Head-hunters, black, white, and brown

by Alfred C. Haddon

I have already pointed out that the physical features of Borneo prove that there are indications that it has undergone changes of level in recent geological times. The geological structure of the island shows that it formed part of a continent, as it contains formations of the Palæozoic, Mesozoic, and Cainozoic periods, and is thus very different from what are termed oceanic islands, that is, islands composed solely of recent volcanic rocks or built upon coral banks. As Wallace[6] points out: “A subsidence of five hundred feet would allow the sea to fill the great valleys of the Pontianak, Banjarmassing, and Coti rivers, almost to the centre of the island, greatly reducing its extent, and causing it to resemble in form the island of Celebes to the east of it.”

About a hundred and forty species of mammals have been discovered in Borneo, and of these “more than three-fourths,” according to Wallace, “are identical with those of the continent. Among these are two lemurs, nine civets, five cats, five deer, the tapir, the elephant, the rhinoceros, and many squirrels, an assemblage which could certainly only have reached the country by land.”

The most interesting of those species peculiar to the island, that is not found elsewhere, are the long-nosed monkey and the tailless porcupine. These peculiar forms, which amount to something over thirty in number, “do not, however, imply that the separation of the island from the continent is of very ancient date, for the country is so vast, and so much of the once connecting land is covered with water, that the amount of speciality is hardly, if at all, greater than occurs in many continental areas of equal extent and remoteness.” The same story is told by the birds, although one would imagine that possessing power of flight their distribution would be more uniform than it is. Wallace concludes that the majority of forest birds are restricted by narrow watery barriers to an even greater extent than mammals.

Mr. John Whitehead has made some valuable collections on Mount Kina Balu, the highest mountain in Borneo. “The Chinese Widow” is an isolated mountain mass which rises to a height of 13,698 feet; at an elevation of about 4,000 feet Mr. Whitehead began to find traces of a new fauna which linked that mountain with the Himalayas. Hose has made a similar discovery on Mounts Dulit and Mulu, so that Dr. R. B. Sharpe has stated (Ibis, 1894, p. 542): “it is evident that Mount Mulu belongs to the same system of the Himalayan offshoots, such as Kina Balu, Dulit, and Kalulong” (The Geographical Journal, i. 1893, p. 203).

Hose has stated that “the fauna of Mount Dulit resembles that of Kina Balu in a great number of instances, but it is a curious fact that all the species above 2,000 feet are found at a higher altitude on Kina Balu than they are on Mount Dulit. This, I think, can be accounted for by the fact that Mount Kina Balu has been cleared of all the old jungle, and farmed by the natives to a height of about 2,000 feet, whilst on the Dulit there are no traces of human habitation within miles of the mountain [this is a slight exaggeration on Hose’s part]. I think it is reasonable to suppose that many of the Kina Balu birds and animals, which prefer to live in the old jungle, have been in this way driven to a higher elevation” (Proc. Zool. Soc., 1889, p. 228).

In a paper on the mammals of Kina Balu, Mr. Oldfield Thomas points out the affinity of the mammalian fauna of the mountain at great heights with that of the Himalayan region. For example, a water-shrew (Chimarrogale himalayica) had previously been recorded from Sikhim, Assam, and the Katchin Hills in the north of Burmah. On the other hand, a certain mouse (Mus musschenbroecki) was previously known from Celebes, and its occurrence on Kina Balu suggests that other members of the Oriental element in the peculiar Celebean fauna may also prove to have survived on the tops of the Bornean mountains. Dr. R. B. Sharpe (Ibis, 1892, p. 430) also states that some of the Kina Balu species of birds have been obtained in high Sumatra.

There is evidence that during the Miocene Age Java was at least three thousand feet lower than it is now, and, as Wallace suggests, “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,” with the exception of those forms which were cut off on isolated mountain masses, where they survived in those places where the conditions were not very dissimilar from those they were accustomed to.

In other words, these more northern forms retreated from the deluge of the typical Malayan fauna up the mountains. The lower mountains were overwhelmed by the equatorial forests and the profusion of animals that are adapted for that peculiar condition of existence. The lesser spurs of the high mountains shared the same fate, but the struggle between the rival faunas became less keen at altitudes of three or four thousand feet. Here the temperature is cooler, and so the conditions of life become less favourable for the tropical lowland fauna, and more so to the relic-fauna of the northern mountains, and in consequence we have these faunistic islands.