232 ANIMALS OF THE PAST 



to be slowly but surely approaching extinction 

 in spite of all efforts to preserve the race, and 

 no reason can be assigned for this save that the 

 small size of the herds has led to in-breeding 

 and general decadence. 



In other ways, too, local calamity may be 

 sweeping in its effects, and that is by the de- 

 struction of animals that resort to one spot dur- 

 ing the breeding season, like the fur-seals and 

 some sea-birds, or pass the winter months in 

 great flocks or herds, as do the ducks and elk. 

 The supposed decimation of the INIoas by severe 

 winters has been already discussed, and the 

 extermination of the great auk in European 

 waters was indirectly due to natural causes. 

 These birds bred on the small, almost inac- 

 cessible island of Eldey, off the coast of Ice- 

 land, and when, through volcanic disturbances, 

 this islet sank into the sea, the few birds were 

 forced to other quarters, and as these were, un- 

 fortunately, easily reached, the birds were slain 

 to the last one. 



From the great local abundance of their re- 

 mains, it has been thought that the curious 

 short- legged Pliocene rhinoceros, Aphclops fos- 



