The Migrations of the Lemming.

Otago Witness, Issue 2161, 25 July 1895, Page 52

The Migrations of the Lemming.

Uader the tltla " Myodes L?mmas : Its Habits and Migrations in Norway," Professor R. Oollett, of Christiania, gives a valuable account of bis researches into the habits and migrations of that interesting little rodent, the lemming, which has become so notorious on account of its periodic wanderings in vast hordes down the Scandinavian valleys. Professor Oollett finds the earliest notice of the lemming in an old Norse manuscript dating from the latter end of the thirteenth century, and reproduces a curious and striking woodcut from the great history of Olaus Magnus (1555), in which is graphically figured the descent of the lemmings from the clouds accordiDg to the prevalent belief. But the most valuable parts of the memoir are those which depend upon the author's personal knowledge of the lemming. The nature and habits of the lemming are clearly described, and much light is thrown upon the causes which from time to time lead such vast numbers of these animals to leave their native uplands and to begin their suicidal wanderings. The migrations seem to be directly due to over-population. In certain years, termed by the writer " prolific years, 1

an abnormal fecundity is exhibited by the lemming. This phenomenon is not, however, confined to thia species, but is shown also in numerous families of mammals, birds, and insects. The consequences of this great multiplication- in the case of the lemming are thus described by Professor Oollett : -" The enormous multitudes require iccreased space, and the individuals, which, under normal conditions, have each an excessively large tract at their disposal, cannot, on account of their disposition, bear the unaccustomed proximity of the numerous neighbours. Involuntarily the individuals are pressed out to the sides until the edge of the mountain is reached. In a short time they enjoy themselves there, and the old individuals willingly breed in the upper regions of the forests, where, at other times, they are entirely wanting. New swarms, however, follow on ; they could not return, but the journey proceeds onwards down the sides of the mountains, and when they once reach the valleys, they meet with localities which are quite foreign to them. They then continue blindly on, endeavouring to find a home corresponding to that they have left, but which they never regain. The migratory individuals proceed hopelessly on to a certain death." Sooner or later all the wanderers meet their death — thousands are drowned in rivers or fjords, thousands are attacked by beasts and birds of prey, and thousands parish from the effects of cold and damp ; but the greater number die from the effects of a peculiar epidemic which attacks them In the lowlands. It is pointed out by the writer that the wandering instinct developed during migratory years is probably of distinct service to the species in reducing the surplus population. — Nature.