PERCENT CHANGE IN ACTIVITY WITH EACH l°F. DECREASE IN TEMPERATURE 
INFLUENCE OF TEMPERATURE ON INTENSITY OF ACTIVITY 
EACH POINT REPRESENTS THE COMPARISON BETWEEN TWO ADJOINING NIGHTS 
WHEN THERE WAS AT LEAST A TWO DEGREE DIFFERENCE IN TEMPERATURE 
AVERAGE DIFFERENCE'6-9°F (96 PAIRS) %6.6 
A = MEDIANS ° T 
MEAN TEMPERATURE 
TEMPERATURE IN DEGREES FAHRENHEIT ON THE NIGHT OF THE PAIR 
WHICH HAD THE HIGHER TEMPERATURE 
Figure 98. — Influence of temperature on intensity of activity. The reason, that at any specific temperature, a decrease in 
temperature may be accompanied by either large increments or decrements in activity, is temperature accounts for only 
1 3 percent of the total variability in activity. Even so, the median changes in activity with 1 degree Fahrenheit decreases 
in temperature probably reflect accurately the effect of temperature on intensity of activity. 
index of the activity at the mean temperature of 
63.7° F., the amount of activity expected at lower 
temperatures may be calculated by utilizing the 
trend of change in activity with each degree change 
in temperature shown in figure 98. These calcu- 
lations along with the observed mean activity at 
each temperature are shown in figure 99 and 
table 23. Because temperature determines only 
13 percent of the variance in activity (see table 23) 
the observed points in figure 99 poorly fit the 
calculated changes in activity. Nevertheless, a 
crude estimate may be made from table 23 which 
does indicate the effect of temperature upon 
intensity of activity. The mean temperature for 
the 149 nights ranging between 15° and 45° F. 
was 35.2°, and the mean number of activity units 
per rat was 17.9. In contrast to this, the mean 
temperature for the 122 nights ranging between 
45° and 75° F. was 57.6°, and the mean number of 
activity units per rat was 23.8. There was thus a 
127 
