Table 28. — Summary of history of introduced rats 
Approximate 
age in days 
Feb. 1, 1947 
Rat 
No. 
Sex 
1947 weights 
Times and place 
captured March- 
October 1947 
Date 
last 
Feb. 
1 
Mar. 
27 
May 
17-30 
Southeast 
Northwest 
recorded 
257 
6 
M 
476 
405 
420 
10 
5 
7-19-47 
During part of time occupied 
South Alley Burrow with Female 
10. Found dead with no wounds; 
head buried in shallow scratchings 
in soil. 
112 
12 
M 
316 
378 
350 
19 
6 
10-28-48 
Became dominant male during 
1 947 but dropped to very low 
social status in 1948. 
357 
4 
F 
476 
404 
420 
18 
6 
9-27-47 
Became pregnant 3 times but 
raised no litters. 
77 
7 
F 
176 
212 
264 
21 
10 
11-20-47 
Became pregnant 3 times but 
raised no litters. Avoided contact 
with other rats. Death as for 6. 
142 
“Southea 
10 
ist rats” 
F 
total . . 
292 
327 
440 
2 
70 
3 
30 
2-29-48 
Died from exposure in trap at time 
of poor health and extensive in- 
fection of throat muscles. Was 
pregnant April, June, and August. 
Raised April (L-2) and August 
(L-5) litters. Mainly inhabited 
South Alley Burrow. 
109 
5 
M 
312 
353 
336 
2 
4 
5-17-47 
On this last date it had many 
scars over pelvis, and one large 
and six small wounds. 
104 
8 
M 
296 
327 
291 
8 
18 
5-17-48 
He was quite definitely the most 
subordinate male. 
104 
9 
M 
300 
345 
370 
4 
5 
6- 7-47 
Death followed head injuries re- 
ceived in fight with Male 6. 
162 
2 
F 
316 
316 
337 
3 
13 
5-30-47 
Found eaten by other rats. Not 
pregnant to May 30. 
97 
“North 
11 
west rat 
F 
s” total 
224 
264 
324 
4 
21 
22 
62 
7-30-47 
Pregnant twice, April and May. 
Raised only second litter (L-3). 
boxes between March 27 and May 21 the following 
frequencies of size of aggregates were observed: 
Size of aggregate in a 
harborage box 0 1 2 3 4 5 
Number of aggregates 
of each size 332 49 12 1 1 2 
The much lower temperature during the former 
period contributed in two ways to the greater fre- 
quency of larger aggregates. First, aggregating 
would favor conservation of body temperature. 
Second, it was cold enough to produce a retraction 
of the testes into the abdominal cavity and thus 
fighting among males was reduced. 
The influence of this initial differentation is re- 
flected in the genealogical history of the colony 
(fig. 102). As a background for understanding 
this, it will be necessary to make further comment 
on the first surviving litter (L-2) and the fourth 
(and last) surviving litter (L-6) born during 1947. 
Litter 2 was born to the Southeast female 10 at the 
South Alley Burrow. Female 10 was apparently 
also the rat responsible for initiating the North 
139 
