Size, Weight and Habitat

A female orang-utan weighs 30 - 50 kg (66 - 110 lb) and grows to about 1.1 m (3.5') in height. A male weighs 50 - 90 kg (110 - 200 lb) and stands 1.2 - 1.5 m (4 - 5') tall. The orang-utan is found in tropical, swamp and mountain forests.

In Sumatra, orang-utans are largely lowland animals, being rare above 1000 m (3300') and virtually absent above 1500 m (4900'). The availability of fruit containing soft pulp (rather than dry or fibrous fruits) appears to be a major factor in their abundance patterns. Altitudinal limits are even lower in Borneo where the mountain ranges also tend to be lower and thus vegetation zones are more altitudinally compressed. (van Schaik et al. 2001)

The orang-utan is one of the species that live in the Sundaland Biodiversity Hotspot (Cons. Intl. 2005) as well as the Northern Borneo-Palawan Moist Forests, Mt. Kinabalu Montane & Alpine Scrub & Forest, Sumatran-Nicobar Islands Lowland Forests, and Central Borneo Montane Forests Global 200 Ecoregions.

Behavior

The orang-utan is arboreal and diurnal, with peaks of activity in the morning and late afternoon. It exhibits a sophisticated use of tools for gathering fruit and insects for food. An orang-utan utilizes twigs and branches to construct a large nest-platform in a tree that it sleeps in at night. It usually makes a new nest each night but sometimes reuses one.

Why is the Orangutan in Danger?

Orangutans are an endangered species according to most wildlife monitoring organizations and conservation groups. Ten thousand years ago, orangutans were found throughout Southeast Asia ranging all the way into southern China. Their populations probably numbered in the hundreds of thousands.

Unfortunately, the species today is found only in limited populations on the islands of Borneo and Sumatra. Due to the destructive activities of humans, the wild population may have diminished in the past decade by as much as 50%. Estimates of the current population are from less than 50,000 to 60,000 with more than three quarters of all orangutans found on Borneo.

The destruction and degradation of the tropical rain forest, particularly the lowland forests, is the main reason orangutans are threatened. This has been caused primarily by human activity (intense permitted logging, illegal logging, conversion to palm oil plantations and farm lands, mining, settlements, road construction) and also by natural phenomena (large-scale fires). Additionally, the illegal animal trade has been a significant factor in the decline the wild orangutan population. Finally, orangutans are occasionally hunted and eaten by some of the indigenous peoples of Borneo as well as immigrant loggers who do not have a dietary prohibition to eating primate bushmeat.