Owing to its fecundity, conjoined with its voracity, it sometimes fails to obtain food in its own district, and migrates southward.
The strangest point about this migration is its exceeding uncertainty. Fortunately, there is seldom an interval of less than seven years between the migrations, and seventeen years have been known to pass before the coming of the lemming. Yet, whatever the interval may be, the whole of the lemmings of vast northern districts begin their march southward through Norway and Sweden in search of food.
They are divided into two vast armies, which are kept apart by the Kiolens range; and it is very curious that they direct their course toward the southwest and southeast. Nothing seems to stop their progress. They only have one idea, namely, to press onward. If a wall or house be in their line of march they will try to climb it rather than go round it, and if they come upon a stack of corn they will eat it and then go forward.
Rivers, and even lakes, are swum by the lemmings, thousands of which are eaten by the fishes. They are admirable swimmers as long as the surface of the water is smooth, but the least ripple is too much for them, so that if the day be windy very few of those which enter the water are seen to leave it alive.
Their ranks are perpetually thinned by birds and beasts of prey which accompany their columns. These parasites are wolves, foxes, wild cats, stoats and other weasels, eagles, hawks and owls. It is said that even the reindeer feed upon them. Man eats them, and so obtains some trifling compensation for the destruction of his crops. But, while its invasion lasts, the lemming is nearly as destructive as the locust itself, not leaving even a blade of grass behind it. Despairing of checking this terrible foe by ordinary means, the people turned to religion, and had a special service of exorcism prepared against the lemmings.
The end of the migration is as unaccountable as its beginning. I have mentioned the instinct which forces the creature to proceed onward on the line which it has taken. Now, Norway and Sweden form a peninsula, toward the apex of which the course of the lemmings is directed. It follows that sooner or later the animals must arrive at the coast. And, having reached the shore, they still must needs go into the sea, where the waves almost immediately drown them.
Now we will turn from cold to heat, and imagine ourselves in South Africa. From the migrants of that country we will take the springbok as our example.
Many travelers in that country have mentioned the “trek-bokken,” as the Boers call these pilgrimages, but none have painted them more vividly than the late Captain Gordon Cumming, whose description I have had the pleasure of hearing as well as seeing.
One morning, as he had been lying awake in his wagon for some two hours before daybreak, he had heard the continual grunting of male springboks, but took no particular notice of the sound.
“On my rising, when it was clear, and looking about me, I beheld the ground to the northward of my camp actually covered with a dense living mass of springboks, marching steadily and slowly along, extending from an opening in a long range of hills on the west, through which they continued pouring like the flood of some great river, to a ridge about half a mile to the east, over which they disappeared. The breadth of the ground which they covered might have been somewhere about half a mile.