The Vietnamese orangutan (''Pongo hooijeri'') is an extinct species of

orangutan Orangutans are great apes native to the rainforests of Indonesia and Malaysia. They are now found only in parts of Borneo and Sumatra, but during the Pleistocene they ranged throughout Southeast Asia and South China. Classified in the genus ...

from the

Pleistocene The Pleistocene ( , often referred to as the ''Ice age'') is the geological Epoch (geology), epoch that lasted from about 2,580,000 to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fina ...

Vietnam Vietnam or Viet Nam ( vi, Việt Nam, ), officially the Socialist Republic of Vietnam,., group="n" is a country in Southeast Asia, at the eastern edge of mainland Southeast Asia, with an area of and population of 96 million, making i ...

. It was named in honor of paleontologist

Dirk Albert Hooijer Dirk Albert Hooijer (30 May 1919 – 26 November 1993) was a Dutch paleontologist. Hooijer was born in Medan on Sumatra, but spent his youth in Bogor on Java. In 1932, his family moved to The Hague where he finished his high school education at ...

. Fossils of the ape were found in the Tham Hai Cave. It is unclear whether ''Pongo hooijeri'' is truly a distinct species or merely a Vietnamese population of one of the extant orangutan species.

Paleoecology

The Vietnamese orangutan likely resembled modern orangutans found on the island of Sumatra in appearance, habitat preference and behavior with a possible physical resemblance to the

Tapanuli orangutan The Tapanuli orangutan (''Pongo tapanuliensis'') is a species of orangutan restricted to South Tapanuli in the island of Sumatra in Indonesia. It is one of three known species of orangutan, alongside the Sumatran orangutan (''P. abelii''), found ...

s of northern Sumatra. Orangutans favor lowland

dipterocarp Dipterocarpaceae is a family of 16 genera and about 695 known species of mainly tropical lowland rainforest trees. The family name, from the type genus ''Dipterocarpus'', is derived from Greek (''di'' = two, ''pteron'' = wing and ''karpos'' = fru ...

forests and old

secondary forest A secondary forest (or second-growth forest) is a forest or woodland area which has re-grown after a timber harvest or clearing for agriculture, until a long enough period has passed so that the effects of the disturbance are no longer evident. ...

s with population densities at their greatest near sources of fresh water. Despite being adapted to an arboreal existence, modern orangutans show tolerance of grasslands and forest clearings to a small degree. This habitat tolerance likely bore resemblance to mainland orangutans during the

. It is important to note the climate conditions of the Pleistocene are characterized by cooler, drier conditions that would have likely reduced the area of dense forest available to the Vietnamese orangutan and other rainforest inhabitants. The mainland orangutan appears to have been sympatric to numerous species that are found in Southeast Asia today or were present in the region during the

Holocene The Holocene ( ) is the current geological epoch. It began approximately 11,650 cal years Before Present (), after the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene togethe ...

epoch as conditions within the region are similar to today and therefore would have supported a similar biologically rich ecosystem that existed in the region in the pre-industrial and pre-colonial era. Orangutans of mainland Southeast Asia may have shared their forests with the now extinct

giant tapir The giant tapir (''Tapirus augustus'') is an extinct species of tapir that lived in southern China, Vietnam and Laos, with reports suggesting it also lived in Taiwan, Java, and potentially Borneo. The species has been recorded from Middle and La ...

along with northern hairy rhinoceros,

Javan rhinoceros The Javan rhinoceros (''Rhinoceros sondaicus''), also known as the Javan rhino, Sunda rhinoceros or lesser one-horned rhinoceros, is a very rare member of the family Rhinocerotidae and one of five extant rhinoceroses. It belongs to the same ge ...

gaur The gaur (''Bos gaurus''; ), also known as the Indian bison, is a bovine native to South Asia and Southeast Asia, and has been listed as Vulnerable on the IUCN Red List since 1986. The global population was estimated at a maximum of 21,000 m ...

Asian elephant The Asian elephant (''Elephas maximus''), also known as the Asiatic elephant, is the only living species of the genus ''Elephas'' and is distributed throughout the Indian subcontinent and Southeast Asia, from India in the west, Nepal in the no ...

along with representatives of ''

Cervus ''Cervus'' is a genus of deer that primarily are native to Eurasia, although one species occurs in northern Africa and another in North America. In addition to the species presently placed in this genus, it has included a whole range of other sp ...

'' and '' Sus''. Orangutans of Vietnam and other regions of mainland Asia would have likely lived alongside a vast array of primates including various ancestral

langur The Colobinae or leaf-eating monkeys are a subfamily of the Old World monkey family that includes 61 species in 11 genera, including the black-and-white colobus, the large-nosed proboscis monkey, and the gray langurs. Some classifications spli ...

s, ''

Rhinopithecus __NOTOC__ Snub-nosed monkeys are a group of Old World monkeys and make up the entirety of the genus ''Rhinopithecus''. The genus is rare and not fully researched. Some taxonomists group snub-nosed monkeys together with the genus '' Pygathrix''. ...

'' and

lesser ape Gibbons () are apes in the family Hylobatidae (). The family historically contained one genus, but now is split into four extant genera and 20 species. Gibbons live in subtropical and tropical rainforest from eastern Bangladesh to Northeast India ...

s. Although it is unknown whether orangutans within the region preyed upon

prosimian Prosimians are a group of primates that includes all living and extinct Strepsirrhini, strepsirrhines (lemurs, Lorisoidea, lorisoids, and Adapiformes, adapiforms), as well as the Haplorhini, haplorhine tarsiers and their extinct relatives, the O ...

loris Loris is the common name for the strepsirrhine mammals of the subfamily Lorinae (sometimes spelled Lorisinae) in the family Lorisidae. ''Loris'' is one genus in this subfamily and includes the slender lorises, ''Nycticebus'' is the genus contain ...

es have been present in the fossil records of South East Asia since the Miocene and would have likely encountered the great apes. Orangutans are invulnerable to most arboreal predators due to their large size and strength. However, if Vietnamese orangutans traveled across the forest floor similar to modern Bornean orangutans, they would have become possible prey for the ancestors of

Indochinese leopard The Indochinese leopard (''Panthera pardus delacouri'') is a leopard subspecies native to mainland Southeast Asia and southern China. In Indochina, leopards are rare outside protected areas and threatened by habitat loss due to deforestation as w ...

tiger The tiger (''Panthera tigris'') is the largest living cat species and a member of the genus '' Panthera''. It is most recognisable for its dark vertical stripes on orange fur with a white underside. An apex predator, it primarily preys on u ...

s and packs of

dhole The dhole (''Cuon alpinus''; ) is a canid native to Central, South, East and Southeast Asia. Other English names for the species include Asian wild dog, Asiatic wild dog, Indian wild dog, whistling dog, red dog, red wolf, and mountain wolf. It ...

s. Both the

sun bear The sun bear (''Helarctos malayanus'') is a species in the family Ursidae (the only species in the genus ''Helarctos'') occurring in the tropical forests of Southeast Asia. It is the smallest bear, standing nearly at the shoulder and weighing ...

and

Asiatic black bear The Asian black bear (''Ursus thibetanus''), also known as the Asiatic black bear, moon bear and white-chested bear, is a medium-sized bear species native to Asia that is largely adapted to an arboreal lifestyle. It lives in the Himalayas, sou ...

may have been potential threats to young, infirm or weakened individuals. Orangutans near large, continuous bodies of water would be vulnerable to saltwater and

Siamese crocodile The Siamese crocodile (''Crocodylus siamensis'') is a medium-sized freshwater crocodile native to Indonesia (Borneo and possibly Java), Brunei, East Malaysia, Laos, Cambodia, Myanmar, Thailand and Vietnam. The species is critically endangered an ...

s as well as

reticulated python The reticulated python (''Malayopython reticulatus'') is a python species native to South and Southeast Asia. It is the world's longest snake, and is among the three heaviest. It is listed as least concern on the IUCN Red List because of its w ...

s. Fossil and

subfossil A fossil (from Classical Latin , ) is any preserved remains, impression, or trace of any once-living thing from a past geological age. Examples include bones, shells, exoskeletons, stone imprints of animals or microbes, objects preserved in ...

evidence from human "trash piles" suggests orangutans were targeted by human hunter-gatherers as well. Adult Female and Infant Vietnamese Orangutan

Adult Female and Infant Vietnamese Orangutan

References

Pleistocene primates Prehistoric apes Fossil taxa described in 1995 Prehistoric Vietnam Pleistocene mammals of Asia {{Paleo-primate-stub