The Laboratory Rat, Rattus norvegicus

Abstract

The common laboratory rat, Rattus norvegicus, has had a colorful history in its progression from feral origins to the research laboratory. Apparently indigenous to the steppes of Asia, the species is thought to have migrated down the Norwegian peninsula and arrived in England via ship in the early 18th century (Donaldson, 1924; Castle, 1947; Richter, 1954). From there, R. norvegicus spread rapidly throughout Europe, gradually replacing and pushing southward its plague-carrying predecessor, the smaller, common black rat, Rattus rattus or Rattus alexandrine. The latter, which had apparently arrived in Europe more directly from India via the Mideast between 400–1100 A.D. (Zinsser, 1935), prefers a warmer climate and is still the most commonly encountered rat in southern latitudes. The Norway rat arrived, again as unwelcome ship cargo, in North America in the late 18th century. As in Europe, it gradually displaced R. rattus, which was forced southward except for the few isolated northern pockets which still exist (Castle, 1947).