Lemmus Lemmus Research Articles

LEMMINGS AND POPULATION PROBLEMS

always lead to new questions. A good scientist seldom contemplates any accomplished piece of work without seeing new unsolved problems, scarcely suspected before, rising from it. A good example is the subject of lemmings, the legendary rodents which march into the sea?or at least so folklore proclaims. In recent years, the lemming question has been removed from the realm of myth, and biologists have collected much new information to clarify and redefine the problem. But study has uncovered new mysteries, and this particular biological phenomenon now appears even more complex and provocative than before. The periodic wanderings of masses of Norwegian lemmings (Lemmus lemmus) in the mountain regions of Scandinavia stimulated many imagi native and superstitious explanations in former centuries. Some of these tales persist today. While I was in Norway in 1963 and 1964, some people questioned me about the suicidal urge which is supposed to cause the lemmings to fling themselves into the sea, or inquired if I had seen any angry lemmings burst apart with excess rage. Though serious scientists have long since dismissed such legends, the fanciful myths have been replaced in the scientific literature by a set of equally imaginative hy potheses. These have been built by critical biologists upon firm observa tions and experimental results, but they remain temporary ideas suggest ing what new studies should be made in order to learn more. Much of what we have learned, in addition, may have bearing on the problems created by human population increase and rapid technological develop ment of our environment. Two facets of the lemming's life are of tremendous interest and impor tance. The first is that their population numbers change so drastically from time to time. The second is that, occasionally, great numbers of lemmings move considerable distances from their original homes. These two aspects of lemming biology may not be so closely related as was once thought. The Norwegian lemming is one species of a rodent sub-family (Micro tinae) whose 70 or so species are very common throughout the north temperate and arctic zones. Various mice, voles, and lemmings are in cluded here, all with the same general appearance of compact body, short neck, and small ears and tail. Most of these small rodents exhibit marked fluctuations in their numbers over periods of 3 to 4 years. Some times, as in an outbreak in Oregon and Washington in 1959-60, some of these animals will become so abundant that they cause much damage to man's crops. Five species of this group are called lemmings?three 199

DEVELOPMENT OF THE ACROSOMIC SYSTEM OF THE SPERMATOZOON IN THE NORWEGIAN LEMMING (LEMMUS LEMMUS).

An electronmicroscopic study on the development of the acrosome system of the spermatozoon in the Norwegian lemming (Lemmus lemmus) has been performed. The proacrosomal granules were found to be few and to consist of a dense center and a less dense periphery, and the acrosomal vesicle to contain stainable material of the same structure but of lower density than that of the acrosomal granule. Like in the guinea pig, two zones of different density exist throughout acrosome development and are visible also in mature spermatozoa. A large osmiophilic formation consisting of saccular, tubular, and lamellar structures, was found between the apex of the condensed nucleus and the acrosome and was identified as perforatorium.

The Irruption of the Norway Lemming in Sweden during 1960

The period of 1959–60 was the first “total” lemming year in Sweden in 18 years. This period of high population of the Norwegian lemming (Lemmus lemmus) was characterized by high reproductive rates and possibly breeding through the winter. As population densities increased there was more movement and a spreading out to new habitats. The cause for the moving appeared to be psychological rather than from a lack of food. The population crash did not appear to be associated with either lack of food or predation. It is postulated that the crash was due to a physiological unbalance.

[The Norway Lemming] Myodes lemmus, its Habits and Migrations in Norway , by R. Collett. Christiania. 1895. 8°. pp. 62.

<i>[The Norway Lemming] Myodes lemmus, its Habits and Migrations in Norway</i> , by R. Collett. Christiania. 1895. 8°. pp. 62.

The Migration of the Lemming

IN discussing the much-debated subject of the westward migration of the Norwegian lemming, the primary cause—as it appears to me—has been altogether overlooked.

The Migration of the Lemming

HAVING resided during the summer months for more than twenty years on the plateau from which the migrations of the Norwegian lemming are supposed by many to take their origin, I can speak from personal observation. Some years ago I had the honour to read a rather lengthy paper before the Linnean Society on these animals, and, with one exception, to which reference will be presently made, I am happy in having nothing to alter or recant. The increase of the Lemmings is not cumulative, but rather periodic, as indeed is usual among the voles as well as among many other forms of life. The migrations are not caused by insufficient food now, whatever they may formerly have been, and this is evident from the fact that the swarms pass through, but do not exhaust the fertile districts which they encounter on their pilgrimage. Nor are they affected by any personal struggles between these most pugnacious of animals, for the young litters, when reared, go singly on the journey from which none have ever been observed to return. They do not follow the watershed, and they do not always migrate to the west—an error into which I was betrayed by trusting to common report and insufficient personal experience. But they do go straight. It is well known that the eyes of the lemming are so placed on the top of the head as to render it impossible for the animal when swimming, to discern any object not far above the plane of its horizon. On a calm morning last summer, I often placed my boat in the path of the swimmers, and noticed that they crossed my lake in an absolute “bee-line,” and that they could not discern my presence until the angle subtended by the boat was infinitely higher than that of the opposite shore. This latter migration was south-east, and in the late autumn the steamer on Lake Mjosen made its way through thousands of these hapless wayfarers; whilst, still later, large numbers were to be seen close to Christiania; but I venture to prophesy that none will be found in that neighbourhood next year, nor, for the matter of that, in Heimdalen itself, though it is obvious that some must remain. Probably the explanation of these apparently capricious and suicidal migrations may be that they are the result of hereditary instinct, which formerly was of service if not necessary to the species. The straight course which they pursue must be owing to the sense of direction common to migrants, and I would hazard the conjecture that the changes of destination may be due to an instinct which, owing to its present inutility, is gradually diminishing in precision and intensity.

The Migration of the Lemming

HAVING resided during the summer months for more than twenty years on the plateau from which the migrations of the Norwegian lemming are supposed by many to take their origin, I can speak from personal observation. Some years ago I had the honour to read a rather lengthy paper before the Linnean Society on these animals, and, with one exception, to which reference will be presently made, I am happy in having nothing to alter or recant. The increase of the Lemmings is not cumulative, but rather periodic, as indeed is usual among the voles as well as among many other forms of life. The migrations are not caused by insufficient food now, whatever they may formerly have been, and this is evident from the fact that the swarms pass through, but do not exhaust the fertile districts which they encounter on their pilgrimage. Nor are they affected by any personal struggles between these most pugnacious of animals, for the young litters, when reared, go singly on the journey from which none have ever been observed to return. They do not follow the watershed, and they do not always migrate to the west—an error into which I was betrayed by trusting to common report and insufficient personal experience. But they do go straight. It is well known that the eyes of the lemming are so placed on the top of the head as to render it impossible for the animal when swimming, to discern any object not far above the plane of its horizon. On a calm morning last summer, I often placed my boat in the path of the swimmers, and noticed that they crossed my lake in an absolute “bee-line,” and that they could not discern my presence until the angle subtended by the boat was infinitely higher than that of the opposite shore. This latter migration was south-east, and in the late autumn the steamer on Lake Mjosen made its way through thousands of these hapless wayfarers; whilst, still later, large numbers were to be seen close to Christiania; but I venture to prophesy that none will be found in that neighbourhood next year, nor, for the matter of that, in Heimdalen itself, though it is obvious that some must remain. Probably the explanation of these apparently capricious and suicidal migrations may be that they are the result of hereditary instinct, which formerly was of service if not necessary to the species. The straight course which they pursue must be owing to the sense of direction common to migrants, and I would hazard the conjecture that the changes of destination may be due to an instinct which, owing to its present inutility, is gradually diminishing in precision and intensity.

The Norwegian Lemming and its Migrations

The Norwegian Lemming and its Migrations

Additional Note relative to the Norwegian Lemming.

Additional Note relative to the Norwegian Lemming.

On the Migration and Habits of the Norwegian Lemming.

On the Migration and Habits of the Norwegian Lemming Get access W. Duppa Crotch, Esq., M.A., P.L.S. W. Duppa Crotch, Esq., M.A., P.L.S. Search for other works by this author on: Oxford Academic Google Scholar Zoological Journal of the Linnean Society, Volume 13, Issue 65, September 1876, Pages 27–34, https://doi.org/10.1111/j.1096-3642.1876.tb00941.x Published: 23 December 2008

Migration and Habits of the Norwegian Lemming

WITH all our recent knowledge of the Northern Fauna, and the ample opportunities of the Scandinavian naturalists, the animal in question still seems to have evaded a thorough scrutiny and complete solution of the why and wherefore of its remarkable migrations. Ten consecutive summers spent in Norway have led Mr. W. Duppa Crotch,1 in studying the creature, to propound a novel view as to the impetus of its recurrent irruptions. Passing by the traditional lore respecting its sudden appearance in myriads, he discountenances the later informed writers' explanation of hunger, or of the approach of severe weather, being the cause. Even “survival of the fittest,” with its cogent subsidiary clauses, according to our author, fails to serve as a substantial reason, for, as he observes, none of the travellers survive. His own theory is a very simple one. The bands of migrants always head westward, and at last, in diminished numbers, perish in the sea. In one well authenticated instance (Collet), a ship sailed for fifteen minutes through a swarm, the water being literally alive with them far as the eye could reach. This migratory instinct, Mr. Crotch assumes, is hereditary, their progenitors in the good old times of geological age having sojourned in a land of plenty, now submerged beneath the Atlantic. According to him the migration is not all completed in one year, as formerly supposed, nor do they, as stated, form processions and cut their way through obstacles; but breeding several times in the season, they gather in batches, and at intervals make a move westward. Their pugnacity, he states, is astonishing, and the approach of any animal, or even the shadow of a cloud, arouses the anger of this small creature like a guinea-pig, and they back against a stone or rock uttering shrill defiance. Our author found, in most examples, a bare patch on the rump, due to their rubbing against the said buttress of support when at bay. He wonders why a bare patch, and not a callosity, should not result from this innate, apparently hereditary habit. They cross wide lakes by swimming, but when in the water they are easily frightened, and lose all idea of direction, and are inevitably drowned by a slight ruffling of the surface. It seems the reindeer trample them under foot whenever the chance may occur, and other enemies in the shape of hovering rapacious birds and small carnivora thin the numbers considerably as the Lemmings in force drive westward. The writer also called attention to the fact that fossil remains of the Lemming exist in England, as an evidence that the animal had penetrated hither before this island was severed from the continent. The subject altogether is a most interesting and suggestive one, well worthy of the investigation and observation of northern sojourners. Even the recent views of Mr. Crotch, it seems, does not set the whole question at rest. There possibly may be some physical or physiological reason underneath; at all events it is certainly remarkable how a settled westward course is that chosen, calling to mind the similar direction which races of men are assumed to follow.