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The IUCN Red List of Threatened Species™
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IUCN 2008: T17975A17966347
Pongo pygmaeus, Bornean Orangutan
Assessment by: Ancrenaz, M., Gumal, M., Marshall, A.J., Meijaard, E., Wich ,
S.A. & Husson, S.
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Citation: Ancrenaz, M., Gumal, M., Marshall, A.J., Meijaard, E., Wich , S.A. & Husson, S. 2016. Pongo
pygmaeus. The IUCN Red List of Threatened Species 2016: e.T17975A17966347.
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Kingdom Phylum Class Order Family
Animalia Chordata Mammalia Primates Hominidae
Taxon Name:ÊÊPongo pygmaeus (Linnaeus, 1760)
Simia pygmaeus Linnaeus, 1760
Infra-specific Taxa Assessed:
Pongo pygmaeus ssp. morio
Pongo pygmaeus ssp. pygmaeus
Pongo pygmaeus ssp. wurmbii
Common Name(s):
• English: Bornean Orangutan
• French: Orang-outan de Bornéo
• Spanish: Orang-után
Taxonomic Source(s):
Mittermeier, R.A., Rylands, A.B. and Wilson D.E. 2013. Handbook of the Mammals of the World: Volume
3 Primates. Lynx Edicions, Barcelona.
Taxonomic Notes:
Although there is ongoing debate about the taxonomic status of the Bornean Orangutan (see review in
Goossens et al. 2009); three subspecies are currently recognized for the taxon:
P. p. pygmaeus: Northwest Bornean Orangutan:
• State of Sarawak (Malaysia)
• Province of West Kalimantan (Indonesia)
P. p. wurmbii: Southwest Bornean Orangutan:
• Province of West Kalimantan (Indonesia)
• Province of Central Kalimantan (Indonesia)
P. p. morio: Northeast Bornean Orangutan:
• State of Sabah (Malaysia)
• Province of North Kalimantan (Indonesia)
• Province of East Kalimantan (Indonesia)
Assessment Information
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
Red List Category & Criteria: Critically Endangered A4abcd ver 3.1
Year Published: 2016
Date Assessed: February 8, 2016
Bornean Orangutans are lowland forest specialists, rarely found above 500 m asl. In the 1950s, the
habitat suitable for orangutans extended across ~255,000 km² of the island of Borneo (see below).
The two major reasons why most Bornean Orangutans populations are in sharp decline are (1)
destruction, degradation and fragmentation of their habitats, and (2) hunting. Recurrent forest fires,
especially in peat forests, cause additional sharp declines about once every decade. Bornean
Orangutans decreased by more than 60% between 1950 and 2010, and a further 22% decline is
projected to occur between 2010 and 2025 (see below). Combined, this equates to a loss of more than
82% over 75 years, 1950–2025. Given that a Bornean Orangutan's generation length is ~25 years (Wich
et al. 2009), this decline will occur in a period of three generations. Each of the Pongo pygmaeus
subspecies is roughly equally affected. Only one comprehensive quantitative survey of Bornean
Orangutans has been conducted, in 2010, which prohibits quantitative assessment of changes in
numbers for most populations. Temporal changes in population status are therefore best assessed via
the proxies of habitat loss and hunting rates. A detailed rationale for a population decline of more than
86% between 1950 and 2025 follows.
The most accurate estimate of the geographic range of Bornean Orangutans showed that in 2010, 59.6%
of the forest remaining in Borneo was suitable habitat (155,106 km² of 260,109 km² of forest: Wich et al.
2012, Gaveau et al. 2014). Considering that in 1973, 75.7% of Borneo (424,753 km²) was under natural
forest (Gaveau et al. 2014), we estimate that 253,153 km² of forest was orangutan habitat at this time.
Mechanized logging in Borneo started in the early 1950s, and industrial logging and forest conversion
intensified in the late 1960s. The rate of forest conversion is difficult to estimate prior to 1973 due to the
lack of satellite imagery, but a recent spatial analysis evaluated forest persistence, clearance and logging
spanning the 37 years between 1973 and 2010 (Gaveau et al. 2014). We take the rate of forest loss
documented from 1973 to 2010 as conservative and de facto lower than if data were available from
1. Habitat loss and orangutan decline
During the period 1973–2010, 39% of Bornean forests were lost (Gaveau et al. 2014), representing a net
loss of 98,730 km² of prime orangutan habitat. It is estimated that a further 37% of suitable orangutan
habitat (155,106 km²) will be converted to plantations between 2010 and 2025, which accounts for the
loss of an additional 57,140 km² of orangutan habitat (Wich et al. 2012). Compared to the baseline
(253,153 km²), more than 155,867 km² or of 61.5% of orangutan habitat will be gone by 2025; see Table
1 in Supplementary Material.
The orangutan habitat remaining in 2010 (97,716 km²) was either protected or designated for timber
production (Wich et al. 2012). Nonetheless, forest loss is expected to occur here too, owing to fires,
encroachment and smallholder plantation development. Rates of forest loss measured at two sites with
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
the largest Borneo orangutan populations are: 1.9% per year (1991–2000) and 1.5% per year
(2000–2007) at Sebangau National Park (Husson et al. 2015); and 2.4% per year including the buffer
zone, or 1.1% excluding the buffer zone (1988–2002) at Gunung Palung National Park (Curran et al.
2004). The rate of loss in production forests outside formally protected areas will undoubtedly be higher
(Santika et al. 2015). Thus we conservatively estimate the ongoing rate of loss in this administrative type
of forest to be 1.5% per year. This will represent another 19,821 km² of forest lost between 2010 and
2025: 20.2% of the orangutan habitat in 2010, or 8.7% in 1973.
2. Habitat degradation and orangutan decline
In addition to habitat loss, selective logging has degraded 56% of Bornean Orangutan habitat since 1973
(Gaveau et al. 2014). The impacts of logging on orangutan density are variable, from little change in
lightly-logged forest to major negative impacts in heavily-logged forest (Ancrenaz et al. 2010). For
example, selective artisanal logging reduced orangutan densities in peat-swamp forests by 21–30%
(Husson et al. 2009), while mechanised logging in dryland forests is presumed to have a greater impact.
Thus, 56% of the Bornean Orangutan range could undergo a 20% decrease in carrying capacity. This
estimate is conservative, considering that in Kalimantan the total area of natural forest allocated for
timber extraction is increasing. Reduction in carrying capacity due to logging would then equate to a
loss of 7% of the 1973 population by 2010, and overall accounts for 4% of the total projected 1973–2025
population decline.
3. Hunting and orangutan decline
The widespread impacts of illegal hunting had not been quantified prior to a major questionnaire study
throughout Kalimantan in 2008–2009 (Meijaard et al. 2011). The authors estimated that 630–1,357
Bornean Orangutans were killed in 2008 and that an average of 2,383–3,882 per year had been killed
during the lifetimes of the survey respondents. The mean estimate (2,256 orangutans poached in
Kalimantan each year) equates to 2.6% of the 2010 population for Kalimantan. Population losses due to
hunting may be partially offset by population growth, which has a maximum theoretical rate of 2%
annually (Marshall et al, 2009). The only study to have measured growth in a Bornean Orangutan
population was carried out in Sebangau National Park in a population recovering from a logging-induced
crash. Here, growth was relatively uninhibited and estimated to increase at an average annual rate of
1.6% between 2001 and 2013 (Husson et al. 2015). It is highly unlikely that a continuously-hunted
population could recover at this rate, but in order to take into account uncertainties in determining the
level of hunting, a 1.5% growth rate is applied, resulting in a net population decrease due to hunting of
1.1% annually. This equates to an additional loss (once habitat clearance and impacts of logging are
factored in) of 18% of the 1973 population by 2010 and 7% of the 2010 population by 2025. Overall,
poaching contributes 12% to the estimated 1973–2025 population decrease.
The combined impacts of habitat loss, habitat degradation and illegal hunting equate to an 86%
population reduction between 1973 and 2025 which qualifies the species for listing as Critically
Endangered. This estimate is relatively conservative, as it does not include additional future population
losses anticipated due to stochastic effects that will reduce populations inhabiting increasingly small
forest fragments.
Orangutan habitat loss and killing were already significant threats during the period 1950–1973, and the
species was already declining at this time. However the paucity of data for this period prevents to
estimate a specific rate of population decline for this specific period of time. However, if we assume that
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
orangutan abundance in 1950 was similar to that in 1973 (which is not the case because any declines
that occurred between 1950 and 1973 are not accounted for), our analysis shows that the species will
suffer a more than 80% decline in three generations (1950–2025).
For further information about this species, see Supplementary Material.
Previously Published Red List Assessments
2008 – Endangered (EN) –
2007 – Endangered (EN)
2000 – Endangered (EN)
1996 – Vulnerable (VU)
1994 – Endangered (E)
1990 – Endangered (E)
1988 – Endangered (E)
1986 – Endangered (E)
1965 – Very rare and believed to be decreasing in numbers
Geographic Range
Range Description:
The Bornean Orangutan is endemic to the island of Borneo where it is present in both the Malaysian
states of Sabah and Sarawak, as well as in four of the five Indonesian Provinces of Kalimantan: North,
East, Central and West Kalimantan. The distribution of Bornean Orangutans is highly patchy throughout
the island; they are apparently absent or uncommon in the southeast, the forests between the Rejang
River in central Sarawak, and the Padas River in western Sabah (including the Sultanate of Brunei). The
Bornean Orangutan occurs preferentially in lowland forests below 500 m asl, but some individuals can
also be found in highland habitats, for example, up to 1,500 m asl in Kinabalu National Park. Large rivers
are natural barriers that are impassable to these animals and limit their dispersal (Goossens et al. 2005).
Country Occurrence:
Native: Indonesia (Kalimantan); Malaysia (Sabah, Sarawak)
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
Distribution Map
Pongo pygmaeus
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
Climatic change and human pressure have resulted in significant reductions in the range and numbers of
Bornean Orangutans during the recent historic past (Goossens et al. 2006, Meijaard et al. 2010).
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 (Ancrenaz et al. 2005). The most recent (2004) estimate for the species is that c. 55,000
Bornean Orangutans inhabit 82,000 km² of forest (Wich et al. 2008). 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 (Wich et al. 2012). 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.
Compounding loss of habitat, recent interview surveys in Kalimantan have concluded that 2,000–3,000
orangutans were killed every year in Indonesian Borneo during the past four decades alone (Meijaard et
al. 2011). This would represent a loss of 44,170–66,570 individuals (Davis et al. 2013), or more than 50%
of the original population in just 40 years. Such a rate of killings is unsustainable (Marshall et al. 2009)
and many populations will be reduced or become extinct in the next 50 years (Abram et al. 2015).
Current Population Trend:ÊÊDecreasing
Habitat and Ecology (see Appendix for additional information)
Bornean Orangutans are the largest arboreal mammals in the world, although they walk significant
distances on the ground (Ancrenaz et al. 2014). Historically, Bornean Orangutans were most abundant in
inundated and semi-inundated lowland Dipterocarp mosaic forests, where movement between different
habitat types could buffer them against shortages in food availability in a particular habitat type. Their
diet consists primarily of fruits, but also includes leaves, barks, flowers and insects (Russon et al. 2009).
Bornean Orangutans live a semi-solitary life and rarely aggregate in groups. Males are the dispersing sex:
upon reaching sexual maturity (at 10–12 years old), they leave the area where they were born to
establish large territories covering several hundred hectares. Females’ territories are smaller, with actual
size depending on forest type and availability of food resources. Bornean Orangutans are very slow
breeders and produce on average one offspring every 6–8 years, which explains their extreme sensitivity
to hunting pressure. Females reach maturity at 10–15 years old; they generally give birth to a single
infant after a gestation period of approximately 254 days (Kingsley 1981).
Use and Trade
For information on use and trade, see under Threats.
Threats (see Appendix for additional information)
Major threats include:
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
Habitat loss. Between 2000 and 2010, the mean annual rate of deforestation for Borneo was 3,234
km² per year (Gaveau et al. 2014). 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
(Wich et al. 2015). In the early 2010s, only 22% of the current Bornean Orangutan distribution was
located in protected areas (Wich et al. 2012). 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 (Davis et al. 2013). Overall
Bornean Orangutan mortality rates in Kalimantan seem to significantly exceed the maximum rates that
populations of this slow-breeding species can sustain (Marshall et al. 2009, Meijaard et al. 2011). 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 (Rijksen and Meijaard 1999); 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 (Gaveau et al. 2013). Several orangutan PHVAs have
shown that Bornean Orangutan populations of fewer than 50 individuals are not viable in the long term
(Marshall et al. 2009), and that many small populations will go extinct unless they are actively managed
(Bruford et al. 2010).
Lack of awareness. A recent study suggested that 27% of the people in Kalimantan did not know that
orangutans are protected by law (Meijaard et al. 2011). 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 (Struebig et al. 2015). 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 P. p. wurmbii and P. p. morio are found.
Conservation Actions (see Appendix for additional information)
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
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 (Wich et al. 2012). 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
(Meijaard et al. 2011). These forests need to contain the ecological gradients that will provide the key
resources to sustain orangutans through climate and other gradual environmental changes (Gregory et
al. 2012). 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.
Assessor(s): Ancrenaz, M., Gumal, M., Marshall, A.J., Meijaard, E., Wich , S.A. & Husson, S.
Reviewer(s): Williamson, L. & Mittermeier, R.A.
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
Abram, N.K., Meijaard, E., Wells, J.A., Ancrenaz, M., Pellier, A.S., Runting, R.K., Gaveau, D.L.A., Wich, S.,
Nardiyono, Tiju, A., Nurcahyo, A. and Menkersen, K. 2015. Mapping perception of species’ threats and
population trends to inform conservation efforts: the Bornean orangutan case study. Diversity and
Distributions 21: 487–499.
Ancrenaz, M., Ambu, L., Sunjoto, I., Ahmad, E., Manokaran, K., Meijaard, E. and Lackman, I. 2010. Recent
surveys in the forests of Ulu Segama Malua, Sabah, Malaysia, show that orang-utans (P. p. morio) can be
maintained in slightly logged forests. PLoS One 5: e11510.
Ancrenaz, M., Gimenez, O., Ambu, L., Ancrenaz, K., Andau, P., Goossens, B., Payne, J., Tuuga, A. and
Lackman-Ancrenaz, I. 2005. Aerial surveys give new estimates for orang-utans in Sabah, Malaysia. PLoS
Biology 3(1): 30–37.
Ancrenaz, M., Sollmann, R., Meijaard, E., Hearn, A.J., Ross, J., Samejima, H., Loken, B., Cheyne, S.M.,
Stark, D.J., Gardner, P.C., Goossens, B., Mohamed, A., Bohm, T., Matsuda, I., Nakabayasi, M., Lee, S.K.,
Bernard, H., Brodie, J., Wich, S., Fredriksson, G., Hanya, G., Harrison, M.E., Kanamori, T., Kretzschmar, P.,
Macdonald, D.W., Riger, P., Spehar, S., Ambu, L.N. and Wilting, A. 2014. Coming down the trees: is
terrestrial activity in orangutans natural or disturbance-driven? Nature Scientific Reports 4(4024): 1–4.
Bruford, M.W., Ancrenaz, M., Chikhi, L., Lackman-Ancrenaz, I., Andau, M., Ambu, L. and Goossens, B.
2010. Projecting genetic diversity and population viability for the fragmented orangutan population in
the Kinabatangan floodplain, Sabah, Malaysia. Endangered Species Research 12: 249–261.
Davis, J.T., Mengersen, K., Abram, N., Ancrenaz, M., Wells, J. and Meijaard, E. 2013. It’s not just conflict
that motivates killing of orangutans. PLoS One 8: e75373.
Gaveau, D.L.A., Kshatriya, M., Sheil, D., Sloan, S., Molidena, E., Wijaya, A., Wich, S., Ancrenaz, M.,
Hansen, M., Broich, M., Guariguata, M.R., Pacheco, P., Potapov, P., Turubanova, S. and Meijaard, E. 2013.
Reconciling forest conservation and logging in Indonesian Borneo. PLoS One 8: e69887.
Gaveau, D.L.A., Sloan, S., Molidena, E., Yaen, H., Sheil, D., Abram, N.K., Ancrenaz, M., Nasi, R., Quinones,
M., Wielaard. N. and Meijaard, E. 2014. Four decades of forest persistence, clearance and logging on
Borneo. PLoS One 9(7): e101654.
Goossens, B., Chikhi, L., Ancrenaz, M., Lackman-Ancrenaz, I., Andau, P. and Bruford, M.W. 2006. Genetic
signature of anthropogenic population collapse in orang-utans. PLoS Biology 4: 285–291.
Goossens, B., Chikhi, L., Jalil, F., Ancrenaz, M., Lackman-Ancrenaz, I., Mohammed, M., Andau, P. and
Bruford, M.W. 2005. Patterns of genetic diversity and migration in increasingly fragmented and declining
orangutan (Pongo pygmaeus) populations from Sabah, Malaysia. Molecular Ecology 14: 441–456.
Goossens, B., Chikki, L., Jalil, F., James, S., Ancrenaz, M., Lackman-Ancrenaz, I. and Bruford, M.W. 2009.
Taxonomy, geographic variation and population genetics of Bornean and Sumatran orangutans. In: S.A.
Wich, S.S. Utami Atmoko, T. Mitra Setia and C.P. van Schaik (eds), Orangutans: Geographic Variation in
Behavioral Ecology and Conservation, pp. 1–13. Oxford University Press, Oxford.
Gregory, S.D., Brook, B.W., Goossens, B., Ancrenaz, M., Alfred, R., Ambu, L.N. and Fordham, D.A. 2012.
Long-term field data and climate-habitat models show that orangutan persistence depends on effective
forest management and greenhouse gas mitigation. PLoS One 7(9): e43846.
Husson, S.J., Morrogh-Bernard, H., Santiano, Purwanto, A., Harsanto, F., McLardy, C. and D’Arcy, L. 2015.
Long-term temporal trends in ape populations in four case studies: Bornean orangutans in the Sabangau
peat-swamp forest. In: Arcus Foundation (ed.), State of the Apes 2015: Industrial Agriculture and Ape
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
Conservation, pp. 200–207. Cambridge University Press, Cambridge, UK.
Husson, S.J., Wich, S.A., Marshall, A.J., Dennis, R.D., Ancrenaz, M., Brassey, R., Gumal, M., Hearn, A.J.,
Meijaard, E., Simorangkir, T. and Singleton, I. 2009. Orangutan distribution, density, abundance and
impacts of disturbance. In: S.A. Wich, S.S. Utami Atmoko, T. Mitra Setia and C.P. van Schaik (eds),
Orangutans: Geographic Variation in Behavioral Ecology and Conservation, pp. 77–96. Oxford University
Press, Oxford, UK.
IUCN. 2016. The IUCN Red List of Threatened Species. Version 2016-1. Available at:
(Accessed: 30 June 2016).
Kingsley, S. 1981. The reproductive physiology and behaviour of captive orangutans (Pongo pygmaeus).
University of London.
Marshall, A.J., Lacy, R., Ancrenaz, M., Byers, O., Husson S.J., Leighton, M., Meijaard, E., Rosen, N.,
Singleton, I., Stephens, S., Traylor-Holzer, K., Utami Atmoko, S.S., van Schaik, C.P. and Wich, S.A. 2009.
Orangutan population biology, life history, and conservation. Perspectives from population viability
analysis models. In: S.A. Wich, S.S. Utami Atmoko, T. Mitra Setia and C.P. van Schaik (eds), Orangutans:
Geographic Variation in Behavioral Ecology and Conservation, pp. 311–326. Oxford University Press,
Oxford, UK.
Meijaard, E., Buchori, D., Hadiprakarsa, Y., Ancrenaz, M. et al. 2011. Quantifying killing of orangutans
and human-orangutan conflict in Kalimantan, Indonesia. PLoS One 6(11): e27491.
Meijaard, E., Welsh, A., Ancrenaz, M., Wich, S., Nijman, V. and Marshall, A.J. 2010. Declining orangutan
encounter rates from Wallace to the present suggest the species was once more abundant. PLoS One
5(8): e12042.
Meijaard, E., Wich, S., Ancrenaz, M. and Marshall, A.J. 2012. Not by science alone: why orangutan
conservationists must think outside the box. Annals of the New York Academy of Science 1249: 29–44.
Rijksen, H.D. and Meijaard, E. 1999. Our Vanishing Relative: The Status of Wild Orangutans at the Close
of the Twentieth Century. Kluwer, Dordrecht, The Netherlands.
Russon, A.E., Wich, S.A., Ancrenaz, M., Kanamori, T., Knott, C.D., Kuze N., Morrogh-Bernard, H.C., Pratje,
P., Ramlee, H., Rodman, P., Sawang, A., Sidiyasa, K., Singleton, I. and van Schaik, C.P. 2009. Geographic
variation in orangutan diets. In: S.A. Wich, S.S. Utami Atmoko, T. Mitra Setia and C.P. van Schaik (eds),
Orangutans: Geographic Variation in Behavioral Ecology and Conservation, pp. 135–156. Oxford
University Press, Oxford, UK.
Santika, T., Meijaard, E. and Wilson, K.A. 2015. Designing multifunctional landscapes for forest
conservation. Environmental Research Letters 10: 114012–114020.
Struebig, M.J., Fischer, M., Gaveau, D.L.A., Meijaard, E., Wich, S.A., Gonner, C., Sykes, R., Wilting, A. and
Kramer-Schadt, S. 2015. Anticipated climate and land-cover changes reveal refuge areas for Borneo's
orangutans. Global Change Biology 21: 2891–2904.
Wich, S.A., de Vries, H., Ancrenaz, M., Perkins, L., Shumaker, R.W., Suzuki A. and van Schaik, C.P. 2009.
Orangutan life history variation. In: S.A. Wich, S.S. Utami Atmoko, T. Mitra Setia and C.P. van Schaik (eds),
Orangutans: Geographic Variation in Behavioral Ecology and Conservation, pp. 65–75. Oxford University
Press, Oxford, UK.
Wich, S.A., Gaveau, D., Abram, N., Ancrenaz, M., Baccini, A. et al.. 2012. Understanding the impacts of
land-use policies on a threatened species: is there a future for the Bornean orangutan? PLoS One 7(11):
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
Wich, S.A., Meijaard, E., Marshall, A., Husson, S., Ancrenaz, M., Lacy, R., van Schaik, C., Sugardjito, J.,
Simorangkir, T., Traylor-Holzer, K., Doughty, M., Supriatna, J., Dennis, R., Gumal, M., Knott, C. and
Singleton, I. 2008. Distribution and conservation status of the orangutan (Pongo spp.) on Borneo and
Sumatra: how many remain? Oryx 42: 1–11.
Wich, S.A., Singleton, I., Nowak, M.G., Utami Atmoko, S.S., Nisam, G., Arif, S.M., Putra, R.H., Ardi, R.,
Fredriksson, G., Usher, G., Gaveau, D.L.A and Kühl, H.S. 2016. Land-cover changes predict steep declines
for the Sumatran orangutan (Pongo abelii). Science Advances 2(3): e1500789.
Wich, S.A., Struebig, M., Refisch, J. Wilting, A., Kramer-Schadt, S. and Meijaard, E. 2015. The Future of
the Bornean Orangutan: Impacts of Change in Land Cover and Climate. UNEP/GRASP, Nairobi.
Ancrenaz, M., Gumal, M., Marshall, A.J., Meijaard, E., Wich , S.A. & Husson, S. 2016. Pongo pygmaeus.
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Habitat Season Suitability Major
1. Forest -> 1.6. Forest - Subtropical/Tropical Moist Lowland Resident Suitable Yes
Threat Timing Scope Severity Impact Score
1. Residential & commercial development -> 1.1.
Housing & urban areas
Ongoing Minority (50%) Slow, significant
Low impact: 5
Stresses: 1. Ecosystem stresses -> 1.1. Ecosystem conversion
1. Ecosystem stresses -> 1.2. Ecosystem degradation
11. Climate change & severe weather -> 11.1. Habitat
shifting & alteration
Ongoing Whole (>90%) Slow, significant
impact: 7
Stresses: 1. Ecosystem stresses -> 1.1. Ecosystem conversion
1. Ecosystem stresses -> 1.2. Ecosystem degradation
2. Agriculture & aquaculture -> 2.1. Annual &
perennial non-timber crops -> 2.1.2. Small-holder
Ongoing Minority (50%) Rapid declines Medium
impact: 6
Stresses: 1. Ecosystem stresses -> 1.1. Ecosystem conversion
1. Ecosystem stresses -> 1.2. Ecosystem degradation
2. Agriculture & aquaculture -> 2.1. Annual &
perennial non-timber crops -> 2.1.3. Agro-industry
Ongoing Majority (50-
Very rapid
High impact: 8
Stresses: 1. Ecosystem stresses -> 1.1. Ecosystem conversion
1. Ecosystem stresses -> 1.2. Ecosystem degradation
2. Agriculture & aquaculture -> 2.2. Wood & pulp
plantations -> 2.2.2. Agro-industry plantations
Ongoing Minority (50%) Very rapid
impact: 7
Stresses: 1. Ecosystem stresses -> 1.1. Ecosystem conversion
1. Ecosystem stresses -> 1.2. Ecosystem degradation
3. Energy production & mining -> 3.2. Mining &
Ongoing Minority (50%) Slow, significant
Low impact: 5
Stresses: 1. Ecosystem stresses -> 1.2. Ecosystem degradation
2. Species Stresses -> 2.2. Species disturbance
5. Biological resource use -> 5.1. Hunting & trapping
terrestrial animals -> 5.1.1. Intentional use (species is
the target)
Ongoing Majority (50-
Very rapid
High impact: 8
Stresses: 2. Species Stresses -> 2.1. Species mortality
5. Biological resource use -> 5.1. Hunting & trapping
terrestrial animals -> 5.1.3. Persecution/control
Ongoing Minority (50%) Very rapid
impact: 7
Stresses: 2. Species Stresses -> 2.1. Species mortality
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
5. Biological resource use -> 5.3. Logging & wood
harvesting -> 5.3.5. Motivation
Ongoing Minority (50%) Slow, significant
Low impact: 5
Stresses: 1. Ecosystem stresses -> 1.2. Ecosystem degradation
7. Natural system modifications -> 7.1. Fire & fire
suppression -> 7.1.1. Increase in fire
Ongoing Majority (50-
Rapid declines Medium
impact: 7
Stresses: 1. Ecosystem stresses -> 1.1. Ecosystem conversion
1. Ecosystem stresses -> 1.2. Ecosystem degradation
Conservation Actions in Place
Conservation Actions in Place
In-Place Research, Monitoring and Planning
Action Recovery plan: No
Systematic monitoring scheme: No
In-Place Land/Water Protection and Management
Conservation sites identified: Yes, over part of range
Occur in at least one PA: Yes
Percentage of population protected by PAs (0-100): 31-40
Area based regional management plan: Yes
In-Place Species Management
Harvest management plan: No
In-Place Education
Included in international legislation: Yes
Subject to any international management/trade controls: Yes
Conservation Actions Needed
Conservation Actions Needed
1. Land/water protection -> 1.1. Site/area protection
2. Land/water management -> 2.1. Site/area management
5. Law & policy -> 5.1. Legislation -> 5.1.1. International level
5. Law & policy -> 5.1. Legislation -> 5.1.2. National level
5. Law & policy -> 5.4. Compliance and enforcement -> 5.4.1. International level
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
Research Needed
Research Needed
1. Research -> 1.2. Population size, distribution & trends
2. Conservation Planning -> 2.2. Area-based Management Plan
3. Monitoring -> 3.1. Population trends
3. Monitoring -> 3.4. Habitat trends
Additional Data Fields
Lower elevation limit (m): 0
Upper elevation limit (m): 500
Continuing decline of mature individuals: Yes
Extreme fluctuations: No
Population severely fragmented: Yes
Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: Unknown
All individuals in one subpopulation: No
Habitats and Ecology
Continuing decline in area, extent and/or quality of habitat: Yes
Generation Length (years): 25
Movement patterns: Not a Migrant
© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
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ISSN 2307-8235 (online)
IUCN 2008: T17975A17966347
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The IUCN Red List of Threatened Species™ is produced and managed by the IUCN Global Species
Programme, the IUCN Species Survival Commission (SSC) and The IUCN Red List Partnership.
The IUCN Red List Partners are: BirdLife International; Botanic Gardens Conservation International;
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© The IUCN Red List of Threatened Species: Pongo pygmaeus – published in 2016.
... It is well-known for its abundant and diverse wildlife, including spectacular species, such as Bornean elephant (Elaphas maximus borneensis), Bornean orangutan (Pongo pygmaeus), and proboscis monkey (Nasalis larvatus). Many of these rare and endangered animals are on the IUCN's RED list [27,28]. More than 80% of the lower parts of the Kinabatangan floodplain land area have been converted to oil palm plantations over the past 40 years [29]. ...
Full-text available
... Two Orangutan species and one subspecies are in the top 20 ranking of the TIS (Table 1). Some of these animals are on the path to extinction within the next ~ 50 years due to habitat loss and illegal hunting (Ancrenaz et al. 2016;Singleton et al. 2017). Mammal herbivores face similar threats (e.g. ...
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Megafauna are amongst the most threatened species on our planet. Understanding threats to megafauna is important to plan effective protection. Previous studies identified threats to these species, but did not define the level of risk. In this paper, I have investigated the megafauna threat level and the associated conservation measures. First, I have used a semi-quantitative approach to define megafauna species based on body mass, trophic level and system (e.g. marine, land). My initial data includes more than 24,076 species, accounting for 96.2% of the IUCN Red List data for mammals, reptiles and birds (including sub-species and sub-populations). Second, I estimated the IUCN Threat Impact Score (TIS) on the species defined as megafauna (n = 404). Finally, based on the TIS and other parameters, I investigated the most threatened megafauna to pinpoint conservation priorities and strategies for their respective functional groups. Results show that megafauna conservation priorities are category-specific. For instance, each category of species (e.g. terrestrial predator) is sensitive to specific threats and requires various levels of protection depending on a variety of parameters (e.g. spatial scale, number of threats). I propose category-specific conservation priorities and a global strategy based on six pillars of action to improve megafauna protection: education and awareness; sanctions; regulated eco-tourism, coordination; data; and climate change.
... These 'conservation areas' were much smaller than Bornean orangutan home ranges (0.4-3.0 km 2 for females and 1.0-6.0 km 2 for males) (McConkey, 2005). A full High Conservation Value (HCV) area assessment, therefore, should be made obligatory by law prior to establishing such large-scale plantations, and HCV areas should be given legal protection (Colchester et al., 2009). ...
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Abstract Of the three subspecies of Critically Endangered Bornean orangutans, Pongo pygmaeus pygmaeus has the smallest population size. One of its most important habitats is the tropical forest within and around Danau Sentarum National Park (DSNP). Research in the late 1990s estimated that ca. 1025 orangutans inhabited DSNP, while ca. 1717 orangutans inhabited the forest beyond DSNP's boundaries. However, concerns were later raised that incorrectly estimated nest decay rates (t values) may have led to the overestimation of the population size. Furthermore, the area experienced forest degradation and land use change between 2000 and 2013. Given these changing landscapes, updated population estimates were needed to inform policy makers and land‐use planners on the implications of habitat loss for resident orangutans. We conducted this study to recalculate nest decay rates based on current recommended methods, and to update our knowledge on the orangutan population in the region. Our average nest decay rate was 288.3 days; applying this to the study in the late 1990s generated estimates of 807 individuals within DSNP and 1578 beyond DNSP's boundaries. New surveys of the transects undertaken between 2010 and 2014 revealed that the population size had declined substantially in these two areas, to 202 and 71 individuals respectively. Both declines are considerable, but larger losses occurred in logged‐over and cleared forests outside the park. We discuss factors potentially driving these declines, emphasizing the need to improve habitat protection both inside and outside of DSNP, and make recommendations for improving the prospects for future orangutan conservation.
... It is well-known for its abundant and diverse wildlife, including spectacular species, such as Bornean elephant (Elaphas maximus borneensis), Bornean orangutan (Pongo pygmaeus), and proboscis monkey (Nasalis larvatus). Many of these rare and endangered animals are on the IUCN's RED list [27,28]. More than 80% of the lower parts of the Kinabatangan floodplain land area have been converted to oil palm plantations over the past 40 years [29]. ...
Full-text available
Garnering support from multiple stakeholders to increase the number or size of protected areas remains a key challenge for wildlife conservation efforts in Malaysia. Human–wildlife conflict often arises when local socio-economic development compromises wildlife survival due to negative landscape changes. It is essential to assess both human–wildlife conflict and human–human conflicts about wildlife, in order to promote mutually beneficial human–wildlife coexistence. This paper examines pertinent factors influencing wildlife conservation by integrating ecological and social approaches using a conservation planning framework. The findings demonstrate the importance of appraising social values to address issues such as size limits for protected areas and compensation for wildlife damage to property. It shows that monetary incentives are not the sole determinant in gaining the support of indigenous people in reporting wildlife crimes and their active participation in conservation programs. Therefore, developing effective communication with stakeholders, empowerment of rural communities, and proper appraisal of social values are all urgently needed to promote effective rural wildlife conservation programs.
The interface of sexual behavior and evolutionary psychology is a rapidly growing domain, rich in psychological theories and data as well as controversies and applications. With nearly eighty chapters by leading researchers from around the world, and combining theoretical and empirical perspectives, The Cambridge Handbook of Evolutionary Perspectives on Sexual Psychology is the most comprehensive and up-to-date reference work in the field. Providing a broad yet in-depth overview of the various evolutionary principles that influence all types of sexual behaviors, the handbook takes an inclusive approach that draws on a number of disciplines and covers nonhuman and human psychology. It is an essential resource for both established researchers and students in psychology, biology, anthropology, medicine, and criminology, among other fields. Volume 4: Controversies, Applications, and Nonhuman Primate Extensions addresses controversies and unresolved issues; applications to health, law, and pornography; and non-human primate evolved sexual psychology.
Orangutan females live semi-solitarily, spending 50–80 percent of their time alone, with only their dependent offspring for company (van Schaik, 1999). They are philopatric (Arora et al., 2012; van Noordwijk et al., 2002) and establish their home ranges in an area that overlaps with their natal range as well as with those of other females, both maternal relatives and nonrelatives (Ashbury et al., 2020; Morrogh-Bernard, 2009). Males disperse from their natal range as they become independent of their mother around the age of ten to twelve years (Nietlisbach et al., 2012) and settle far away from their natal area. Adult males are not territorial, and their home ranges overlap with those of females, but are far larger (Singleton et al., 2009). Determining male ranging patterns is challenging because their ranging area far exceeds the size of all study areas covered by earth-bound researchers, and individual males may not be around for several months or even years (Dunkel et al., 2013; Spillmann et al., 2017; Utami Atmoko et al., 2009a). In sum, orangutans have a dispersed social and mating system with high female site fidelity and widely roaming males.
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This paper aimed to provide a narrative review of the current conditions of orangutan ecotourism on Sumatra Island, problems in the current management systems, and some recommendations for further development. Orangutan conservation centers have been developed on Sumatra Island since 1973. The Bukit Lawang Conservation Station is one of the orangutan conservation centers that have practiced ecotourism to overcome ecological and socio-economic issues. Even though the Bukit Lawang Conservation Station has operated for decades, this station has faced several issues, in particular a monetary crisis in 1997, a flash flood in 2003, and the COVID-19 pandemic. We identified that orangutan conservation centers on Sumatra Island have the potential to support orangutan ecotourism. These conservation centers have ecological support, available facilities, and rich local wisdom that can provide added value for orangutan ecotourism. Therefore, we propose that the development of orangutan ecotourism on Sumatra Island should accommodate surrounding communities through community-based wildlife ecotourism. We also recommend the following strategies to develop orangutan ecotourism on Sumatra Island: (1) mapping the location and distribution of wild orangutans in their natural habitats; (2) managing captive and semi-captive orangutans in conservation centers; (3) provision of tour packages; (4) community empowerment; (5) institutional strengthening of community-based ecotourism management (CBEM); (6) developing ecotourism through a benefit-sharing model; (7) anticipating and minimizing the negative impacts of ecotourism on orangutans; and (8) integrating orangutan tourism with local wisdom.
Objectives We applied stable carbon and nitrogen isotope analyses to wild Bornean orangutans ( Pongo pygmaeus morio ) to investigate the feeding ecology of wild orangutans. Compared with African great ape species, orangutans are adapted to environments with chronic lower nutrition. But the usefulness of stable isotope analysis in the study of wild orangutan feeding ecology has not been fully explored. Methods The study site was a primary lowland dipterocarp forest in the Danum Valley, Sabah, Malaysia. A total of 164 plant and 94 fecal samples collected across 18 months were analyzed. Results Carbon and nitrogen stable isotope ratios of plant food samples do not systematically vary by plant parts (i.e., bark, fruits, and leaves). Elemental composition and stable isotope ratios of orangutan feces do not systematically vary by orangutans' sex and age classes, although fecal stable isotope ratios showed seasonal fluctuations. No isotopic contribution of breast milk was found in fecal samples collected from individuals at 2.7–6.5 years of age. Conclusions This study revealed key characteristics of the stable isotope ecology of wild orangutans living in a primary lowland forest. Although there was little isotopic variation among plant foods and orangutan individuals, seasonal fluctuations in baseline isotope ratios or orangutans' diet were found in Danum valley.
Deforestation is an alarming issue that is prolific throughout world forests. Endemic fauna, flora, and wildlife habitat loss are serious concerns for world heritage. That is why Goal 15 of the Sustainable Development Goals (SDGs) promotes on the conserved use of these natural resources. Sabah, Malaysia is fortunate to have “Orang Hutan” literally “Jungle People” in the Sepilok Forest area. The government had designated the Sepilok Orangutan Rehabilitation Centre to their safeguard. Indeed, this is the world's first Rehabilitation Centre for Orangutans. However, the wildlife conservation of Orangutans needs to be translated into economic values. This study aims to determine the economic valuation of wildlife conservation through visitors’ Willingness to Pay (WTP) via applying the Contingent Valuation Method (CVM). A total of 143 questionnaires were distributed randomly to international and local visitors. The Logistic Regression was used to estimate the Mean WTP. Results showed that several significant socio‐demographic variables influence the respondent’s willingness to pay. Nevertheless, most respondents were willing to pay a maximum of MYR16.73, while the mean was MYR7.27 only. In 2017, the estimated annual economic value of the Rehabilitation Centre was MYR9, 697,074.96 compared to the estimated conservation value of MYR96, 970,749.60. The findings of this study demonstrate the possible beneficial role of economic valuation in assisting not just Orangutan conservation but threatened species conservation elsewhere. The study has assisted the centre's management in determining the appropriate entrance fees for the future, as they have not been revised in over a decade. This article is protected by copyright. All rights reserved.© 2022 Society of Environmental Toxicology & Chemistry (SETAC).
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Introduction Cardiovascular diseases have been identified as a major cause of mortality and morbidity in Borneo orangutans ( Pongo pygmaeus pygmaeus ). Transthoracic echocardiography is usually performed under anesthesia in great apes, which may be stressful and increase risks of peri-anesthetic complications in case of cardiac alteration. The aim of the present pilot study was hence to develop a quick and non-stressful echocardiographic method (i.e., the COOLEST method) in awake Borneo orangutans (CardiOvascular examination in awake Orangutans: Low-stress Echocardiography including Speckle Tracking imaging) and assess the variability of corresponding variables. Materials and methods Four adult Borneo orangutans trained to present their chest to the trainers were involved. A total of 96 TTE examinations were performed on 4 different days by a trained observer examining each orangutan 6 times per day. Each examination included four two-dimensional views, with offline assessment of 28 variables (i.e., two-dimensional (n = 12), M-mode and anatomic M-mode (n = 6), Doppler (n = 7), and speckle tracking imaging (n = 3)), representing a total of 2,688 measurements. A general linear model was used to determine the within-day and between-day coefficients of variation. Results Mean±SD (minimum-maximum) images acquisition duration was 3.8±1.6 minutes (1.3–6.3). All within-day and between-day coefficients of variation but one (n = 55/56, 98%) were <15%, and most (51/56, 91%) were <10% including those of speckle tracking systolic strain variables (2.7% to 5.4%). Discussion Heart morphology as well as global and regional myocardial function can be assessed in awake orangutans with good to excellent repeatability and reproducibility. Conclusions This non-stressful method may be used for longitudinal cardiac follow-up in awake orangutans.
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Positive news about Sumatran orangutans is rare. The species is critically endangered because of forest loss and poaching, and therefore, determining the impact of future land-use change on this species is important. To date, the total Sumatran orangutan population has been estimated at 6600 individuals. On the basis of new transect surveys, we estimate a population of 14,613 in 2015. This higher estimate is due to three factors. First, orangutans were found at higher elevations, elevations previously considered outside of their range and, consequently, not surveyed previously. Second, orangutans were found more widely distributed in logged forests. Third, orangutans were found in areas west of the Toba Lake that were not previously surveyed. This increase in numbers is therefore due to a more wide-ranging survey effort and is not indicative of an increase in the orangutan population in Sumatra. There are evidently more Sumatran orangutans remaining in the wild than we thought, but the species remains under serious threat. Current scenarios for future forest loss predict that as many as 4500 individuals could vanish by 2030. Despite the positive finding that the population is double the size previously estimated, our results indicate that future deforestation will continue to be the cause of rapid declines in orangutan numbers. Hence, we urge that all developmental planning involving forest loss be accompanied by appropriate environmental impact assessments conforming with the current national and provincial legislations, and, through these, implement specific measures to reduce or, better, avoid negative impacts on forests where orangutans occur.
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A multifunctional landscape approach to forest protection has been advocated for tropical countries. Designing such landscapes necessitates that the role of different land uses in protecting forest be evaluated, along with the spatial interactions between land uses. However, such evaluations have been hindered by a lack of suitable analysis methodologies and data with fine spatial resolution over long time periods.Wedemonstrate the utility of a matching method with multiple categories to evaluate the role of alternative land uses in protecting forest. We also assessed the impact of land use change trajectories on the rate of deforestation. We employed data from Kalimantan (Indonesian Borneo) at three different time periods during 2000–2012 to illustrate our approach. Four single land uses (protected areas (PA), natural forest logging concessions (LC), timber plantation concessions (TC) and oil-palm plantation concessions (OC)) and two mixed land uses (mixed concessions and the overlap between concessions and PA) were assessed. The rate of deforestation was found to be lowest for PA, followed by LC. Deforestation rates for all land uses tended to be highest for locations that share the characteristics of areas in which TC or OC are located (e.g. degraded areas), suggesting that these areas are inherently more susceptible to deforestation due to foregone opportunities. Our approach provides important insights into how multifunctional landscapes can be designed to enhance the protection of biodiversity.
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The native forests of Borneo have been impacted by selective logging, fire, and conversion to plantations at unprecedented scales since industrial-scale extractive industries began in the early 1970s. There is no island-wide documentation of forest clearance or logging since the 1970s. This creates an information gap for conservation planning, especially with regard to selectively logged forests that maintain high conservation potential. Analysing LANDSAT images, we estimate that 75.7% (558,060 km2) of Borneo's area (737,188 km2) was forested around 1973. Based upon a forest cover map for 2010 derived using ALOS-PALSAR and visually reviewing LANDSAT images, we estimate that the 1973 forest area had declined by 168,493 km2 (30.2%) in 2010. The highest losses were recorded in Sabah and Kalimantan with 39.5% and 30.7% of their total forest area in 1973 becoming non-forest in 2010, and the lowest in Brunei and Sarawak (8.4%, and 23.1%). We estimate that the combined area planted in industrial oil palm and timber plantations in 2010 was 75,480 km2, representing 10% of Borneo. We mapped 271,819 km of primary logging roads that were created between 1973 and 2010. The greatest density of logging roads was found in Sarawak, at 0.89 km km-2, and the lowest density in Brunei, at 0.18 km km-2. Analyzing MODIS-based tree cover maps, we estimate that logging operated within 700 m of primary logging roads. Using this distance, we estimate that 266,257 km2 of 1973 forest cover has been logged. With 389,566 km2 (52.8%) of the island remaining forested, of which 209,649 km2 remains intact. There is still hope for biodiversity conservation in Borneo. Protecting logged forests from fire and conversion to plantations is an urgent priority for reducing rates of deforestation in Borneo.
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The orangutan is the world's largest arboreal mammal, and images of the red ape moving through the tropical forest canopy symbolise its typical arboreal behaviour. Records of terrestrial behaviour are scarce and often associated with habitat disturbance. We conducted a large-scale species-level analysis of ground-based camera-trapping data to evaluate the extent to which Bornean orangutans Pongo pygmaeus come down from the trees to travel terrestrially, and whether they are indeed forced to the ground primarily by anthropogenic forest disturbances. Although the degree of forest disturbance and canopy gap size influenced terrestriality, orangutans were recorded on the ground as frequently in heavily degraded habitats as in primary forests. Furthermore, all age-sex classes were recorded on the ground (flanged males more often). This suggests that terrestrial locomotion is part of the Bornean orangutan's natural behavioural repertoire to a much greater extent than previously thought, and is only modified by habitat disturbance. The capacity of orangutans to come down from the trees may increase their ability to cope with at least smaller-scale forest fragmentation, and to cross moderately open spaces in mosaic landscapes, although the extent of this versatility remains to be investigated.
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We investigated why orangutans are being killed in Kalimantan, Indonesia, and the role of conflict in these killings. Based on an analysis of interview data from over 5,000 respondents in over 450 villages, we also assessed the socio-ecological factors associated with conflict and non-conflict killings. Most respondents never kill orangutans. Those who reported having personally killed an orangutan primarily did so for non-conflict reasons; for example, 56% of these respondents said that the reason they had killed an orangutan was to eat it. Of the conflict-related reasons for killing, the most common reasons orangutans were killed was fear of orangutans or in self-defence. A similar pattern was evident among reports of orangutan killing by other people in the villages. Regression analyses indicated that religion and the percentage of intact forest around villages were the strongest socio-ecological predictors of whether orangutans were killed for conflict or non-conflict related reasons. Our data indicate that between 44,170 and 66,570 orangutans were killed in Kalimantan within the respondents' active hunting lifetimes: between 12,690 and 29,024 for conflict reasons (95%CI) and between 26,361 and 41,688 for non-conflict reasons (95% CI). 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.
Aim We demonstrate a robust approach for predicting and mapping threats and population trends of wildlife species, invaluable for understanding where to target conservation resources. We used the endangered Bornean orangutan (Pongo pygmaeus) as our case study to facilitate and strengthen conservation efforts by the Indonesian government to stabilize populations by 2017. Location Kalimantan, Indonesian Borneo. Methods Local knowledge of threats to orangutan populations was gathered through questionnaire interviews in 531 villages (512 in Kalimantan) within known orangutan range. These data were integrated with 39 environmental/socio-economic spatial variables using boosted regression tree modelling to predict threat levels and population trends across Kalimantan and to identify key combinations of threats and trends that can help to direct appropriate conservation actions. Results Nineteen percentage of villages surveyed in Kalimantan reported human–orangutan conflicts. High-predicted conflict likelihood was extensive, strongly associated with road density (very low or high) and temperature seasonality. Recent orangutan killings were reported in 23% of villages. High killing risk was highly associated with greater surrounding orangutan habitat and for villages more than 60 km from oil palm plantations. Killings by respondents were reported in 20% of villages with higher likelihoods associated with greater range in rainfall and temperature, and higher proportion of Christian believers. Orangutan populations were predicted to decline/become locally extinct across the majority of their range in Kalimantan over the next decade, with few regions predicted to support stable populations. Main conclusions Human–orangutan conflicts and killings occur extensively in Kalimantan, with many populations at risk of decline or localized extinctions. Effective conservation actions are therefore urgently needed. Our approach better informs conservation managers in understanding the extent, spatial patterns and drivers of threats to endangered species such as the orangutan. This is essential to better design management strategies that can minimize or avert the species’ decline.
Habitat loss and climate change pose a double jeopardy for many threatened taxa, making the identification of optimal habitat for the future a conservation priority. Using a case study of the endangered Bornean orang-utan, we identify environmental refuges by integrating bioclimatic models with projected deforestation and oil-palm agriculture suitability from the 1950s to 2080s. We coupled a maximum entropy algorithm with information on habitat needs to predict suitable habitat for the present day and 1950s. We then projected to the 2020s, 2050s and 2080s in models incorporating only land-cover change, climate change or both processes combined. For future climate, we incorporated projections from four model and emission scenario combinations. For future land cover, we developed spatial deforestation predictions from 10 years of satellite data. Refuges were delineated as suitable forested habitats identified by all models that were also unsuitable for oil palm – a major threat to tropical biodiversity. Our analyses indicate that in 2010 up to 260 000 km2 of Borneo was suitable habitat within the core orang-utan range; an 18–24% reduction since the 1950s. Land-cover models predicted further decline of 15–30% by the 2080s. Although habitat extent under future climate conditions varied among projections, there was majority consensus, particularly in north-eastern and western regions. Across projections habitat loss due to climate change alone averaged 63% by 2080, but 74% when also considering land-cover change. Refuge areas amounted to 2000–42 000 km2 depending on thresholds used, with 900–17 000 km2 outside the current species range. We demonstrate that efforts to halt deforestation could mediate some orang-utan habitat loss, but further decline of the most suitable areas is to be expected given projected changes to climate. Protected refuge areas could therefore become increasingly important for ongoing translocation efforts. We present an approach to help identify such areas for highly threatened species given environmental changes expected this century.