The Orangutan is found on the isolated chain of islands that comprise Indonesia and part of Malaysia. They are primarily found on the two islands of Borneo and Sumatra. Each island has its own subspecies of Orangutan that spend most of their lives high up in the canopy of the rainforests where food can easily be found.
Their diet primarily consists of fruits and vegetation, including Jackfruit, Durian, Lychees, Figs, Mangoes, young leaves, shoots and over 400 species of other plants. They also aren’t afraid to eat bugs, eggs and smaller invertebrates if the opportunity arises.
Flanged Orangutan, Photocredit: David Arvidson
Their arm-span can be 7 feet long, meaning they have the long arms adapted to life in the treetops. On the ground they travel on their knuckles, and are clumsy on the ground. Thus, when they come down from the trees, are much more susceptible to predators such as tigers and leopards.
Since tigers are very few in number themselves, the leopard is their main predator and the young are the most likely to be their victims. Yet, Orangutans can spend half of their daytime foraging on the ground for food and this leaves adults exposed to danger as well.
However, they tend to be safer far up in the trees, where they play an imperative role in the restoration of the forest. Orangutans eat and disperse the seeds of the fruits that they consume, and therefore spread them around as they travel around their territories. These fallen seeds can be the beginning of new sprouts if sufficient light and nutrients are readily available.
The fallen seeds and discarded fruit also become food for the Bearded Pig, a suid who is known to follow primates for their leftovers. As a result, the Orangutan’s eating behaviors influences the growth of the flora and fauna, as well as the lives of other species dwelling in the rainforest. Hence they earn their namesake Orangutan, which means “man of the forest” in the native Malay language.
Baby Orangutan, Photocredit: Schristia
Orangutans tend to live out solitary lives with both genders living within their own territories. Male orangutans will ensure that their territory, however, will overlap with several females for breeding. Female orangutans will have the company of their infant for many years, who are weaned when they are 3-4 years old but can remain with her until independence at 5-7 years of age.
Since the young orangutans remain with their mothers for an extended period of time, there can be as much as an 8-10 year period between the first and second birth. Orangutans typically give birth to only a single infant after bearing them for eight months. Their singular births and long birthing interval means that the Orangutan has a very slow reproductive rate. This also means that the population is also equally as slow to recover or rebound from threats to their species.
Male orangutans actually come in two variations: un-flanged and flanged. Un-flanged males look very similar to adult females, while flanged males have large facial disc and a bulbous throat sack for warning calls. These calls are intended to threaten other males to stay out of their territory, or to prepare for a fight. These differences in male physicality is unknown, but even stranger still is that males that were originally un-flanged can become flanged later in life.
Clyde the Orangutan @ San Diego Zoo
There are two subspecies of Orangutan: the Sumatran Orangutan and the Bornean Orangutan, who have been separated on their individual respective islands for over a million years. Sumatran Orangutans are identifiable by lengthier facial hair and their tendency to gather together at abundant fruiting sites. They also tend to be a bit more social and the adults will interact with younger, inexperienced Orangutans. Sumatran Orangutans are much more reluctant to descend the ground in comparison to Bornean Orangutans.
Bornean Orangutans, particularly males, are much more likely to be found foraging on the ground. They don’t socialize or gather in temporary groups as nearly as often as Sumatran Orangutans, and the Bornean Orangutans are known to breed faster. This helps in growing the Bornean Orangutan population, which is much larger than the Sumatran.
Both Orangutan species are unfortunately threatened by increased logging and the conversion of rainforest into palm tree oil fields. Bornean Orangutans have been listed as an Endangered species since 1986, their population ranging between 45,000 to 69,000. Sumatran Orangutans are listed as Critically Endangered since the year 2000, their population is estimated to be a mere 7,300.
These species have continued to decline, and are projected to do so due to continual threats to their habitat. These threats, combined with their slow reproductive rate, means that the Orangutan is believed to eventually go extinct by 2050 as their habitat is continued to be destroyed.