Rats in Western Samoa — Marples 
173 
Habitat 
Rattus exulans is commonest in the thick 
undergrowth of soft plants standing about 
•2 feet high which grows in profusion in the 
coconut and banana plantations. The rats ap- 
pear to be more common near to human 
settlements, but do not seem to be as de- 
pendent on man as the introduced R. rattus 
and R. norvegicus. These latter were rare on 
Manono, but both did exist, one R. rattus 
being caught and one R. norvegicus being seen. 
No evidence was seen of exulans climbing the 
coconut palms, but many small nuts lay 
around the trees and it has been suggested 
that rats are the cause of this fall of small 
nuts. However, we were told that in the Toke- 
lau Islands, the rats do live in trees descending 
to forage. 
Some rat holes were found but the main 
place of shelter seemed to be in piles of stones 
or walls. 
Trapping carried out along the edge of the 
rainforest at Ahamalu produced only two rats 
which appeared to be exulans but were black 
in colour. Thus it seems that fewer rats in- 
habit the true rainforest at the higher cooler 
levels. 
Pellage 
The colour and texture of the fur of con- 
color type rats has been used in separating 
the different races. Rats collected in Samoa 
from the different areas were not identical in 
colouration but it is difficult to evaluate the 
worth of the variations. 
Rattus exulans is generally: brown above, 
darker in the mid-dorsal line, and becoming 
paler down the sides. There is a fairly definite 
line of change to the yellowish-grey of the 
ventral surface. A tendency was noted for a 
yellower patch to occur at the front of the 
chest and for a yellow mid-ventral line to run 
backwards from this patch, fading into the 
basal colour. This line and patch were more 
obvious in the Manono series but were not 
confined to these rats. 
The brown colour of the back runs on to 
the hand while the sides of the arm are paler 
TABLE l. 
Skin Measurements of Rattus exulans 
MEASUREMENT 
LOCALITY 
NUMBER 
meas’d 
AVERAGE 
S 
t 
t 
PREDICTED 
FOR .01P 
P 
SIGNIFICANCE 
Length 
Samoa 
42 
259.3 
15.8 
Upolu 
12 
270.5 
15.1 
3.225 
2.750 
<.01 
Significant 
Manono 
30 
254.8 
13.9 
Tail 
Samoa 
42 
136.4 
8.1 
Upolu 
12 
140.8 
8.7 
2.46 
2.75 
<.05 
Probably 
Manono 
30 
134.3 
7.2 
significant 
Ear 
Samoa 
41 
15.4 
1.1 
Upolu 
10 
15.6 
1.3 
.501 
2.75 
>.05 
None 
Manono 
31 
15.4 
1.1 
Foot c. u 
Samoa 
44 
26.4 
1.1 
Upolu 
12 
27.4 
1.2 
4.027 
2.75 
<.01 
Significant 
Manono 
32 
26.1 
0.9 
Foot s. u 
Samoa 
44 
24.8 
0.9 
Upolu 
12 
25.7 
0.9 
4.676 
2.75 
<.01 
Significant 
Manono 
32 
24.5 
0.7 
Weight 
Samoa 
44 
51 
10 
Upolu 
12 
56 
10 
.7 
2.75 
>.05 
None 
Manono 
32 
49 
9 
