The central Bornean orangutan (Pongo pygmaeus wurmbii) is classified as Endangered (A2cd ver 3.1) on the IUCN Red List 2008 (Ancrenaz et al., 2008) indicating that it has a very high risk of extinction in the wild in the near future. It is also listed on Appendix I of CITES.

Historically, Bornean and Sumatran orangutans were considered subspecies of Pongo pygmaeus but recent taxonomic reviews support the widely accepted and adopted distinction of the Bornean (Pongo pygmaeus) and Sumatran orangutan (Pongo abelii) as distinct species (Goossens et al., 2009; Groves, 2001). Pongo pygmaeus wurmbii also known as the central subspecies, is one of three recognized subspecies of the Bornean orangutan.

As the name suggests the Bornean orangutan is endemic to the island of Borneo. The central subspecies is present in West Kalimantan south of the Kapuas River and Central Kalimantan west of the Barito River. To learn more about their distribution please activate the Pongo pygmaeus wurmbii range layer in the interactive map.

Pongo pygmaeus wurmii is the most numerous of the subspecies with over 34,000 individuals estimated to occur in ten populations of more than 1,000 individuals, and seven populations of more than 250 individuals (Ancrenaz et al., 2008; McConkey, 2005; Wich et al., 2008). The largest populations of this subspecies are found in Sabangau, Tanjung Puting and the Arut-Belantikan area which each supports more than 6,000 individuals (Wich et al., 2008).

The decline of the central subspecies is currently driven by habitat loss for plantation and agriculture expansion. Large oil palm plantations have been established in the lowland area between the Sampit River in Central Kalimantan and Gunung Palung National Park in West Kalimantan. Drought and peatland drainage led to large-scale forest fires in much of the central subspecies range in southern Borneo, leaving virtually no lowland forests in south-east Central Kalimantan between the Sabangau and Barito rivers (Husson et al., 2009). The implementation of regional autonomy and decentralization of forest management since 1998, and local government support for the development of plantations and commercial harvesting of wood has seriously increased rates of deforestation ((Soehartono et al., 2009). A recent analysis of agricultural and deforestation statistics for 1990-2005 shows that more than half of oil-palm development in Malaysia and Indonesia had resulted in deforestation (Koh and Wilcove, 2008) and that primary forests were the source of nearly 60% of new plantations established in Southeast Asia between 1980 and 2000 (Koh et al., 2011). Oil-palm plantations cover 2.4 million ha in Borneo (Koh et al., 2011). Secondary consequences of habitat loss include increased risk of fires in bordering forests and high prevalence of poaching and capture for the pet-trade of displaced orangutans, expansion of human settlements, and mining.

In the mid-1990’s a million hectare rice programme in Central Kalimantan was responsible for draining 15,000 km2 of peat swamp, including up to 7,000 km2 of prime orangutan habitat (McConkey, 2005). After it became apparent rice would not grow, it was abandoned in 1998, and the land burnt in 2002. It is estimated that approximately 8,000 orangutans died in the fires, and the land was transformed from rainforest to wasteland (Singleton et al., 2004). It is estimated that forest fires have reduced the total Bornean orangutan population by 33% (Ancrenaz et al., 2008).

Not surprisingly then orangutan numbers across Borneo have declined over 50% during the last 60 years (Ancrenaz et al., 2008). Slow-moving and with low reproductive rates (first birth occurs at 15-16 years with 6-8 years between births) orangutan populations are vulnerable to decline due to rapid forest clearance (Wich et al., 2004). Heavily logged forests have much lower orangutan density than unlogged and lightly logged forests. Traditional logging operations target only a small number of tree species important to orangutans however this significantly increases in illegal logging operations and impacts orangutan density (Husson et al., 2009). Whilst illegal logging, forest conversion and associated fires occur in most Indonesian national parks containing orangutan populations (Singleton et al., 2004) the threat of extinction is even higher in forests outside conservation areas where there is great demand to convert these lands for commercial agriculture and plantations (Tiju et al., in press). Although some major orangutan populations are found within protected areas the majority live outside of protected forests (Ancrenaz et al., 2008).

The opening up of the forest for logging increases opportunities for hunters. In areas where hunting is prevalent, its effects can outweigh those of logging (Marshall et al. 2006, Meijaard et al. 2010) and in some areas may be directly responsible for shaping the distribution of orangutans that we see today (Meijaard et al. 2010). Killing of orangutans occurs for the bushmeat and pet trades, traditional medicine, to mitigate conflicts with agriculture, and as a consequence of harvesting other forest products (Ancrenaz et al., 2008). Whilst the trade in orangutans is less open than before there is no indication it is dissipating (Nijman, 2009).

Field studies of Bornean orangutans began in the late 1960’s in East Kalimantan and Sabah, and have since extended elsewhere, focusing on ecology, feeding behaviour, adaptation to disturbance, and behavioral adaptations of rehabilitated individuals. Camp Leakey in Taman National Tanjung Puting, Kalimantan Tengah is one of the oldest orangutan field research sites; it is still running today and has generated much of what we know about Bornean orangutans (Soehartono et al., 2009). Since the 1970’s researchers have been witness to escalating habitat destruction and orangutan populations coming under increasing pressure, and many of these researchers are now involved, if not focusing, on conservation (McConkey, 2005).

The continuing decline of Bornean (and Sumatran) orangutan populations led experts to recognise the need for accurate data on population status and a conservation strategy to secure its’ future. In 1993, and then again in 2004 and 2005 Population and Habitat Viability Assessment (PHVA) workshops were conducted to assess the current status and future of wild orangutan populations and their habitat (Singleton et al., 2004). Taking taxonomy, habitat diversity and distribution into consideration, the process identified habitat units considered to offer the greatest potential for sustaining the Bornean orangutan. For the central subspecies, five areas of equal high importance were chosen for priority conservation action representing lowland dipterocarp forest, peat swamp and hill terrain. These are Tanjung Puting National Park, Sabangau, Mawas, Arut-Belantikan and Gunung Palung National Park

As a follow-up to the PHVA workshops, a series of focused group discussions were held across Indonesia in 2007 resulting in the development of a National Strategy and Action Plan for Orangutan Conservation (2007-2017) which was officially endorsed by the Government of Indonesia. The formulation of this strategy and action plan summarized all points from previous recommendations and provides a common framework to conserve orangutans and their lowland forest habitats. The goal of the plan is to provide a framework for all stakeholders in determining the priority for ex-situ and in-situ conservation activities (Soehartono et al., 2009).

Among the actions listed in the plan, the most important for the subspecies is making conservation a greater priority in land-use planning and local legislation. Managing land-use planning in a multi-stakeholder framework can help mitigate environmental impacts. For example, it can influence the allocation of land given to legal logging concessions and prevent forest conversion to plantations as well as ensuring that environmental regulations are followed such as preventing the use of fire to clear land (Tjiu et al., in press). Improving enforcement of wildlife and forest laws to increase the number and frequency of prosecutions, and to stop illegal logging is also important. This will require training (police, judges, prosecutors, forestry police), supplemented salaries, regular patrols, and for communities to play a greater role in monitoring and protecting their local wildlife areas although the latter must be accompanied by educational, economic, or health care benefits

Conservation awareness is needed to prevent hunting and collection, and to minimise habitat destruction. At the same time communities close to orangutan habitat may need support in developing alternative sources of income to relieve the pressure of illegal logging and collection of orangutans for the illegal wildlife trade.

More areas need protected status and their boundaries need to be clearly demarcated. In Central Kalimantan there is a need to elevate Mawas, Arut Belantikan, and Samba Kahayan to protected status and for West Kalimantan, the Bukit Rongga-Bukit Perai complex (Singleton et al., 2004). As most of Borneo is highly fragmented, corridors are needed, and these should be included in land-use plans. Areas that are degraded could become potential corridors linking existing sites if the land is protected and reforested.

Examples that combine good logging practice with orangutan conservation could benefit all the Bornean subspecies. Sustainable logging practices in the Deramakot Forest Reserve (part of the Upper Kinabatangan forests), implement a rotation system of reduced impact logging. The result is a mosaic of lowland habitats at different stages of exploitation and regeneration that supports one of the highest orangutan (Pongo pygmaeus morio) densities in Sabah. A well-managed logging concession does have potential to support orangutan populations, and it is imperative that conservation organisations work with timber companies so that their activities are compatible (Ancrenaz et al., 2008; Singleton et al., 2004). At the same time timber companies need to work together as an industry to solve the problem of illegal logging in legal concessions.

The northeast Bornean orangutan (Pongo pygmaeus morio) is classified as Endangered (A2cd ver 3.1) on the IUCN Red List 2008 (Ancrenaz et al., 2008) indicating that it has a high risk of extinction in the wild in the near future. It is also listed on Appendix I of CITES.

Historically, Bornean and Sumatran orangutans were considered subspecies of Pongo pygmaeus but recent taxonomic reviews support the widely accepted and adopted distinction of the Bornean (Pongo pygmaeus) and Sumatran orangutan (Pongo abelii) as distinct species (Goossens et al., 2009; Groves, 2001). Pongo pygmaeus morio also known as the northeast subspecies, is one of three recognized subspecies of the Bornean orangutan, and was only officially recognized in 2004 (Warren et al., 2001; Singleton et al. 2004)

As the name suggests, the Bornean orangutan is endemic to the island of Borneo. The northeast subspecies is present in East Kalimantan (Indonesia) and Sabah (Malaysia) with rivers forming the main barriers between the subspecies (Ancrenaz et al., 2008; Arora et al., 2010; Goossens et al., 2005; Jalil et al., 2008). To learn more about their distribution please activate the Pongo pygmaeus morio range layer in the interactive map.

Sabah is estimated to hold around 11,000 (range of 8,000 to 18,000) of the northeast subspecies and is considered to be their main stronghold. About 3,000 are estimated to survive in East Kalimantan (Ancrenaz et al., 2008) although surveys in 2010 suggest numbers may be higher than previously thought (Meijaard et al., 2010). There is some evidence that the populations living in Sabah and East Kalimantan may also be distinct but this is not been fully accepted (Warren et al., 2001).

From the late 1960’s to the 1990’s, Sabah’s forests were severely depleted and they are now virtually exhausted. In Eastern Sabah only 25% of land area remains forested and much of it is heavily logged (McConkey, 2005). The remaining forests are dedicated to timber production, watershed protection or biodiversity conservation. In Kalimantan official timber concessions overlap the fragmented distribution of orangutan populations. However, illegal as well as legal forest conversion is causing the deforestation crisis in Kalimantan. Whilst the threat of conversion per se is less problematic for protected areas, illegal activities damage their integrity and decimate orangutan populations. Illegal logging and other forms of forest conversion, along with associated fires, occur in most Indonesian national parks containing orangutan populations (Singleton et al., 2004). It is estimated that forest fires have reduced the total Bornean orangutan population by 33% (Ancrenaz et al., 2008).

East Kalimantan was one of the worst affected provinces by the forest fires in 1997-1998, burning around 52 000 km2 of forest, and Kutai National Park lost 95% of its lowland forest (McConkey, 2005). As a result of logging, mining, settlements and fires, the orangutan population in Kutai National Park is estimated to have dropped from 4000 to ca 600 (Rijksen and Meijaard 1999; Singleton et al., 2004). Surveys in 2010, however, suggest good recovery with estimates greater than 1000 orangutans (Meijaard et al., 2010)

Indonesian forests are being increasingly converted to plantations (especially for oil palm and Acacia). A recent analysis of agricultural and deforestation statistics for 1990-2005 shows that more than half of oil-palm development in Malaysia and Indonesia had resulted in deforestation (Koh and Wilcove, 2008) and that oil-palm plantations cover 2.4 million ha in Borneo (Koh et al., 2011). Primary forests were the source of nearly 60% of new plantations established in Southeast Asia between 1980 and 2000 (Koh et al., 2011). The threat of extinction is higher in forests outside conservation areas where there is great demand to convert these lands for commercial agriculture and plantations (Tiju et al., in press). Although some major morio orangutan populations are found within protected areas the vast majority live outside protected forests (Ancrenaz et al., 2005). Approximately 60% of morio in Sabah in production forests that have and are being intensively exploited for timber (Ancrenaz et al., 2005). Coal mining has also long been a threat to morio habitat in East Kalimantan, especially in and around Kutai National Park, which provides important habitat for the northeast subspecies. It is also becoming a problem for other areas (McConkey, 2005).

Not surprisingly then orangutan numbers have declined over 50% during the last 60 years (Ancrenaz et al., 2008). Slow-moving and with low reproductive rates (first birth occurs at 15-16 years with 6-8 years between births) orangutan populations are vulnerable to decline due to rapid forest clearance (Wich et al., 2004). The decline in numbers however is not only attributable to habitat loss; poaching, the pet-trade and killing orangutans as pests remains a major threat across most of Borneo and cumulatively may advance the risk of extinction (Meijaard et al., 2010; Marshall et al., 2006). Hunting has been found to be a far more serious threat to orangutans in East Kalimantan than light to moderate logging operations (Marshall et al., 2006) and whilst the trade in orangutans is less open than before there is no indication it is dissipating (Nijman, 2009).

Field studies of Bornean orangutans began in the late 1960’s in East Kalimantan and Sabah, and have since extended elsewhere, focusing on ecology, feeding behaviour, adaptation to disturbance, and behavioural adaptations of rehabilitated individuals. Since the 1970’s researchers have been witness to escalating habitat destruction and orangutan populations coming under increasing pressure, and many of these researchers are now involved, if not focusing, on conservation (McConkey, 2005).

The continuing decline of Bornean (and Sumatran) orangutan populations led experts to recognise the need for accurate data on population status and a conservation strategy to secure its’ future. In 1993, and then again in 2004 and 2005 Population and Habitat Viability Assessment (PHVA) workshops were conducted to assess the current status and future of wild orangutan populations and their habitat (Singleton et al., 2004). As a follow-up, a series of focused group discussions were held across Indonesia in 2007 resulting in the development of a National Strategy and Action Plan for Orangutan Conservation (2007-2017) which was officially endorsed by the Government of Indonesia. The formulation of this strategy and action plan summarized all points from previous recommendations and provides a common framework to conserve orangutans and their lowland forest habitats. The goal of the plan is to provide a framework for all stakeholders in determining the priority for ex-situ and in-situ conservation activities (Soehartono et al., 2009).

Among the actions in the plan, the most important include improving enforcement of wildlife and forest laws to increase the number and frequency of prosecutions, and to stop illegal logging. Conservation awareness is needed at all levels of society and support for communities close to orangutan habitat in developing alternative sources of income to relieve the pressure of illegal logging and collection of orangutans for the illegal wildlife trade (Soehartono et al., 2009). More areas need protected status and their boundaries need to be clearly demarcated. As most of Borneo is highly fragmented, corridors are needed, and should be included in land-use plans (Bruford et al., 2010). Areas that are degraded could become potential corridors linking existing sites if the land is protected and reforested.

In recognition of the importance of Sabah for the northeast subspecies, and with 60% of populations being found outside of protected areas in Commercial Forest Reserves that are exploited for timber, the Sabah government recognized a set of actions to ensure these areas are properly managed (Sabah Wildlife Department, 2011). The actions include: reviewing forest management plans and provision of practical guidelines to foresters; incorporating the needs of orangutans into agricultural practice (including the control of land development for oil-palm plantations); adoption of policies to develop sustainable and responsible orangutan tourism to minimize its impact on the environment and to enhance the conservation of orangutan populations; more research on Sabah’s populations; and increase awareness of legal frameworks among policy makers, forestry and plantation managers and workers (Sabah Wildlife Department, 2011).

A well-managed logging concession does have potential to support orangutan populations, and it is imperative that conservation organisations work with timber companies so that their activities are compatible (Ancrenaz et al., 2008; Singleton et al., 2004). Sustainable logging practices in the Deramakot Forest Reserve (part of the Upper Kinabatangan forests), implement a rotation system of reduced impact logging. The result is a mosaic of lowland habitats at different stages of exploitation and regeneration supporting one of the highest orangutan densities in Sabah. This is a good model that combines logging practices with orangutan conservation and could be rolled out in other areas (Ancrenaz et al., 2010). The production forests of Sabah are the stronghold of the northeast subspecies and they need to stay under natural-forest management. At the same time timber companies need to work together as an industry to solve the problem of illegal logging in legal concessions.

The northwest Bornean orangutan (Pongo pygmaeus pygmaeus) is classified as Endangered (A2cd ver 3.1) on the IUCN Red List 2008 (Ancrenaz et al., 2008) indicating that it has a very high risk of extinction in the wild in the near future. It is also listed on Appendix I of CITES.

Historically, Bornean and Sumatran orangutans were considered subspecies of Pongo pygmaeus but recent taxonomic reviews support the widely accepted and adopted distinction of the Bornean (Pongo pygmaeus) and Sumatran orangutan (Pongo abelii) as distinct species (Goossens et al., 2009 Groves, 2001). Pongo pygmaeus pygmaeus, also known as the northwest subspecies, is one of three recognized subspecies of Bornean orangutan.

As the name suggests the Bornean orangutan is endemic to the island of Borneo. The northwest subspecies is present in north-western Kalimantan (Indonesia) from north of the Kapuas River to north-eastern Sarawak (Malaysia), with core populations centred in four conservation areas: Batang Ai National Park and Lanjak Entimau Wildlife Sanctuary (BALE) in Sarawak-Malaysia, and Betung Kerihun National Park (BKNP) and Danau Sentarum National Park (DSNP) in West Kalimantan-Indonesia (McConkey, 2005; Tjiu et al., in press). To learn more about their distribution please activate the Pongo pygmaeus pygmaeus range layer in the interactive map.

Whilst all the subspecies are endangered, the northwest subspecies is considered the most severely threatened, with only 3,000-4,500 individuals remaining, spread across 7,500 km2 of habitat (Tjiu et al., in press; Wich et al., 2008). The Lanjak Entimau Wildlife Sanctuary in Malaysia and Betung Kerihun National Park in Indonesia are considered the most important for the subspecies as the populations contain more than 1,000 individuals (Wich et al, 2008).

Recent surveys of the northwest subspecies show a significant decline in numbers over the past decade (unpublished Tjiu et al, 2010; Tiju el al., in press; Russon, 2001). This is a direct consequence of deforestation and degradation driven by illegal logging, forest fires and land clearing. These slow-moving and slow-breeding mammals (first birth occurs at 15-16 years with 6-8 years between births), dependant on fruit in fruit-poor lowland forests, are extremely vulnerable to rapid forest clearance (McConkey, 2005; Wich et al., 2004). Another pressure on orangutan populations in this region is poaching (Tiju et al., in press).

At BALE, logging and forest conversion to agricultural or forest plantations is not a threat and the number of orangutans appears stable. In contrast, there has been a rapid decline in orangutan numbers in BKNP and DSNP due to illegal logging, large-scale forest conversion for agriculture and plantation, forest fires and poaching for the pet trade and food. The threat of extinction is even higher in forests outside conservation areas as there is a great demand for these forested lands for commercial agriculture and plantations, and due to direct persecution. (Tiju et al., in press). Although some major orangutan populations are found within protected areas the vast majority live outside protected forests (Ancrenaz et al., 2008). More than half of the population in DSNP is concentrated in the eastern side of the park or corridor areas that connect BKNP and DSNP. This corridor is classified as production and multiple-use forest. The boundary of this region is delineated by water bodies, and the forest blocks integral to this ecosystem are not included into the national park but are designated for commercial agriculture and forestry, within multiple-use areas or production forest. Future degradation and forest conversion into plantations for palm oil appear inevitable as the land status is legally termed multiple-use area and production forest. Several companies have already started land-conversion of forests into oil palm plantations (unpublished Tjiu et al, 2010). Recent surveys have also revealed orangutans in patchy and fragmented forest between Sambas towards Kapuas Hulu near the border of West Kalimantan and Sarawak but more than 60% of this area is also classified as production and multi-function forest (unpublished Tjiu, A. 2010). A recent analysis of agricultural and deforestation statistics for 1990-2005 shows that more than half of oil-palm development in Malaysia and Indonesia had resulted in deforestation (Koh and Wilcove, 2008) and that oil-palm plantations cover 2.4 million ha in Borneo (Koh et al., 2011). Furthermore, primary forests were the source of nearly 60% of new plantations established in Southeast Asia between 1980 and 2000 (Koh et al., 2011).

The continuing decline of Bornean (and Sumatran) orangutan populations led experts to recognise the need for accurate data on population status and a conservation strategy to secure its’ future. In 1993, and then again in 2004 and 2005 Population and Habitat Viability Assessment (PHVA) workshops were conducted to assess the current status and future of wild orangutan populations and their habitat (Singleton et al., 2004). As a follow-up, a series of focused group discussions were held across Indonesia in 2007 resulting in the development of a National Strategy and Action Plan for Orangutan Conservation (2007-2017) which was officially endorsed by the Government of Indonesia. The formulation of this strategy and action plan summarized all points from previous recommendations and provides a common framework to conserve orangutans and their lowland forest habitats. The goal of the plan is to provide a framework for all stakeholders in determining the priority for ex-situ and in-situ conservation activities (Soehartono et al., 2009).

A number of actions are required to protect the survival of this endangered orangutan subspecies. These include an improvement in enforcement of wildlife and forest laws, and much greater consideration for environmental issues in spatial planning decisions. Increasing the number and frequency of prosecutions, stopping illegal logging, halting legal logging and forest conversion to plantations, promoting forest restoration, addressing human-orangutan conflicts, cooperation among stakeholders in monitoring the protection of orangutan and their habitat, increasing protected areas by evaluating and reconstructing regional land use patterns where rare and endangered species (especially orangutan) are known to exist, and providing connectivity in the landscape to allow for genetic exchange are all essential for the subspecies survival (Tiju et al., in press).

Managing land-use planning in a multi-stakeholder framework can help mitigate environmental impacts through influencing the allocation of land given to legal logging concessions and preventing forest conversion to plantations. As most of Borneo is highly fragmented, corridors are needed, and should be included in land-use plans (Bruford et al., 2010). Areas that are degraded could become potential corridors linking existing sites if the land is protected and reforested. Orangutans are frequently encountered in corridors between BKNP and DSNP which connect with Landjak Entimau Wildlife sanctuary in Sarawak. Changing the current classification of the corridor from production and multiple-use forest is extremely important for the northwest subspecies (Tjiu et al., in press). Ground surveys are needed to determine the distribution and abundance of orangutans in the highly fragmented forests between Sambas towards Kapuas Hulu near the border of West Kalimantan and Sarawak. If these orangutans are found to be threatened by habitat loss, a legally gazetted forest corridor to connect the forest patches is needed. Designating these patches and the corridor as conservation areas will support the long term conservation strategy of the species at the landscape level.

At the same time, more areas need protected status and their boundaries need to be clearly demarcated. In 2010 Ulu Sebuyau National Park and Sedilu National Park in the north-western part of Sarawak were officially gazetted and there a proposal to extend Ulu Sebuyau National Park by another 100 km2. In Sarawak, The International Tropical Timber Organisation (ITTO) and Sarawak Forest Department collaborated to develop a contiguous Trans-boundary Biodiversity Conservation Area of Sarawak and West Kalimantan. This initiative also includes the establishment of a permanent monitoring and research site in Meliau, West Kalimantan. Whilst data on the density and abundance of the northwest subspecies is improving, we know little about their behaviour. Long-term research needs to be developed and this should include baseline data on demographic-life history, genetics and socio-ecology (Tiji et al., in press).

The Sumatran orangutan (Pongo abelii) is classified as Critically Endangered (A2cd ver 3.1) on the IUCN Red List 2008 (Singleton et al., 2008) indicating it is considered to be facing an extremely high risk of extinction in the wild. It is also listed on Appendix I of CITES.

Historically, Sumatran and Bornean orangutans were considered subspecies of Pongo pygmaeus but recent taxonomic reviews support the now widely accepted and adopted distinction of the Sumatran orangutan Pongo abelii as a separate species from its Bornean relative Pongo pygmaeus (Goossens et al., 2009; Groves, 2001; Singleton et al. 2008).

As the name suggests the Sumatran orangutan is endemic to the island of Sumatra, Indonesia, and is now mainly restricted to the north of the island (north of the Batang Toru River on the west coast of North Sumatra province). The Leuser Ecosystem, in the provinces of Aceh and North Sumatra, is considered to contain 91% of the remaining wild population (Wich et al., 2008). This conservation area (26,000 km2) includes the Gunung Leuser National Park (10,950 km2) and the Singkil Swamps Wildlife Reserve (1,025 km2) (Singleton et al., 2009). Whilst this is largely a mountainous area, orangutans exist in greater numbers and at higher densities in the remaining lowlands (regions below 1000m). It is these lowlands that contain the three largest populations (1000+ individuals). Outside of the Leuser Ecosystem, the most important population occurs in the Batang Toru area, southwest of Lake Toba (Wich et al., 2008). Several additional relatively small fragments of forest also still contain small populations of orangutans, but few, if any of these, are considered likely to be viable in the long-term (Singleton et al., 2008). The southernmost populations in North Sumatra (i.e. the Batang Toru populations) may be genetically and culturally distinct from their more northern relatives, due to their isolation (Singleton et al., 2009). To learn more about their distribution please activate the Pongo abelii range layer in the interactive map.

Current population estimates point toward a total of 6,600 wild Sumatran orangutans remaining (Wich et al., 2008). A new population (currently circa 70 individuals) is being established in the Bukit Tigapuluh National Park (Jambi and Riau Provinces) by reintroducing rehabilitant wild-born orangutans, confiscated as illegal pets (Singleton et al., 2008).

In 1993 it was estimated that 12,500 Sumatran orangutans still survived in the wild and it was predicted that by 2020 approximately 7,500 individuals would remain (Rijksen & Meijaard, 1999). Whilst the 1993 population estimate is now considered overly optimistic (as it included unconfirmed populations further south of the Batang Toru which were not found during subsequent surveys, and therefore almost certainly no longer exist) Sumatran orangutan numbers in the wild already appear to be less than 7,500 ten years earlier than predicted in 1993, and the downward trend continues unabated (Wich et al., 2008).

Although the extent and impact of threats differ across Sumatra, some are common to all habitats. These are: habitat loss and degradation attributable to both legal and illegal logging, conversion of forests for agriculture (especially palm oil plantations), mining and road development; encroachment; lack of law enforcement; hunting, persecution of orangutans as pests (i.e. human-orangutan conflict), and illegal trade; regional planning issues; and a general lack of awareness regarding laws, protected area boundaries and the value of intact forest ecosystems (Ellis et al., 2006).

Illegal logging occurs within both protected areas and legal logging concessions, changing the function of the forest and leading to habitat fragmentation (Ellis et al., 2006). Plantations, particularly palm oil, pose an extremely serious threat as they completely convert habitat to monoculture, resulting in the loss, fragmentation and isolation of orangutan populations. Plantations are frequently owned by outside interests, either based elsewhere in Indonesia or abroad, and they often make use of non-local labour sources, leading to social issues among local communities, which can itself also result in more land pressure, conversion of greater areas to palm oil, and additional damage to forests and the environment (Ellis et al., 2006).

New roads open up access to areas for logging, encroachment, conversion and settlements, and fragment wildlife populations. Of particular concern are roads planned in the Singkil Swamps Wildlife Reserve, as Sumatra’s peat swamp forests support the highest densities of orangutans in the world (Singleton et al., 2009), but roads in other areas are also predicted to lead to forest loss and subsequent losses in orangutan numbers (Gaveau et al., 2009). New settlements often result in forest encroachment. Javanese transmigrants formerly residing within Aceh fled to North Sumatra during civil unrest. Many have stayed, establishing new settlements (e.g., within the Gunung Leuser National Park itself) and converting large tracts of land to agriculture, including palm oil (Ellis et al., 2006). Forest loss rates in Aceh dropped dramatically as a consequence of the heightened civil conflict between 1999 and 2005, and a moratorium on logging imposed by the Provincial Governor in 2007. Despite the current moratorium, political stability has since returned to Aceh and the re-emergence of logging concessions and palm oil plantations is once again a threat to the Aceh’s forests, especially if the moratorium is revoked (Ellis et al., 2006; Singleton et al., 2008).

Despite it being illegal to capture, kill, keep or trade an orangutan within Indonesia, with the risk of a 5 year prison sentence and 100 million rupiah fine (approx. USD 11,000), orangutans are still killed and captured on a regular basis. Surviving infants may be kept as illegal pets, or enter the national and international wildlife trade. Military, police and local government officials themselves are often found keeping orangutans and other protected species as pets, despite being the ones responsible for enforcing the country’s laws (Ellis et al., 2006). In Sumatra at least, pet orangutans tend to be largely a by product of habitat conversion; orangutans are most frequently killed or captured when forests are being converted for agricultural purposes or when they are involved in wildlife conflict (e.g. raiding farmer’s fruit crops) at the forest edge. Hunting for meat does still occur in some areas, particularly in the province of North Sumatra, but it seems that orangutans are targeted opportunistically (Singleton et al., 2008). Even very low levels of killing and hunting threatens the survival of Sumatran orangutan populations given their exceptionally low reproductive rates (first birth occurs at 15-16 years and interbirth interval is 8-9 years) and their extremely precarious conservation status.

Inadequate law enforcement and capacity is also a threat to safeguarding the future of orangutan populations and their habitat. There is poor awareness and knowledge of existing laws, inadequate law enforcement (including low levels of integrity in enforcement practice), and unclear forest boundary demarcation. All of this facilitates the illegal killing and capture of orangutans and deforestation, forest degradation and fragmentation. The number and capacity (training and motivation) of protected area management authorities and provincial conservation agencies is inadequate for effective law enforcement.

The first detailed field studies of Sumatran orangutan behaviour and ecology began in the late 1960’s. The research station at Ketambe, in the Gunung Leuser National Park, has remained active since 1971, and a second long-term study site, at Suaq Balimbing in the Kluet peat swamp forests in the south west of the park was established in 1993. These two sites have yielded almost all that is known about Sumatran orangutans in the wild (McConkey, 2005, Wich et al., 2009). Ketambe is not only an ecological research centre but it also serves as conservation training area for both Indonesian and foreign participants. Research has contributed to the way humans understand orangutans but has also provided crucial information to guide decision-making and action planning for orangutan conservation. The importance of long-term research has been proven, and includes for example, the role of orangutans in forest regeneration as agents of seed dispersal. The research projects have benefitted not only the scientific world but its presence has also preserved the primary forests in the area (Soehartono et al., 2009).

The continuing decline of Sumatran (and Bornean) orangutan populations led governments and experts to seek sustainable solutions for Asia’s only great ape amidst expanding socio-economic development. This resulted in a series of meetings with the aim of building a conservation strategy for orangutans. In 1993, and then again in 2004, 2005 and 2006 Population and Habitat Viability Assessment (PHVA) workshops were held to look in detail at remaining population sizes and distributions of the two species, the threats and trends, and to make recommendations for improved protection (Singleton et al., 2004). As a follow-up, a series of focused group discussions were held across Indonesia in 2007 resulting in the development of a National Strategy and Action Plan for Orangutan Conservation (2007-2017) which was officially endorsed by the Government of Indonesia The formulation of this strategy and action plan summarized all points from previous recommendations and provides a common framework to conserve orangutans and their lowland forest habitats. The goal of the plan is to provide a framework for all stakeholders in determining the priority for ex-situ and in-situ conservation activities, and also represents an attempt to evaluate the achievement of conservation efforts since the declaration of the action plan, as well as updating information about orangutan populations and distribution (Soehartono et al., 2009).

Key conservation interventions for Sumatran orangutans rely on a drastic improvement in the enforcement of wildlife and forest laws and far greater consideration for environmental issues in spatial planning. Implementing effective patrols, improving law enforcement (especially the number and frequency of prosecutions), stopping illegal logging, halting legal logging and forest conversion to plantations, promoting forest restoration, halting road construction, addressing human-orangutan conflict, and providing connectivity in the landscape to allow for genetic exchange are prerequisites for the species survival. Effective long-term solutions to conserve northern Sumatra’s remaining lowland primary forests are urgently needed (Singleton et al., 2009).

The development of the National Strategy and Action Plan for Orangutan Conservation and the moratorium on all logging in the Aceh Province are positive for orangutan conservation. The key however is effective implementation and enforcement (Singleton et al., 2009; Soehartono et al., 2009).