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The Tapanuli orangutan: Status, threats, and steps for improved conservation

The Tapanuli orangutan: Status, threats, and steps for improved
Serge A. Wich
| Gabriella Fredriksson
| Graham Usher
| Hjalmar S. Kühl
Matthew G. Nowak
School of Natural Sciences and Psychology, Liverpool John Moores
University, Liverpool, UK
Institute for Biodiversity and Ecosystem Dynamics, University of
Amsterdam, Amsterdam, the Netherlands
Conservation Division, The PanEco Foundation - Sumatran Orangutan
Conservation Programme, Berg am Irchel, Switzerland
Department of Primatology, Max Planck Institute for Evolutionary
Anthropology, Leipzig, Germany
Sustainability and Complexity in Ape Habitat Group, German Centre for
Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig,
Department of Anthropology, Southern Illinois University, Carbondale,
Serge A. Wich, School of Natural Sciences and Psychology, James Parsons Building, Byrom street, L33AF, Liverpool, UK.
KEYWORDS: Batang Toru, hydrodam, Tapanuli orangutan
Ever since the Tapanuli orangutan (Pongo tapanuliensis)
was described two years ago (Nater et al., 2017) it has fre-
quently been in the news for two primary reasons. First,
because of the excitement generated by the discovery of the
first new extant great ape species since 1929. Second,
because of the immediate threat posed to the new species by
the development of a hydrodam to generate electricity
(Sloan, Supriatna, Campbell, Alamgir, & Laurance, 2018).
As the species has only been described recently there is no
paper that summarizes its status and threats even though
some of that information is available from a previous study
where this species was still considered a population of the
Sumatran orangutan (Pongo abelii) (Wich et al., 2016). In
this letter, we aim to remedy this gap by providing a succinct
overview of the status of and threats to the Tapanuli orangu-
tan, as well as by identifying key steps toward improved
conservation. This is particularly relevant as there is a need
to be able to determine the impact of the hydroelectric dam
development which is best achieved from a clear baseline.
As with the other two orangutan species, the Tapanuli
orangutan is considered to be Critically Endangered by the
International Union for Conservation of Nature (IUCN)
(Nowak, Rianti, Wich, Meijaard, & Fredriksson, 2017). The
species is only found in the forests of the Batang Toru Eco-
system in the province of North Sumatra, Indonesia
(Figure 1). Based on extensive survey work from 2000 to
2012 it has been determined that the total extent of its distri-
bution covers 1,023 km
(Wich et al., 2016). It is found in
three main forest blocks with a total of 767 individuals (95%
confidence intervals [CI] [2311,597]): the west block
which houses 581 individuals (95%CI [1801,201] [sum of
533, 42, and 6 in Figure 1]), the east block with 162 individ-
uals (95% CI [46341]), and the Sibual-buali Reserve with
24 individuals (95% CI [653], based on (Wich et al., 2016),
with possibly small populations to the north and/or in the
Lubuk Raya Reserve). Of this distribution, roughly 85% is
under some form of protection status, but 15% is land for
other uses (Nowak et al., 2017). The west block and the
Received: 8 February 2019 Accepted: 27 March 2019
DOI: 10.1111/csp2.33
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original
work is properly cited.
© 2019 The Authors. Conservation Science and Practice published by Wiley Periodicals, Inc. on behalf of Society for Conservation Biology
Conservation Science and Practice. 2019;1:e33. 1of4
Sibual-buali Reserve are still moderately connected and
orangutan dispersal is expected to occur between those areas
based on the locations where nests have been found during
surveys (Figure 1). It is less clear if orangutans can still
move between the west and east block because of the pro-
vincial road from Tarutung to Padangsidempuan separating
these blocks as well as the Batang Toru River.
There are several threats to the Tapanuli orangutan.
Between 1985 and 2007, 43.3% of the forests in the province
of North Sumatra (where the Tapanuli orangutan occurs)
have been lost (Wich, Riswan, Jenson, Refisch, &
Nellemann, 2011). Annual deforestation rates were particu-
larly high from 1985 to 1990 (4.2%), decreased from 1990
to 2000 (1.2%), and then increased again from 2000 to
2008/2009 (2.3%). Particularly recent losses of peat swamp
areas on the coast where the species had been found in the
past (Wich et al., 2003) have led to a reduction of forest for
the Tapanuli orangutan as well as the slower but steady for-
est loss that occurs around all three blocks. During
1990-2009, annual forest loss for the area in which the
Tapanuli orangutan occurs was calculated as 0.11%, with a
range of <0.010.84% (Wich et al., 2011). This is lower
than the overall annual forest loss for North Sumatra due to
the Tapanuli orangutan occurring in more mountainous areas
which have lower deforestation rates than areas at lower ele-
vations. The other main threat is killing of orangutans. This
occurs in two circumstances. First, orangutan hunting still
occurs in the area (Wich et al., 2012). Even though hunters
do not seem to go into the forest to specifically hunt for
orangutans, they do opportunistically hunt/kill them for food
when encountered (Wich et al., 2012). Second, orangutans
that venture into community plantations have been killed as
a result of human-orangutan conflict (Nater et al., 2017). As
orangutans are long-lived and have slow reproductive rates,
even low levels of extrinsic mortality (i.e., >1% per year,
which in this case is just a few individuals) represent a major
threat to the long-term growth, stability, and persistence of
the small-sized Tapanuli orangutan populations (Marshall et
al., 2009).
In addition to these threats there is a hydroelectric dam
with associated infrastructure planned in the area (Sloan
et al., 2018). The area of influence of the dam is planned in
an area with the highest Tapanuli orangutan densities and
covers 5.5% (42 individuals, 95%CI [1484]) of the total
FIGURE 1 Map showing the distribution of the Tapanuli orangutans, their population numbers and threats. The 95% confidence intervals (CI)
for the various areas are: West block: 164105, East block: 46341, Hydro AoI: 1484, Corridor: 212, Sibual-buali: 653
2of4 WICH ET AL.
Tapanuli orangutan population (Wich et al., 2016). Orangu-
tans in this area and surroundings will be negatively impacted
through habitat degradation and loss. This is of particular con-
cern for orangutan females because they are philopatric and
tend not to move when they lose parts of their home range
(van Schaik, 2004) and risk starvation or being killed when
this occurs. Such home range loss and subsequent dispersal
can also lead to compression of orangutans in adjacent areas
and inflated densities past the carrying capacity and hence
lead to food shortages and future reductions in density
(Husson, personal communication, January 15, 2019). If parts
of their home range are lost, orangutans in disturbed areas will
have to use the remaining parts of their own home range more
intensively than before, which can also lead to social tension
between females (Ashbury et al., 2015).
Additionally, the hydroelectric dam and its associated
infrastructure will separate the Sibual-buali Reserve from the
west block and will also impact the options for reconnecting
the east and west block. Over 20 km of road and 14 km of
electricity transmission lines through Tapanuli orangutan
habitat are planned, and at least 3 million m3 of excavated
spoil is planned to be dumped in orangutan habitat
(Comanditaire Venotschap (CV) Global Inter System, 2014,
2016). Furthermore, it is well-established that infrastructure
development, especially roads, can facilitate human access
into previously inaccessible areas, eventually leading to
additional and often unrestricted levels of habitat degrada-
tion and loss, hunting, and/or human-animal conflict
(Laurance, 2015; Laurance & Arrea, 2017; van der Ree,
Smith, & Grilo, 2015).
Taken together, the hydroelectric project will drive the
Sibual-buali and Sitandiang corridor population (30 individ-
uals, 95% CI [865]) and east block population (162 individ-
uals) to a status of nonviable, which is defined here as a
population with 0% probability of extinction and >90%
retention of genetic diversity for a minimum of 1,000 years
(Singleton et al., 2004; Marshall et al., 2009). Following the
results of the 2004 orangutan Population and Habitat Viabil-
ity Assessment (PHVA) workshop, a population of >500
individuals is considered viable using this definition (Single-
ton et al., 2004). This will leave the west block as the last
remaining viable Tapanuli orangutan population. But given
the current and projected threats of habitat degradation and
loss, hunting, human-orangutan conflict, an expanding
goldmine, and a neutralized logging concession in the area
(GoNSP, 2017; MoEF, 2017; MoF, 2014), this is an
extremely risky scenario and should therefore be avoided at
all costs, because these threats could drive this population to
nonviable status within as few as 12 generations.
In conclusion, the Tapanuli orangutan was the latest
extant great ape to be discovered, but given its extremely
small population numbers and current and projected threats,
it might well be the first one to go extinct. This would con-
travene the Indonesian Law Regarding the Conservation of
Biological Resources and Ecosystems (Law No. 5/1990), as
well as the Aichi targets to which the Indonesian govern-
ment has committed (Darajati et al., 2016; PoRI, 1990). As
such, it is imperative that the Government of Indonesia takes
some bold steps to secure its future, of which the most
important short-term ones are: (a) to halt the hydroelectric
dam development; (b) change the land use status of the
unprotected 15% of the area where the Tapanuli orangutan
occurs to a protected status; and (c) establish a corridor
between the west and east block and improve the corridor
between the west block and Sibual-buali Reserve. In addi-
tion, the ongoing hunting and small-scale deforestation need
to be halted through serious enforcement of Indonesia's reg-
ulations concerning protected species.
The authors declare no potential conflict of interest.
S.A.W., G.F., G.U., and M.G.N. conceived the paper,
S.A.W., G.U., M.G.N., and H.S.K. conducted the analyses,
S.A.W., G.F., G.U., H.S.K., and M.G.N. wrote the paper.
No ethics approval was needed for this study. All data are
available on request from the authors.
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How to cite this article: Wich SA, Fredriksson G,
Usher G, Kühl HS, Nowak MG. The Tapanuli
orangutan: Status, threats, and steps for improved
conservation. Conservation Science and Practice.
4of4 WICH ET AL.
... The primary forested blocks occupied by P. tapanuliensis are: Batang Toru protected forest and three nature reserved forests (Dolok Sipirok, Dolok Sibual-buali, and Lubuk Raya). While no collection of accurate trend data to date, some analysis suggested that the population is declining (Wich et al., 2008;Wich et al., 2012;Nater et al., 2017;Wich et al., 2019). Factors acknowledged to be contributing to this reduction are similar to those affecting orangutan throughout their range in Indonesia and Malaysia, namely land conversion for agriculture, settlement, and resource extraction (mining, legal and illegal logging); orangutan-human conflict; and poaching for the illegal wildlife trade and bushmeat (Utami-Atmoko et al., 2017;Wich et al., 2019). ...
... While no collection of accurate trend data to date, some analysis suggested that the population is declining (Wich et al., 2008;Wich et al., 2012;Nater et al., 2017;Wich et al., 2019). Factors acknowledged to be contributing to this reduction are similar to those affecting orangutan throughout their range in Indonesia and Malaysia, namely land conversion for agriculture, settlement, and resource extraction (mining, legal and illegal logging); orangutan-human conflict; and poaching for the illegal wildlife trade and bushmeat (Utami-Atmoko et al., 2017;Wich et al., 2019). Current population trend estimates P. tapanuliensis suggest a potential 1.2% decline over the next ten years (Utami-Atmoko et al., 2019). ...
... Ongoing concerns over the impact of the Batang Toru Hydro Electric Project (HEP) for P. tapanuliensis, have focused on several issues, the main ones being: 1) That they developed the runoff river hydropower project in an area with the highest density of Tapanuli orangutan (Wich et al., 2012;Wich et al., 2019) 2) The project will flood 96 Km 2 of orangutan habitat (Sloan et al., 2018); 3) The project construction would negatively impact the habitat for several resident individuals (Wich et al., 2019); 4) The project would genetically isolate the small P. tapanuliensis sub-population found in the Sibual-buali reserve area from those in the much larger west block population; and 5) The establishment of the construction activities would facilitate human access to P. tapanuliensis habitat and bring with it increased risk of hunting, illegal logging, development of previously isolated private lands, and human-animal conflict. Based on those concerns, Wich et al. (2019) assumed that the Batang Toru hydropower project's establishment would accelerate the decline in P. tapanuliensis populations in the Sibual-buali and Sipirok reserve areas and, when combined with other risk factors, result in eventual species extinction. ...
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To protect Tapanuli orangutan it is essential to understand the actual situation. It has been studied 15% of its population live outside the protected area facing a density disruption due to forest conversion. Several best management practices have been created and tested for different natural concession types. Yet, the main objective to reduce the impact and increase wildlife survival is far away from the goal. To improve our understanding of the species survival within ongoing project construction, we conducted population density monitoring prior- to post-construction time frames within the hydroelectric dam project. Also, we carried out spatial analysis to understand the land cover change and orangutan’s suitable habitat distribution. This study found that during high construction activities, orangutans were avoiding the threat sources, and returned when the disturbances reduced. These findings indicated orangutans are ecology flexible and have the capability to increase its survival, although the company’s involvement is crucial to facilitate the successes. Our study is based on indirect observation, and spatial modeling, which may lead to an uncertain conclusion. Further research on orangutan ecology and behavior is prioritized.
... The growing threat of the Tapanuli Orangutan population in recent decades has resulted in a smaller living space for the remaining Tapanuli Orangutan. Even though the Tapanuli orangutan is the late great ape discovered in the 21st century, threats to its small population could make them the first great ape to become extinct (5). ...
... The role of government and industry, and local farmers is very vital if we want to see the Tapanuli Orangutan population survive for the long term. Companies must have systematic conflict mitigation and responsible practices such as building biological corridors to connect and reconnect the Batang Toru forest blocks and agroforests (5,33). ...
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... Amongst all the future developments, the hydropower dam development in the currently undammed Batang Toru catchment in North Sumatra is a cause for concern. This is because the 510 MW Batang Toru dam is going to be sited on the mainstream, and the construction activities would fragment the forest and disrupt the largest subpopulation of Tanpanuli orangutan, a critically endangered species of orangutan endemic to the region [46,47]. The dam may also be vulnerable to future earthquakes, given its proximity to the Sumatran fault [48]. ...
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Dams are infrastructural projects with multiple uses that include hydropower, irrigation, water storage, flood management, and recreation. Most research on dams in Southeast Asia focuses on the Mekong River Basin and there is limited research on dams in Indonesia. Here, we developed a comprehensive database of dams in Indonesia derived from global and local datasets. We also used Google Earth Pro to locate additional dams and to validate the presence of all the dams. Our database had a total of 1506 dams (from large to mini dams and run-of river dams) in operation or under construction, and this was three times the number of dams reported in Indonesia's national database for dams. There were another 250 planned dams, of which, only 30 had known locations. Our database also includes information such as the geographical coordinates of each dam, their physical characteristics, and what each dam is used for. Ultimately, we hope that our work will help researchers, non-government organizations, and government agencies with hydrological and socio-ecological research in Indonesia.
... Without a resolution that allows for academic research, the continued usage of outdated and incorrect taxonomic classifications will result in an error cascade of conservation decisions. This is counterproductive to the aims of the CBD as the discovery and recognition of new species likely would shift conservation aims tremendously (see for instance Nater et al. 2017 andWich et al. 2019 for a prominent mammalogical example). ...
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... The rate of forest loss is unabated in Indonesian Borneo (Kalimantan) but has slowed in Sumatra and Malaysian Borneo, mainly due to a lack of large tracts of land suitable for industrial-scale oil palm plantation development (Santika et al., 2017;Xu et al., 2020;Yunikartika, 2016). Furthermore, land conversion for other uses (e.g., mining, dam construction, and road building, including the Pan Borneo Highway) is ongoing throughout the orangutan's range, including the imminent threat to the newly described Tapanuli species (Pongo tapanuliensis) in Sumatra (Alamgir et al., 2019;Laurance et al., 2020;Wich et al., 2019). Thus, habitat insecurity from encroachment and further fragmentation is an ongoing and central concern for wild orangutan conservation Gaveau et al., 2019;Voigt et al., 2021). ...
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Throughout the equatorial tropics, forest conversion to agriculture often fragments crucial primate habitat. In 30 years, 80% of the alluvial lowland forests along the Kinabatangan River in Sabah, Malaysian Borneo, have been supplanted by oil palm (Elaeis guineensis) plantations. Today, only about 20% of the former orangutan (Pongo pygmaeus morio) population remains in the region. Because most of the land is now under the tenure of agribusiness companies, we used a pragmatic approach of mixed biosocial methods and citizen science engagement of oil palm growers (N = 6) as active conservation partners to study orangutan use of the privately administered landscape between protected forest fragments. We found that 22 of 25 remanent forest patches (0.5 to 242 hectares) surveyed within plantations contained food or shelter resources useful for orangutans. Of these, 20 are in regular transitory use by wider-ranging adult male orangutans, and in 9 patches, females are resident and raising offspring isolated within oil palm plantations. These findings indicate that orangutans retain a measure of normal metapopulation dynamics necessary for viability at the landscape level despite drastic habitat modification. We found that barriers to in situ conservation in these agroforest matrices were due to the following misconceptions across sectors: 1) Good farming practices require exclusion of wildlife; 2) Orangutans seen in plantations must be “rescued” by people; and 3) Translocation is an appropriate conservation strategy, and nondetrimental to orangutans. Our exploratory study exemplifies the value of biosocial methods and collaboration with industrial-scale farmers to support primate resilience in forests fragmented by agriculture.
... Another activity that could threaten Tapanuli orangutans is the hydroelectric power project on the Batangtoru River. The project has the potential to impede the movement of orangutans in the East and West Blocks, including the South-West Block (Wich et al., 2019;Laurance et al., 2020). On the other hand only 122 ha of land will be used for the project, which is 0.07% of the entire Batang Toru ecosystem. ...
Biological and ecological information on the Tapanuli orangutan (Pongo tapanuliensis) remains limited. This study was designed to analyze the demographic parameters and build a growth model of the Tapanuli orangutans to help guide policy in developing a conservation program for them. Data were collected from tapanuli orangutans that were directly observed over four years in the Batang Toru Landscape, South Tapanuli Regency, North Sumatra. There were 32 distinct individual orangutans, 27 of which were adults or sub-adults. Only five were children or infants. The adult sex ratio, male to female, was 1: 0.83, the birthrate was 0.13, and the highest mortality rate was among sub-adults and adults. The population growth rate (r) was estimated to be 0.051 per year and predicted to reach the potential carrying capacity of the habitat they now occupy in about 60–80 years from 2020. Conservation activities that might help to increase the tapanuli orangutan population include increasing the number of food plants in production forests around nature reserves and increasing patrols to monitor the population and minimize potential damage to the animal and their habitat due to human activities.
... This is especially the case for primates that have adapted well to anthropogenic environments outside of protected areas, such as howler mon-keys (genus Alouatta) and colobus monkeys (genus Colobus), and hence make frequent use of human infrastructure (Lokschin et al., 2007;Cunneyworth & Duke, 2020). Pipelines associated with hydroelectric, gas, and oil projects severely fragment primate habitats (e.g., Thurber et al., 2005;Wich et al., 2019). They also require the creation of additional access roads for construction and maintenance, potentially boosting other activities, such as logging and hunting (Laurance et al., 2006). ...
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Most primate populations are declining, with 60% of species facing extinction. The expansion of transportation and service corridors (T&S), i.e. roads, rail, and utility and service lines, poses a significant yet underappreciated threat. With the development of T&S corridors predicted to increase across primates' ranges, it is necessary to understand the current extent of its impacts on primates, the available options to mitigate these effectively, and recognize research and knowledge gaps. By employing a systematic search approach to identify literature that described the relationship between primates and T&S corridors, we extracted information from 327 studies published between 1980 to 2020. Our results revealed that 218 species and subspecies across 62 genera are affected, significantly more than the 92 listed by the IUCN Red List of Threatened Species. The majority of studies took place in Asia (45%), followed by mainland Africa (31%), the Neotropics (22%), and Madagascar (2%). Brazil, Indonesia, Equatorial Guinea, Vietnam, and Madagascar contained the greatest number of affected primate species. Asia featured the highest number of species affected by roads, electrical transmission lines, and pipelines and the only studies addressing the impact of rail and aerial tramways on primates. The impact of seismic lines only emerged in literature from Africa and the Neotropics. Impacts are diverse and multifaceted, e.g. animal‐vehicle collisions, electrocutions, habitat loss and fragmentation, impeded movement and genetic exchange, behavioural changes, exposure to pollution, and mortality associated with hunting. Although several mitigation measures were recommended, only 41% of studies focused on their implementation, whilst only 29% evaluated their effectiveness. Finally, there was a clear bias in the species and regions benefiting from research on this topic. We recommend that government and conservation bodies recognise T&S corridors as a serious and mounting threat to primates and that further research in this area is encouraged. This article is protected by copyright. All rights reserved
Primates that live within fragmented and disturbed habitat are facing population declines and a higher probability of extinction due to gene flow inhibition. To address this problem, land managers, practitioners, and primatologists have applied several approaches to enhance primates’ habitat quality and connectivity through habitat restoration and canopy bridge installation. In some cases, artificial canopy bridges have shown to be effective to facilitate movement between fragmented habitats for several primates’ taxa. However, while several types of canopy bridge designs are available, there is no clear evidence on which is the best for primates. Here we evaluated the effectiveness of three artificial canopy bridge designs within a hydroelectric project in Sumatra, Indonesia from 2019 to 2021. The hydroelectric project was located at the edge of a forest block within the Batang Toru Ecosystem which could disconnect the primate’s population from this protected forest to the other forest blocks. During 595 days of camera trapping, we captured 988 independent crossing events from six diurnal primate species ( Pongo tapanuliensis , Hylobates agilis , Symphalangus syndactylus , Presbytis sumatrana , Macaca nemestrina , and Macaca fascicularis ). Our initial observation finds the ladder canopy bridge design was commonly used by primates and Presbytis sumatrana was the species that often crossed the canopy bridge. These findings are important to improve species management plans and primate conservation in Indonesia.
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Lampiran ini menyajikan hasil estimasi kelimpahan kera pada tingkat lokasi. Istilah 'lokasi' merujuk pada kawasan lindung dan/atau zona penyangganya, konsesi pembalakan atau kelompok konsesi, atau area khusus lain yang dalam dua dekade terakhir menjadi lokasi survei. Lampiran ini juga mencantumkan beberapa lokasi yang disur-vei terakhir kali pada tahun 1970-an dan 1980-an. Sebagian besar hasil estimasi berasal dari publikasi yang telah melalui penelaahan sejawat dan literatur kelabu. Beberapa hasil estimasi telah dikonfirmasi kembali oleh para ahli yang memiliki akses terhadap materi yang tidak bera-da dalam ranah publik (misalnya data mentah dan dokumen dari pihak ketiga yang tidak dapat disebarkan secara kes-eluruhan tanpa izin). Beberapa tabel menerakan 'tahun survei' , yang menunjukkan waktu pengumpulan data di lapangan, sedangkan beberapa tabel lainnya menggunakan 'tahun hasil estimasi' , yang menunjukkan waktu pemodelan suatu prediksi. Karena catatan mengenai jumlah mutlak kera jarang tersedia, lampiran ini menggunakan kelas kelimpahan dari kisaran populasi, seperti yang ditetapkan dalam Tabel 1. Untuk kera kecil, estimasi kepadatan yang tersedia juga disajikan.
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Global infrastructure expansion must balance social benefits and environmental hazards
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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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To conserve species it is essential to understand which factors determine their distribution and density. Here we focus on the critically endangered Sumatran orang-utan and examine factors that influence the distribution and density in the Batang Toru area, the southernmost area where wild orang-utans occur on Sumatra. We contrast a scenario in which orang-utan distribution is mainly determined by ecological, and topographic variables with a model that includes hunting and human impact. We show that orang-utan distribution and density are best explained by hunting pressure and elevation. These results indicate that an assessment of anthropogenic factors that might influence density such as hunting needs to be included in surveys that aim to predict orang-utan distribution and density. As anthropogenic impact becomes higher with increasing human population density and increased forest access in most areas where orang-utans occur the consequence is that orang-utan conservation will have to be achieved in an environment modified by humans. In such areas the potential for a range of conflicts such as hunting that lead to human-caused mortality for orang-utans will remain a constant threat and need to be mitigated.
Nater, et al.[1] recently identified a new orangutan species (Pongo tapanuliensis) in northern Sumatra, Indonesia-just the seventh described species of living great ape. The population of this critically-endangered species is perilously small, at only ∼800 individuals [1], ranking it among the planet's rarest fauna. We assert that P. tapanuliensis is highly vulnerable to extinction because its remaining habitat is small, fragmented, and poorly protected. While road incursions within its habitat are modest-road density is only one-eighth that of northern Sumatra-over one-fifth of its habitat is zoned for agricultural conversion or is comprised of mosaic agricultural and regrowth/degraded forest. Additionally, a further 8% will be affected by flooding and infrastructure development for a hydroelectric project. We recommend urgent steps to increase the chance that P. tapanuliensis will persist in the wild.
Six extant species of non-human great apes are currently recognized: Sumatran and Bornean orangutans, eastern and western gorillas, and chimpanzees and bonobos [1]. However, large gaps remain in our knowledge of fine-scale variation in hominoid morphology, behavior, and genetics, and aspects of great ape taxonomy remain in flux. This is particularly true for orangutans (genus: Pongo), the only Asian great apes and phylogenetically our most distant relatives among extant hominids [1]. Designation of Bornean and Sumatran orangutans, P. pygmaeus (Linnaeus 1760) and P. abelii (Lesson 1827), as distinct species occurred in 2001 [1, 2]. Here, we show that an isolated population from Batang Toru, at the southernmost range limit of extant Sumatran orangutans south of Lake Toba, is distinct from other northern Sumatran and Bornean populations. By comparing cranio-mandibular and dental characters of an orangutan killed in a human-animal conflict to those of 33 adult male orangutans of a similar developmental stage, we found consistent differences between the Batang Toru individual and other extant Ponginae. Our analyses of 37 orangutan genomes provided a second line of evidence. Model-based approaches revealed that the deepest split in the evolutionary history of extant orangutans occurred ∼3.38 mya between the Batang Toru population and those to the north of Lake Toba, whereas both currently recognized species separated much later, about 674 kya. Our combined analyses support a new classification of orangutans into three extant species. The new species, Pongo tapanuliensis, encompasses the Batang Toru population, of which fewer than 800 individuals survive.
Roads greatly influence the footprint of human activity, but they are often constructed with little consideration of their environmental impacts, especially in developing nations. Here, differences between environmentally 'good' and 'bad' roads are highlighted, and it is argued that a proactive road-zoning system is direly needed at international and national scales. Such a zoning system could identify areas where the environmental costs of roads are likely to be high and their socioeconomic benefits low, as well as areas where road improvements could have modest environmental costs and large societal benefits. 1 Land-use pressures will rise sharply this century and will be strongly influenced by roads. 2 Agricultural yield increases alone will not spare nature - land-use zoning is crucial too. 3 Roads in pristine areas are environmentally dangerous - the first cut is critical. 4 Paved highways have especially large-scale impacts. 5 Roads can be environmentally beneficial in certain contexts. 6 Roads are amenable to policy modification. 7 A recently proposed global road-mapping scheme could serve as a potential model for these efforts. This road-planning scheme could be an important tool for prioritising road investments and for underscoring the transformative role of roads in determining environmental change. An overriding priority is to proactively zone roads at a range of spatial scales while highlighting their critical role in provoking environmental change. Keeping roads out of surviving irreplaceable natural areas is among the most tractable and cost-effective ways to protect crucial ecosystems and the vital services they provide, whereas roads in the right places can facilitate increases in agricultural productivity and efficiency.
Global road length, number of vehicles and rate of per capita travel are high and predicted to increase significantly over the next few decades.2The ‘road-effect zone’ is a useful conceptual framework to quantify the negative ecological and environmental impacts of roads and traffic.3The effects of roads and traffic on wildlife are numerous, varied and typically deleterious.4The density and configuration of road networks are important considerations in road planning.5The costs to society of wildlife-vehicle collisions can be high.6The strategies of avoidance, minimisation, mitigation and offsetting are increasingly being adopted around the world – but it must be recognised that some impacts are unavoidable and unmitigable.7Road ecology is an applied science which underpins the quantification and mitigation of road impacts.
Orangutans (genus Pongo) are the largest arboreal mammals, but Bornean orangutans (P. pygmaeus spp.) also spend time on the ground. Here, we investigate ground use among orangutans using 32,000 hr of direct focal animal observations from a well-habituated wild population of Bornean orangutans (P. p. wurmbii) living in a closed-canopy swamp forest at Tuanan, Central Kalimantan, Indonesia. Ground use did not change with increasing observation time of well-habituated individuals, suggesting it was not an artifact of observer presence. Flanged males spent the most time on the ground (ca. 5% of active time), weaned immatures the least (around 1%). Females and immatures descended mainly to feed, especially on termites, whereas flanged males traveled more while on the ground. Flanged males may travel more inconspicuously, and perhaps also faster, when moving on the ground. In addition, orangutans engaged in ground-specific behavior, including drinking from and bathing in swamp pools. Supplementary records from 20 ground-level camera traps, totaling 3986 trap days, confirmed the observed age-sex biases in ground use at Tuanan. We conclude that ground use is a natural part of the Bornean orangutan behavioral repertoire, however it remains unclear to what extent food scarcity and canopy structure explain population differences in ground use. Am. J. Primatol. © 2015 Wiley Periodicals, Inc. © 2015 Wiley Periodicals, Inc.