HIBERNATION IN MAMMALS— LYMAN and CHATFIELD 95 



had luvv bluod sugars and llicrcforc cuiicluded that prolonged fasting and hiberna- 

 tion were dissimilar processes, insofar as blood sugar was concerned. Lyman and 

 Leduc^°- found that the blood sugar in hibernating golden hamsters actually aver- 

 aged slightly higher than the active animals and suggested that the reported differ- 

 ences in hibernators may be due to a difference in the habits of the animals involved. 

 While ground squirrels and woodchucks are able to live in hiljernation for a long 

 time utilizing their fat as a source of energy, the hamster depends principally on 

 stored food which he eats during periodic awakenings from hibernation. The pe- 

 riods of uninterrupted hibernation in woodchucks and ground squirrels are much 

 longer than in hamsters, and the authors hypothesized that the blood sugar declines 

 during the prolonged hibernating period. In a small series of European ground squir- 

 rels, Feinschmidt and Ferdmann^"'' found that the blood sugar did decrease as hiber- 

 nation progressed. If the results of Feinschmidt and Ferdmann are valid for the 

 European ground squirrel, then arctic ground squirrels may have a different sugar 

 metabolism during hibernation than the European species.®^ In this regard it is inter- 

 esting that the range of blood sugars found in hibernating woodchucks by McBirnie, 

 et al.,^^ was from 36 to 140 mg.%, showing that this animal can tolerate a hypogly- 

 cemia in hibernation but that this condition is not universal. (Glycogen levels in the 

 hibernator are discussed under Metabolism, page 108.) 



Blood. The changes which may take place in the blood picture during hiberna- 

 tion are open to some dispute. Rasmussen^""* reviewed the previous literature, but 

 failed to agree with earlier authors that the number of circulating red blood cells or 

 the hemoglobin in the woodchuck decreased markedly during hibernation. Since 

 there was no change in the size of the red blood cells, it may be assumed that the 

 hematocrit also would have remained unchanged. On the other hand, he agreed with 

 Dubois''- and others that the number of leucocytes was decreased by about one half 

 in the hibernating state. Rasmussen and Rasmussen*'^ found that the amount of 

 blood relative to the body weight varied with the fatness of the animal. Obese wood- 

 chucks in the fall of the year, whether hibernating or not, had less blood relative to 

 body weight than the leaner animals of late winter or early summer. On the other 

 hand, McBirnie, et al.,^'" found a decrease in average hematocrit from 48.8 in hiber- 

 nating woodchucks to 31.4 after hibernation. 



Stuckey and Coco^°" reported a marked decrease in the erythrocyte count of hiber- 

 nating thirteen-lined ground squirrels, with a concurrent drop in hemoglobin. The 

 leucocyte count dropped only 2.3%. Using the same species, Svihla and Bowman''^ 

 reported a decrease in the average blood volume of over 50% in hibernating ground 

 squirrels, with an increase in erythrocyte count of from 6,700,000 in the awake 

 animals to 12,000,000 in the hibernators. It is difficult to understand why the aver- 

 age hemoglobin determinations only increased from 15.6 in the active animals to 

 17.1 in the dormant ones under these conditions. The same criticism applies to the 

 hematocrit values which were reported to "increase on an average of 0.09 to 0.14" 

 (units not specified). In a later paper^°^ the reported change in erythrocyte count 

 was less dramatic — an average of 7,072,000 in awake animals to 9.042,000 in dor- 

 mant ones. The hematocrits paralleled the erythrocyte counts, with an average of 

 37.26 in the awake to 50.15 in the dormant animals. Brace^°*' found no lympho- 



