516 PROCEEDINGS OP SECTION D. 



11.— SOME REMARKS ON THE NATURAL HISTORY AND 

 DISEASES OF THE RATS OF PERTH AND FRE- 

 MANTLE, WESTERN AUSTRALIA. 



By J. BURTON CLE LAND, M.D., Gh.M., Government Bacteriologist and 



Pathologist, and M.O.H. to the Central Board of Health, 



Western Australia. 



Mr. Woodward, Director of the Western Australian Museum, has 

 published a list, consisting of 11 species, of the members of the genus 

 Mus so far found in this State. Of these only six were recorded for 

 the more southern portions. They are Mus rattus, the " Black Rat "; 

 Mus decumanus, the " Brown or Norway Rat " ; Mus musculus, the 

 " Common Mouse," three introduced by man, and the three following 

 indigenous — Mus nanus, Mus assimilis, Mus fuscipes. 



As the first three are the only species we have met with during the 

 extensive trapping necessitated in combating plague, my remarks will 

 apply to them alone. It is, however, interesting to know that apparently 

 no native members of the genus have become domesticated. 



When it became obvious that the study of the natural history of 

 the rat might be of great service in plague prevention it was clearly 

 our duty to ascertain the nature of the species with which we were 

 dealing, and what were their habits. We were at once struck, in trying 

 to differentiate the species, with the great superficial differences between 

 individuals. In otherwise similar rats the tail would vary in length. 

 In the same litter might be some with pure white bellies, others with 

 pronounced gray bellies ; some of the rats had, generally, dark greyish- 

 black hair, others snow-white bellies, with an indistinct fawn edge and 

 gray back. Consulting Mr. Woodward on the matter, we decided to 

 take the skins and skulls of these various types and forward them 

 through the Western Australian Museum to Mr, Oldfield Thomas, of 

 the British Museum. From the latter gentleman Mr. Woodward has. 

 received the following interesting reply : — 



" Nearly all are, as I expected, the white or yellow bellied race of 

 M. rattus, which occurs in ships and seaports all over the world. It 

 may be called M. rattus alexandrinus, or simply M. alexandrinus, but 

 is really essentially the same species as the black-bellied M. rattus- 

 — the old English black rat, to which most of your Albany specimens. 

 belong. 



" Two onh^ from Perth, are the common grey rat, M. norwegicus, 

 better known as M. decumanus. 



" With regard to plague — to which, I suppose, your inquiries. 

 refer — there is no doubt whatever that the M. rattus alexandrinus 

 crowd are guilty, and it is possible that M. norwegicus is innocent. 

 It has been suggested that the disappearance of plague in Western 

 Europe has been due to the killing out of M. rattus by M. norwegicus, 

 but I do not make any assertion about it. 



" The M. rattus and M. alexandrinus lot are very good climbers^ 

 and can get on ships, along ropes, &c., and, therefore, go all over the world.. 



