White. — On the Rats of Neio Zealand. 249 



common rat of Europe till, in the beginning of the eighteenth 

 century, the large brown rat (M. decumanus) appeared on the 

 lower Volga, and there spread more or less rapidly till it over- 

 ran Europe and generally drove out the black rat, which in 

 most parts is now comparatively rare or quite extinct. This 

 invading rat " (M. decumanus. — T. W .) " has now been carried 

 by commerce all over the world, and in New Zealand has com- 

 pletely exterminated a native rat, which the Maoris allege 

 they brought with them in their canoes from their home in 

 the Pacific." 



From this you will see that Dr. Wallace, and, as far as I 

 can judge, all scientific naturalists, have in an unaccountable 

 manner overlooked Dr. Dieffenbach's report, taken from the 

 Maoris in 1840, that it was M. rattus and not M. decumanus 

 which had decimated their native rat ; so I may take the 

 credit for having turned up this remarkable fact after the 

 lapse of so many years. 



From the above it would seem that M. decumanus, the 

 Norway rat, appeared on the confines of Eussia or the centre 

 of Europe nearly two hundred years ago, and, from our experi- 

 ence of the habits of migration common to most rodents, we 

 may assume that they came in regular armies, in which case 

 their influence would be as speedily apparent as that of a vic- 

 torious incursion of the human race, and the black rat would be 

 quickly swept away. How, then, do we find the black rat in 

 New Zealand previous to 1840, and can it really have been 

 brought from Europe, or is it from a country south of the 

 line? 



This black rat had, in 1840, been so long in the North 

 Island of New Zealand that it had exterminated the native 

 rat, or, rather, caused it to be almost procurable. When it 

 first arrived it could only be by the advent of a very few 

 animals, and not in the army of myriads which would come 

 forward to invade Europe — for this rat must have come by 

 ship, possibly from a wrecked ship. These few black rats 

 w 7 ould take a number of years to increase to a formidable 

 number, and we must not compare their rate of increase with 

 that of M . decumanus in after-years, which latter rat would 

 have a constant accession to its numbers from the continued 

 stream of shipping arriving in New Zealand from Europe. 

 When the vessels come alongside the wharf the rats during 

 the night escape along the ropes connecting the vessel with 

 the pier. 



The black rat is, I believe, not yet found in Canterbury, 

 Otago, or Southland, which would seem to indicate that it is 

 not spread by the shipping, or very rarely. Professor Hutton 

 tells me that he has no knowledge of its existence in Canter- 

 bury. 



