Bornean Orangutan

Bornean Orangutan(Pongo pygmaeus)

The Bornean orangutan is the second-largest ape after the gorilla, and the largest truly arboreal animal alive today. Body weights broadly overlap with the considerably taller Homo sapiens, but the latter is considerably more variable in size. By comparison, the Sumatran orangutan is similar in size but, on average, is marginally lighter in weight. The Bornean orangutan has a distinctive body shape with very long arms that may reach up to 1.5 metres in length.

It has grey skin, a coarse, shaggy, reddish coat and prehensile, grasping hands and feet. Its coat does not cover its face unlike most mammals, although Bornean orangutans do have some hair on their faces including a beard and mustache. It also has large, fatty cheek pads known as flanges as well as a pendulous throat sac. The male's face pad widens as he grows older. Bornean orangutans are highly sexually dimorphic and have several features that differ between males and females. Males have much larger cheek pads, or flanges, that are composed of muscle and large amounts of fat. In females, the flanges are mostly composed of muscle. Males have relatively larger canines and premolars. Males have a more pronounced beard and mustache. The throat sac in males is also considerably larger. There are two body types for sexually mature males: smaller or larger. Larger males are more dominant but smaller males still breed successfully. There is little sexual dimorphism at birth.

The Bornean orangutan has three subspecies:

Northwest Bornean orangutan – Sarawak (Malaysia) & northern West Kalimantan (Indonesia)
Central Bornean orangutan – Southern West Kalimantan & Central Kalimantan (Indonesia)
Northeast Bornean orangutan – East Kalimantan (Indonesia) & Sabah (Malaysia)

Habitat

The Bornean orangutan lives in tropical and subtropical moist broadleaf forest in the Bornean lowlands, as well as mountainous areas up to 1,500 m above sea level. This species lives throughout the canopy of primary and secondary forest, and moves large distances to find trees bearing fruit. It is found in the two Malaysian states of Sabah and Sarawak, and four of the five Indonesian Provinces of Kalimantan.

Due to habitat destruction, the species distribution is now highly patchy throughout the island; the species has become rare in the southeast of the island, as well as in the forest between the Rajang River in central Sarawak and the Padas River in western Sabah.

Diet

The Bornean orangutan diet is composed of over 400 types of food, including wild figs, durians, leaves, seeds, bird eggs, flowers, honey, insects, and, to a lesser extent than the Sumatran orangutan, bark. They have also been known to consume the inner shoots of plants and vines. They get the necessary quantities of water from both fruit and from tree holes. Bornean orangutans have been sighted using spears to attempt (unsuccessfully) to catch fish. The species has been observed using tools such as leaves to wipe off faeces, a pad of leaves for holding spiny durian fruit, a leafy branch for a bee swatter, a bunch of leafy branches held together as an "umbrella" while traveling in the rain, a single stick as backscratcher, and a branch or tree trunk as a missile. In some regions, orangutans occasionally eat soil to get minerals that may neutralise the toxins and acids they consume in their primarily vegetarian diets. On rare occasions, orangutans will prey upon other, smaller primates, such as slow lorises.

Breeding

Males and females generally come together only to mate. Subadult males (unflanged) will try to mate with any female and will be successful around half the time. Dominant flanged males will call and advertise their position to receptive females, who prefer mating with flanged males. Adult males will often target females with weaned infants as mating partners because the female is likely to be fertile.

Females reach sexual maturity and experience their first ovulatory cycle between about six and 11 years of age, although females with more body fat may experience this at an earlier age. The estrous cycle lasts between 22 and 30 days and menopause has been reported in captive orangutans at about age 48. Females tend to give birth at about 14–15 years of age. Newborn orangutans nurse every three to four hours, and begin to take soft food from their mothers' lips by four months. During the first year of its life, the young clings to its mother's abdomen by entwining its fingers in and gripping her fur. Offspring are weaned at about four years, but this could be much longer, and soon after they start their adolescent stage of exploring, but always within sight of their mother. During this period, they will also actively seek other young orangutans to play with and travel with. On average, juveniles do not become completely independent until they are about seven years of age. The birth rate for orangutans has been decreasing largely due to a lack of sufficient nutrients as a result of habitat loss.

Population

According to the IUCN Red List, they are classed as Critically Endangered(CR). The total number of orangutans in Borneo is not precisely known, except for Sabah, where comprehensive aerial surveys in the early 2000s provided an estimate of 11,000 individuals for the entire State . The most recent (2004) estimate for the species is that c. 55,000 Bornean Orangutans inhabit 82,000 km² of forest. However, using modelling and the latest field data available for Borneo, a revised map of their current distribution gives a larger range estimate of 155,000 km², or 21% of Borneo’s landmass. If the mean average orangutan density recorded in 2004 (0.67 individuals/km²) is applied to the updated geographic range, then the total population estimate would be 104,700 individuals. This represents a decline from an estimated 288,500 individuals in 1973 and is projected to decline further to 47,000 individuals by 2025.

Threats

Major threats include:

Habitat loss. Between 2000 and 2010, the mean annual rate of deforestation for Borneo was 3,234 km² per year. Assuming a similar deforestation rate in the future, 32,000 km² of forest could be lost by 2020; 129,000 km² by 2050 and 226,000 km² by 2080. In the early 2010s, only 22% of the current Bornean Orangutan distribution was located in protected areas. Approximately a third of the entire Bornean Orangutan range was in commercial forest reserves exploited for timber, and about 45% was in forest areas earmarked for conversion to agriculture or other land uses. A business-as-usual scenario, whereby non-protected forests would be converted along the lines of current development plans, will result in the loss of more than half of the current orangutan range on the island of Borneo in the next 50 years or so.
Illegal hunting. Illegal killing of Bornean Orangutans is a major cause of their decline. Recent interview surveys conducted in Kalimantan revealed that several thousand individuals are killed every year for meat consumption, as a way to mitigate conflict, or for other reasons. Overall Bornean Orangutan mortality rates in Kalimantan seem to significantly exceed the maximum rates that populations of this slow-breeding species can sustain. If hunting does not stop, all populations that are hunted will decline, irrespective of what happens to their habitat. These findings confirm that habitat protection alone will not ensure the survival of orangutans in Indonesian Borneo, and that effective reduction of orangutan killings is urgently needed.
Fires. Fires occur in Borneo on a yearly basis and are responsible for significant forest loss with dramatic results for certain orangutan populations. For example, 90% of Kutai National Park was lost to massive fires in 1983 and 1998 and its Bornean Orangutan population was reduced from an estimated 4,000 individuals in the 1970s to a mere 600; over 4,000 km² of peatland forest in southern Kalimantan was burnt to ashes in six months of 1997–1998, resulting in an estimated loss of 8,000 orangutans. In 2015, more than 20,000 km² of forest were lost to fires, which resulted in hundreds (or more) of additional orangutan deaths.
Habitat fragmentation. With the current scale of habitat exploitation and forest conversion to other types of land uses in Borneo, only a small percentage of current orangutan habitat will remain undisturbed by infrastructure development by 2030. Several orangutan PHVAs have shown that Bornean Orangutan populations of fewer than 50 individuals are not viable in the long term , and that many small populations will go extinct unless they are actively managed.
Lack of awareness. A recent study suggested that 27% of the people in Kalimantan did not know that orangutans are protected by law. Campaigns to effectively inform the public and encourage rural people to support the principles of environmental conservation and be actively responsible for the management of their resources are therefore a crucial requirement for successful orangutan conservation.
Climate change. Spatial models point to the possibility that a large amount of current orangutan habitat will become unsuitable because of changes in climate. Across all climate and land-cover change projections assessed in a recent analysis, models predicted that 49,000–83,000 km² of orangutan habitat will remain by 2080, reflecting a loss of 69–81% since 2010. This projection represents a three to five-fold greater decline in habitat than that predicted by deforestation projections alone. A major reduction in the extent of suitable orangutan habitat can be expected. However, core strongholds of suitable orangutan habitat are predicted to remain to the west, east and northeast of the island where populations of Central and Northeast Orangutans are found.

Conservation

The Bornean Orangutan is fully protected in Malaysia and Indonesia, and is listed on Appendix I of CITES. However, its forest habitat is not necessarily protected: about 20% of the current orangutan range in Sabah, and 80% in Kalimantan is not protected. Innovative mechanisms to ensure the long-term survival of Bornean Orangutans outside protected forests are urgently needed. The future of Bornean Orangutans will very much depend on the long-term security of large, strictly-protected forests where illegal logging and hunting will be efficiently controlled and the orangutan populations large enough to cope with catastrophic events such as fires and disease outbreaks. These forests need to contain the ecological gradients that will provide the key resources to sustain orangutans through climate and other gradual environmental changes. In the larger landscape, scientifically-based, regional land-use planning is needed to delineate zones of interaction around protected forests and their surroundings, encompassing hydrological, ecological and socio-economic interactions. Ideally, the core protected areas will remain connected to other areas of forest that could be used sustainably for (commercial) timber extraction. The design of such living landscapes must be approached across the whole landscape rather than at the site level.