EVOLUTIONARY ASPECTS IN MAMMALS 



^ - 30° 

 ^ 0° 



■■^ 



-10° 



4 5 



TIME IN HOURS 



Figure 12. Continuous records of deep rectal temperatures of the armadillo 

 at various air- temperature levels. (Johansen, 1961). 



the governing thermostatic control which fails in the armadillo 

 with several degrees. You may rightly ask how long this unsteady 

 condition goes on. P^igure 12 demonstrates the events during long- 

 time exposure to various ambient temperatures. When an experi- 

 ment began at 30 C, the deep rectal temperature fluctuated 



o o 



between 33.9 C and 34.5 G, as can be seen in Figure 12. The 



animals were quiet and relaxed. Occasionally they walked around, 

 but the activity was always transient and on a low level. The ani- 

 mals responded to an air temperature of C with a rapid increase 

 in body temperature like that recorded in the metabolic studies. 

 This response was accompanied by curling into a ball as described 

 earlier, and shivering began immediately. These bodily responses 

 continued throughout the test. At the end the animal showed no 

 signs of exhaustion. The curve for C in Figure 12 illustrates 

 the typical variation in deep rectal temperature. It rose rapidly 

 to 36.3 G in this animal within the first half hour. After an hour 

 the temperature dropped slightly to 35.5 G and remained between 

 35 C and 35.5 G for more than 6 hours. Toward the end of the 



109 



