ORANGUTANS OF INDONESIA
orangutans are two species of great apes known for their
intelligence, long arms and reddish-brown hair. Native
to Indonesia and Malaysia, they are currently found only
in rainforests on the islands of Borneo and Sumatra,
though fossils have been found in Java, Vietnam and
China. They are the only surviving species in the genus
Pongo and the subfamily Ponginae (which also includes
the extinct genera Gigantopithecus and Sivapithecus).
Their name derives from the Malay and Indonesian phrase
orang hutan, meaning "man of the forest". The orangutan
is an official state animal of Sabah in Malaysia.
The word orangutan (also written orang-utan, orang utan
and orangutang) is derived from the Malay and Indonesian
words orang meaning "person" and hutan meaning "forest",thus
"person of the forest". Orang Hutan is the common term
in these two national languages, although local peoples
may also refer to them by local languages. Maias and
mawas are also used in Malay, but it is unclear if those
words refer only to orangutans, or to all apes in
The word was first attested in English in 1691 in the
form orang-outang, and variants with -ng instead of -n
as in the Malay original are found in many languages.
This spelling (and pronunciation) has remained in use in
English up to the present, but has come to be regarded
as incorrect by some.
The name of the genus, Pongo, comes from a 16th century
account by Andrew Battell, an English sailor held
prisoner by the Portuguese in Angola, which describes
two anthropoid "monsters" named Pongo and Engeco. It is
now believed that he was describing gorillas, but in the
late 18th century it was believed that all great apes
were orangutans; hence Lacépède's use of Pongo for the
Orangutans are the most arboreal of the great apes,
spending nearly all of their time in the trees. Every
night they fashion nests, in which they sleep, from
branches and foliage. They are more solitary than the
other apes, with males and females generally coming
together only to mate. Mothers stay with their babies
until the offspring reach an age of six or seven years.
There is significant sexual dimorphism between females
and males: females can grow to around 4 ft 2 in or 127
centimetres and weigh around 100 lbs or 45 kg, while
flanged adult males can reach 5 ft 9 in or 175
centimetres in height and weigh over 260 lbs or 118 kg.
The arms of an orangutan are twice as long as their
legs. Much of the arm's length has to do with the length
of the radius and the ulna rather than the humerus.
Their fingers and toes are curved, allowing them to
better grip onto branches. Orangutans have less
restriction in the movements of their legs unlike humans
and other primates, due to the lack of a hip joint
ligament which keeps the femur held into the pelvis.
Unlike gorillas and chimpanzees, orangutans are not true
knuckle-walkers, and walk on the ground by shuffling on
their palms with their fingers curved inwards.
Adult male orangutans exhibit two modes of physical
development, flanged and unflanged. Flanged adult males
have a variety of secondary sexual characteristics,
including cheek pads (called "flanges"), throat pouch,
and long fur, that are absent from both adult females
and from unflanged males. Flanged males establish and
protect territories that do not overlap with other
flanged males' territories. Adult females, juveniles,
and unflanged males do not have established territories.
A flanged male's mating strategy involves establishing
and protecting a territory, advertising his presence,
and waiting for receptive females to find him. Unflanged
males are also able to reproduce; their mating strategy
involving finding females in estrus and forcing
copulation. Males appear to remain in the unflanged
state until they are able to establish and defend a
territory, at which point they can make the transition
from unflanged to flanged within a few months. The two
reproductive strategies, referred to as "call-and-wait"
for flanged male and "sneak-and-rape" for the unflanged
male, were found to be approximately equally effective
in one study group in Sumatra, though this
observation did occur during a period of instability in
flanged male rank and unflanged male mating success may
be lower in Borneo.
Fruit makes up 65% of the orangutan diet. Fruits with
sugary or fatty pulp are favored. The fruit of fig trees
are also commonly eaten since it is easy to both harvest
and digest. Other food items include: young leaves,
shoots, seeds and bark. Insects and bird eggs are also
Orangutans are thought to be the sole fruit disperser
for some plant species including the climber species
Strychnos ignatii which contains the toxic alkaloid
strychnine. It does not appear to have any effect on
orangutans except for excessive saliva production.
Orangutans use plants of the genus Commelina as an
Like the other great apes, orangutans are remarkably
intelligent. Although tool use among chimpanzees was
documented by Jane Goodall in the 1960s, it was not
until the mid-1990s that one population of orangutans
was found to use feeding tools regularly. A 2003 paper
in the journal Science described the evidence for
distinct orangutan cultures.
According to recent research by the psychologist Robert Deaner and his colleagues, orangutans are the world's
most intelligent animal other than humans, with higher
learning and problem solving ability than chimpanzees,
which were previously considered to have greater
abilities. A study of orangutans by Carel van Schaik, a
Dutch primatologist at Duke University, found them
capable of tasks well beyond chimpanzees’ abilities —
such as using leaves to make rain hats and leakproof
roofs over their sleeping nests. He also found that, in
some food-rich areas, the creatures had developed a
complex culture in which adults would teach youngsters
how to make tools and find food.
A two year study of orangutan symbolic capability was
conducted from 1973-1975 by Gary L. Shapiro with Aazk, a
juvenile female orangutan at the Fresno City Zoo (now
Chaffee Zoo) in Fresno, California. The study employed
the techniques of David Premack who used plastic tokens
to teach the chimpanzee, Sarah, linguistic skills.
Shapiro continued to examine the linguistic and learning
abilities of ex-captive orangutans in Tanjung Puting
National Park, in Indonesian Borneo, between 1978 and
1980. During that time, Shapiro instructed ex-captive
orangutans in the acquisition and use of signs following
the techniques of R. Allen and Beatrix Gardner who
taught the chimpanzee, Washoe, in the late-1960s. In the
only signing study ever conducted in a great ape's
natural environment, Shapiro home-reared Princess, a
juvenile female who learned nearly 40 signs (according
to the criteria of sign acquisition used by Francine
Patterson with Koko, the gorilla) and trained Rinnie, a
free-ranging adult female orangutan who learned nearly
30 signs over a two year period. For his dissertation
study, Shapiro examined the factors influencing sign
learning by four juvenile orangutans over a 15-month
The first orangutan language study program, directed by
Dr. Francine Neago, was listed by Encyclopedia
Britannica in 1988. The Orangutan language project at
the Smithsonian National Zoo in Washington, D.C., uses a
computer system originally developed at UCLA by Neago in
conjunction with IBM. .
Zoo Atlanta has a touch screen computer where their two
Sumatran Orangutans play games. Scientists hope that the
data they collect from this will help researchers learn
about socializing patterns, such as whether they mimic
others or learn behavior from trial and error, and hope
the data can point to new conservation strategies.
Although orangutans are generally passive, aggression
toward other orangutans is very common; they are
solitary animals and can be fiercely territorial.
Immature males will try to mate with any female, and may
succeed in forcibly copulating with her if she is also
immature and not strong enough to fend him off. Mature
females easily fend off their immature suitors,
preferring to mate with a mature male.
Orangutans have even shown laughter-like vocalizations
in response to physical contact, such as wrestling, play
chasing, or tickling.