Abstract

The chapter examines differences in the activity budgets of wild orangutans (Pongo spp.) within and between a large number of study sites in Sumatra and Borneo. The authors of the chapter found that each orangutan population appeared to follow one of two distinct foraging strategies: either (1) ‘sit and wait’, in which orangutans aim to minimize their energy expenditure by spending long periods of time resting and relatively short periods feeding and travelling; or (2) ‘search and find’ in which orangutans aim to maximize their energy intake by resting little and mainly feeding or moving in search of food. Orangutans adopt the first strategy in mixed-dipterocarp forests characterized by mast-fruiting events and irregular fruit availability; and adopt the second strategy in swamp forests with a regular supply of fruit, or in dryland forests with high strangling-fig density. The chapter proposes that the determining factor for which strategy is adopted is the temporal availability of fruit in the habitat, as opposed to other possibilities such as orangutan taxonomy.