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BONOBO
CHIMPANZEE
SUMATRAN ORANGUTAN
BORNEAN ORANGUTAN
2010; Kormos
et al.
2003; Morgan
et al.
2011). Habitat destruc-
tion and fragmentation, poaching, respiratory diseases, and
other diseases such as the Ebola virus and anthrax are among
the primary threats that chimpanzees face.
Orangutan
The orangutan is the only great ape found in Asia, and histori-
cally is thought to have once ranged across Indochina. Today,
two distinct species are found on the islands of Borneo and
Sumatra, respectively. The Bornean orangutan is divided into
three further sub-species.
Sumatran orangutan
The Sumatran orangutan (
Pongo abelli
) has been listed as
Critically Endangered since 2000 and its population has de-
creased by 80 per cent over the last 75 years (Wich
et al.
2011).
This species is native to the Indonesian island of Sumatra and
today mainly inhabits the northern end of the island as a re-
sult of habitat loss and human encroachment. An estimated
6,600 wild individuals are left, based on nest density surveys
and models applied to satellite images of forest distribution
(Wich
et al.
2008; Mittermeier
et al.
2009), although exten-
sive forest clearance and fires in Tripa in 2012 are likely to
have reduced the overall number.
Bornean orangutan
The Bornean orangutan (
Pongo pygmaeus
) is found on the
island of Borneo, in areas governed by Indonesia and Ma-
laysia. The species is divided into three sub-species: the
Southern Bornean orangutan (
Pongo pygmaeus wurmbii
); the
Northeastern Bornean orangutan (
Pongo pygmaeus morio
);
and the Western Bornean orangutan (
Pongo pygmaeus pyg-
maeus
). The species has been classified as Endangered on
the IUCN Red List since 1986 – with an exception in 1996,
when it was briefly listed as Vulnerable. As with its Suma-
tran relative, the population of Bornean orangutans has de-
clined by 50 per cent over the last 60 years, and an estimated
1,950 to 3,100 individuals have been killed annually over
the last few decades in Indonesian Borneo, which is higher
than the rate at which the species can reproduce (Meijaard
et al.
2011). The Bornean orangutan is endemic to Borneo,
where it inhabits patchy areas in the central, north eastern
and north western part of the island. The latest population
estimates indicate a total population of 54,000 remaining in
Borneo (Wich
et al.
2008).