328 MR. B. COLLETT ON MTODES LEMMTJS IK NOEW AT. 



Myodes lemmus inhabits all the high fells of Norway from the 

 Bouthern branches of the Lemgfjeldene in Christiansand Stift to 

 the North Cape and the Varangerfjord. South of the Arctic 

 Circle its habitat is exclusively confined to the plateaux above the 

 conifer region ; in Troinso Amt and in Finmarken it occurs on 

 ail suitable localities down to the level of the sea, and here, too, it 

 is resident on the larger islands on the coast. 



None of the eastern species and no constant race of the Lem- 

 iniag are found in Norway, and accidental varieties are exceedingly 

 scarce. A few specimens of albinos are known. 



Under ordinary circumstances it inhabits portions of the birch- 

 regions nu the fells, intermixed with dry juniper-covered ground 

 and wet soil covered with the Dwarf Birch (Betula nana) ; in 

 the daytime it remains hidden and is seldom observed, but is, how- 

 ever, never wanting on places of any extent with the above- 

 mentioned natural qualifications. 



The nest is found under a tussock, constructed of dry short 

 straws, and is often, but not always, lined with hairs cast off by 

 the animals themselves. The number of the young ones (except- 

 ing in years of migration) is generally five, sometimes only three, 

 seldom seven to eight ; and at least two sets are annuallj'- pro- 

 duced. 



It feeds entirely on vegetable matter, especially grass-roots and 

 straws, in winter bark of diiferent species of Willow {Salix) and 

 Birch (Betula) ; and it forms the staple food of the Snowy Owl 

 {Nyctea scandiaca), the Eough-legged Buzzard {Buteo lagopus), 

 the Short-eared Owl {Asio accipitrinus), the Arctic Fox (Vulpes 

 lagopus), tlie Grliitton {Gxolo horealis), the Stoat {Mustela erminea), 

 and, to some extent, Baffou's Skua (Lestris parasitdca). 



The wandering of the Lemmings, is a necessary consequence of 

 their temporarily strong vitality together vrith an extreme mi- 

 gratory instinct, which is chiefly developed when they are in 

 numbers. This tendency to appear in large numbers at irregular 

 intervals of years is common to all the species of the subfamily 

 Arvicolinae; but in the present species (i^oJes lemmus) it is pro- 

 bably more developed than in any other mammal. 



During some years more families are produced than in others, 

 without a migration, consequently arising. Should the circumstances 

 be favourable, and the families still more numerous, the increase in 

 iiumbp.r causes smaller migrations, which every year take place here 



