THE MIGRATIONS OF MAMMALS. 255 



before it is over these are partly withered, partly devoured by the 

 greedy teeth of the insatiable rodents. Scarcity of food begins to 

 be felt, and their comfortable life comes to an end in panic. Their 

 fearless, bold demeanour gives place to a general uneasiness, and 

 soon a mad anxiety for the future takes possession of them. Then 

 they assemble together and begin to migrate. The same impulse 

 animates many simultaneously, and from them it spreads to others; 

 the swarms become armies; they arrange themselves in ranks, and 

 a living stream, flows like running water from the heights to the 

 low grounds. All hurry onwards in a definite direction, but this 

 often changes according to locality and circumstances. Gradually 

 long trains are formed in which lemming follows lemming so closely 

 that the head of one seems to rest on the back of the one in front 

 of it; and the continuous tread of the light, little creatures hollows 

 out paths deep enough to be visible from a long distance in the 

 mossy carpet of the tundra. The longer the march lasts, the greater 

 becomes the haste of the wandering lemmings. Eagerly they fall 

 upon the plants on and about their path and devour whatever is 

 edible; but their numbers impoverish even a fresh district within 

 a few hours, and though a few in front may pick up a little food, 

 nothing is left for those behind; the hunger increases every minute, 

 and the speed of the march quickens in proportion; every obstacle 

 seems surmountable, every danger trifling, and thousands rush on 

 to death. If men come in their way they run between their legs; 

 they face ravens and other powerful birds of prey defiantly; they 

 gnaw through hay-stacks, climb over mountains and rocks, swim 

 across rivers, and even across broad lakes, arms of the sea, and 

 fjords. A hostile company, like that behind the migrating squirrels, 

 follows in their wake: wolves and foxes, gluttons, martens and 

 weasels, the ravenous dogs of the Lapps and Samoyedes, eagles, 

 buzzards, and snowy owls, ravens and hooded crows fatten on the 

 innumerable victims which they seize without trouble from the 

 moving army; gulls and fishes feast on those which cross the water. 

 Diseases and epidemics, too, are not awanting, and probably destroy 

 more than all their enemies together. Thousands of carcasses lie 

 rotting on the wayside, thousands are carried away by the waves; 



