Modern cities have rats. So did medieval cities. The typical rats of European and now American cities are the black rat and the brown rat, the latter the so-called Norway rat (not to be confused with the Norway spruce). In spite of the evocation of Scandinavia, rats actually originated in eastern Asia, but they have spread around the world, now being found on every continent except Antarctica.
(The above photo is by Nikolett Emmert.)
Rats have adopted very well to humans. In fact, although their ancestors lived in the wild, rats do not do well unless closely associated with humans. They can survive in very cold climates by staying inside with the humans. Their favorite food is whatever their local humans have left over and dump in the trash. Italian rats, for example, favor spaghetti.
Cities are always trying to get rid of rats, but it's an uphill battle. For one thing, rats are smart. They can evade traps, hide so they won't be spotted, fight back against cats and terriers. They have large litters of pups at regular intervals, so even if sizeable numbers of rats are killed, they can quickly come back.
One of the few places that I know that has successfully beaten back rat populations for good is in the Galapagos Islands, out in the Pacific on the equator. There are a number of unique species there, not only the famous Galapagos tortoises, and those species had few natural enemies until the whaling ships showed up, complete with rats. In subsequent years, the rats were very harmful to the nests of ground-nesting birds and other creatures. However, recent vigorous trapping efforts have eradicated them from some of the islands where no humans live.
Because rats are intelligent and adaptable, they have been used in scientific research since the end of the nineteenth century (think of the expression, "like a rat in a maze"). They can be used for studying behavior and also digestion, since they eat the same range of foods that humans do. Lab rats are generally white, descendants of an albino strain, and have become quite tame after generations of living directly with humans, rather than hidden in their walls. Such rats are also sometimes kept as pets. Medieval people would be appalled.
The story of the Pied Piper of Hamelin, a man who lures all the rats out of the city of Hamelin with his magical pipe playing, has its origins in thirteenth-century Germany. It has appeared in many guises over the centuries—I used a version of it myself in my novel Daughter of Magic. Most versions of the story take on a darker tone when the piper is not properly paid for ridding the city of rats. But for medieval people, the underlying premise was obvious: their cities needed fewer rats (people in New York City today would understand).
Rats were considered to spread disease in the closely-packed late medieval cities. They were accused, accurately, for helping spread the Black Death in the fourteenth century. They carried the fleas who transmitted the disease to humans. People killed their cats and dogs to try to get rid of the fleas, but the fleas just jumped onto humans, and the rats, carrying fleas, eluded efforts to eliminate them.
Even when they weren't spreading disease, rats were a major problem for medieval people because they would eat the grain. Keeping the grain away from rats and mice is always important, especially as it represents both this year's food and next year's seed, and it was an especially critical concern for a society in which bread was the principal food. Cats were valued as rodent-hunters more than as pets. There's a reason even now that farms have barn cats.
© C. Dale Brittain 2026
For more on various aspects of life in the Middle Ages, see my ebook, Positively Medieval, available from Amazon and other major ebook platforms. Also available in paperback!







