The Orang-Utan is found only in Sumatra and Borneo, and is common in
either of these islands--in both of which it occurs always in low,
flat plains, never in the mountains. It loves the densest and most
sombre of the forests, which extend from the seashore inland, and thus
is found only in the eastern half of Sumatra, where alone such forests
occur, though, occasionally, it strays over to the western side.

On the other hand it is generally distributed through Borneo, except
in the mountains, or where the population is dense. In favorable
places the hunter may, by good fortune, see three or four in a day.

[Illustration: HEAD OF ORANG-UTAN.]

Except in the pairing time, the old males usually live by themselves.
The old females and the immature males, on the other hand, are often
met with in twos and threes; and the former occasionally have young
with them, though the pregnant females usually separate themselves,
and sometimes remain apart after they have given birth to their
offspring. The young Orangs seem to remain unusually long under their
mother's protection, probably in consequence of their slow growth.
While climbing the mother always carries her young against her bosom,
the young holding on by the mother's hair. At what time of life the
Orang-Utan becomes capable of propagation, and how long the females go
with young is unknown, but it is probable that they are not adult
until they arrive at ten or fifteen years of age. A female which lived
for five years at Batavia had not attained one-third the height of the
wild females. It is probable that, after reaching adult years, they go
on growing, though slowly, and that they live to forty or fifty years.
The Dyaks tell of old Orangs which have not only lost all their
teeth, but which find it so troublesome to climb that they maintain