ORDER RODENTIA: RODENTS 207 



of volcanic rock. The specimens brought back by this expedition 

 indicated a deposit of phosphate rock, to exploit which a settlement 

 was founded at Flying-fish Cove, the only anchorage. Shortly after 

 this, Dr. Andrews made a three-months' visit (in 1897) in order 

 to survey the natural conditions there. His account contains prac- 

 tically all that is known of the species, which was then by far the 

 commonest of the mammals found in the island. He wrote: 



In every part I visited it occurred in swarms. During the day nothing 

 is to be seen of it, but soon after sunset numbers may be seen running 

 about in all directions, and the whole forest is filled with its peculiar 

 querulous squeaking and the noise of frequent fights. These animals, like 

 most of those found in the island, are almost completely devoid of fear, and 

 in the bush if a lantern be held out they will approach to examine the new 

 phenomenon. As may be imagined, they are a great nuisance, entering the 

 tents or shelters, running over the sleepers, and upsetting everything in their 

 search for food. They seem to eat anything, and destroy any boots or skins 

 incautiously left within their reach. Their natural food appears to be mainly 

 fruits and young shoots, and to obtain the former they ascend trees to a 

 great height. ... In the settlement they utterly destroy all the fruit they 

 can get at, and frequently come into conflict with the fruit-bats on the 

 tops of the papaia-trees. A number of dogs is kept to keep them in check, 

 and near the settlement they are certainly already less numerous than else- 

 where. In the daytime these rats live in holes among 1 the roots of trees, in 

 decaying logs, and shallow burrows. They seem to breed all the year round. 



After 10 years' absence, Andrews (1909) again visited Christmas 

 Island for the purpose of ascertaining what changes had taken 

 place in the interim as a result of white occupation. Such changes 

 were "chiefly noticeable in the immediate neighbourhood of the 

 settlement and quarries, while the rest of the island, although tra- 

 versed by roads in several directions, is practically unchanged." The 

 rats, however, had gone. For whereas 10 years earlier they were 

 found everywhere all over the island in abundance, in 1908, in spite 

 of continual search, not a single specimen of this tree-climbing 

 species or of the other burrowing rat, R. nativitatis, could be found 

 in any part of the island. He says further: 



This complete disappearance of two such common animals seems to have 

 taken place within the last five or six years, and to have been the result of some 

 epidemic disease, possibly caused by a trypanosome, introduced by thfe 

 ship-rats. These are a variety of Mus rattus, and have been introduced in 

 considerable numbers, though they do not seem to have spread to the 

 remoter parts of the island at present, at least to any great extent. The 

 disappearance therefore of the native forms cannot be due to direct com- 

 petition with the intruders, but must be the result of disease, a conclusion 

 supported by an observation made by the medical officer, Dr. McDougal, 

 who told me that some five or six years ago he frequently saw individuals 

 of the native species of rats crawling about the paths in the daytime, 

 apparently in a dying condition. 



Since Andrews's second visit in 1908, one or two other zoologists 

 have visited Christmas Island for the study of its fauna, notably 



