Population Of Orangutans: Important Facts And Figures

By Amber Pariona on December 13 2017 in Environment

An orangutan in Borneo.

The orangutan is a great ape species that is native to Sumatra and Borneo, where it prefers rainforest habitats. This species is divided into three subspecies: the Sumatran orangutan, the Bornean orangutan, and the newly described Tapanuli orangutan. As their name suggests, each subspecies is found only in one of the previously mentioned countries, with the Tapanuli orangutan located in the South Tapanuli region of northern Sumatra. The Bornean orangutan is further divided into 3 subspecies, named for the region they inhabit: northeast, northwest, and central.

The orangutan has been the subject of many research projects due to its high level of intelligence. It shares just under 97% of its DNA with humans. This species is known to use tools for collecting food and spends the majority of its time in treetops, where it builds nests to sleep comfortably. Orangutans are easily recognizable by their reddish-brown color hair, which is longer on the face of the Sumatran subspecies. This species grows between 3 feet 9 inches and 4 feet 6 inches in height and weighs between 82 and 165 pounds. The males are significantly larger than the females. Additionally, orangutans tend to be solitary in nature and usually only the mother and her babies can be found living together.

Conservation Status of the Orangutan

Orangutans once inhabited large rainforest areas of the islands of Borneo and Sumatra with a population size estimated at approximately 230,000. Today, however, both its population size and inhabited range have drastically declined and only 112,500 are thought to be living in the wild. This species is protected by the Convention on International Trade in Endangered Species of Wild Fauna and Flora. Additionally, several international non-profit groups work to conserve this species, Borneo Orangutan Survival Foundation is perhaps the most well-known and far-reaching of these organizations.

The International Union for Conservation of Nature (IUCN) has classified both species as critically endangered. Efforts to conserve and protect this species have been underway since the 1970’s. Orangutan conservation typically focuses on protecting the habitat, creating a sustainable lumber industry, preventing poaching, and prohibiting the pet trade.

Threats to the Orangutan Population

The primary threats facing orangutans include: poaching and habitat loss.

While poaching is a problem on both islands, it seems to be concentrated in Borneo. Poachers target orangutans for a number of reasons. This species is valued as a food source for humans and for their role in traditional medicine. Additionally, many locals believe orangutans cause extensive damage to their agricultural crops. In order to prevent this, orangutans are trapped and killed. The illegal pet trade is also a thriving industry on these islands, which has resulted in the loss of large numbers of baby orangutans that would have otherwise grown up in the wild.

Deforestation, agriculture, mining, and increasing human populations have resulted in habitat loss and fragmentation throughout Borneo and Sumatra. For example, more than half of the Bornean orangutan habitat has been destroyed by the logging industry since 1973. Additionally, increasing numbers of roads have divided orangutan habitats, fragmenting the areas in which this species may search for food and shelter.

Population of Orangutans in the Wild

Current orangutan population estimates have the Bornean orangutan numbered at around 104,700, the Sumatran orangutan at 7,500, and the Tapanuli orangutan at only 800.

Within Borneo, the only sub-population size that is known with accuracy is that found in the state of Sabah, which has 11,017 orangutans. Other significant (though estimated) populations are found in the following regions: Central Kalimantan (estimated at over 31,300), West Kalimantan and Sarawak (7,425), and East Kalimantan (4,825). The entire population estimate of 104,700 represents a 60% decrease in Bornean orangutans. Most of this loss occurred between 1950 and 2010, when industrial activities began to threaten the survival of this species. From 2010 to 2025, researchers expect an additional 22% loss in population. These figures mean that over 3 generations of the Bornean orangutan life cycle, this subspecies will suffer an 82% decrease in population size. Today, just under 60% (or an area of 59,886.76 square miles) of the rainforests of Borneo are considered habitable for this primate. Most of the habitat loss suffered here is believed to have occurred between 1973 and 2010. Habitat destruction is expected to continue threatening the wild Bornean orangutan population, with an additional 25% decrease estimated from 2010 to 2025. By 2025, the entire island is expected to have a population of only 47,000.

Within Sumatra, roughly 60% of the rainforest was destroyed from 1985 to 2007. A large percentage of this destruction occurred in the Aceh province after 2005, when civil war in the area ended and the economy began to improve. This improvement was propelled by logging, mining, and agricultural industries. Unfortunately, this province is also home to the majority of the Sumatran orangutan population. An estimated 78.6% of this species lives here and most of this population is confined to the Leuser Ecosystem. It is the only place in the world where the Sumatran tiger, Sumatran rhinoceros, Sumatran orangutan, and Sumatran elephant can be found living together. A recent report suggests the Sumatran orangutan population is actually around 14,600 and occupies an area of 3,471 square miles.

Tapanuli orangutans find their ecological niche in tropical and subtropical watery forests south of Lake Toba in Sumatra. Tapanuli orangutans spread in a region of 1,000 square kilometers in the said habitat. The estimated total number of Tapanuli orangutans is less than 800, making the species incredibly rare. Tapanuli orangutans build nests to live in and are extremely shy. Tapanuli orangutans are extremely imperiled species. The survival of this rare species of great apes is hard due to conflict with humankind, wildlife trade, logging, and hunting. There is a gold mine near them, and an even more dangerous threat is the proposed establishment of a hydroelectric power within their niche. Thus, the Tapanuli orangutan faces a danger of habitat loss.

Orangutan Population in Captivity

Estimating the population of orangutans in captivity is difficult given the unknown number kept as pets around the world. This species is held in zoos for public education and captive breeding purposes, research facilities for scientific investigations, and even in circuses or by the movie industry for public entertainment purposes. Additionally, this species is also found in rescue and rehabilitation centers, where staff prepare them for life in the wild. Those orangutans that have been fully rehabilitated are released into protected forest areas.

Some estimates suggest that around 900 orangutans are currently kept in captivity around the world. Orangutans living in captivity may live as long as those in the wild, up to 30 years of age, depending on their environment. In one investigative project, researchers found that the life expectancy of captive orangutans is directly related to its level of happiness. Those that were rated as having a higher level of overall well-being by their caretakers were found to live longer lives.

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