ADAPTATIONS TO TROPICS AND ALTITUDES 



HANNON: As yet, we have not had any comment on temperature 

 regulation in the shrew. Dr. Morrison's name has long been asso- 

 ciated with shrew metabolism. Would you care to comment on the 

 temperature regulation of these animals? 



MORRISON; I think all one can say is that temperature regula- 

 tion represents an adjustment so that heat output equals heat pro- 

 duction, and that these animals are obviously so adjusted. They 

 do not really have a problem because of their high metabolic rate; 

 obviously the heat flux from these animals per gram of tissue is 

 very great. 



HANNON: Have you ever studied the metabolic response of 

 shrews when they are exposed to different temperatures? Have 

 you ever determined the lower temperature limit for the main- 

 tenance of homeothermy? 



MORRISON: You mean to exceed their limit of regulation. 



HANNON: Yes. 



MORRISON: Yes, we have done that, and our Sqrex from 



o 



Wisconsin could not take more cold than -10 to -15 depending 



on the wind. We used this limit to estimate the maximum meta- 

 bolic rate; the value was close to that which we observed for 

 short periods of sporadic activity. But we did not run them on a 

 treadmill. 



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