- Suborder: Haplorhini
- Infraorder: Simiiformes
- Superfamily: Hominoidea
- Family: Hominidae
- Genus: Pongo
- Pongo abelii
- Pongo pygmaeus
- p. morio
- p. pygmaeus
- p. wurmbii
Orangutans are great apes located within Southeast Asia. Orangutans are made up of two species; Sumatran orangutan (P. abelii) and Bornean orangutan (P. pygmaeus). They differed based upon phenotype. Sumatran orangutans have thinner hair and more orange fur while Bornean orangutans have paler red fur, longer hair and longer faces. Adult males in both species have prominent cheek pads (flanges). Bornean males have larger throat pouches and cheek pads compared to Sumatran orangutans (Courtenay et al., 1988; Rowe, 1996). Males and females are sexually dimorphic with males weight nearly twice the weight of females (192 lbs (87 kg) vs 81.6 Ibs (37kg)) (Markham and Groves, 1990).
Orangutans are morphologically built for traveling through trees. They have thumb and big toes that act like hooks that allow for movement through the canopy (Galdikas and Briggs, 1999). When orangutans are on the ground they move quadrepedally on their fists and will occasionally move bipedally (Rowe, 1996).
Orangutans mainly utilize tropical rain forests and secondary forests (Galdikas, 1988). Bornean orangutans live in fragmented forests with hilly or mountainous areas and lowland swampy areas (Kaplan and Rogers, 1994; Rijksen and Meijaard, 1999). Sumatran orangutans live in forests of wide plateaus, mountains and lowland swamps (Rijksen and Meijaard, 1999).
Orangutans are mainly frugivores but will also eat buds, flowers, leaves, bark, sap, vines, orchids, reed roots, bird eggs, spider webs, termites, caterpillar, ants, fungi, honey and other plants parts (Rijksen, 1978; Galdikas 1988).
Orangutans are solitary. Adult males and male and female adolescents range alone while adult females with dependent will range with their dependent and weaned offspring (te Boekhorst et al., 1990). Sometimes sub adults, transient males and females may travel within small groups but will not continue this into adulthood. Females with their dependent offspring will live in home ranges that overlap with other adult’s females. These other adults’ females are often their mothers and sisters their home ranges are located with a larger adult male home range that overlaps with several other females (te Boekhorst et al., 1990; Rodman, 1993; Singleton and van Schaik, 2002).
Male can be non-resident and resident. Resident males have the large home ranges that include several females and he is the primary breeder of the females located in their home ranges. Non-resident males and females range broadly without belonging to specific home ranges (Rijksen, 1978; te Boekhorst et al., 1990; Mitani et al., 1991; Rodman, 1993). Although they are solitary because of the overlapping territories orangutans will encounter each other and will sometime have social interactions (te Boekhorst et al., 1990; Mitani et al., 1991). Sometimes females and males will form consorship group in which the male and the female stay together for a few days to months after copulation. The group will also include female’s infant and juvenile offspring (Utami, et al., 2002).
Females are philopatric and will pick a home range that overlaps with their mothers (Galdikas, 1984; van Schaik and van Hoff, 1996). Males will disperse over long distances from home ranges of their mothers and will continuous move until settling in a home range through the displacement of dominant and resident males in a particular territory (Delgado and van Schaik, 2002). Males have dominance hierarchies, these more dominant males tend to be the largest and healthiest (van Schaik et al., 2004).
Although orangutans are solitary they will often gather a feed in large fruiting trees (van Schaik and van Hoff, 1996).
Female orangutans gestate for nine months and wild females will give birth between 14 and 15 (Kaplan and Rogers, 1994). Males have bimaturism. Sexual maturity occur from 8 to 15 for males however they will not show the flanging and size increase of social dominant male until 15 to 20 years (Rijksen, 1978). Although sub adult males or unflanged males do not have secondary sexual characteristics but are still capable to reproduce. As son as the social dominant male is removed they will begin to develop cheek pads, throat pouch long fur and other behaviors of a resident male (Rijksen, 1978).
Parental care is incredibly important for orangutans. Mothers are the primary caregivers and will often care for their offspring until 8 years of age (Rijksen, 1978; Munn and Fernandez, 1997).
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