TEMPERATURE RESPONSES AND ADAPTATIONS 

 IN DOMESTIC ANIMALS 



Max KLeiber 



The body temperature of homeotherms is nearly the same as 

 that of man, about 37 C. Consistent changes from the average do 

 occur, but they are not related to body size or to geographic dis- 

 tribution of the animal. Rat and elephant temperatures are about 1 

 C cooler than those of man; cow, sheep, and swine, about 1 C hot- 

 ter, rabbit and dog about 2 C* hotter; and the camel lets its body 



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temperature vary from 34 C to36 C and seems not to mind a tem- 

 perature of 40 C if this is necessary for saving water. 



Figure 1, somewhat schematized from data of Johnson, et al. 

 (1958) shows that below an environmental temperature of 80 F 

 (27 C) , cow and man regulate their body temperatures somewhat 

 more accurately than does the rabbit. Man is much more strict 

 in keeping cool in a hot environment than cow or rabbit. The cow's 

 body temperature rises when the environmental temperature is 

 higher than 80 F (27 C). This is also the case for cold adapted 

 rabbits, whereas rabbits adapted to a warm climate do not raise 

 their body temperatures before the air temperature exceeds 90 F 

 (32° G). 



I am not aware of any biological theory which would explain 

 why in the evolution of homeotherms that 36 C to 40 C body tem- 

 perature has been so much more advantageous than other body tem- 

 peratures. For all conditions under which homeotherms live and for 

 all their sizes, this thermal level has been fixed by natural selec- 

 tion with a very small variation. It is fixed, however, and so is the 

 basal metabolic rate of homeotherms large and small, tropical and 

 arctic. It can be predicted with about 10% accuracy by the equation: 



♦Rabbit's normal temperature is 39.6 C; its variation is generally not more 

 than 1.8° C. Robert C. Lee (1939). 



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