Probably the major source of error in this com- 
parison lies in the subjective ability of the author 
to judge the age of feces during the June 1947 
period. I can only say that I am convinced that 
this judgment is fairly accurate. Even if the feces 
on June 5 had been deposited during the previous 
4 days, rather than on the 2 previous days, as I 
believe to be true, there would still have been three 
times as much aboveground defecation in June as 
during January. Thus, even when considerable 
latitude is allowed for possible errors in the assump- 
tions it is quite apparent that there is a considerable 
decrease in the aboveground activity, produced by 
severe weather. 
A count of feces a year later on February 1, 1949, 
lends further information on the effect of tempera- 
ture and other factors on the amount of above- 
ground activity. During the dawn hours of 
January 31, 1949, 4 inches of hard, ball-like snow 
fell. By mid -morning it began to rain; this froze 
upon falling and so formed a glaze of ice over the 
snow (see table 26). 
Thus, with a comparable snow cover on the 
second date there was 10 times as many above 
ground feces per rat per day. The warmer nightly 
temperature certainly contributed to this greater 
aboveground activity. However, there is another 
condition which probably acted to negate the 
tendency of the rats to remain underground during 
cold weather. That factor was the increased 
social friction accompanying the fivefold increase 
in population density. In Area IV between boxes 
33, 34, and 36 a group of box traps were piled 
during the February 1949 snows. At the beginning 
of activity in the early evening several rats from 
the same burrow or box would at short intervals 
head for this pile of traps and begin fighting. 
This indicates that although the rats may aggre- 
gate together during the day hours for the conser- 
vation of body heat, there is sufficient antagonism 
between the members of the group to break off 
the close association during the night hours. The 
continuation of this situation should keep the rats 
above ground more continuously during the night. 
Table 26. — Feces above ground during two periods of 
comparable snow cover 
Date 
Number of 
rats 
Above ground 
feces per rat 
per day 
Mean 5 p.m. 
to 7 a.m. 
temperature* 
Jan. 26, 1948 to 
Jan. 31, 1948. . . 
25 
0. 77 
22. 9 
Ja»i. 31, 1949 to 
Feb. 1, 1949. . . 
135 
8. 01 
33. 3 
*Temperatures were probably lower than this in the 
hilly area north of Baltimore where the pen was located. 
(Baltimore City Weather Office.) 
E. Observed Activity oj the Rats as it Relates to 
Periodicity. Prior sections on periodicity of activity 
dealt mainly with quantitative records of the 
passages of rats in and out of the Food Pen. The 
interpretation of these activity records have in 
large part depended upon other observations or 
sources of data. Representative observations 
reveal the type of phenomena upon which the 
interpretations of the quantitative records of 
activity were based. 
Fluctuations in intensity, type, and place of 
activity. 
1. June 29, 1948 
6:25 p.m. 
6:30 p.m. 
2. July 7, 1948 
7:45 p.m. 
3. September 30, 1948 
5:33 p.m. 
I have been in tower for an hour and yet have seen only two rats go to the 
food hopper, although many have been out. 
The rats have certainly been doing a lot of wandering about and seem little 
interested in food. Several rats at a time may be active in Areas I or II 
with little sign of hostility. 
Earlier in the evening the rats seemed little interested in eating, but explored 
about and showed markedly little antagonism. Now fights are occurring 
more frequently. 
So far this afternoon very little activity centered about the food hopper, 
although many rats passed through the Food Pen. Even those who ate, 
also spent considerable time in spontaneous or wandering activity. 
132 
