19 



the others. The house mouse everywhere holds its own against the 

 brown rat by its ability to escape into retreats too small for the rat 

 to follow. 



The brown rat inhabits most of the thickly populated parts of 

 America. North of Panama it occurs generally except in the arid 

 interior, from the Isthmus to the Yukon Valley and southern Green- 

 land. In the Great Basin it is practically unknown, and in New Mex- 

 ico and Arizona it is confined chiefly to towns along the railroads. 

 The Biological Survey is without records of its presence in Nevada, 

 Utah, Wyoming, Idaho, and the greater part of Montana. The reason 

 for its absence in that region is not understood, but its ability to with- 

 stand extreme cold is proved by the fact that it flourished in latitude 

 78 37' north on board Doctor Kane's ship Advance, in the Second 

 Grinnell Expedition, during the two winters when that vessel was 

 icebound. It has also adapted itself to the continuous low tempera- 

 tures of cold-storage warehouses, in which it appears to breed freely. 



HISTORY OF THE BROWN RAT. 



We know little of the history of this species. Greek and Roman 

 writers make no mention of rats of any kind, but possibly knew the 

 animals and included them in their frequent references to mice. 

 Pallas, in 1778, described the brown rat under the name Mus decu- 

 manus, and this was generally used until it was found that Erxleben 

 had called it M. norvegicus in 1777. Previously, the common name 

 Norway rat had often been used for this species. 



The brown rat is generally supposed to be of Asiatic origin. Vari- 

 ous modern writers have asserted that it came originally from Persia 

 or India; but W. T. Blanford states that the species is at present 

 unknown in Persia, and that in India the black rat is the generally 

 distributed species, while the brown rat occurs only along the coast and 

 the navigable rivers. This implies that the latter species is a com- 

 paratively recent immigrant into India. 



As regards the arrival of the brown rat in Europe, two facts are 

 known. The species reached England from some eastern port 

 about 1728 or 1729, and according to Pallas, a little earlier, 1727, 

 crossed the Russian frontier from Asia and soon spread over the 

 greater part of that country. 6 This statement, taken in connection 

 with that of Blanford, makes it highly probable that before this 

 migration the Asiatic home of the species was north, rather than 

 south, of the high mountains of northern India. This view, which has 

 been adopted by several naturalists, is further strengthened by the 

 fact that the animal flourishes better in temperate than in tropical 

 climates. 



Fauna of British India^ Mammals, p. 409, 1891. 

 l> Zoographica Rosso- Asiatica, vol. 1. p. 165, 1831. 



