Rattus exulans in Western Samoa 
R. R. Marples 1 
The common rat of Polynesia is Rattus 
exulans (Peale). It appears to be closely re- 
lated to, and probably derived from Rattus 
concolor of the Malay region. The concolor 
group, and its derivatives, occur all oyer the 
Pacific, being represented in the Oceanic is- 
lands by R. exulans , R. micronesiensis and R. 
hawaiiensis. Other species have been erected 
for the Polynesian forms, but it may be sim- 
pler to regard these as synonymical with R. 
exulans at least until larger series have been 
collected. Tate (1935) lists as synonyms of 
R . exulans (Peale) : 
Mus exulans Peal 1848: Tahiti 
Mus vitiensis Peale 1848: Fiji 
Mus maorium Hutton (1878) 1879: New 
Zealand 
Mus jessook Jentink 1879: New Hebrides 
Mus huegli Thomas 1880: Fiji. 
Rattus hawaiiensis Stone (1917) has been 
erected mainly on colour differences, but the 
individuals appear to be of a smaller general 
size though with larger skulls than the Sa- 
moan specimens. This form may not require 
specific rank, but is widely sccepted as differ- 
ing from R. exulans . R. micronesiensis Tokuda 
(1933) is also a different form. 
Most of the work on R. exulansh&s been done 
on preserved specimens and, though a large 
number of individuals have been examined, 
these form only very short series from any one 
locality. An attempt was made, therefore, 
1 Department of Zoology, University of Otago, 
Dunedin, New Zealand. Manuscript received June 
23 , 1954 . 
while on a trip to Western Samoa, to collect 
as large a series as possible from one group 
of islands, to measure these rats in order to 
derive some statistics of the populations for 
later comparison with similar or larger series 
from elsewhere, especially with the New Zea- 
land native rat, and to examine them for 
parasites. Also it was thought that colour 
variations would be more easily observed in 
fresh specimens. 
Western Samoa is volcanic in origin and 
consists of two large islands, Savai’i and 
Upolu, with two small islets, Apolima and 
Manono, lying between the larger two, the 
whole group forming a line running roughly 
east and west. The capital of the territory is 
Apia on the northern shore of Upolu. Upolu 
was originally covered with tropical rain- 
forest but now a wide belt of coconut, cocao, 
and banana plantations lies round the coast. 
Rats were collected on Upolu from Afiamalu 
on the edge of the rainforest, from plantations 
near Apia and on the prison farm at Tafagiata. 
The major part of the collecting was done on 
Manono which is covered with coconut 
plantations except for a small forest area on 
the northern face. This island is about 1 mile 
in diameter and rises to about 200 feet. It is 
within the reef bounding Upolu but some 3 
miles offshore. 
METHODS 
The method of collecting was by trapping. 
The traps used were commercial breakback 
rat traps previously soaked in wax to prevent 
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