The extraordinary migrations of these lemmings have attracted attention far back in the early history of northern Europe. At intervals, through favorable conditions, they become superabundant over a large area, and then a sudden resistless desire to migrate in a certain direction appears to seize the entire lemming population. The little beasts start in a swarming horde, sometimes containing millions, and traverse the country.
In their travels they appear indifferent to all obstacles and with dogged and unwavering persistence swim the streams and lakes encountered on their way. Similar migrations have been observed at various points in Arctic America, several of them in Alaska, where the lemmings abound on the open tundras.
These migrations sometimes continue for more than one season, the animals meanwhile being killed in countless numbers by disease, by accident in field and flood, and, in addition, through the heavy toll taken from their numbers by their winged and four-footed foes, which always gather in numbers to accompany them.
The migrations sometimes wear out through the diminution in numbers, and sometimes when they reach the sea, as in Norway, they are said to enter the water and swim offshore until they perish. When one of these swarms of rodents passes through a farming district it cleans up the crops and other surface vegetation like a visitation of locusts.
These lemmings do not hibernate, but, active throughout the severest winters, are abroad almost equally by day and by night. Their burrows consist of winding tunnels, often many-branched and with more than one opening. A dry bed of peat or a dense growth of moss is often pierced by a network of them. Well-defined runways often lead away from the burrows or from the entrance of one burrow to that of another.
Their tunnels run everywhere under the snow, with occasional passages leading to the surface. When fierce gales blow away the snow or a winter rain melts it, many lemmings lose touch with their burrows and wander about until they perish from cold or are caught by some enemy. They are sometimes found several miles from shore, where they have strayed out on the sea ice.
In winter in the fur countries, in company with field mice, they invade storehouses and habitations in search of food. Among their enemies are ravens and all northern hawks and owls, as well as foxes, weasels, lynxes, bears, and other beasts of prey of all degree.
Within their underground tunnels and often in dense vegetation on the surface lemmings make warmly lined nests of grass and moss in which their young, from two to eight in number, are born. The young appear at varying times, thus indicating several litters each year.
When taken alive, the old ones are fierce and courageous, growling and fighting savagely; but several half-grown young brought me during my residence in Alaska proved to be most amusing and inoffensive little creatures. From the first they permitted me to handle them without offering to bite and showed no signs of fear.
They were kept in a deep tin box, from which they made continual efforts to escape. When I extended one finger near the bottom of the box they would stand erect on their hind feet and reach up toward it, using their forepaws like little hands. If my finger was lowered sufficiently they would climb up into my hand and thence to my shoulder, showing no sign of haste, but much curiosity, continually sniffing with their noses and peering at everything with their bright beadlike eyes.