header: Orang-utan
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line Pongo pygmaeus (Hoppius, 1763)


INTRODUCTION

Two subspecies have been described: the Sumatran Orang-utan, Pongo pygmaeus abelii and the Bornean Orang-utan, Pongo pygmaeus pygmaeus.

Weighing up to 90 kg, the orang-utan is the largest tree-living mammal and the only great ape in Asia. The species is primarily arboreal, and inhabits tropical moist forests, from swamp and lowland (Dipterocarp) forests at sea level to hill and montane fo rests up to 1,800 m. The orang-utan rarely descends to the ground, and moves by climbing and walking through large trees, and swinging from branch to branch with its long arms. The arms can attain a spread of 2.25 m, and reach the ankles when the animal i s erect.10 The orang-utan is mainly frugivorous, the preferred foods are Wild Figs (Ficus spp.) and Durians (Durio spp.), although a wide range of plant and insect foods are also taken.10,15 A solitary animal, the orang-utan generally constructs a fresh nest each night although this may be re-used on occasion. Maturity is reached at 7-10 years of age, and the potential lifespan of the species in the wild may be up to 40 years. 15 Observations of orang-utans in the wild suggest that individuals usually occur in very small groups or alone.10

The orang-utan is a highly K-selected species: ie. survival is high, interbirth interval is long (mean = 8 years), and the female makes a high investment in her young. The gestation period for the orang-utan is 233-265 days, with a single young or occasio nally twins.10 Weaning of the young is completed after about 3.5 years.10 Adult females are the most valuable members of an orang-utan population and the death of an adult female has the greate st influence on increasing extinction rates.16


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