DISTRIBUTION OF MAMMALS 169 does not offer proper environmental conditions to attract or preserve these mammals.
The Formosa macaque monkey, although usually given specific rank, is closely related to the common rhesus of southern China. The Formosan hare, described as a species of LepuSy may be related to the coarse-haired rabbit of the Chinese coast (Caprolagus). The moles, shrews, ferret badger, yellow-throated marten, mink, otter, Asiatic black bear, civets, palm civets, mongoose, clouded leopard, fishing cat, leopard cat, scaly anteater, hedgehog, squirrels and flying squirrels, and rats are either local races of Chinese species or identical to the mammals on the mainland. Formosa may have been formerly connected with China ; the depth of the strait is now about fifty fathoms. The Philippine Islands, excluding Palawan, the Calamianes, and Balabac which belong to the Malayan Subregion, are often separated as a distinct subregion. Their mammal fauna seems to have been derived chiefly from Malayan sources. It becomes progressively poorer as one proceeds northward, while the forms peculiar to the islands are concentrated in Luzon and Mindanao. Rodents and bats are widespread and diversified. Shrews occur on all the islands. The long-tailed or crab-eating macaque monkey, the civet, palm civet, pigs, and a small sambar deer are also almost everywhere. Squirrels, tarsiers, and flying lemurs or caguans are found only on several of the more southern islands. The tamarau or Philippine native representative of the water buffalo, is found only on Mindoro; however, introduced domesticated buffaloes have in some instances gone wild on various islands of the group. The slow loris, tree shrew, and one of the gymnure insectivores reach Mindanao.
Palawan, although it does not have all the Malay mammals, has so many of them that it is placed with the Greater Sunda Islands in the Malay Subregion. It was part of the mainland and connected with Borneo in all probability during the Pleistocene, while the other Philippine Islands have always been either separated from the continent or were connected so long ago that
170 MAMMALS OF THE PACIFIC WORLD there is little evidence of this connection so far as the mammals are concerned.
The Malayan Subregion is characterized by two gymnures (rat-like insectivores), tree shrews, flying lemurs or caguans, a number of fruit bats (the short-nosed and certain of the longtongued fruit bats), a false vampire, the slit-faced bat {Nycteris), naked free-tail bat (Cheiromeles) , slow loris, crab-eating and pig-tailed macaques, a variety of leaf monkeys and gibbons (except the hoolock), small-clawed otter, linsang, binturong, marbled cat, several small flying squirrels, striped and longnosed ground squirrels, pygmy squirrels, and the mouse-deer or chevrotain.
Virtually all of the mammals of the Malay Peninsula are found in Sumatra; only a few are lacking from Borneo and Java. Fossil evidence indicates that the fauna may have once been more uniform ; remains of elephants and tapirs have been found in Java where they are now absent. Extinction may account for some cases of discontinuous distribution, such as those of the tiger and of the leopard. The tiger is absent from Borneo and the leopard is known only from Java and the Kangean Islands, but both are present on the Malay Peninsula. Sumatra, Java, Bali, Borneo, and Palawan are all on the Asiatic continental shelf, and were part of the mainland in the not very distant past.
The islands to the east and north (Celebes and Philippines) have been separated for a very long time, since early in the Age of Mammals at least. Islands, especially the smaller ones, offer little variety of habitats, so that even if they were connected with the mainland as a cape or peninsula, they would not have a large mammal fauna. On the other hand, isolation of small populations on islands may result sometimes in more rapid evolutionary change than would be possible in large areas in the case of a widespread population. Inbreeding of small populations may fix characters that otherwise would be swamped. The Malayan fauna is closely allied to those of the Indian
DISTRIBUTION OF MAMMALS 171 and Chinese Subregions, but it lacks some of the northern elements present in each. On the Malay Peninsula there are likewise several forms that do not occur on any of the nearby islands ; those elements are chiefly Indian or Chinese forms, such as the gaur, a large species of bamboo rat, several squirrels, the large Indian and Burma civets, and the stump-tailed macaque monkey.
Sumatra is populated by mammals closely related to those of the Malay Peninsula ; a few Malay forms absent from the other islands are tapir, serow, brush-tailed porcupine, and the siamang gibbon. Faunal relationships between Sumatra and Borneo are close; the tana tree shrew, the tarsier, the orang, the thickspined porcupine, and the whitish species of the Oriental squirrel are elements present on both islands but absent from the Malay Peninsula and Java. On the other hand, several mammals are common only to Java and Sumatra: the Java tree shrew, the mink-like Java weasel, and one of the shrew rats. A native rabbit or hare, short-eared and striped with black, is thought to be allied to the coarse-haired rabbits of the Himalayan foothills and southern China.
The Mentawi Islands, off western Sumatra, have some wellmarked local forms such as the dwarf gibbon, a distinctive leaf monkey and the peculiar pig-tailed langur. The relationships of the other mammals are Sumatran.
Borneo, the largest of the islands, has more varied climatic and environmental conditions than other Greater Sunda Islands, or even than the Malay Peninsula. The mountains of the interior are a barrier dividing the lowlands of the northwestern part of the island from those of the southeastern. They provide conditions suitable for mountain-living species. Some of the large rivers also form barriers and restrict the ranges of certain species and races. A few high peaks, such as Kina Balu in the north and isolated Poi and Penrissen in the western corner of the island, have races, species, or even genera restricted to them.
172 MAMMALS OF THE PACIFIC WORLD Some of the mammals of Borneo appear to be related to present Chinese or Indo-Chinese forms: a red-cheeked ground squirrel, one of the slender-tailed tree shrews, and the proboscis monkey which is probably allied to the golden monkeys and the pied langurs. The ferret badger and banting may have reached Borneo from Indo-China but they also occur in Java. Several mammals known only from Borneo may have originated there, although derived from continental ancestral types. They are well-marked local species or genera such as several kinds of bats, the maroon and white-fronted leaf monkeys, the proboscis monkey, a form of banded palm civet, the Bornean mongoose, the bay cat, several squirrels, and the pygmy tree rat. In addition to these mammals shared by Borneo only with Sumatra, several mammals unknown in Java occur on Borneo and Sumatra and also on the mainland. The pen-tailed tree shrew, the large gymnure or "moonrat," the water shrew, several kinds of bats, the pig-tailed macaque, banded leaf monkey, Malay bear, a weasel, the hairy-nosed otter, the masked and banded palm civets, otter civet, short-tailed mongoose, clouded leopard, marbled cat, several sorts of flying squirrels, the longnosed ground squirrel, and the two-horned rhinoceros are such mammals.
Palawan and the nearby Caliamanes are related to Borneo faunally much as Bali is to Java. Their fauna is much poorer ; it includes none of the species found only in Borneo. The common tree shrew, scaly anteater, Malay badger, binturong, smallclawed otter, mouse-deer, porcupine, and the Palawan flying squirrel are mammals typical of the Malay Subregion. Java with Bali and Madura, which have less varied faunas, is the home of fewer mammals than Sumatra and Borneo. Most of the mammals are local races of species common to the Greater Sunda Islands, but a few, like the Javan wild pig, are restricted to the island. The banting and ferret badger, absent from Sumatra and the lower Malay Peninsula, are common to Java and Borneo.
DISTRIBUTION OF MAMMALS 173 Java is the only island in the group in which mammalian fossils have been found. Even those are relatively recent fossils of the Ice Age or Pleistocene. The most interesting discoveries in those deposits have been the remains of fossil man (Pithecanthropus), a man with many ape-like features, famed as the "missing link" between man and the ape. Actually this creature was much more human than is commonly supposed. Other relatively enormous forms closely related to Pithecanthropus, found in the Javan deposits, had teeth and jaws much larger than the gorillas.
There, too, were found remains of hyenas and bones of an extinct species of hippopotamus ; hyenas are no longer found in the Malay Subregion and the hippo today occurs only in Africa. A distinct species of wild ox, related to the banting, a saber-toothed tiger, a mastodon, and primitive kinds of elephants called stegodonts, as well as several animals long thought to be giraffes but actually related to cattle, formerly lived in Java. The Eld deer or thamin, now found no nearer than Burma and Indo-China, lived in Java until a few thousand years ago.
The Australo-Oriental Subregion or Wallacea is here considered to include Celebes, the Lesser Sunda Islands from Lombok to Timor, and the Moluccas. This is the zone of overlap of Oriental and Australian mammals, in which the former greatly predominate.
Celebes, much the largest land mass in the Australo-Oriental Subregion, has a fauna largely Oriental in origin. This includes the anoa or pygmy buffalo, wild pigs, the babirusa, sambar deer, shrews, two distinctive macaques, the tarsier, several extraordinary rats, a long-nosed ground squirrel, civets and palm civets. The civets and sambar may have reached Celebes by human agency, and one of the shrews, the house musk shrew, was perhaps transported in canoes like house mice and rats. Deer and pigs are good swimmers ; they may sometimes have advanced naturally through the chain of the Lesser Sunda Islands. The
174 MAMMALS OF THE PACIFIC WORLD anoa may have reached Celebes by the same route or from the Philippines. The presence on Mindoro of a dwarf buffalo, similar to the anoa, is not conclusive on this point, even if that similarity is considered evidence of close relationship rather than accidental convergence. The depths of the straits separating Celebes from Borneo, the Lesser Sundas, and Philippines are such that, considering also the faunal evidence, Celebes cannot have been connected with any of these during the later Tertiary. These straits were probably narrower than at present during part of the Ice Age; lowering of the sea level six hundred feet would reduce the width of the strait between south Celebes and Borneo to twenty-five miles. Smaller mammals were probably carried to Celebes from Borneo and other islands on drifting masses of trees and vegetation, such as are frequently torn loose by swollen rivers. The chances of survival under such conditions are especially poor for larger mammals, but shrews, rats, squirrels, several of which are closely related to Bornean species, palm civets, and monkeys may have arrived in Celebes in this way. The various degrees of differentiation shown by the rats and squirrels, some of which are generically distinct, some specifically, and some only racially, suggest that arrivals took place through a great length of time.
The only Australian element in Celebes consists of two species of cuscus (Phalanger) , distinct from the several species of that genus present in New Guinea. The spinal-winged fruit bat (Dohsonia), although sometimes found as far west as Bali, is characteristic of the Papuan Subregion, as is the tube-nosed fruit bat (Nyctimene) and one of the long-tongued bats {Syconycteris). Two genera of fruit bats are known only from Celebes and its small associated islands. The lesser mosaic-tailed rat (Melomys) is a member of a large genus of rats with headquarters in New Guinea. This genus is represented also on the Talaut Islands between Celebes and the Philippines. Saleyer, Sanghir, and Talaut Islands have many of the mammals found in Celebes. On the Sanghir group and Talaut are
DISTRIBUTION OF MAMMALS 175 phalangers, on the Sanghirs alone a tarsier. The spotted cuscus of New Guinea is represented on Saleyer. The presence of the tarsier on the Sanghir group may indicate that it came to Celebes from the Philippines by way of the Sanghirs; but it might have come from Borneo more easily.
The Molucca Islands are a scattered group, not uniform faunally. A flying phalanger (Petaurus) is found on Obi and Batjan; on these and on Halmahera (Gilolo) cuscuses and a bandicoot occur. The babirusa of Celebes occurs also in Buru. Other pigs, and sambar deer which reach east as far as Buru and the Gilolo group are found in Ceram. Pigs and deer are especially likely to be carried about by natives and to go wild. This fact explains their presence in New Guinea. The Lesser Sundas, with the exception of the gray cuscus on Timor and Wetar, have no Australian land mammals. The Australian long-eared bat (Ni/ctophilus), reported from Timor, has not been certainly found there but the tube-nosed fruit bat {Nyctimene) reaches this island. Spinal-winged bats, widespread in the Australo-Oriental Subregion, are found throughout the Lesser Sunda chain. Bats are more limited by water barriers than may be thought but nevertheless may be carried about by storms. Consequently the distribution of these mammals is frequently erratic.
Relatively few Oriental mammals extend as far east as Timor. They include the long-tailed macaque monkey (not recorded from the other islands, however), sambar deer, pigs, shrews, the palm civet, and the slit-faced bat {Nycteris). This bat, as yet unrecorded from the other Lesser Sundas, may be found later on some of the larger ones. Porcupines reach east as far as Sumbawa and possibly Flores, while a single unsatisfactory record in 1867 of palm civet is known from the Aru Islands, off western New Guinea.
The Australian Faunal Region, including the Australian continent, Tasmania, New Guinea, the Bismarck and Solomon groups, has a mammal fauna characterized by many varieties
176 MAMMALS OF THE PACIFIC WORLD of marsupials, a few egg-laying mammals, and a number of peculiar bats and rats, especially the water rats and giant rats. Native mammals of other orders — insectivores, carnivores, ungulates, and primates (except man himself) — are absent, except in the cases of the wild descendants of animals brought by man. The Australian and Papuan Subregions based upon geography are not wholly satisfactory. The savannas of the extreme south of New Guinea are f aunistically Australian ; the rain forests of North Queensland are inhabited in part by species belonging to genera characteristic of New Guinea.
The Australian Subregion is populated mainly by primitive and ancient mammalian types, including a wide variety of kangaroos and wallabies, possums and flying phalangers, the koala, the wombat, bandicoots, the marsupial mole, the marsupial ant^ eater, the Tasmanian devil, marsupial or "tiger" cats, marsupial mice, and finally the egg-laying monotremes which include the duckbill and spiny anteater. This fauna has probably been in Australia for millions of years, but there is little doubt that the first marsupials reached Australia from the northwest. At that time the present chain of East Indian islands may have connected with Asia. The pioneer marsupials which were probably small arboreal mammals, some perhaps a little like the American opossums and others like the modern Australian phalangers, can have reached the Australian Region on natural rafts almost as easily as across such a land bridge. From those pioneer forms the various families of Australian marsupials have branched out adaptively to take the places filled in other parts of the world by true carnivores, insectivores, squirrels, and hoofed mammals. During Pleistocene time — the ice ages — the Australian marsupials were even more varied than they are today ; they included kangaroos as large as donkeys, a groundliving phalanger as large as a lion and with great shearing teeth, giant wombats bigger than tapirs, and a massive clumsy beast that must have compared in size with the hippopotamus. The many peculiar rats of Australia came long after the