Borneo is the third largest island in the world and is divided up between three countries – Brunei, Indonesia and Malaysia. A third of the island is covered by the world’s oldest rainforest, believed to be 130 million years old.
Conservative estimates say the island is home to well over 15,000 species of plants, at least 6000 of which exist nowhere else on Earth. Furthermore 1400 different species of amphibians, reptiles, mammals, fish and an undetermined amount of insect species live on the island. More than 600 new species were discovered on Borneo between 1995 and 2010 alone and the trend continues with on average three new species being discovered every month!
The Sunda clouded leopard is the largest feline on Borneo, adults weighing in at up to 25 kilograms. With its canine teeth growing to over 5 centimetres in length it has the longest canines of any feline in comparison to its skull size.
Comparatively little is known about the habits of the Bornean clouded leopards as they are extremely shy. What is known however is that they are excellent climbers, spending much time in the trees, and that they hunt a wide variety of prey including deer, monkeys, bearded pigs, civets, fish and porcupines.
The scientific name of the trilobite beetle, Duliticola, stems from Mount Dulit in Borneo. The photo shows a female trilobite beetle which can grow up to 8 centimetres in length. In contrast the males only grow to 9 millimetres and have more of a stereotypical beetle-like appearance. Borneo is immensely rich in insect life: some types of tree have been found to hold as many as a thousand different species of insects.
Borneo, together with Sumatra, is home to the greatest diversity of carnivorous tropical pitcher plants. Their prey usually consists of insects but larger species occasionally also catch vertebrates such as lizards or rats.
One Bornean pitcher plant, Nepenthes lowii, has become known as the “shrew toilet” as it attracts tree shrews and birds with its nectar, whose droppings fall into its pitcher and provide most of the plants’ foliar nitrogen requirements.
The binturong is also known as the Asian bearcat, but is in fact neither cat nor bear, and belongs to the same family as civets and genets. It primarily eats fruit but will also hunt small animals.
Bearcats spend most of their life in the trees and are excellent climbers who can use their tail as a fifth hand. However, due to their weight (9-14 kilograms) they often need to descend to move onto another tree, and are able to rotate their hind legs so that their claws still provide grip when descending head first. The musk released by the bearcat’s scent glands is reported to smell like hot popcorn.
The yellow-throated marten is an omnivore who will feed on anything ranging from fruit to small deer. It’s a daytime hunter and usually hunts in pairs but may also form packs on occasion. Despite the presence of larger carnivores it has no natural enemies as it can secrete a strong smelling liquid from its anal glands for defensive purposes.
The yellow-throated marten can cover up to 20 kilometres in a single day whilst patrolling its territory. Whilst it does predominantly hunt on the ground it is a proficient climber, and has been observed jumping up to 9 metres between branches.
Horsfield’s tarsier is a primate found on Borneo, Sumatra and a few neighbouring islands. Its big eyes are larger than that of any other mammal in proportion to body size. It spends about 95% of its life off the ground and can jump between trees covering distances equal to 45 times its body length (about 5.8 metres) in a single jump. Tarsiers are carnivores and predominantly eat insects but have also been noted to catch and eat bats, birds, poisonous snakes and other animals as large as themselves.
Rafflesia Arnoldii is the world’s largest flower and can be found on Borneo. It can reach up to 100 centimetres in diameter and weigh up to 10 kilograms. The plant is further characterized by giving off the smell of rotting flesh, giving it the nickname ‘corpse plant’.
There are about 28 different species of Rafflesia throughout Southeast Asia and all are parasitic. They do not have roots and instead grow on other plants from which they obtain their nutrients and water. Rafflesia challenge traditional definitions of what a plant is, as they do not have chlorophyll and are incapable of photosynthesis.
Proboscis monkeys are endemic to Borneo and are easily recognizable by their large noses and pot bellies. When excited or agitated their noses swell even larger and turn red. Proboscis monkeys primarily eat fruit and leaves and have stomachs which are divided into compartments to house different digesting bacteria which allow them to both neutralize toxins in leaves and to digest them. Their stomach contents make up about a quarter of their overall weight, accounting for their permanent pot bellies.
Borneo’s rainforests are home to a staggering variety of orchids, many of which are extremely rare and endangered. Some estimates consider there to be as many as 3000 different species on the island, making for a greater variety and number than anywhere else on Earth.
Today wild orangutans are only found in the rainforests of Borneo and Sumatra. They are the most solitary of the great apes and spend most of their time in the trees. Adult male orangutans can grow to 175 centimetres and weigh up to 118 kilograms whereas females are considerably smaller.
The large cheek flaps are only seen on mature dominant male orangutans who also develop throat pouches, which allow them to make loud calls. They live primarily off fruit but will also eat other plants, insects and bird eggs. Orangutans frequently live to over 30 years of age in the wild.
Sun bears are the smallest members of the bear family, averaging a mere 120-150 centimetres in length. Honey bears, as they are also called, possess a long slender tongue of up to 25 centimetres which they use to get at honey in beehives. They are excellent climbers and during the day can often be found asleep in trees.
Despite its name and appearance the lantern fly does not emit light from the yellow tip of its ‘snout’. The insect belongs to the Laternaria genus, which was falsely believed to be luminous at night. In fact the snout-like projection is used to access tree sap, which the insect feeds on. There are approximately 60 species of Laternaria throughout Southeast Asia and almost all have wings with bright and contrasting patterns of colour.
The rhinoceros hornbill is one of the largest hornbill species, growing as large as a swan. Next to fruit and insects this hornbill will also feed on small reptiles, rodents and other birds. Females nest within hollows in tree trunks and once inside the nest close off the entrance to it with mud and debris which the male brings. All that remains is a small slit through which the male can provide food and the female can defecate. The female remains in the nest for the next five months, first incubating the eggs and then rearing the new-born.
Borneo is home to a number of species of Draco, or flying lizards, which live in the forest canopies. Draco lizards are able to extend their ribs and the skin covering them to create a wing and also have a flap of skin around their throat which acts a horizontal stabilizer whilst in flight. They are not capable of self-propelled flight but are instead gliders, who nonetheless have been observed covering over 50 metres in a single flight.
Cat geckos name comes from their habit of sleeping with their tail curled up around them, much in the same way as cats do. Unlike most other geckos that have toe pads which allow them to climb sheer surfaces, the cat gecko instead relies on small retractable claws and its tail to climb trees.
The Bornean bearded pig is an inhabitant of rainforests and mangroves. The trademark white beard is longer on males and is accentuated by the dark skin beneath it. Bearded pigs are omnivores and regularly follow gibbons and macaques to feed on the fruit they drop. They are known to be good climbers, jumpers and excellent swimmers – to the extent that they will swim to other oceanic islands.
The black-webbed treefrog or green flying frog is a canopy-dwelling species which only ever descends the trees to breed in pools on the ground. The frog is just one example of at least 100 recorded species of amphibians on Borneo. Most famously these include the Bornean flat-headed frog, the only known lungless frog, which breathes through its skin.