Travel Reference
In-Depth Information
Figure 29
In an image captured by my daughter, a proboscis monkey dives into Kaliman-
tan's Sekonyer River. You can see another monkey waiting its turn on the branch. (Photograph
by Anne-Marie Wills Rivera.)
other bank. Their swimming style was impressive, a swift dog paddle with an
occasional overhand stroke that reminded me of the Australian crawl.
Swimming speed is essential for these monkeys, because the rivers of
Kalimantan are full of crocodiles. And their ability to swim is more than
some frantic splashy attempt to escape danger. It has been refi ned through a
long period of natural selection. The webs between their fi ngers and toes are
more extensive than those of any other primate.
Like the hoatzins, the proboscis monkeys have highly specialized diges-
tive systems. Fermentation begins in their foregut chambers from the very
moment the food is swallowed. As with other fermenters, a small change in
their diet can lead to a wide range of problems. They must limit their intake
of sugar-rich fruits, because an infl ux of sugar would be enough to disturb
the bacterial ecosystem on which the fermentation depends. Similar distur-
bances in bacterial ecology can lead to the often fatal conditions of acidosis
and bloat in domestic cattle.
These monkeys' specialized diet may be why they cannot be raised in
captivity. It seems that we have not learned to duplicate the conditions in the
