Tropical nature, and other essays

by Alfred Russel Wallace

Among birds the most important group is certainly the small-sized, but highly-organized warblers (Sylviidæ), which, although almost universally distributed, are more numerous, and have more peculiar and characteristic genera here than in any other region. Most of our song-birds, and many of the commonest tenants of our fields, woods, and gardens, belong to this family; and identical or representative species are often found ranging from Spain to China, and from Ireland to Japan. The reedlings (Panuridæ), the tits (Paridæ), and the magpies (Pica), are also very characteristic; while among the finches (Fringillidæ), a considerable number of genera are peculiar. A large number of peculiar groups of grouse (Tetraonidæ), and pheasants (Phasianidæ) are also characteristic of this region. Although the reptiles and fresh-water fishes are comparatively few, yet many of them are peculiar. Thus, no less than 2 genera of snakes, 7 of lizards, and 16 of batrachia, are confined to the Palæarctic region, as well as 20 genera of fresh-water fishes.

The insects and land-shells offer their full proportion of peculiar types; but it would lead us beyond our special object to enter into details with regard to these less known groups of animals.[65]

[65] Details will be found in the Author’s work on The Geographical Distribution of Animals.

The Ethiopian Region.

The Ethiopian region, consisting of Africa south of the Tropic of Cancer with Madagascar, is of very small area compared with the Palæarctic region; yet owing to the absence of extreme climates, and the tropical luxuriance of a considerable portion of its surface, it supports a greater number and variety of large animals than any other part of the globe of equal extent. Much of the speciality of the region is, however, due to the rich and isolated fauna of Madagascar, the peculiarities of which may be set aside till we come to discuss the past history of the Ethiopian region.

Considering then, first, the zoological features of tropical and southern Africa alone, we find a number of very peculiar forms of mammalia. Such are the golden moles, the Potamogale, and the elephant-shrews among Insectivora; the hippopotami and the giraffes, among Ungulata; the hyæna-like Proteles (Aard-wolf), and Lycaon (hyæna-dog), among Carnivora; and the Aard-varks (Orycteropus) among Edentata. These are all peculiar; but among highly characteristic forms are the baboons, and several genera of monkeys and apes; several peculiar Lemurs; a great variety of the civet-family (Viverridæ), and of rodents; peculiar genera of swine (Potamochærus and Phacochærus), and a greater abundance and variety of antelopes than are to be found in all the other regions combined. But the Ethiopian region is strikingly distinguished from all others, not only by possessing many peculiar forms, but by the absence of a number of common and widely distributed groups of mammalia. Such are—the bears, which range over the whole northern hemisphere, and as far south as Sumatra in the eastern and Chili in the western hemisphere, yet they are totally wanting in Tropical and South Africa;—the deer, which are still more widely distributed, ranging all over North and South America, and over all Asia to Celebes and the Moluccas, yet they are totally absent from the Ethiopian region; goats and sheep, true oxen (Bos), and true pigs (Sus), are also absent; though as to the last there is some doubt, certain wild pigs having been observed, though rarely, in various parts of Tropical Africa, but it is not yet determined whether they are indigenous, or escaped from domestication. The absence of such wide-spread families as the bears and deer is, however, most important, and must be taken into account when we come to consider the geographical changes needed to explain the actual state of the Ethiopian fauna.

The birds are not proportionately so peculiar, yet there are many remarkable forms. Most important are the plantain-eaters, the ground-hornbills, the colies, and the anomalous secretary-bird;—while among characteristic families there are numbers of peculiar genera of flycatchers, shrikes, crows, sun-birds, weaver-birds, starlings, larks, francolins, and the remarkable subfamily of the Guinea-fowls. There are not such striking deficiencies among birds as among mammals, yet there are some of importance. Thus, there are no wrens, creepers, or nut-hatches, and none of the wide-spread group comprising the true pheasants and jungle fowl—a deficiency almost comparable with that of the bears or the deer. Among the lower vertebrates there are 3 peculiar families of snakes and 1 of lizards, as well as 1 of toads and 3 of fresh-water fishes.

The Oriental Region.

The Oriental region comprises all tropical Asia east of the Indus, with the Malay Islands as far as Java, Borneo, and the Philippines. In its actual land-area it is the smallest region except the Australian; but if we take into account the wide extent of shallow sea connecting Indo-China with the Malay Islands, and which has, doubtless, at no distant epoch, formed an extension of the Asiatic Continent, it will not be much smaller than the Ethiopian region. Here we find all the conditions favourable to the development of a rich and varied fauna. The land is broken up into great peninsulas and extensive islands; lofty mountains and large rivers everywhere intersect it; while along its northern boundary stretches the highest mountain-range upon the globe. Much of this region lies within the equatorial belt, where the equability of temperature and abundance of moisture produce a tropical vegetation of unsurpassed luxuriance. We find here, as might be expected, that the variety and beauty of the birds and insects is somewhat greater than in the Ethiopian region; although, as regards mammalia, the latter is the most prolific, both in genera, species, and individuals.

The families of Mammalia actually peculiar to this region are few in number, and of limited extent. They are,—the Galeopithecidæ, or flying lemurs; the Tarsiidæ, consisting of the curious little tarsier, allied to the lemurs; and the Tupaiidæ, a remarkable group of squirrel-like Insectivora. There are, however, a considerable number of peculiar genera, forming highly characteristic groups of animals—such as the various apes, monkeys, and lemurs, almost all the genera of which are peculiar; a large number of civets and weasels; the beautiful deer-like Chevrotains, often called mouse-deer; and a few peculiar antelopes and rodents. It must be remarked that we find here none of those deficiencies of wide-spread families which were so conspicuous a feature of the Ethiopian region—the only one worth notice being the dormice (Myoxidæ), a small family spread over the Palæarctic and Ethiopian regions, but not found in the Oriental.