502 THE AGE OF MAMMALS 



as in the case of aquatic mammals. The well-knoAvn cases of adaptation 

 to extreme cold amon§ elephants (E. primigenius, woolly mammoth), rhi- 

 noceroses (R. antiquitatis, woolly rhinoceros), steppe camels of Asia (Ca- 

 melus badrianus), steppe horses {Equus przewalskii), and steppe antelopes 

 (Saiga tartarica) indicate that we must not assume that cold was in all 

 cases the direct cause of extinction. 



Cold and the numerical diminution of herds. — As suggested by Darwin, 

 a temporary diminution in numbers, whether caused by cold waves, long or 

 repeated droughts, floods, epidemics, or other unfavorable conditions of 

 life, may indirectly lead to extinction. The protection of a herd of animals 

 from hostile Carnivora often depends on its numbers. It has been observed 

 recently that the woodland bison (B. athahascoe) of British Columbia is in 

 danger of extinction because the bulls are not sufficiently numerous to pro- 

 tect the young. Numerical diminution may in this way become a cause of 

 extinction. 



The observations of Prichard ^ in Patagonia give an interesting instance 

 of the influence of severe winters on the very hardy guanacos and deer of 

 that region. 



"Around the lake lay piled the skulls and bones of dead game, guanaco (Lama 

 huanachus) and a few huemules (Furcijer ckilensis). These animals come down 

 to live on the lower ground and near unfrozen water during the cold season, and 

 there, when the weather is particularly severe, they die in crowds. We saw their 

 skeletons in one or two places literally heaped one upon the other" (op. cit., p. 132). 

 "Again we came upon a second death-place of guanaco, which made a scene strange 

 and striking enough. There cannot have been less than five hundred lying there in 

 positions forced and ungainly as the most ill-taken snapshot photograph could 

 produce. Their long necks were outstretched, the rime of the weather upon their 

 decaying hides, and their bone-joints glistening through the wounds made b}^ the 

 beaks of carrion-birds. They had died during the severities of the previous winter, 

 and lay literally piled one upon another" (op. cit., p. 189). "The meaning of this 

 I gathered from Mr. Ernest Cattle. He told me that in the winter of 1899 enor- 

 mous numbers of guanaco sought Lake Argentino, and died of starvation upon its 

 shores. In the severities of wanter they seek drinking-places, where there are 

 large masses of water likely 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). 



Diminished herds and inbreeding. — Another danger attending dimin- 

 ished herds in restricted regions is close inbreeding. On this familiar 

 subject see Gerrit S. Miller's - paper "Fate of the European Bison Herd," 

 in which the author shows the possibly fatal influence of inbreeding on 

 diminished herds, although it must be pointed out that these bison are 

 protected and are thus living under unnatural conditions. 



1 Prichard, H. H., Through the Heart of Patagonia. New York, 1902. 

 - Miller, G. S., Jr. The Fate of the European Bison Herd. Science, n.s., Vol. IV, no. 99. 

 Nov. 20, 1896, pp. 744-745. 



