In this paper the author places the rock art of Uganda in context. It probably belongs to the Late Stone Age period to the Holocene and its symbolism may be interpreted in the light of later belief systems recorded amongst the historical Pygmy people. Pongo is the bark cloth used to make the distinctive loin cloths of men and aprons of women. Pongo are probably depicted in the rock art to evoke the fecundity of ndura, linking the real and supernatural within the Pygmy cosmos.

Orang-utans (Pongo spp.) are primarily frugivorous (Morrogh-Bernard et al. 2009) and are often regarded as important seed dispersers (Corlett 1998). In Tanjung Puting, Borneo, Galdikas (1982) found intact seeds in 94% of faecal samples, with a median 111 seeds per defecation; and in Ketambe, Sumatra, Rijksen (1978) found seeds in 44% of faecal samples. Furthermore, orang-utans have large day ranges (e.g. mean = 968 m, range = 280–2834 m across adults in Sabangau; Harrison 2009) and slow passage rates of digesta through the gut (Caton et al. 1999), and, hence, may disperse seeds far from parent trees. Many seeds are also spat out or discarded at distances up to 75 m from parent trees (Galdikas 1982).

Nest surveys are widely employed to assess the population density of orang-utans (Pongo spp.) and evaluate alternative management scenarios relevant to the protection of these threatened great apes. However, this method is less accurate and prone to much greater error than is generally acknowledged. Here we highlight the limitations of orang-utan nest surveys, discuss the risks of ignoring these limitations, and note conditions under which standard nest survey methods are appropriate.

In recognition of the fact that orang-utans (Pongo spp.) are severely threatened, a meeting of orang-utan experts and conservationists, representatives of national and regional governmental and non-governmental organizations, and other stakeholders, was convened in Jakarta, Indonesia, in January 2004. Prior to this meeting we surveyed all large areas for which orang-utan population status was unknown. Compilation of all survey data produced a comprehensive picture of orang-utan distribution on both Borneo and Sumatra. These results indicate that in 2004 there were c. 6,500 P. abelii remaining on Sumatra and at least 54,000 P. pygmaeus on Borneo. Extrapolating to 2008 on the basis of forest loss on both islands suggests the estimate for Borneo could be 10% too high but that for Sumatra is probably still relatively accurate because forest loss in orang-utan habitat has been low during the conflict in Aceh, where most P. abelii occur. When those population sizes are compared to known historical sizes it is clear that the Sumatran orang-utan is in rapid decline, and unless extraordinary efforts are made soon, it could become the first great ape species to go extinct. In contrast, our results indicate there are more and larger populations of Bornean orang-utans than previously known. Although these revised estimates for Borneo are encouraging, forest loss and associated loss of orang-utans are occurring at an alarming rate, and suggest that recent reductions of Bornean orang-utan populations have been far more severe than previously supposed. Nevertheless, although orang-utans on both islands are under threat, we highlight some reasons for cautious optimism for their long-term conservation.