1936] MAMMALS OF OREGON 169 



before its larger and more aggressive rival. At present it is found 

 in localities scattered over the country, mainly near the coast, but an 

 occasional individual may be carried to any part of the country. 



The only record the writer has found for Oregon is based on a 

 half -grown young taken in a trap set under old logs in the Sitka 

 spruce forest near the shore at Empire. It is likely to be found near 

 any of the shipping ports of the State and probably in the woods 

 or among trees where it can escape from the brown rats. 



General habits. An expert climber, the black rat often makes its 

 home in trees, thatched roofs, or any place that is inaccessible to the 

 brown rat. In other ways it seems to be similar in habits to the 

 brown rat, but has been given less study on account of its scarcity. 



The mammae have the same arrangement as in the brown rat and 

 the breeding habits are said to be approximately the same. 



Economically the black rat is of local importance only. 



RATTUS RATTUS ALEXANDRINUS (GEOFFEOY) 

 ROOF RAT 



Mus alexandrinus Geoffrey, Catal. Mainmif. Mus. Nat. Hist Nat., Paris, p. 192, 

 1803. 



Type locality. Alexandria, Egypt. 



General characters. Similar in form and' general characters to the black rat, 

 but grayish brown above and clear white or yellowish white below. Tail very 

 long and slender ; ears small and naked ; hair on back coarse and bristly. 



Measurements. A fair-sized individual : Total length, 435 mm ; tail, 230 ; foot, 

 37; ear (dry), 21. 



Distribution and habitat. While native around the Mediterranean, 

 these rats have been carried in ships around the world and have 

 become established in many parts of North America, especially near 

 the coast. In Oregon there are two specimens in the Jewett collec- 

 tion from Netarts Bay and one in the Gabrielson collection taken at 

 Portland. 



General habits. Apparently these smaller, lighter bodied rats are 

 driven out or killed by the common brown rat and thus prevented 

 from gaining a foothold over the country at large. They are found 

 at most of the principal shipping ports and near the coast in colonies 

 where they occasionally get a start, but usually in the woods or at 

 some spot where brown rats do not occur. Being expert climbers, 

 they often build nests in trees or vines or inhabit the roofs of old 

 buildings reached by climbing vines or tree trunks. Heaps of drift- 

 wood along the shores or river banks sometimes afford shelter and 

 protection to colonies of them. 



Usually they are counted of little economic importance except on 

 islands or in places where other rats do not occur. 



MUS MUSCULUS MUSCULUS LINNAEUS 



HOUSE MOUSE 



[Mus] musculus Linnaeus, Syst. Nat. ed. 10, v. 1, p. 62, 1758. 



Type locality. Upsala, Sweden. 



General characters. Small, slender, with medium long tapering and half- 

 naked tail ; ears large ; soles naked ; incisors not grooved ; fur rather thin and 



