Anatomy
The orang-utans resemble man in many
anatomical features even though outwardly they
have developed many superficial differences. The
long shaggy hairs of orang-utan may grow as
long as 18 inches and tends to be longer over the
shoulders and arms. The coats comes in shades of
orange to blackish brown. This colouration
however appears darker with increasing age.
Young orang-utans generally have hairs that stick
up from the crown of their heads but becomes
short and flattened in adults. The face and the
abdomen are hairless exposing tough dark
brownish skin.
The adult male orang-utan appears formidable
and grotesque by human standards. In close up,
his face is an extraordinary arrangements of
folded skins and protruding bulges of fat. Their
massive bulky frame compel them to move only
slowly and cautiously through the forest trees.
The female orang-utan is much smaller and
daintily assembled than her masculine mate. Thus
orang-utan are said to exhibit marked sexual
dimorphism - the difference in appearance
between males and females of the same species -
in this case males may grow to double the weight
of females.
This slightly exaggerated sexual dimorphism
present the males with special mate-winning
characteristics when competing among
themselves for the females. The males also
display threatening gestures in the presence of
other males and the effectiveness of these
exaggerated and awe-inspiring acts involve visual
contacts. The female orang-utans are more likely
to yield to the biggest and the fittest-looking
males. A dominant male may in fact exercise
control over more than one female in his territory.
Males are known to fight for the possession of a
female at mating time. A peculiar prelude to
mating is "singing" by the male which consists of
prolonged vibrating burr starting low and
increasing in volume to a deep roar before
decreasing again and finally ceasing. Pairs may
also play prior to mating. They wrestle, slap and
mockingly bite each other around the neck and
face; all along accompanied by low grunts.
Mating takes place in trees and in a hanging
position, usually face to face.
Menstruation cycle for a female orang-utan is
about 29 days and pregnancy takes roughly eight
months. The infant usually weighs between
2 to 3 ½ pounds at birth and will cling to
mother's fur from the start. Normally the baby
orang-utan remains under the close protection of
its mother until it is weaned at about 4 years of
age. During this time it is cared for with a
devotion paralleled only by human mothers. She
would emit high-pitch screams should the baby
try to wonder separately too distant away from
her. The male on the other hand plays no part in
child-rearing. The mother nurses the baby with
her milk for 2 or 3 years and gradually starts
feeding its supplementary food in the form of
pre-chewed fruits or vegetables. Soon a young
orang-utan is able to fend for itself and began
associating with others of its own age. The
mother now becomes ready to mate again.
|
