208 EXTINCT AND VANISHING MAMMALS 



M. W. F. Tweedie in 1932, but apparently no one has since found 

 a trace of the two indigenous rats or of the shrew (Crocidura 

 fuliginosa trichura) that were abundant before the settlement. No 

 doubt the supposition that they were exterminated through the 

 spread of some disease brought in by introduced House Rats is the 

 most likely explanation of their disappearance. Chasen (1933) , who 

 has written of the birds of the island, adds that in addition to Rattus 

 rattus (subsp. ?) , the House Mouse (Mus musculus) and the small 

 Rattus concolor, a member of a group adaptable to colonization as a 

 human acolyte, have also been introduced in this island. 



G. M. A. 



Christmas Island Burrowing Rat; "Bulldog Rat" 



RATTUS NATIVITATIS (Thomas) 



Mus nativitatis Thomas, Proc. Zool. Soc. London 1888, p. 533, 1889. (Christ- 

 mas Island, eastern Indian Ocean.) 



FIGS.: C. W. Andrews, 1900, pi. 2 (col. fig.) ; pi. 2 bis, figs. 2, 4, 5, 9, 10 (skull 

 and teeth). 



This rat and Rattus macleari (q. v.) are the only indigenous ter- 

 restrial rodents known from Christmas Island, Indian Ocean, and 

 are both now believed to be extinct. 



Rattus nativitatis was first collected by J. J. Lister in 1887, when 

 as naturalist aboard H. M. S. Egeria, in the year following the 

 visit of Captain Maclear, he explored part of the island. On this 

 occasion, a landing party under Captain Aldrich cut a way through 

 the jungle to the highest part of the island. 



In contrast to the other species, R. macleari, this rat was a more 

 stoutly built animal of burrowing habits. It is described as a large 

 species about 17 inches in total length with a tail much shorter than 

 head and body, of a thickset clumsy form, but having a peculiarly 

 small and delicate head. In color it was a dark umber brown all 

 over, the belly not or scarcely paler. The fur of the back, though 

 long, thick, and coarse, was without the elongated piles characteristic 

 of R. macleari. The claws were broad and strong, adapted for 

 digging. Mammae abdominal, three pairs. There is a slight degree 

 of variation in color, some individuals being a warmer brown than 

 others, and occasional ones having a small irregular patch of white 

 fur on the belly. Teeth relatively small and weak. Measurements: 

 head and body, 275 mm.; tail, 182; hind foot, 50; ear, 24 (these 

 for the largest of nine specimens). Skull: basal length, 46.8 mm.; 

 zygomatic width, 24.8; nasals, 20.5; diastema, 15.5; upper cheek 

 teeth, 7.6. A comparison of the forearm and hand bones in the two 

 species is given by Forsyth Major (with figures) in Andrews's 

 (1900) Monograph of Christmas Island. 



