The Hibernation of Mammals' 



By L. Harrison Matthews 



Director and Permanent Secretary 

 Zoological Society of London 



[With 2 plates] 



Most animals are cold-blooded: in all the invertebrates, and in 

 the vertebrates, except the birds and mammals, the temperature of the 

 body is approximately the same as that of the surrounding medium, 

 rising and falling in harmony with its fluctuations. All animals that 

 live in the sea are subjected to a comparatively small range of temper- 

 ature variation that is not great enough to preclude an active existence 

 throughout the year. Even in the sea, however, many of the inhabi- 

 tants of the upper strata and of shallower waters show seasonal out- 

 bursts of activity (mainly in connection with reproduction), and the 

 feeding activities of a great number of species are restricted during 

 the colder times of winter. But animals living on land with air 

 as the surrounding medium, particularly those that live outside the 

 Tropics, are subjected to a far greater variation of temperature with 

 the course of the seasons, and have been forced to adopt various means 

 for coping with it. Hibernation is one of them. 



In cold-blooded animals the metabolic rate varies, being greatest 

 at high temperatures, and least at low ones. No animal can long 

 withstand a temperature of much over 100° F.; for one thing, the 

 proteins of the tissues are coagulated by great heat — though most 

 animals could not survive even up to the temperature necessary for 

 that to occur. Members of only a few groups, in which there are 

 special arrangements for resisting frost, can withstand being frozen. 

 With the onset of the chill of winter cold-blooded animals must there- 

 fore seek out some sheltered spot, to which frost will not penetrate, 

 where they may safely remain until warmer conditions return. But 

 many go further than this and enter into a state of torpidity in which 

 the metabolism is reduced to the absolute minimum consistent with 

 the preservation of life. Most people have at some time seen a queen 

 wasp hibernating, perhaps behind a picture on the wall of an unheated 



* Reprinted by permission from Discovery, vol. 15, No. 10, November 1954. 



370930—56 27 407 



