magpies, squirrels, hawks, coyotes, seagulls, etc... Sometimes we also have white tail deer and pelicans.<p>Oh, and we have almost no snakes or other reptiles, too! The only one I've seen is the gartner snake but here in Edmonton it is just a little bigger than an earthworm.