The Norway rat is easily maintained and relatively resistant to disease. During the past century, R. norvegicus has become increasingly important as a laboratory animal. At present, the rodent is extensively employed in both biomedical and behavioral research studies.
Rattus norvegicus adult males range in weight from 450 to 520 grams. In contrast, at between 250 and 300 grams, the females of the species are somewhat smaller (2:49). The animal's coat is typically brown, although mink, pearl, and albino mutants do exist. The mink rat is a light brown with a variable light or white undercolor; the pearl rat is white with dark brown pigment in the tips of its hairs (7:142).
The zoological nomenclature for the Norway rat was devised in 1924. The scientist, H. H. Donaldson, named the species (6:1-6). Like other mammals, R. norvegicus belongs to the animal kingdom, the Phylum Chordata, and the Class Mammalia. Furthermore, the Linnean system of taxonomic classification also places the species in the Suborder Rodentia and the Family Muridae (8:121, 135, 209).
The history of the Norway rat can be traced back to the eighteenth century. The animal has no obvious connection to Norway. However, it is widely believed that the organism originated in the temperate regions of central Asia (2:47-54). More specifically, the species may have evolved in the "wild country between the Caspian Sea and Tobolsk (6:1-6)."
During the eighteenth century, R. norvegicus migrated east along trade and military routes. It spread across Europe very rapidly. The continent's major capital cities reported the rat's presence in "quick succession (6:1-6)." In England, early chroniclers date its arrival at between 1728 and 1730. By 1775, the rodent had reached the East coast of North America.
It wasn't until late in the eighteenth century though that people began domesticating the Norway rat. Around 1800, there was a popular ...