The most noteworthy features of the fauna are the preponderance of bats (16 species) and rats (13 species)—which together constitute nearly three-fourths of the total number of mammals known to occur in the islands—and the absence of practically all representatives of the ungulates, squirrels, carnivores, and flying lemurs, which are characteristic of the surrounding regions and abound on other islands at equal distance from the mainland. From the Malayan islands where these occur they differ in that "they are surrounded by water of relatively great depth, while the others lie within the 50-fathom line. This paucity of mammalian life cannot be regarded as due to an unfavourable environment, since all the natural conditions on both Andamans and Nicobars are perfectly suited to the support of a rich and varied fauna"; yet so great is it that it appears safe to assume that these, "contrary to the case with the shallow-water islands, were isolated at a time when the mammals now characteristic of the mainland did not exist there." In fact, we are almost driven to conclude that they never were at any time a portion of the continent, but were formerly only far nearer to it, far larger and far more compactly situated—a hypothesis that is further supported by an investigation of the birds appertaining to them.
"As yet no species have been discovered whose origin may be referred to the remote period of a land connection: such mammals as are now known are evidently of very recent origin, as in scarcely an instance has their differentiation progressed further than in the case of members of the same genera found on islands lying in shallow water. The question at once arises, therefore, as to the means by which they have arrived where they now are. Flights from the mainland would readily account for the distribution of the bats; but the presence of the other mammals seems impossible to explain otherwise than through the agency of man. With the single exception of Tupai nicobarica,[219] all are types well known to be closely associated with man throughout the Malayan region. Moreover, the period of time necessary to the development of the peculiarities of the native Andamanese would undoubtedly be ample to allow the formation of any of the species known from either group of islands, since in a biologic sense it has been vastly longer to the smaller, more rapidly breeding, animals than to man. The introduction, intentional or otherwise, of a pig, a monkey, a palm-civet, two or three species of rats, a shrew, and perhaps also a tree-shrew, at about the time when the various islands were peopled by their present human inhabitants, would amply account for the existence of the present mammal fauna with its striking peculiarities."
The following tabular summary shows the distribution of the fauna among the islands. (The letter A indicates material obtained by Dr Abbott, the letter R a previous record; an asterisk denotes occurrence beyond the Andamans and Nicobars; doubtful species have a note of interrogation placed against them; and those in italics have been described as new from the collections made during the cruise of the Terrapin):—
Synopsis of the Mammalian Fauna of the Andaman and Nicobar Islands.[220]
| Name. | Andaman Islands. | Nicobar Islands. | |||||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| South Andaman. | Rutland Island. | Little Andaman. | Henry Lawrence Island. | Little Jolly Boy. | Barren Island. | No island specified. | Kar Nicobar. | Tilanchong Island. | Trinkat Island. | Kamorta Island. | Nankauri Island. | Kachal Island. | Little Nicobar. | Great Nicobar. | No island specified. | ||
| *Dugong dugon | R | ||||||||||||||||
| Sus andamanensis | R | RA | |||||||||||||||
| Sus nicobaricus | A | R | |||||||||||||||
| *Mus musculus | R | ||||||||||||||||
| Mus palmarum | R | ||||||||||||||||
| Mus bowersi(?) | R | ||||||||||||||||
| Mus stoicus | A | ||||||||||||||||
| Mus taciturnus | A | ||||||||||||||||
| Mus flebilis | A | ||||||||||||||||
| Mus andamanensis | RA | ||||||||||||||||
| Mus pulliventer | A | ||||||||||||||||
| Mus atratus | A | ||||||||||||||||
| Mus burrus | A | ||||||||||||||||
| Mus burrulus | A | ||||||||||||||||
| Mus burrescens | A | ||||||||||||||||
| *Mus alexandrinus | A | ||||||||||||||||
| Paradoxurus tytleri | RA | ||||||||||||||||
| *Felis chaus(?) | R | ||||||||||||||||
| Tupaia nicobarica nicobarica | RA | ||||||||||||||||
| Tupaia nicobarica surda | A | ||||||||||||||||
| Crocidura nicobarica | A | ||||||||||||||||
| Crocidura andamanensis | A | ||||||||||||||||
| *Scotophelus temminchii | R | ||||||||||||||||
| *Tylonycteris pachypus | R | ||||||||||||||||
| *Pipistrellus tichelli | R | ||||||||||||||||
| *Pipistrellus tenuis(?) | R | ||||||||||||||||
| Pipistrellus camortæ | A | ||||||||||||||||
| *Miniopterus pusillus | R | ||||||||||||||||
| Rhinolophus andamanensis | R | ||||||||||||||||
| Hipposideros nicobaricus | R | ||||||||||||||||
| Hipposideros nicobarulæ | A | R | |||||||||||||||
| *Hipposideros murinus(?) | R | ||||||||||||||||
| *Pteropus nicobarus | R | R | R | A | A | R | |||||||||||
| Pteropus faunulus | A | ||||||||||||||||
| *Pteropus rampyrus | R | R | |||||||||||||||
| Cynopterus brachyotis | R | ||||||||||||||||
| Cynopterus brachysoma | R | ||||||||||||||||
| Cynopterus scherzeri | RA | ||||||||||||||||
| *Macacus coininus | R | ||||||||||||||||
| Macacus umbrosus | A | A | A | R | |||||||||||||
Birds.
The birds of the Andamans and Nicobars have always been better known than the mammals, particularly since Mr A. O. Hume, with a number of collectors, made a cruise round the islands in a steamer in 1873, which resulted in the discovery of many new species, and a careful analysis of the avifauna.
In spite of what is to be expected from their position, the islands derive the bulk of their species from the distant Indian region, while the Indo-Burmese and Indo-Malayan regions are represented to a far less degree.
One of the most striking features is the extreme paucity of rasorial birds—peafowl, junglefowl, pheasants, partridges, or any of the natural genera into which these divide, and which are all well represented in the Arakan Hills. The next point is the highly specialised character of the ornis, for, excluding waders and swimmers, more than a third of the species are peculiar to the islands; while still more remarkable is the extent to which it is localised in the several groups between which is nowhere a break of more than 80 miles. Even more noteworthy are the details: for instance, the Andaman Hypothymis, which, as a rule, is a very distinct form, is replaced in the Nicobars by one which, although not precisely identical with the Indian form, is far more closely allied to this than the Andaman Tytleri. Each group has its distinct harrier eagle, red-cheeked paroquet, oriole, sunbird, and bulbul. Two woodpeckers are peculiar to the Andamans, but neither extends to the Cocos or Nicobars. The latter group possesses three distinct but closely allied species of Astur, each confined to separate islands.