Sweeney: Habitat

Geographic Range: Gibbons are distributed throughout the rainforests of Southeast Asia, Northwest India and Bangladesh (Reichard 1998). The ranges of 11 of the 12 gibbon species are almost always separated by rivers or straits, so little species overlap occurs (Geissmann 2001). The exception is the largest of the gibbon species, the siamang (Fisher & Geissmann 1990), Found in Sumatra and the Malaysian peninsual (AZA 1995) , the distribution of siamangs greatly overlaps with those of smaller gibbon species, particularly the white-handed and agile gibbon species (Fisher & Geissmann 1990, AZA 1995).

Habitat: Gibbons are almost exclusively arboreal, and live primarily in the middle and upper canopies of dense forests (Whitten 1982, Wilson 1975). Key resources in gibbon habitats are food and sleeping trees. Gibbons are mainly frugivorous, selectively feeding on a wide range of fruit (Whitten 1982), though they may eat shoots, stems, some flowers, and some invertebrates (Gittins 1982); the diets of specific gibbon species vary somewhat, with black-crested gibbons particularly eating a high proportion of leaves relative to other gibbon species (Jiang & Wang 1999). Gibbons are picky in their food choice, however, and this restrictive diet may require them to live at a lower density than most other primates (Gittins 1982).

Food resources-mainly fruit trees-- are either distributed in large, rich sources, which are available only seasonally, and at which an entire group can feed upon at once, or in smaller, more reliable sources, which will feed only one individual at a time. Both kinds of food sources tend to be found in each gibbon territory, but the existence of the latter means that gibbons have always have predictable, though small and inconspicuous, food resources available (Gittins 1982). These food resources tend to be fairly evenly distributed across gibbon home ranges (Whitten 1982).

Sleeping and calling trees are other key resources of a gibbon territory. Gibbons sleep in tall trees each night, and then sing their dawn calls from the tops of those trees; they also sing and have territorial displays in the highest branches of tall "calling" trees which allow them to broadcast their songs for a long distance (Gittins 1982, Whitten 1982). There are a wide number of sleeping trees spread across the gibbon group's territory, and they rarely will spend the night in the same tree twice; one study group had at least 178 different sleeping trees (Reichard 1998). Sleeping trees and their wide distribution probably help gibbons in maintaining warmth (Gittins 1982), in parasite and/or predation-avoidance (Reichard 1998), and in territory-maintenance through dawn sound broadcasting and their locations throughout the range (Reichard 1998).