ABOVE: North Borneo Gibbons Hylobates funereus feeding on ripe F. sundaica figs at the Danum Valley Field Center in Sabah. In most parts of Borneo gibbons rely on figs to provide their staple diet. Other types of preferred fruit are only seasonally or intermittently available whilst there is almost always at least one fig fruiting at any one time in a gibbon family territory. Thus the density of figs in most areas of lowland forest determines the density of the gibbon population. The exception to this rule is in areas of peat swamp forest in Kalimantan (e.g Sabangau) where the fig density is low and the majority of trees fruit throughout the year.
