The Norway rat, scientifically known as Rattus norvegicus, is a large, brown or grayish rodent that is now one of the most widespread mammals. It is characterized by a stocky body, a blunt muzzle, and a tail slightly shorter than its head and body combined, often reaching weights between 140 and 500 grams. Despite the misleading name, this rodent is not native to Scandinavia or Norway. The name is a historical accident, raising the question of where this highly adaptable species truly originated.
The True Geographic Origin
The Norway rat’s origin is traced back to Central and East Asia. Experts pinpoint the species to the plains of northern China and neighboring areas, likely including Mongolia. The wild ancestors of the brown rat thrived in natural environments, primarily inhabiting burrows along river systems and in brushy areas.
The species earned the alternative name of “water rat” in some regions. Its original diet consisted of plant materials, but its adaptability allowed it to quickly become a commensal species, living alongside humans. This close association with early human settlements in Asia provided the necessary conditions for its eventual dispersal across continents.
The Historical Misnomer
The name “Norway Rat” is a misnomer assigned during the 18th century. The binomial nomenclature Rattus norvegicus was assigned to the species by the English naturalist John Berkenhout in 1769. Berkenhout mistakenly believed the rodents had first arrived in England by way of Norwegian ships around 1728.
The naming was based on a geographical assumption tied to the supposed point of entry into Great Britain, not the actual origin of the species. This lack of accurate knowledge about the rat’s true Asian homeland led to the confusing designation. Earlier in England, the brown rat was also known as the “Hanover rat,” a name used by those who wished to link the rodent problem with the unpopular House of Hanover dynasty. Academics later recognized that the animal was rare in Norway when it became common in England, confirming the name was a factual error.
Global Migration and Establishment
The dispersal of Rattus norvegicus began along ancient trade routes, traveling overland and eventually by sea. The species spread westward into Europe via Russia, reaching Eastern Europe by the early 18th century. Historical records suggest the rat’s establishment in Europe occurred rapidly, with reliable sightings documented in Ireland by 1722 and England around 1730.
The species’ arrival coincided with maritime trade expansion, and its ability to thrive in proximity to humans made it an ideal stowaway. Brown rats successfully exploited the shipping industry, establishing themselves in port cities across the world. They reached North America shortly after their establishment in Europe, with first sightings recorded between 1750 and 1775 as they disembarked from ships arriving at New World ports. This opportunistic nature and tolerance for diverse environments allowed the brown rat to become the dominant rat species, displacing the smaller black rat in many temperate regions.