Sumatran Orangutan
Pongo abelii
Kingdom: Animalia, Phylum: Chordata, Class: Mammalia, Order: Primates,
Family: Hominidae, Subfamily: Ponginae, Genus: Pongo, Species: Abelii
Status: Habitat: Range: Height: Weight: Diet: Lifespan: Critically
endangered
Tropical rainforests
Only on the island of
Sumatra in Indonesia
Male up to 5 feet;
females up to 3 1/2
feet
Males up to 300
pounds; females up to 150 pounds
Mostly fruit, but also leaves, shoots,
insects, bark, eggs, small invertebrates,
and woody lianas
30 to 35 years; up to 50 years in captivity
Sumatran Orangutan Range
In the Malay language, the word orangutan means “person
of the forest”. There are two distinct orangutan species: Sumatran orangutan and Bornean
orangutan. Athough their habits are almost identical, the two species live on the separate
islands of Sumatra and Borneo in the South Pacific. Orangutans, along with chimpanzees,
bonobos, and gorillas, are referred to as great apes. The great apes are highly intelligent
animals and are closely related to humans, sharing much of our DNA.
The highly-intelligent, gentle orangutan is the largest arboreal (tree-dwelling) mammal in the
world. This ape is so well adapted to a tree-dwelling lifestyle that it rarely has to descend to
the ground. While the other great apes can climb and nest in trees, orangutans spend most
of their lives on the ground. Orangutans sleep in the forks of trees where they pull in other
branches to form a nest that includes a roof to provide shelter from heavy downpours. They
will usually find a new place to sleep and make a new nest each night.
The hands and feet of the orangutan are well adapted for hanging from tree limbs. The
big toe, as well as the thumb, is opposable, meaning it can be moved around to touch the
other toes, or fingers, giving the ability to grasp things, pick up small objects and eating with
one hand. Their arms are 1½ times longer than their legs and are extremely powerful. Males
may have arm spans up to eight feet long! Plus, orangutans have tremendous strength that
enables them to swing from branch to branch and to hang upside-down for long periods
of time to retrieve food. These traits make it possible for orangutans to perform almost all of
their necessary behaviors while suspended in the trees – including feeding, traveling, mating,
nesting, and child rearing.
Orangutans are semi-solitary, with the largest family unit consisting of one female and two
offspring. Mature males are primarily solitary and make plenty of rumbling, howling calls as
they move through the forest to ensure that they stay out of each other’s way. The “long
call” can be heard a little over a mile away. Mothers and their young, however, share a
strong bond.
Baby orangutans nurse until they are about six years of age, slowly learning how to eat fruit
and other solid food as they travel through the forest with their mother. A young orangutan
maintains constant physical contact with its mother for the first year of its life. It may
occasionally encounter another young orangutan or may play with an older sibling, but
usually its mother is its sole companion. At two years of age, a young orangutan will begin to
leave its mother for short periods of time. However, it never ventures too far and still shares a
sleeping nest with her. Young orangutans are usually weaned at 3 to 4 years of age.
Female orangutans usually don’t have their first offspring until 13 to 16 years of age and only
give birth about once every eight years after that, the longest time between births of any
mammal on earth. This means they normally have only 3 to 4 babies in their lifetime. This low
reproductive rate is why orangutan populations are very slow to recover from disturbances.
Many wild orangutans have developed an amazing ability to use tools. They’ve been
observed using twigs like probes to extract insects and honey from tree trunks, as well as
blunt tools to scrape seeds from fruit. They have also been observed making tools to scratch
themselves, using leafy branches like umbrellas to shelter themselves from sun and rain,
using branches as fly-swatters, using “leaf gloves” to handle prickly fruits, or creating “seat
cushions” to sit comfortably in thorny trees.
About 10,000 years ago, orangutans were widespread throughout the forests of Asia,
even in southern China. Scientists estimate there were probably hundreds of thousands of
orangutans. However, the latest data (2008) from the International Union for Conservation
of Nature (IUCN) estimate only around 6,600 still survive in the tropical forests of the islands
of Borneo and Sumatra. This estimate suggests that orangutans could be the first great ape
species to become extinct in the wild in as little as 5 years due to habitat loss, poaching, and
illegal pet trade.
Both Bornean and Sumatran orangutans have been in dire trouble for some time. The primary
reasons are habitat loss and degradation from logging, forest fires, and timber clearing for
farming (including palm oil plantations) and human settlements. Orangutans are also hunted
and killed for their meat (bushmeat), and young orangutans are captured for sale in the
illegal pet trade.
Though the situation is critical for orangutans, there are organizations and individuals in many
countries trying to reverse their severe decline. They are working to stop illegal logging, to
increase sustainable economic alternatives for communities surrounding orangutan habitat,
helping instill national pride in orangutans and their environment, and rehabilitating excaptive orangutans into protected habitat.
Sumatran Orangutans at
Rolling Hills Zoo:
Rusa, a 34-year-old female
(right), and Clyde, a
38-year-old male (left).
Visit Rolling Hills Zoo soon to
meet both of
our orangutans!
Rolling Hills Zoo, October 2014