SUMATRAN
ORANGUTAN
PRIMATA
Family: Pongidae
Genus: Pongo
Species: abelii
female
male
Range: endemic to the island of Sumatra, Indonesia, generally restricted to the north of the island
Habitat: primary tropical rain forests, lowland and hilly including dipterocarp (type of tree) and
peat-swamp forest
Niche: almost exclusively arboreal in the canopy, diurnal, omnivorous- largely frugivorous
Wild diet: primarily frugivores, but also eat leaves, insects (termites and ants) and on occasion,
the meat of slow loris
Zoo diet: fruits, vegetables, monkey chow
Life Span: Wild- ~ 44 yrs, Captivity- up to 55 yrs
Sexual dimorphism: M almost 2x weight of F, M has large cheek pads (see photo top right)
Location in SF Zoo: Across from the bird short string near the Lemur Cafe
APPEARANCE & PHYSICAL ADAPTATIONS:
Orangutans are great apes with thick reddish brown hair. Their legs are short and relatively
weak, while hands and arms are powerful and arms are longer than legs. Their bodies are
adapted to arboreal locomotion (quadrumanous - having all four feet adapted to function as
hands). The orangutans’ long, narrow hands and feet are especially useful for grasping branches
and swinging. Their opposable thumbs and big toes are short to
facilitate the hook-like function of hands and feet, particularly in
Weight: F 66 - 110 lbs
brachiation and hanging on to tree branches. They have highly
M 110 – 198 lbs
mobile hip and shoulder joints that allow them to easily move from
Height: F ~ 4.3 ft
M ~ 5.9 feet
branch to branch and tree to tree. The opposable thumb is helpful in
TL:
none
picking fruits. Orangutans have tremendous strength, which enables
them to brachiate and hang upside-down from branches for long
periods of time to retrieve fruit and eat young leaves.
Males have secondary sexual characteristics of large cheek pads (flanges) of fibrous material that
are covered in a fine white hairs and throat sacs. Male’s arm span can be up to 8 feet.
STATUS & CONSERVATION
Sumatran Orangutans are Critically Endangered on the IUCN Red List and on Appendix I of
CITES. They are protected under Indonesian domestic legislation. Despite this legal protection
since 1931, this species is seriously threatened by logging, fires for the conversion of forest to
agricultural land and palm oil plantations, and fragmentation by roads. In parts of North Sumatra
orangutans are also hunted occasionally for food and are still captured and kept in households as
status symbols. Their habitat is being lost at an extremely high rate. Orangutans are frugivores
and play a vital role in the dispersal of seeds over a huge area; if orangutans were to disappear,
so would several tree species, especially those with larger seeds.
COMMUNICATION AND OTHER BEHAVIOR
Orangutans are the largest arboreal animals in the world, usually spending over 95% of their time
in the trees’ canopies; exceptionally large males spend more time traveling on the ground, walk
on all fours, using their palms or fists. Nests are built with bent branches, sticks, and leaves and
orangutans nap or sleep in them.
Male Sumatran orangutans are capable of a “long call,” exceptionally loud calls that carry through
forests for up to 1 km. These calls help males claim territory, call to females, and keep out
intruding male orangutans. Males have a large throat sac that amplifies this sound. They may
also pull small trees and limbs down to add a crashing sound along with the call. Male-male
competition for access to sexually receptive females is a major factor in orangutan adaptation.
Sumatran orangutans are more social than Bornean orangutans, spending more time in small
groups. This has been attributed to mass fruit on fig trees, where groups of Sumatran orangutans
can come together to feed. Adult males are typically solitary while females are accompanied by
offspring. Grooming is a major source of social interaction in most primates, but there are few
grooming techniques used by orangutans.
COURTSHIP AND YOUNG
The primary mating tactic involves "harassment" of female by males. Most mating occurs in the
heaviest fruiting months (December to May). Birthing intervals are every 3 – 4 years. After a
female orangutan has given birth, her next 8 to 9 years are devoted to her offspring's survival;
orangutans have the longest “infancy” of the great apes. Fathers play no direct role in the
upbringing of their offspring. For the first few years, young hold tight to their mother’s body as she
moves through the forest canopy.
Estrous: Polyestrous, cycle 29 – 32 days
Gestation: 8.5 mos
Sexual Maturity: M ~ 10 - 15 years
F ~ 8 years
# of Mammae: 1 pr
Weaning Age: ~ 48 mos
# of Young: 1 (twins rare)
Weight at birth: 3.5 lbs
MISCELLANEOUS
In Malay orang means “person” and utan is derived from hutan, which means “forest.” Thus,
orangutan literally means “person of the forest.” Sumatran orangutans may be distinguished
from Bornean orangutans by their longer, paler red fur, their slender build, and white hairs on
their face and groin, and long beards on both males and females. Orangutans share 97% of their
DNA with humans.
Sources:
Created: 10/01
updated: 3/16
Walker's Mammals of the World, 6th edition, Ronald M. Nowak, © 1999 Johns Hopkins University Press
The Natural History of the Primates, Napier, J.R. © 1985 The MIT Press, Cambridge, Mass.
http://animaldiversity.org/accounts/Pongo_abelii/
http://www.worldwildlife.org/species/sumatran-orangutan
http://www.iucnredlist.org/details/39780/0
https://orangutan.org/