JOHANSEN 



exposure, the temperature dropped slightly; the last temperature 

 recorded in this animal was 34 C. In similar experiments at 

 -10 C, the initial increase in rectal temperature was even more 

 rapid and pronounced (Fig. 12). After slightly more than an hour, 

 the rectal temperature had declined to the level recorded at the 

 beginning of the experiment. For the next 2 1/2 hours the tempera- 

 ture fluctuated around 35 G. Then suddenly the animal began to 



run about the room scratching at the walls, the rectal temperature 



o 

 started to drop, and within five hours it had fallen to 25.5 C. At 



this low body temperature, the animal showed no signs of severe 

 fatigue and was amazingly coordinated. Its movements were harmon- 

 ized and it eagerly drank some milk which it was offered. The highly 

 organized behavior at such a low body temperature seems to be 

 unique among non- hibernating mammals and is probably of great 

 functional value to the armadillo. Although the pattern of -10 C 

 shown in Figure 12 is typical, the length of time the body tempera- 

 ture was maintained near 35 C varied from animal to animal, being 

 less than 2 l/2 hours in some and as long as 5 l/2 hours in others. 

 The period of relatively constant temperature terminated when the 

 animal abandoned the protective posture, which no doubt provided 

 good insulation. It should be emphasized that this kind of exposure 

 does not at all give a true picture of the armadillo's tolerance to 

 severe cold in natural environments. It will be pointed out later that 

 the armadillo is very much concerned with and dependent upon nest 

 building and social habits for survival at low ambient temperatures. 



I should like to spend a few minutes commenting upon the intact- 

 ness of coordinated behavior at drastically low body temperatures. 

 Other workers have mentioned the fact that normal behavior per- 

 sists at very low body temperatures in many primitive animals. 

 This fact has, however, never been appropriately evaluated. It 

 strikes me since it is a common characteristic among most of the 

 lower mammals studied in this respect. Comparing this with the 

 lethargic condition and the concurrent impairment of coordination 

 that appear in higher mammals, for example carnivores and 



ungulates at temperatures which are for them only slightly hypo- 



o o 



thermic (30 G to 33 G), it seems of the highest significance. I 



think the persistence of coordinated behavior at low body tempera- 

 tures in primitive forms has great survival value and greatly 



110 



