Mammals

From the large armour-plated rhino to the small tree-climbing slow loris, the Heart of Borneo offers shelter to world famous mammals and newly discovered ones.

The orang-utan is probably the most well recognised mammal in Borneo.

The largest tree-climbing mammal and the only great ape found in Asia, it is estimated that about one third of its population was lost during the 1997/98 forest fires. The Sarawak orang-utan population is virtually confined to one protected area. The species is mainly threatened by habitat conversion and hunting .
Find out more about the orang-utan

Apart from the orang-utan, some 12 other primate species are known from Borneo, including two species of gibbons, five species of leaf monkeys, and two species of macaques, as well as the nocturnal and thus rarely encountered slow loris and western tarsier. The tarsier is active only at night and has huge goggle eyes, grasping hands and a long straw-like tail.

A rhino confined in a corner of the Heart of Borneo
In the northeast corner of the Heart of Borneo lives the eastern Sumatran rhinoceros, 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 240-400 individuals in fragmented populations on the Malay Peninsula, Sumatra and Borneo. Whereas the Bornean subspecies was formerly widespread across the island, only a population of about 50 individuals remains, confined to eastern and central Sabah.
Find out more about the Sumatran rhinoceros

The Heart of Borneo is also home to the Bornean pygmy elephant. 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.

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 two decades.
Find out more about the elephant

Small mammals: hiding in the shadows
Whereas the number and variety of non-mammal species � such as reptiles and fish - discovered in recent years is high, small Bornean mammals remain severely understudied. Bats are the most common mammals (about 90 species), the flying fox being the largest one .

They normally make up about 40-50% of any tropical mammal community, and have important roles in forest ecology and as pollinators and seed dispersers. They have also been recognised as important forest health indicators.

The dense cover of high forests throughout the island of Borneo has led to the evolution of many squirrel species, from the tiny pygmy squirrel - no larger than your average mouse - to the giant squirrel - larger than your average house cat - which can sometimes be observed hopping from branch to branch.

Even more unusual are the flying squirrels, of which no less than 12 species are known from 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.

Trapped!
Other mammals that occur in high numbers and which play a major role in the rainforest ecosystem are the smaller carnivores of Borneo. Because these animals are very hard to observe, the best way to get a closer look at them is to take their picture when they least expect it - by using "camera traps" set up in the forest at strategic points, which are only triggered when animals pass by.

During a long-term camera trapping programme in Kayan Mentarang National Park for instance, WWF collected a family portrait of all the cat species found in Borneo (including the extremely rare bay cat) as well as most of the civets and mongooses.