primarily of goldenrod, the vegetation immediately 
surrounding Boxes 22 and 25. 
June 15 (16 days old): Three inches of rain fell 
during the previous 48 hours. Female 11 and her 
young were no longer in Box 20. A large new 
hooded nest of goldenrod was in Box 28, and 
although I could not see in it, I suspected that 
they were there. 
June 18 (19 days old): The overhead covering of 
the nest in Box 28 was now sufficiently trampled 
that the young could be seen. The mother was 
not in the box at 5:30 p.m. when these observa- 
tions were made. During the 5 minutes they 
were watched no sound was emitted. They 
walked unsteadily about the box, apparently 
paying no attention to me, and finally they clumped 
together in the nest depression. The poor loco- 
motor ability of the rats to this age indicated that 
the prior three transfers of residence were accom- 
plished by their being transported by their 
mother. 
June 19 (20 days old): At 7 a.m. they were 
huddled together in the depression of the nest in 
Box 28. They were still in this position at 10 a.m. 
when they were handled for the first time and 
marked. The mother, female 11, was caught in a 
trap by Box 27. Upon release she wobbled 
unsteadily to Passage 3 where I lost sight of her. 
However, an hour later she was in Box 28 nursing 
her young. Numbers assigned: Males, 18, 19, 23 
and 24; Females, 17, 20 and 25. 
June 21 (22 days old): Young seen in Box 28 
nursing their mother. 
June 28 (29 days old): The seven young, but not 
the mother, were seen in Box 28. Upon this dis- 
turbance of opening the lid to Box 28 three of the 
young rats ran along the trail and into Box 33. I 
then chased them out and back into Box 28. The 
mother was in Box 6 in Area I. 
June 30 (31 days old): Female 11, the mother, 
was in Box 7 alone. 
July 3 (34 days old): Position of capture in 
traps or harborage boxes: male 23 in trap by Box 
21; male 19 in trap by Box 28; male 24 and female 
17 in same trap by Box 30; male 18 in trap by Box 
31 ; females 20 and 25 in Box 36. It will be noted 
that there were two pairs among these captures of 
the young. This indicated a continued social bond 
among the sibs. All the young were released in 
the West Alley. Two hours after this the mother, 
female 11, was found in Box 28 with one of her 
young, although earlier she must have been in a 
burrow since she was not in any of the 36 harborage 
boxes. She must still be nursing her young for 
her teats are in the well worn three-plus condition. 
July 4 (35 days old): Position of rats: Male 18 
in trap by Box 3 in Area I; males 19 and 24 in 
same trap by Passage 3. While trying to read 
their eartags by looking through the ware roof of 
the trap without handling them, they engaged in 
several fights. This behavior of engaging in com- 
bat by two rats captured together in the same trap 
upon the observer making a close approach to them 
was commonly exhibited by rats of all ages. I 
have interpreted this situation as evidence that 
aggressive action is initiated more readily when 
other circumstances increase their anxiety state. 
The mother and three of the young were in Box 
19, and the remaining young were in Box 25. 
July 13 (44 days old): The mother made several 
trips carrying food from the Food Pen into Area 
III. This continued food storage in the general 
region inhabited by her young must reduce the 
number of their excursions to the Food Pen where 
increased competitive action with other adults 
would occur. 
July 18 (49 days old): Female 11 and six of her 
young in Box 21, while the remaining one was in 
Box 19. 
July 25 (56 days old): The mother and three of 
the young were in Box 19, while another was nearby 
in a trap at Passage 3. Two other of these young 
were trapped; one by Box 28 and the other by 
Box 31. One was not captured. The condition 
of the teats of the mother was the two-plus stage 
indicating cessation of lactation. 
July 30 (61 days old): One of the young was 
seen running between Areas I and IV, while another 
was seen running between Boxes 30 and 31. They 
keep to trails previously worn smooth by adults. 
The development of trails by adults produces a 
sociological-biological conditioning of the environ- 
ment which makes it more habitable by juveniles. 
July 31 (62 days old): The mother and all seven 
of her Litter 3 young were in Box 26. Thus despite 
the cessation of lactation the bond of association 
between the mother and young continued. The 
four males of this litter disappeared shortly after 
this date as a result of unknown events. 
September 10 (103 days old): Females 17 and 
25 together in Box 35. There was no new nesting 
material. No wounds on either rat. 
146 
