39 
and lakes, bring forth young frequently on the way, are killed 
during the course of the summer in thousands by men, dogs, cats 
and all kinds of predaceous animals and birds, die in masses of an 
epidemic, which always makes its appearance, where the con- 
dition of a species of animal is disproportionately large, and by the 
arrival of autumn the hosts are already considerably diminished 
in number. In the course of the winter most of them die, and 
in the second year after the beginning of the emigration, there is 
seldom a living Lemming to be found remaining in the valley 
bottom. Not one individual returns alive to the high Fjelds. 
But it is not only this species which has a mass increase in 
these years. Simultaneously other small rodents, especially 
of the genus Avrvicola, increase beyond the normal number ; 
thus in Finmarken the Gray-sided Field-Mouse (A. rufocanus), 
upon the high Fjelds the Mountain Rat (A. ratticeps), in the 
forest districts the Forest Lemming (Myodes schisticolor), and the 
Bank Vole (A. glaveolus), or upon the lowlands the common A. 
agrestis ; yes, even the Shrews, the Hares, and the Ryper are 
wont to be more numerous in these years than in others. 
Then come also all kinds of raptorial birds and carnivorous 
animals, springing as it were from the ground, enticed to the 
place by the profusion of food. The mountains swarm with 
various hawks, especially Rough-legged Buzzards (Archibuteo 
lagopus) and various species of owl; especially Short-eared Owls 
(Asio brachyotus) and Snowy Owls; and Gyr-falcons (Hverofalco 
gyrvfalco) now show themselves comparatively frequently. Among 
the predaceous animals are Arctic Foxes, Stoats, and Weasels, 
ubiquitous everywhere; and they all live almost exclusively on 
the Lemmings. Even the fish are among their enemies; one 
may, not unfrequently in such a year, come across a trout with 
its belly distended by a Lemming, which the voracious fish has 
swallowed, while it was essaying to cross a river or lake. 
Even among the raptorial birds the prolificness of the year 
leaves its traces. The Snowy Owl (Nyctea scandiaca), which in- 
habits all the mountain plateaux of the country right up to North 
Cape (and Spitzbergen), but which in ordinary years is found 
scattered and sparingly, is, during these breeding years, so 
numerous as to be scarcely absent from any part of the mountain, 
