No. 479] 



EXTINCTION OF MAMMALIA 



111 



mous numbers of guanaco sought Lake Argentine, and died of 

 starvation upon its shores. In the severities of winter they seek 

 drinking-places, where there are large masses of water Hkely to 

 be unfrozen. The few last winters in Patagonia have been so 

 severe as to work great havoc among the herds of guanaco 

 (op. cit., p. 255). 



Deforestation and Secular Cold. — After considering the condi- 

 tions in Alaska, Mr. A. G. Maddren^ summarizes his conclusions 

 as follows: "1. That while remnants of the large Pleistocene 

 mammal herds may have survived down to the Recent period 

 and in some cases their direct descendants, as the musk-ox, to the 

 present, most of them became extinct in Alaska with the close of 

 the Pleistocene. 



"II. The most rational way of explaining this extinction of 

 animal life is by a gradual changing of the climate from more 

 temperate conditions permitting of a forest vegetation much farther 

 north than now, to the more severe climate of today, which sub- 

 duing the vegetation and thus reducing the food supply besides 

 directly discomforting tlie animals themselves, has left only those 

 forms capal)le of adapting tliemselves to the Recent conditions 

 surviving in these regions to the ])rosent." 



Influence of Cold and Sun,r on Food Suppb, and Choice of Food, 

 — The deaths of great nnnilxTs of anininls fn. ni hunger or starva- 

 tion through the covering of food during tlie winter season under 

 heavy layers of snow are commonly observed among the large 

 herds of some of the domesticated horses and cattle on the Western 

 plains. In fact, it is most probable that during the glacial period 

 the great winter snow blankets covering the natural food rather 

 than the actual influence of the cold itself, was the chief cause of 



Under tliese conditions horses are driven to food, such as the 

 brandies of willows, which is verv .k-leterious to them. Under the 

 hifliienrc <>f hunger cattU' and sheep also^ will feed eagerly and 



their young, as recorded by Chestnut and others in the United 

 of Mammoth and other Fossil Remains/' Smiths. Misc. Coll., vol. 49, p. 65. 



