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

Wich, Serge A.; Fredriksson, Gabriella; Usher, Graham; Kühl, Hjalmar S.; Nowak, Matthew G.

doi:10.1111/csp2.33

Cited by 23 publications

(43 citation statements)

References 12 publications

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“…The Batang Toru Ecosystem consists of roughly 150,000 ha of primary upland forest located in the North‐, Central‐, and South‐Tapanuli Districts, North Sumatra Province (Wich, Fredriksson, Usher, Kühl, & Nowak, 2019). The Batang Toru study area (1°41′9.1″N/98°59′38.1″E; ca.…”

Section: Methodsmentioning

confidence: 99%

Grouping behavior of Sumatran orangutans (Pongo abelii) and Tapanuli orangutans (Pongo tapanuliensis) living in forest with low fruit abundance

Roth

Rianti

Fredriksson

et al. 2020

American J Primatol

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In contrast to the African great apes, orangutans (Pongo spp.) are semisolitary: Individuals are often on their own, but form aggregations more often than expected by chance. These temporary aggregations provide social benefits such as mating opportunities. When fruit availability is high, costs of aggregating should be lower, because competition is less pronounced. Therefore, average party size is expected to be higher when fruit availability is high. This hypothesis would also explain why orangutans in highly fruit-productive habitats on Sumatra are more gregarious than in the usually less productive habitats of Borneo. Here, we describe the aggregation behavior of orangutans in less productive Sumatran habitats (Sikundur and Batang Toru), and compare results with those of previously surveyed field sites. Orangutans in Sikundur were more likely to form parties when fruit availability was higher, but the size of daily parties was not significantly affected by fruit availability. With regard to between-site comparisons, average party sizes of females and alone time of parous females in Sikundur and Batang Toru were substantially lower than those for two previously surveyed Sumatran sites, and both fall in the range of values for Bornean sites. Our results indicate that the assessment of orangutans on Sumatra as being more social than those on Borneo needs revision. Instead, between-site differences in sociality seem to reflect differences in average fruit availability.

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Section: Methodsmentioning

confidence: 99%

Grouping behavior of Sumatran orangutans (Pongo abelii) and Tapanuli orangutans (Pongo tapanuliensis) living in forest with low fruit abundance

Roth

Rianti

Fredriksson

et al. 2020

American J Primatol

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“…Remnant forests in the Batang Toru region are the last refuge of the critically endangered Tapanuli orangutan (Pongo tapanuliensis) and would be intersected by a highway and hydroelectric developments ( Figure 1C). Although most local forests are nominally protected, their conservation status and utility as habitat are increasingly tenuous and would be jeopardized by these developments (Sloan, Supriatna, Campbell, Alamgir, & Laurance, 2018;Wich, Fredriksson, Usher, Ku¨hl, & Nowak, 2019).…”

Section: Habitat Loss In the Batang Toru Regionmentioning

confidence: 99%

“…The loss of nearby habitat and ongoing deforestation in Batang Toru (Wich, Riswan, Refisch, & Nellemann, 2011) has reduced the Tapanuli orangutan to 800 individuals confined to three forest fragments. Notably, 15% of these forests remain eligible for agricultural conversion (Wich et al, 2019), including one fifth of the large East Block fragment. Small-scale agriculture occurs within protected forests along the fringes of all three fragments as well as within the interior of the East Block to a limited degree (Sloan, Supriatna, et al, 2018).…”

Section: Habitat Loss In the Batang Toru Regionmentioning

confidence: 99%

“…Although opportunities for orangutan habitat reintegration exist , they are largely incompatible with this project. Infrastructure development and flooding would isolate 25% of the species into nonviable communities and destroy prime habitat of the sole viable community in the West Block fragment (Wich et al, 2019).…”

Section: Habitat Loss In the Batang Toru Regionmentioning

confidence: 99%

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Development Corridors and Remnant-Forest Conservation in Sumatra, Indonesia

Sloan

Alamgir

Campbell

et al. 2019

Tropical Conservation Science

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Road-infrastructure development in Southeast Asia is opening new resource frontiers but also consolidating earlier investments in agriculture and trade, as illustrated by the 2,700-km Trans-Sumatra Highway planned for Sumatra, Indonesia. In contrast to earlier broadscale forest losses in Sumatra, driven historically in Sumatra infrastructure and agricultural expansion, the Trans-Sumatra Highway would largely affect remnant forests. We identify Kerinci Seblat National Park and its surrounds, the Leuser Ecosystem, and the Batang Toru area as three remnant-forest areas critical to Sumatra's ecological integrity and facing conservation challenges that would be significantly aggravated by the Trans-Sumatra Highway. If completed as planned, the highway will promote human incursions into the fringes of these areas. New Indonesian regulations concerning road developments in forests are unlikely to prevent such outcomes. The regulations afford weaker protections to ungazetted and noncore protected forests, which typify remnant-forest areas threatened by infrastructure expansion and are often critical for species conservation. We urge that ungazetted protected forests be given equal priority to gazetted protected forests in regard to conservation planning for road development, and also that gazetted forests be expanded in the Leuser Ecosystem and Batang Toru area to hedge against further incursions. Without such provisions, recent legal challenges to road developments in Sumatra's remnant forests have often been unsuccessful. The Trans-Sumatra Highway may conceivably promote an effective legal alliance between conservationists and agricultural communities threatened with land expropriation, given that nearly half of the highway's route remains pending contentious land-acquisition processes.

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“…The species is currently under threat of habitat loss from agriculture, hunting and conflict killing, and development in the area for infrastructure, gold mining, and geothermal and hydro-energy. These threaten to further reduce and fragment remaining habitat, reduce dispersal opportunities for the orangutans between subpopulations, and undermine population viability through unsustainable mortality rates [14,[18][19][20][21]. Due to its restricted current distribution mostly centred around higher elevations (834.4±219.3m asl) compared to 701.7±454.8 m asl for the Sumatran orangutan (P. abelii) and 170.6±187.0 m asl for the Bornean orangutan (P. pygmaeus) [22], it has been argued that the individuals of the species have adapted specifically to the uplands that cover most of its current distribution in Batang Toru [18].…”

Section: Introductionmentioning

confidence: 99%

The historical range and drivers of decline of the Tapanuli orangutan

Meijaard

Ni’matullah

Dennis

et al. 2020

Preprint

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The Tapanuli orangutan ( Pongo tapanuliensis ) is the most threatened great ape species in the world. It is restricted to an area of about 1,000 km 2 of mostly hill forest where fewer than 800 animals survive in three declining subpopulations. Through a historical ecology approach involving analysis of colonial-era and other literature, we demonstrate that historically the Tapanuli orangutan lived in a much larger area, and across a much wider range of habitat types compared to now. Its current range is about 10-20% of the range it had some 150-200 years ago. A combination of historic fragmentation of forest habitats, mostly for small-scale agriculture, and unsustainable hunting likely drove various populations to the south, east and west of the current population to extinction prior to the industrial-scale forest conversion that started in the 1970s. Our findings indicate how sensitive orangutans are to the combined effects of habitat fragmentation and unsustainable mortality or rescue and translocation rates. Saving this species will require prevention of any further fragmentation and any killings or other removal of animals from the remaining population. Without concerted action to achieve this, the remaining populations of Tapanuli orangutan are doomed to become extinct within the foreseeable future.

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

Cited by 23 publications

References 12 publications

Grouping behavior of Sumatran orangutans (Pongo abelii) and Tapanuli orangutans (Pongo tapanuliensis) living in forest with low fruit abundance

Grouping behavior of Sumatran orangutans (Pongo abelii) and Tapanuli orangutans (Pongo tapanuliensis) living in forest with low fruit abundance

Development Corridors and Remnant-Forest Conservation in Sumatra, Indonesia

The historical range and drivers of decline of the Tapanuli orangutan

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