2008-2010” (Mittermeier et al. 2009). With current trends in forest loss, the Sumatran orangutan may well be the first great ape to go extinct in the wild (Wich et al. 2008).

Te Bornean orangutan (Pongo pygmaeus), with a distinctly larg- er, but likewise rapidly declining population of 54,000 (Wich et al. 2008), is classified as Endangered (IUCN 2010). Both oran- gutan species are also listed on Appendix I of the Convention on International Trade in Endangered Species (CITES), prohibit- ing any international trade in wild-caught individuals.

Critical role in the forest ecosystem Orangutans feed predominantly on fruits, including some that contain large seeds that few other species can cope with, and ultimately disperse the seeds over a huge area. If large fruit- eating primates are removed from a tropical forest (e.g. by hunting), those tree species with the largest seeds are either dispersed over much shorter distances, are dispersed less often, or cease to be dispersed at all. In addition, orangutans also play an active role in seed germination for certain species (Ancre- naz et al. 2006). Teir removal can therefore lead to a reduction of the carbon stock in a forest, since large-seeded tree species also tend to have much denser wood, containing more carbon (Wright et al. 2007; Queenborough et al. 2009).

Sumatran orangutan distribution Te total area of natural Sumatran orangutan habitat remain- ing today is approximately 8,641 km2

, less than 0.5% of Indo- nesia’s total land area. Tis figure also represents only 17% of

A Bornean unflanged adult male close to the ground (Madeleine Hardus)

all the remaining forest in Aceh and North Sumatra provinces (51,100 km2

), indicating that many forest areas in both provinc- es have either already lost their orangutan populations, or never

An adolescent orangutan resting on a newly built nest (Adriano Lameira)

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