Primate of the Week: Orangutans

Pongo

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  • Taxonomy
  • Suborder: Haplorrhini
  • Infraorder: Simiiformes
  • Superfamily: Hominoidea
  • Family: Homindae
  • Genus: Pongo
  • Species: Pongo abelii and Pongo pygmaeus
  • Subspecies: P.p morio, P.p. pygmaeusP. p. wurmbii
ARKive image GES114529 - Sumatran orangutan

Photo from ARKive of the Sumatran orangutan (Pongo abelii) – http://www.arkive.org/sumatran-orangutan/pongo-abelii/image-G114529.html

Orangutans are apes within the genus of Pongo and can be split into two separate species Sumatran orangutans (P. abelii) and Bornean orangutans (P. pygmaeus). The two species diverged 1.5 million years ago and have developed phenotypically different characteristics. Sumatran orangutans are thinner with longer hair and faces. Sumatrans orangutans are also paler and males have mustaches and cheek pads that are covered with white hairs. Bornean orangutans have coarse and long hair that will be either orange, brown or maroon. Bornean orangutan males will also have larger pendulous throat pouches and larger cheek pads compared to Sumatran orangutans. Adult males in both species have prominent cheek pads or flanges. Infants in both species are born with pink faces but as they age will turn dark brown to black (Courtenay et al., 1988). Orangutans are sexually dimorphic with males weighing more than females (Markham & Groves, 1990; Rowe, 1996).

ARKive image GES140614 - Sumatran orangutan

Photo from ARKive of the Sumatran orangutan (Pongo abelii) – http://www.arkive.org/sumatran-orangutan/pongo-abelii/image-G140614.html

Orangutans will climb using both hands and feet and will move horizontally through the rain forest canopy (Rodman, 1993). They are able to do this because of the position of their big toes and thumbs allowing them to move hand over hand while grasping branches with their feet. Their toes and fingers are also hooked to help them with their arboreal lifestyle (Galdikas and Briggs, 1999). When orangutans are terrestrial they will move quadrupedally on their fists and will sometimes move bipedally (Rowe, 1996).

ARKive image GES004008 - Sumatran orangutan

Photo from ARKive of the Sumatran orangutan (Pongo abelii) – http://www.arkive.org/sumatran-orangutan/pongo-abelii/image-G4008.html

Bornean orangutans are only found on the island of Borneo and Sumatran orangutans are only found in the island of Sumatra (Kaplan and Rogers, 1994).

IMG_1050.PNG

Both species are found in high densities areas with mosaic habitat qualities that have high quantities of food throughout the year. They are often found in lowland swamp forests with high tree diversity (Rodman, 1988; Kaplan and Rogers, 1994; Russon et al., 2001). Orangutans are mainly frugivores but have been observed eating buds, flowers, young leaves, bark, sap, vines, orchids, reed roots, bird eggs, spider webs, termites, caterpillars, ants, fungi, honey and other plant parts. Most of the orangutan daily activity is spent feeding and foraging.

ARKive image GES113577 - Sumatran orangutan

Photo from ARKive of the Sumatran orangutan (Pongo abelii) – http://www.arkive.org/sumatran-orangutan/pongo-abelii/image-G113577.html

Orangutans are semi solitary (Galdikas, 1984). Adult males and independent adolescents of both sexes are solitary and range alone while females will range with their dependent and weaned offspring (Boekhorst et al., 1990). Subadult males and females will often form small temporary groups that do not extend to adulthood. Males have large home ranges in which many females overlap in smaller home ranges. The females are often related within closely situated home ranges (Boekhorst et al., 1990; Rodman, 1993; Singleton and van Schaik, 2002). When females encounter each other they will either have an aggressive encounter or both will mutually avoid each other (Rijksen, 1978; Galdikas, 1984). When males meet each other they are often aggressive displays (Utami et al., 2002). Orangutans will also sometimes form a breeding pair of adult females and her offspring and a male (Utami et al., 2002).

ARKive image GES113551 - Sumatran orangutan

Photo from ARKive of the Sumatran orangutan (Pongo abelii) – http://www.arkive.org/sumatran-orangutan/pongo-abelii/image-G113551.html

Orangutans exhibit female philopatry, females will choose home ranges close to their mothers’. Galdikas, 1984; van Schaik and van Hooff, 1996; Singleton and van Schaik, 2002). Males will disperse a long distance and will often be nomadic until they establish a home range via displacing a dominant male (Delgado and van Schaik, 2000). Adult males have a very developed and maintained dominance hierarchy. The most dominant male will be larger and flanged (van Schaik et al., 2004).

ARKive image GES117012 - Sumatran orangutan

Photo from ARKive of the Sumatran orangutan (Pongo abelii) – http://www.arkive.org/sumatran-orangutan/pongo-abelii/image-G117012.html

Male orangutans have bimaturism. Bimaturism refers to a type of arrested development. They will develop long calls and flanges later at 15 to 20 years. Males prior than this can still reproduce but look morphologically like females. Males will begin developing these secondary characteristics (such as flanged cheeks or a throat pouch) when a dominant or flanged male is absent from a territory Rijksen, 1978; Schürmann and van Hoof, 1986).

ARKive image GES113447 - Bornean orangutan

Photo from ARKive of the Bornean orangutan (Pongo pygmaeus) – http://www.arkive.org/bornean-orangutan/pongo-pygmaeus/image-G113447.html

Unflanged transient males will often use forced copulation when they find a female in estrus while flanged dominant males will produce long calls and wait. Females will often preferentially mate with flanged males for protection against unflanged males (Fox, 2002; Utami et al., 2002; Setchell, 2003).

ARKive image GES113885 - Bornean orangutan

Photo from ARKive of the Bornean orangutan (Pongo pygmaeus) – http://www.arkive.org/bornean-orangutan/pongo-pygmaeus/image-G113885.html

Females are the primary caregivers and will care for their offspring until approx. eight years of age. However, the offspring will often begin seeking independence at 5 years of age and will begin traveling with a group of peers. The long childhood of orangutans is necessary to learn such things as the right food to eat or building a nest (Rijksen, 1978; Munn and Fernandez, 1997).

ARKive image GES114681 - Bornean orangutan

Photo from ARKive of the Bornean orangutan (Pongo pygmaeus) – http://www.arkive.org/bornean-orangutan/pongo-pygmaeus/image-G114681.html

References/Read more

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