Hibernation is not well understood. The habit 

 probably originated from the scarcity of food. 

 However, in Mexico grizzlies sometimes hibernate 

 even though the climate be mild and food plenti- 

 ful. As these grizzlies probably came from the cold 

 north, the habit may have been fixed in the species 

 when it arrived. Hibernation appears to be helpful 

 and not harmful, and it may therefore continue 

 for ages even though not required. The rest which 

 hibernation gives to mind and stomach, with the 

 entire organism relaxed, may both increase effi- 

 ciency and lengthen life. 



The polar bear has its own peculiar hibernating- 

 habits. The food of this bear is sea food. This is 

 available even in the winter-time, on or beneath 

 the ice. The male polar bears do not hibernate; the 

 females do not except when about to give birth to 

 young. The cubs at birth are small and helpless, 

 and require the mother's constant care and the 

 shelter of the den for some weeks after birth. 



Mr. J. D. Figgins has written one of the best 

 comments on hibernation that I have read. I quote 

 as follows: 



"The period of hibernation in any mammal not 

 only varies in a given species, but is largely influ- 

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