THE BROWN OR COMMON RAT 6ii 



and when introduced in some localities it has quickly disappeared 

 again. At Tromso, however, it appears to have met with suitable 

 hospitality, for rewards were paid for 4104 killed there between 

 September 1909 and February 191 1. 



In America it inhabits most of the thickly populated parts; it 

 occurs from Panama northwards to the Yukon Valley and to Green- 

 land, except on the interior table-lands, and perhaps in a few sections 

 of the south (Lantz). It is very common in California, chiefly in the 

 towns ; but in the San Joaquin and Sacramento valleys it has invaded 

 marshy tracts, and occurs far from human habitations (Grinnell, Proc. 

 Cal. Ac. Sc, 191 3, 322). It is found also in many parts of South America, 

 where it is often the dominant species ; but in the warmer parts of 

 America it is frequently unable to supplant the previously introduced 

 mttus group. 



It was found on the ship Advance of Dr Kane's second Grinnell 

 Land expedition during two icebound winters in 78° 37' N. latitude ; 

 and it also adapts itself to the continuous low temperatures of cold- 

 storage stations (L-antz). Brown says that when carried to Greenland 

 in the time of Fabricius these rats " seemed likely to prove dangerous 

 in houses ; but they gradually and periodically died out, as they could 

 not stand the cold of winter. Some years ago they were again 

 introduced, and still occasionally one is seen in the summer months in 

 some of the warehouses from Upernavik to near Cape Farewell." It 

 is therefore unlikely that this species could survive for many 

 generations under very severe climatic conditions ; and possibly its 

 present discontinuous distribution in Asia, noticed above, is to be 

 explained as a result of the great changes of climate which apparently 

 ensued in the northern and central parts of that continent towards the 

 close of the Pleistocene. 



The species is now widely distributed throughout Great Britain 

 and Ireland, and it has reached the majority of the islands around the 

 coast, being found on Jersey, Guernsey, Wight, Scilly, Lundy 

 (Coward), Anglesey (Coward, in lit), Man, Skye, the Hebrides, Ailsa 

 Craig; on smaller Scotch islands, as Sanda, Sheep, Glenimore near 

 Kintore, Sgat Mhor in Loch Fyne, and Inch Moan (Boyd Watt) ; 

 on Orkney (Barry, op. cit., and Wolley, Zoologist, 1849, 2344), Shet- 

 land, the Saltee Islands (Barrett- Hamilton, Zoologist, 1891, 6), Clare 

 Island, and Inishmore. Drane did not find it on Skomer, and it is not 

 known to occur on St Kilda. 



Distribution in time, and origin : — Nothing is definitely known of 

 the geological history of E. norvegicus. As shown above, its place of 

 origin is apparently temperate Asia, where it probably dates from the 

 Pleistocene. 



Status : — The present species appears to be rather more specialised 



