But the animals Borneo is famous for are the orangutan, pygmy elephant and rhinoceros.
Asia’s only great apeThe Borneo orangutan is the largest tree-climbing mammal and the only great ape found in Asia. It is estimated that about 1/3rd of its population was lost during the 1997/98 forest fires that swept across Indonesia, including Kalimantan (Indonesian Borneo).
Now, the Sarawak (Malaysia) orangutan population is virtually confined to 1 protected area. The species is mainly threatened by habitat conversion and hunting.
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The orangutans share Borneo's forests with 12 other primate species, including 2 gibbon species, 5 langurs, 2 macaques, the tarsier (Tarsius bancanus), the slow loris (Nycticebus coucang), and the endangered proboscis monkey (Nasalis larvatus). Most of these species have overlapping ranges, but they vary with respect to dietary content and foraging strategy.
More than 3 species discovered every month during the past 15 years
Restricted rhinos and elephantsIn the northeast corner of the Heart of Borneo lives the eastern Sumatran rhinoceros (Dicerorhinus sumatrensis harrissoni), which has the distinction of the being the most critically endangered of all rhino species in the world.
This rhino is a subspecies of the Sumatran rhinoceros, represented by at least 13 individuals in fragmented populations on the Malay Peninsula, Sumatra and Borneo. Whereas the Borneo subspecies was formerly widespread across the island, only a population of about 50 individuals remains, confined to eastern and central Sabah (Malaysia).
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The Heart of Borneo is also home to the Borneo pygmy elephant (Elephas maximus borneensis). The population is restricted to the northeast corner of Borneo, in an area extending from eastern and central Sabah into the Sebuku-Sembakung region of east Kalimantan (Indonesia).
The total population was estimated between 500 and 2,000 individuals in the early 1980s, but this number is expected to have decreased significantly over the past 2 decades.
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Small mammals, hiding in the shadowsWhereas the number and variety of non-mammal species - such as reptiles and fish - discovered in recent years is high, small Borneo mammals remain severely understudied.
The dense cover of high forests throughout the island of Borneo has led to the evolution of many squirrels, from the tiny pygmy squirrel (Exilisciurus species)—no larger than your average mouse—to the giant squirrel (Ratufa affinis)—larger than your average house cat—which can sometimes be observed hopping from branch to branch.
Even more unusual are the flying squirrels (Pteromyinae sub family), of which there are 12 known species in Borneo. These animals have developed membranes between their fore and hind legs, allowing them to launch themselves off high trees and glide through the air with outstretched limbs.
Borneo’s elusive carnivoresBorneo lacks some of the larger predators found on the Asian mainland, such as the tiger (Pantera tigris) and the leopard (P. pardus).
This has allowed several small-medium carnivores to dominate lowland forests, including the endangered clouded leopard (Neofelis nebulosa), sun bear (Helarctos malayanus), Sunda otter-civet (Cynogale bennettii), and other mustelids.
Other Borneo mammals that occur in high numbers and which play a major role in the rainforest ecosystem are the smaller carnivores (meat-eating species) of the island.