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.