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Show 94 MIGRATIONS OF [Ch. vr. unusually prolific season, or upon a sudden s~arcity of provisions, great multitudes are threatened by f~mm.e. We shall enumerate several illustrations of these migrations, because they may put us upon our guard against attrib~ti~g ~ high antiquity to a particular species merely because 1~ IS d1ffuscd over a great space ; they show clearly how soo.n, m ~ state of nature, a newly-created species might spread Itself, m every direction, from a single point. In very severe winters, great numbers of ~he black bears of A mer1· ca mt· grat e from Canada into the Umted States; but in milder seasons, when they have been well fed, they remain and hybernate in the north*· 'rhe rein-dee~, which in Scandinavia can scarcely e:xist to the south of the s1xty-fifth parallel, descends, in consequence of the greater coldness of the climate, to the fiftieth degree, in Chinese Tartary, and often roves into a country of more southern latitude than any part of England. In Lapland, and other high latitudes, the common squirrels, whenever they are compelled, by want of provisions, to quit their usual abodes, migrate in amazing numbers, and travel directly forwards, allowing neither rocks, forests, nor the broadest waters, to turn them from their course. Great numbers are often drowned in attempting to pass frithg and rivers. In like manner the small Norway rat sometimes pursues its migrations in a straight line across rivers and lakes; and Pennant informs us, that when, in Kamtschatka, the rats become too numerous, they gather together in the spring, and proceed in great bodies westward, swimming over rivers, lakes, and arms of the sea. Many are drowned or destroyed by waterfowl or fish. As soon as they have crossed the river Penchim, at the head of the gulf of the same name, they turn southward, nnd reach the rivers J udoma and Ochot by the middle of July, a district surprising! y distant from their point of departure. The lemings, also, of Scandinavia, often pour down in myriads from the northern mountains and devastate the coun· * Richardllon's Fauna Boreali-Aroericana, p. 16. Ch. VI.] MAMMIFEROUS QUADRUPEDS. 9o try. They generally move in lines which are about three feet from each other, and exactly parallel, and they direct their tnarch from the north-west to the south-east, going directly forward through rivers and lakes, and when they meet with stacks of hay or corn, gnawing their way through them instead of passing round*· Vast troops of the wild ass, or onager of the ancients, which inhabit the mountainous deserts of Great Tartary, feed. during the summer, in the tracts east and north of Lake Aral. In the autumn they collect in herds of hundreds, and even thousands, and direct their course towards the north of India, and often to Persia, to enjoy a warm retreat during winter t. Bands of two or three hundred quaggas, a species of wild ass, are sometimes seen to migrate from the tropical plains of southern Africa t? the vicinity of the Malaleveen river. During thdr migra~ tJ.ons ~hey are followed by lions, who slaughter them night by mght+. The migratory swarms of the springbok, or Cape antelope, afford anot~er ~llustration of the rapidity with which a species, under certam circumstances, may be diffused over a continent. When the stagnant pools of the immense deserts south of the Orange river dry up, which often happens after intervals of th~ee or four years, myriads of these animals desert the parched soil, and pour down like a deluge on the cultivated regions nearer the Cape. The havoc committed by them resembles that of the African locusts; and so crowded are the herds that " t h e rt on h. as been seen to walk in the midst of the compr'e ssed phalanx With only as much room between him and his victims as th~ fears of those immediately around could procure by pressmg outwards§." Dr. Horsfield mentions a singular fact in regard to the geo- • Phil. Trans., vol. ii. p. 872. t Wood's Zoography, vol. f. p. 11. l On the authority of Mr. Campbell. Library of Entert. Know., Menagerie~~. vol. i. p. 152. -, § Cuvier's Animal Kingdom, by Griffiths, vol. ii. p. 109, Library of Enferl. Know., Meuageries, ,vol. i. p. 366. |