Island Life; Or, The Phenomena and Causes of Insular Faunas and Floras

Besides these absent genera there are some curious illustrations of Javan isolation in the species; there being several cases in which the same species occurs in all three of the typical Malay countries, while in Java it is represented by an allied species. These occur chiefly among birds, there being no less than seven species which are common to the three great Malay countries but are represented in Java by distinct though closely allied species.

From these facts it is impossible to doubt that Java has had a history of its own, quite distinct from that of the other portions of the Malayan area.

Special Relations of the Javan Fauna to that of the Asiatic Continent.—These relations are indicated by comparatively few examples, but they are very clear and of great importance. Among mammalia, the genus Helictis is found in Java but in no other Malay country, though it inhabits also North India; while two species, Rhinoceros javanicus and Lepus kurgosa, are natives of Indo-Chinese countries and Java, but not of typical Malaya. In birds there are five genera or sub-genera—Zoothera, Notodela, Crypsirhina, Allotrius, and Cochoa, which inhabit Java, the Himalayas, and Indo-China, all but the last extending south to Tenasserim, but none of them occurring in Malacca, Sumatra, or Borneo. There are also two species of birds—a trogon (Harpactes oreskios), and the Javanese peacock (Pavo muticus), which inhabit only Java and the Indo-Chinese countries, the former reaching Tenasserim and the latter Perak in the Malay Peninsula.

Here, then, we find a series of remarkable similarities between Java and the Asiatic continent, quite independent of the typical Malay countries—Borneo, Sumatra, and the Malay Peninsula, which latter have evidently formed one connected land, and thus appear to preclude any independent union of Java and Siam.

The great difficulty in explaining these facts is, that all the required changes of sea and land must have occurred within the period of existing species of mammalia. Sumatra, Borneo, and Malacca have, as we have seen, a great similarity as regards their species of mammals and birds, while Java, though it differs from them in so curious a manner, has no greater degree of speciality, since its species, when not Malayan, are almost all North Indian or Siamese.

There is, however, one consideration which may help us over this difficulty. It seems highly probable that in the equatorial regions species have changed less rapidly than in the north temperate zone, on account of the equality and stability of the equatorial climate. We have seen, in Chapter X., how important an agent in producing extinction and modification of species must have been the repeated changes from cold to warm, and from warm to cold conditions, with the migrations and crowding together that must have been their necessary consequence. But in the lowlands, near the equator, these changes would be very little if at all felt, and thus one great cause of specific modification would be wanting. Let us now see whether we can sketch out a series of not improbable changes which may have brought about the existing relations of Java and Borneo to the continent.

Past Geographical Changes of Java and Borneo.—Although Java and Sumatra are mainly volcanic, they are by no means wholly so. Sumatra possesses in its great mountain masses ancient crystalline rocks with much granite, while there are extensive Tertiary deposits of Eocene age, overlying which are numerous beds of coal now raised up many thousand feet above the sea.[143 - "On the Geology of Sumatra," by M. R. D. M. Verbeck. Geological Magazine, 1877.] The volcanoes appear to have burst through these older mountains, and to have partly covered them as well as great areas of the lowlands with the products of their eruptions. In Java either the fundamental strata were less extensive and less raised above the sea, or the period of volcanic action has been of longer duration; for here no crystalline rocks have been found except a few boulders of granite in the western part of the island, perhaps the relics of a formation destroyed by denudation or covered up by volcanic deposits. In the southern part of Java, however, there is an extensive range of low mountains, about 3,000 feet high, consisting of basalt with limestone, apparently of Miocene age.

During this last named period, then, Java would have been at least 3,000 feet lower than it is now, and such a depression would probably extend to considerable parts of Sumatra and Borneo, so as to reduce them all to a few small islands. At some later period a gradual elevation occurred, which ultimately united the whole of the islands with the continent. This may have continued till the glacial period of the northern hemisphere, during the severest part of which a few Himalayan species of birds and mammals may have been driven southward, and have ranged over suitable portions of the whole area. Java then became separated by subsidence, and these species were imprisoned in the island; while those in the remaining part of the Malayan area again migrated northward when the cold had passed away from their former home, the equatorial forests of Borneo, Sumatra, and the Malay Peninsula being more especially adapted to the typical Malayan fauna which is there developed in rich profusion. A little later the subsidence may have extended farther north, isolating Borneo and Sumatra, in which a few other Indian or Indo-Chinese forms have been retained, but probably leaving the Malay Peninsula as a ridge between them as far as the islands of Banca and Biliton. Other slight changes of climate followed, when a further subsidence separated these last-named islands from the Malay Peninsula, and left them with two or three species which have since become slightly modified. We may thus explain how it is that a species is sometimes common to Sumatra and Borneo, while the intervening island (Banca) possesses a distinct form.[144 - Pitta megarhynchus (Banca) allied to P. brachyurus (Borneo, Sumatra, Malacca); and Pitta bangkanus (Banca) allied to P. sordidus (Borneo and Sumatra).]

In my Geographical Distribution of Animals, Vol. I., p. 357, I have given a somewhat different hypothetical explanation of the relations of Java and Borneo to the continent, in which I took account of changes of land and sea only; but a fuller consideration of the influence of changes of climate on the migration of animals, has led me to the much simpler, and, I think, more probable, explanation above given. The amount of the relationship between Java and Siam, as well as of that between Java and the Himalayas, is too small to be well accounted for by an independent geographical connection in which Borneo and Sumatra did not take part. It is, at the same time, too distinct and indisputable to be ignored; and a change of climate which should drive a portion of the Himalayan fauna southward, leaving a few species in Java and Borneo from which they could not return owing to the subsequent isolation of those islands by subsidence, seems to be a cause exactly adapted to produce the kind and amount of affinity between these distant countries that actually exists.

The Philippine Islands

A general account of the fauna of these islands, and of their biological relations to the countries which form the subject of this chapter, has been given in my Geographical Distribution of Animals, Vol. I. pp. 345-349; but since the publication of that work considerable additions have been made to their fauna, having the effect of somewhat diminishing their isolation from the other islands. Four genera have been added to the terrestrial mammalia—Crocidura, Felis, Pteromys, and Mus, as well as two additional squirrels; while the black ape (Cynopithecus niger) has been struck out as not inhabiting the Philippines. This brings the true land mammalia to twenty-one species, of which fourteen are peculiar to the islands; but to these we must add no less than thirty-three species of bats of which only ten are peculiar.[145 - The following list of the mammalia of the Philippines and the Sulu Islands has been kindly furnished me by Mr. Everett.] In these estimates the Palawan group has been omitted as these islands contain so many Bornean species that if included they obscure the special features of the fauna.

Birds.—The late Marquis of Tweeddale made a special study of Philippine birds, and in 1873 published a catalogue in the Transactions of the Zoological Society (Vol. IX. Pt. 2, pp. 125-247). But since that date large collections have been made by Everett, Steere, and other travellers, the result of which has been to more than double the known species, and to render the ornithological fauna an exceedingly rich one. Many of the Malayan genera which were thought to be absent when the first edition of this work was published have since been discovered, among which are Phyllornis, Criniger, Diceum, Prionochilus, and Batrachostomus. But there still remain a large number of highly characteristic Malayan genera whose absence gives a distinctive feature to the Philippine bird fauna. Among these are Tiga and Meiglyptes, genera of woodpeckers; Phænicophaes and Centropus, remarkable cuckoos; the long-tailed paroquets, Palæornis; all the genera of Barbets except Xantholæma; the small but beautiful family Eurylæmidæ; many genera allied to Timalia and Ixos; the mynahs, Gracula; the long-tailed flycatchers, Tchitrea; the fire-backed pheasants, Euplocamus; the argus pheasants, the jungle-fowl, and many others.

The following tabular statement will illustrate the rapid growth of our knowledge of the birds of the Philippines:—

The number of peculiar species is very large, there being about 300 land and forty-two water birds, which are not known to occur beyond the group. We have here, still more pronounced than in the case of Borneo, the remarkable fact of the true land birds presenting a larger amount of speciality than the land mammals; for while more than four-fifths of the birds are peculiar, only a little more than half the mammals are so, and if we exclude the bats only two-thirds.

The general character of the fauna of this group of islands is evidently the result of their physical conditions and geological history. The Philippines are almost surrounded by deep sea, but are connected with Borneo by means of two narrow submarine banks, on the northern of which is situated Palawan, and on the southern the Sulu Islands. Two small groups of islands, the Bashees and Babuyanes, have also afforded a partial connection with the continent by way of Formosa. It is evident that the Philippines once formed part of the great Malayan extension of Asia, but that they were separated considerably earlier than Java; and having been since greatly isolated and much broken up by volcanic disturbances, their species have for the most part become modified into distinct local forms, representative species often occurring in the different islands of the group. They have also received a few Chinese types by the route already indicated, and a few Australian forms owing to their proximity to the Moluccas. Their comparative poverty in genera and species of the mammalia is perhaps due to the fact that they have been subjected to a great amount of submersion in recent times, greatly reducing their area and causing the extinction of a considerable portion of their fauna. This is not a mere hypothesis, but is supported by direct evidence; for I am informed by Mr. Everett, who has made extensive explorations in the islands, that almost everywhere are found large tracts of elevated coral-reefs, containing shells similar to those living in the adjacent seas, an indisputable proof of recent elevation.

Concluding Remarks on the Malay Islands.—This completes our sketch of the great Malay islands, the seat of the typical Malayan fauna. It has been shown that the peculiarities presented by the individual islands may be all sufficiently well explained by a very simple and comparatively unimportant series of geographical changes, combined with a limited amount of change of climate towards the northern tropic. Beginning in late Miocene times when the deposits on the south coast of Java were upraised, we suppose a general elevation of the whole of the extremely shallow seas uniting what are now Sumatra, Java, Borneo, and the Philippines with the Asiatic continent, and forming that extended equatorial area in which the typical Malayan fauna was developed. After a long period of stability, giving ample time for the specialisation of so many peculiar types, the Philippines were first separated; then at a considerably later period Java; a little later Sumatra and Borneo; and finally the islands south of Singapore to Banca and Biliton. This one simple series of elevations and subsidences, combined with the changes of climate already referred to, and such local elevations and depressions as must undoubtedly have occurred, appears sufficient to have brought about the curious, and at first sight puzzling, relations, of the faunas of Java and the Philippines, as compared with those of the larger islands.

We will now pass on to the consideration of two other groups which offer features of special interest, and which will complete our illustrative survey of recent continental islands.

CHAPTER XVIII

JAPAN AND FORMOSA

Japan, its Position and Physical Features—Zoological Features of Japan—Mammalia—Birds—Birds Common to Great Britain and Japan—Birds Peculiar to Japan—Japan Birds Recurring in Distant Areas—Formosa—Physical Features of Formosa—Animal Life of Formosa—Mammalia—Land-birds Peculiar to Formosa—Formosan Birds Recurring in India or Malaya—Comparison of Faunas of Hainan, Formosa, and Japan—General Remarks on Recent Continental Islands.

Japan

The Japanese Islands occupy a very similar position on the eastern shore of the great Euro-Asiatic continent to that of the British Islands on the western, except that they are about sixteen degrees further south, and having a greater extension in latitude enjoy a more varied as well as a more temperate climate. Their outline is also much more irregular and their mountains loftier, the volcanic peak of Fusiyama being 14,177 feet high; while their geological structure is very complex, their soil extremely fertile, and their vegetation in the highest degree varied and beautiful. Like our own islands, too, they are connected with the continent by a marine bank less than a hundred fathoms below the surface—at all events towards the north and south; but in the intervening space the Sea of Japan opens out to a width of six hundred miles, and in its central portion is very deep, and this may be an indication that the connection between the islands and the continent is of rather ancient date. At the Straits of Corea the distance from the main land is about 120 miles, while at the northern extremity of Yesso it is about 200. The island of Saghalien, however, separated from Yesso by a strait only twenty-five miles wide, forms a connection with Amoorland in about 52° N. Lat. A southern warm current flowing a little to the eastward of the islands, ameliorates their climate much in the same way as the Gulf Stream does ours, and added to their insular position enables them to support a more tropical vegetation and more varied forms of life than are found at corresponding latitudes in China.

MAP OF JAPAN AND FORMOSA (with depths in fathoms).

Light tint, sea under 100 fathoms. Medium tint, under 1,000 fathoms. Dark tint, over 1,000 fathoms. The figures show the depth in fathoms.

Zoological Features of Japan.—As we might expect from the conditions here sketched out, Japan exhibits in all its forms of animal life a close general resemblance to the adjacent continent, but with a considerable element of specific individuality; while it also possesses some remarkable isolated groups. Its fauna presents indications of there having been two or more lines of migration at different epochs. The majority of its animals are related to those of the temperate or cold regions of the continent, either as identical or allied species; but a smaller number have a tropical character, and these have in several instances no allies in China but occur again only in Northern India or the Malay Archipelago. There is also a slight American element in the fauna of Japan, a relic probably of the period when a land communication existed between the two continents over what are now the shallow seas of Japan, Ochotsk, and Kamschatka. We will now proceed to examine the peculiarities and relations of the fauna.

Mammalia.—The mammalia of Japan at present known are forty in number; not very many when compared with the rich fauna of China and Manchuria, but containing monkeys, bears, deer, wild goats and wild boars, as well as foxes, badgers, moles, squirrels, and hares, so that there can be no doubt whatever that they imply a land connection with the continent. No complete account of Japan mammals has been given by any competent zoologist since the publication of Von Siebold's Fauna Japonica in 1844, but by collecting together most of the scattered observations since that period the following list has been drawn up, and will, it is hoped, be of use to naturalists. The species believed to be peculiar to Japan are printed in italics. These are very numerous, but it must be remembered that Corea and Manchuria (the portions of the continent opposite Japan) are comparatively little known, while in very few cases have the species of Japan and of the continent been critically compared. Where this has been done, however, the peculiar species established by the older naturalists have been in many cases found to be correct.

List of the Mammalia of the Japanese Islands

1. Macacus speciosus. A monkey with rudimentary tail and red face, allied to the Barbary ape. It inhabits the island of Niphon up to 41° N. Lat., and has thus the most northern range of any living monkey.

2. Pteropus dasymallus. A peculiar fruit-bat, found in Kiusiu Island only (Lat. 33° N.), and thus ranging further north of the equator than any other species of the genus.

3. Rhinolophus ferrum-equinum. The great horse-shoe bat, ranges from Britain across Europe and temperate Asia to Japan. It is the R. nippon of the Fauna Japonica according to Mr. Dobson's Monograph of Asiatic Bats.

4. R. minor. Found also in Burma, Yunan, Java, Borneo, &c.

5. Vesperugo pipistrellus. From Britain across Europe and Asia.

6. V. abramus. Also in India and China.

7. V. noctula. From Britain across Europe and Asia.

8. V. molossus. Also in China.

9. Vespertilio capaccinii. Philippine Islands, and Italy! This is V. macrodactylus of the Fauna Japonica according to Mr. Dobson.

10. Miniopterus schreibersii. Philippines, Burma, Malay Islands. This is Vespertilio blepotis of the Fauna Japonica.

11. Talpa wogura. Closely resembles the common mole of Europe, but has six incisors instead of eight in the lower jaw.

12. Talpa mizura. Günth. Allied to T. wogura.

13. Urotrichus talpoides. A peculiar genus of moles confined to Japan. An American species has been named Urotrichus gibsii, and Mr. Lord after comparing the two says that he "can find no difference whatever, either generic or specific. In shape, size, and colour, they are exactly alike." But Dr. Günther (P. Z. S. 1880, p. 441) states that U. gibsii differs so much in dentition from the Japanese species that it should be placed in a distinct genus, which he calls Neurotrichus.

14. Sorex myosurus. A shrew, found also in India and Malaya.

15. Sorex dzi-nezumi.

16. S. umbrinus.

17. S. platycephalus.

18. Ursus arctos. var. A peculiar variety of the European brown bear which inhabits also Amoorland and Kamschatka. It is the Ursus ferox of the Fauna Japonica.

19. Ursus japonicus. A peculiar species allied to the Himalayan and Formosan species. Named U. tibetanus in the Fauna Japonica.

20. Meles anakuma. Differs from the European and Siberian badgers in the form of the skull.

21. Mustela brachyura. A peculiar martin found also in the Kurile Islands.

22. Mustela melanopus. The Japanese sable.

23. M. Japonica. A peculiar martin (See Proc. Zool. Soc. 1865, p. 104).