The islands of Borneo and Sumatra are two of the most biodiverse areas on earth, known for their extraordinarily rich flora and fauna. Although much of the recent international attention has focused on the islands’ wild orangutans, the forests of Indonesia in fact contain over 10% of the world’s flowering plants, 16% of the world’s reptiles and amphibians, 17% of the world’s birds and 12% of the world’s mammal species (Wakker, 2004). Among these are over 20 species of primate.
OURF has always believed that the key to protecting orangutans is protecting their rainforest home, and ensuring that the remaining rainforests of Borneo and Sumatra remain as intact and inviolate as possible. But protecting orangutans is also important for the very future of that rainforest. Due to their ecological role as seed dispersers and the part they play in breaking up the dense rainforest canopy, studies have shown that rainforests with orangutans present, at their normal densities, can expect the presence of at least 5 other species of primate and hornbill, 50 different species of fruiting tree, and 15 species of liana (Rijksen & Meijaard, 1999). Some of the primate species found are some of the most extraordinary on earth.
Like orangutans, gibbons are apes, but, unlike orangutans, they are considered lesser apes, on account of their smaller body size. There are two species found in Sumatra, the white-handed gibbon (Hylobates lar
The fur color and physical appearance of gibbons varies from species to species, and there is also often variation between members of the same species and between sexes. However, gibbons are unusual amongst apes for the low level of sexual dimorphism shown, with males and females being around the same size, and often hard to distinguish.
Gibbons are born after a gestation period of 7 months, and reach sexual maturity between the ages of 6-9 years, when they form monogamous pairings with a member of the opposite sex, which lasts for the remainder of their lives, occupying a home range of around 40 hectares (Redmond, 2008), although this varies depending on species and the presence of other species of primate (Bartlett, 2007). Territories are defended aggressively.
The interval between births is usually two to four years, so most gibbon groups will consist of no more than two adults and two or three young, adolescents leaving the family group upon maturity. Unlike other apes, gibbons do not make nests, either for day or night rest,
Gibbons are also known for their distinctive vocalizations, which are believed to be used as a spacing mechanism, to defend territories and to attract mates, and their haunting melodies, usually sung in unison, are one of the most beautiful sounds in South East Asian rainforests.
The Siamang is a type of
The life history and adaptation of the siamang is similar to those of other gibbons, but these primates generally have smaller day ranges, and, unusually, male siamangs play a much more active role in the raising of the young than do members of the other gibbon species. Like all apes, they are long-lived, and wild gibbons and siamangs may live until they are 30-40 years old.
Like orangutans, siamangs and gibbons are threatened by habitat loss and the pet trade, particularly for use as tourist attractions on the Asian mainland.
It would be hard to find a more unusually primate than the
The body of the
The digestive system of the
These monkeys live in a harem of one adult male, several females and their offspring, groups that can be as large as 23 animals.
Widespread forest conversion has seen these primates placed on the IUCN endangered list, but it is hoped their increasing popularity with tourists, and the ease with which they can be spotted from boats, could lead to more concerted conservation efforts.
Of all the primates, macaques almost certainly have the worst reputation, being considered a pest throughout much of their range, which is the widest of any non-human primate. But their pest-like status is simply a result of their extraordinary resilience and adaptability, and their ability to thrive in almost any environment.
There are two species of macaque found in both Borneo and Sumatra, the pigtailed macaque (Macaca
Pigtailed macaques have olive-brown fur over their bodies, with white undersides and a black patch on top of their heads, with males of this sexually dimorphic species having a head and body length of 19.4 to 22.2 inches, and weighing 6.2-14.5kg. Females are considerably smaller, weighing between 4.7 & 10.9kg. Long-tailed macaques are the smaller species, with males weighing between 4.7-8.3kg. They are grayish in
Both species of macaque are largely frugivorous, and also eat insects, seeds, young leaves, leaf stems, dirt, and fungus, with long-tailed macaques known to feed on crabs, frogs, shrimp
Although not considered endangered, macaques are the focus of increasing animal welfare efforts, as they are the most common primates used for invasive medical research.
Leaf monkeys, Langurs
Langur means ‘having a long tail’ in Hindi, and almost all species of langur monkey, and their relatives the leaf monkeys and
The life histories and appearance of leaf monkeys, langurs, and surilis differ from genus to genus and species to species, but the species found in Borneo and Sumatra are diurnal, arboreal tropical rainforest dwellers, and feed on leaves, seeds, fruit, shoots, flowers, bark, stems and fungi. Two species of monkey in Borneo, Hose’s langur (Presbytis
The head and body length of these monkeys is between 16-33 inches, and they weigh between 5-8.1kg (Redmond, 2008; Nowak, 1999). They have a gestation period of around 6 months and are believed to reach sexual maturity after a few years. The species found on Borneo and Sumatra usually live in groups consisting a single male and one or two adult females, although, in some species, such as Thomas’s langur, groups with two adult males have been observed. Lone males and small all-male units have been observed, as juvenile males disperse from their natal group on sexual maturity (Nowak, 1999), as have monogamous pairings (Kirkpatrick, 2007).
Although relatively little is known about the various species of langur monkeys, leaf monkeys and surilis in Borneo and Sumatra, all are threatened by deforestation, forest conversion, and hunting, and there is a danger they may become extinct before the full complexity of their social systems is known.
With their large, forward-facing eyes, small wooly bodies and tightly clinging hands and feet, with their human-like nails, slow lorises are among the most unusual looking primates. In fact, so beguiling were these creatures to Dutch officials, their popular western name derives from the Dutch word for clown, ‘loerus’. Highly prized as pets throughout their range, slow lorises are, along with the tarsier, the oldest and most primitive primates found in Borneo and Sumatra.
The taxonomic status of the slow lorises has long been a source of confusion, hampered by the scarcity of wild loris studies, but there are now believed to be two separate species inhabiting the forests of Borneo and Sumatra. The Bornean slow loris (Nycticebus
The Bornean slow loris is one of the smallest loris species, weighing 0.26-0.3kg, and is covered in pale golden to red fur. It is distinguishable by the relative lack of markings on the back of its head, having instead a soft brown crown. In comparison, the greater slow loris weighs 0.59-0.68kg, has a darker, deep red fur, and dark rings around the eyes, which meet a dark dorsal stripe on the back of the head.
Slow lorises are slow-moving, arboreal and nocturnal, and feed on a diet of fruit, seeds, leaves, bark, fungi, gums, shoots, flowers, birds’ eggs insects, small vertebrates and invertebrates (Redmond, 2008). During the day they sleep curled up in branches.
Little is known of the slow loris social systems, although they are thought to be largely solitary creatures, although groups have been observed when home ranges overlap, and relations between males are thought to be highly antagonistic. Slow lorises are born after a gestation period of around 6 months, and sexual maturity is reached between 17 and 24 months, at which time they disperse from their mothers. The lifespan of wild slow lorises has not been determined, but it is believed to be between 20-30 years.
Incredibly popular as pets, slow lorises are the only primate known to be poisonous, having glands on their arms that secrete a substance that contains toxins to paralyze prey. Their status in the wild is believed to be endangered, although the lack of concrete data means exact figures and population estimates are difficult to determine.
Tarsiers are small nocturnal primates found throughout Southeast Asia and known for their huge round eyes, which are larger, relative to the size of the head, than in any other species (Redmond, 2008). Just one species of tarsier is found in Borneo and Sumatra, the Horsfield’s tarsier (Tarsius
Like lorises, tarsiers are small, unusual looking primates, with a head and body length of between 34-63 inches. Unlike lorises, however, they are agile and fast moving, known for being able to jump extraordinary distances between trees. Their leaping ability stems from their powerful legs, which are one and a half times the length of the head and body combined (Redmond, 2008). Entirely carnivorous, tarsiers cling vertically to branches, catching and eating large insects such as beetles, grasshoppers, cockroaches, butterflies, moths, praying mantis, ants, phasmids and cicadas, as well as bats, frogs, and snakes.
Tarsiers are born after a gestation period of 6 months and reach sexual maturity around 1. Surprisingly, the social system of the Horsfield tarsier is similar to that of an orangutan, with the female raising the young until it leaves the natal home range upon sexual maturity, establishing its own territory. Male home ranges, of between 2-8-11 hectares, overlap those of several females, and it is likely that the male will mate with all females in his home range, although he will play no active part in the raising of any young. Territories are defined and enforced by a series of vocalizations and scent markings (Redmond, 2008).
Unlike most nocturnal primates, tarsiers do not possess a tapetum lucidum, the reflective layer in the back of the eye the produces the ‘cat’s eye’ reflections, which makes them difficult to see at night (Redmond, 2008). This adaptation has likely spared tarsiers from higher levels of poaching but has made studying them in the wild difficult
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Rijksen, H.D. & Meijaard, E. (1999). Our vanishing relative: The status of wild
While the islands of Borneo and Sumatra are perhaps best known for their extraordinary array of primate species, they are by no means the only fascinating mammals founds on the islands, and Borneo and Sumatra’s rainforests provide refuge to some of the most iconic species alive. Although increasing rates of deforestation, agricultural expansion
The Sumatran tiger (Panthera tigris
Tigers are largely solitary animals, although they are not anti-social; males are occasionally seen resting with females and cubs, and they may also travel in groups (Burnie, 2001). Active at night, tigers are nocturnal animals, but will hunt during the day during cooler periods, and range over territories of 10-30 or more square miles, which they mark out by spraying their urine or a glandular secretion, by leaving fecal droppings, or by scratching marks in to trees (Sumatran Tiger Trust). The ranges of males overlap with those of several females.
Tigers are born after a gestation period of 16 weeks, and the litter usually consists of around 3-4 cubs, which are born blind and helpless, and raised entirely by their mother. Tiger cubs have a high mortality rate, due to high instances of predation, often by male tigers, who will kill cubs to make the mother sexually receptive. Tiger cubs become independent at around 18 months and will leave their mother's side at around 2-2.5 years of age. Females reach sexual maturity at 3-4 years of age, and males reach sexual maturity at 4-5 years. They have a life expectancy of around 15 years in the wild (Burnie, 2001).
Tigers are carnivorous meat eaters, and Sumatran tigers feed chiefly on different members of the deer family, pigs, rhino’s, snakes, tapirs, and other large mammals, which are usually killed in an ambush from behind, with a bite to its neck breaking the prey’s spinal cord (Sumatran Tiger Trust).
Once widespread throughout the island, deforestation and forest conversion has seen the population plummet, and there are now believed to be around 350 tigers surviving in the wild
Elephants are the largest land mammals in the world and are distributed throughout much of Africa and Asia. There are two subspecies of the Asian elephant found in Indonesia; the Bornean pygmy elephant (Elephas maximus
Sumatran elephants reach a shoulder height of between 2 and 3.2 meters and can weigh between 2,000 and 4,000 kg. Unlike other elephants, males of this subspecies rarely develop long tusks, while those of adult females may be so short they are hidden by the upper lip, and they are also much lighter in color than other elephants. Bornean pygmy elephants are, hence their name, the smallest of all elephants, with males growing to less than 2.5 meters, and are identifiable by their large ears, younger looking faces, longer tails and more rotund shape (WWF, 2011).
All elephants are herbivores, and a single Bornean elephant can eat up to 150 kg’s of vegetation every day, feasting on various species of palms, grasses and wild bananas. They also acquire minerals found in salt licks or from the mineral concentrations in limestone outcrops. Sumatran elephants will usually consume more, around 200 kg’s of vegetation a day, and will feed chiefly on bananas, ginger, young bamboo and leaves of a variety of vine (WWF, 2011).
In comparison to African savannah elephants, Asian elephants live in small family groups, which consist of a female matriarch and other related females of varying ages. Males only join such groups when females are sexually receptive and are otherwise either solitary older bulls or, when young, part of bachelor groups. Adult males have little to do with their young, which are born after a gestation period of 22 months, weaned at around 4 years old and reach sexual maturity at 9-15 years, if it is female, and 12-15 if it is male (Burnie, 2001).
While African elephants have suffered from a long history of hunting, Asian elephants have a long association with humans (Bornean pygmy elephants are particularly docile
There was once thought to be just one species of clouded leopard found throughout Asia, but studies in 2006 confirmed that the species found in Borneo and Sumatra, the Sunda clouded leopard (Neofelis
Clouded leopards inhabit tropical rainforests, with populations in Borneo inhabiting lowland forests, and populations in Sumatra largely inhabiting forests at higher elevations, in hilly, montane areas, possibly because they share their habitat with Sumatran tigers on this island (Hearn et al, 2008).
These leopards have a stocky build and weigh between 12 to 25kg, with a head to body length of 50 to 110cm and a tail length of 55-91 cm. It has a dark coat covered in black-edged, darker-centered ovals, which look like clouds and gives the leopard its common name. They also have extremely long canine teeth in proportion to their skull size, and they are extremely proficient carnivores, feeding chiefly on different species of deer, bearded pigs, civet cats, monkeys, gibbons, porcupines
The leopard is nocturnal and feeds predominantly in
One of the most iconic animals alive, there are five species of rhinoceros found throughout Africa and Asia, with the Sumatran rhinoceros (Dicerohinus
Rhinoceroses are large, heavy built animals, but the Sumatran rhinoceros is the smallest species, with a weight of around 600-950kg, a height of 3-5 feet and a length of 6.5 to 9.5 feet (International Rhino Foundation). Often called the ‘hairy rhino’ due to the
Relatively little is known about the behavior of Sumatran rhinoceroses, but they are believed to be largely solitary. Males have home ranges of around 50 km2, which seem to overlap with those of other males, while females have ranges of 10-15 km2, which appear to be spaced out.
Bears are among the most charismatic animals on earth, but while the brown, black, grizzly, polar and panda bears are internationally known and icons of the conservation movement, many people don’t realize that bears can also be found in Borneo, Sumatra and mainland
Sun bears (Ursus
Shy and elusive, little is known about the sun bear’s social structure, but they are believed to be solitary, with the largest social group consisting of a mother and her dependent offspring. Sun bears do not
A nocturnal animal, sun bears are omnivores and feed chiefly on termites, ants, beetle larvae, bee larvae and a large variety of fruit species. Their propensity for eating honey has given rise to their alternative name, and the sun bear is referred to throughout Indonesia and Malaysia as the honey bear.
Sun bears have extremely long, curved claws, an adaptation for tree climbing and used to dig for worms and insects, and to tear up logs and old bark to expose and extract termites, and remove honey from wild bees’ nests. It also has a tongue that can protrude 10 inches and is used to extract honey, grubs and similar foods from holes & crevices (Burnie, 2001; Fredriksson et al, 2008).
The Malayan tapir (Tapirus indicus) is the only found tapir found in Asia and is found in Sumatra, where it lives in heavily fragmented populations in tropical moist forests.
Tapirs are large, ground-dwelling mammals, weighing around 250-540kg, with a length of between 1.8 and 2.5 meters, and are easily identifiable by their
Malayan tapirs are solitary creatures and live in large territories, which often overlap with those of others and which they mark by spraying urine on plants. Exclusively vegetarian, tapirs feed on the tender shoots and leaves of more than 115 species of plant and tend to eat soon after sunset or before sunrise, being mainly active at night. They have extremely poor eyesight and rely on their strong sense of smell and hearing.
The gestation period for Malayan tapirs is approximately 390-395 days, and single young are born weighing around 6.8kg. They are weaned at around 6 to 8 months, at which time they are fully grown, and sexual maturity is reached at the age of three. They have a life expectancy of 30 years (Burnie, 2001; Lynam et al, 2008).
Due to their size, tapirs have few natural predators and are endangered purely as a result of human activities. Although local traditions in Sumatra mean they are not usually hunted for food, they are prized highly on the international illegal wildlife trade, and forest conversion has forced remaining populations into heavily fragmented areas
The Malayan flying lemur (Galeopterus
Active in twilight and at night, flying lemurs are found in tropical rainforests and feed on soft plant parts such as flowers, fruits, buds, and young leaves, and scrape up nectar and sap with their comb-like incisor teeth.
At between 33-42 cm in length, with a tail of 17.5-27 cm and a weight of 0.9-2kg, these lemurs are small animals, around the size of a domestic cat, and are covered in short, fine fur of a grey, red color, often with lighter flecks that mimic
Like so many animals in Borneo and Sumatra, lemurs are little studied and there is a scarcity of information about their social lives, but they are known to be born after a gestation period of 2 months and are weaned at 6 months, and adults of this species are either solitary, or live in small, loose groups (Burnie, 2001).
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Tropical rainforests are the most biologically diverse ecosystems on earth, and, despite covering just a small portion of the world’s service, are home to around 80% of its biodiversity. Indonesia’s 88,496,000 hectares of forest represents 10% of the world’s remaining tropical forest, and are, despite massive levels of deforestation, the largest contiguous area of forest in Asia (FAO, 2009).
Tropical rainforests are found within 28 degrees north and south of the
Although the types of rainforest vary throughout Indonesia, Malaysia
The unique climate and geology of Borneo and Sumatra
The major tropical forest type found throughout Indonesia and Malaysia is evergreen dipterocarp forest, which is found in both lowland and hill areas, and provides suitable habitat for the islands’ wild orangutans, tigers, rhinos, elephants, leopards and
Although the appearance and structure of dipterocarp forests
Dipterocarp forests are highly unusual in that their plants flower so rarely, usually only once or twice in a 10 year period, a process known as mast fruiting, which is linked to the arrival of the El Nino weather phenomenon. The climatic conditions of El Nino years stimulate synchronous fruiting, and the canopy of
Fossil pollen from dipterocarp trees found in Sarawak has been dated as far back as 30 million years (Rautner et al, 2005), but despite once covering much of the region, huge rates of land clearance, particularly for the Borneo ironwood tree (
Some of the largest populations of orangutans are found in Borneo and Sumatra’s peat swamp forests, with these forests providing
Peats swamp forests are lowland forests that have formed over thousands of years, in areas where waterlogged soils prevent dead leaves and wood from fully decomposing, and where decomposition rates are exceeded by the addition of further dead materials from the forest, leading to an accumulation of peat (Harrison, 2009). Peat swamps are usually found close to the coastline or near the shores of lakes, and form extensive, gently domed deposits, which can extend up to 200 km inland, and reach thicknesses of up to 20 meters (Page et al, 2004). Unlike freshwater swamps, which cover large areas of Borneo and Sumatra and receive water from
Despite their lack of nutrients and the fact that they contain a lower density and diversity of flora and fauna than dryland dipterocarp forests, peat swamp forests contain a large number of endemic species, and are considered important reservoirs of biodiversity (Harrison, 2009), with Borneo’s peat swamp forests home to at least 927 species of flowering plant and ferns (Anderson, 1963).
Tropical peat swamps form over thousands of years, with the oldest peat formation in South East Asia, which began forming around 26,000 years ago, found in the Sebangau area of central Kalimantan, and are incredibly important carbon sinks, with between one-fifth and one-third of global soil carbon locked up in their soils (Harrison, 2009). Despite this, and the implications these massive storage sinks have for the global climate, peat swamp forests in Borneo and Sumatra have suffered from a history of degradation, drainage, fires, logging and conversion for agriculture, and it is believed that, of the 9 million hectares of land in Kalimantan that was damaged by Indonesia’s 1997-1998 forest fires, 40% were peat swamp forests (Rieley, 2002).
Mangroves are among the most unique ecosystems on earth. Found in around 117 countries and covering an area of up to 24 million hectares, mangroves have the highest level of productivity of all natural ecosystems (Rautner et al, 2005), and are comprised of
Mangrove trees are distinguishable by their long, gnarled, twisted roots, which act as stilts, holding the mangrove tree trunks and leaves above the water. These roots not only act as supports and allow trees and plants to grow in the unstable mud flats
Known as ‘rainforests by the sea’, mangrove forests are breeding grounds for many fish, shrimps, prawns, crabs, shellfish and snails, as well as habitat for numerous species of birds, lizards, turtles, crocodiles, and primates including
Heath forest is commonly known as
Heath forests differ from other lowland forests, including dipterocarps, in species composition, structure, texture and colour, and are much smaller than other rainforests, with a low, uniform single-layered canopy, sometimes as low as 4.5-9 meters, formed by the crowns of large saplings and small poles, with a thick underbrush of moss and epiphytes. Heath forests are also known for having small, very leathery leaves.
Although the nutrient level of heath forests in comparison to other types of lowland forest is debated among ecologists, soils of these forests are inherently poor in bases, highly acidic, commonly coarsely textured and free draining, and are often described as white sand soils, and it is believed that toxic phenols, abundant in the soil through leaves and litter, could be responsible for the lack of nutrient uptake (MacKinnon et al, 1997). As such, heath forests are poorer in species than other lowland forests, with one one hectare research plot recording 123 tree species, in comparison to 214 tree species recorded in a neighboring plot of dipterocarp forest (Rautner et al, 2005),
Although these forests do contain some of the world’s most extraordinary plant species, including pitcher plants that obtain their nutrients through insects, a carnivorous habit developed in response to the scarcity of available nitrogen (MacKinnon et al, 1997), fewer plant species mean these forests are generally low in animal species, with forests in Sarawak containing less than half the number of frog species, lizards and snakes than dipterocarp forests, as well fewer endemic species and no recorded populations of turtles (MacKinnon et al, 1997). They do, however, provide habitat for wild orangutans, with a viable and incredibly important population found in the extensive
Despite the unsuitability of these forest soils for agriculture,
Orangutans are creatures of the lowlands, inhabiting tropical rainforests up to elevations of 1,000 meters above sea level. Although peat swamp, dipterocarp,
Occurring at higher elevations, montane forests receive much higher levels of rainfall than lowland
Although the harsh climate, lack of shelter and corresponding lack of food make these forests scarcer in plant and animal species than lowland forest, they are still species-rich and contain a high level of biodiversity. As well as orangutans, montane forests provide homes for gibbons, langur monkeys, macaques, Sumatran rhinos, kingfishers, and numerous other species (WWF, 2010).
Like all forests in Borneo and Sumatra, montane forests are threatened by mining operations, large dams, high altitude timber plantations, conversion to agriculture and shifting cultivation, and animal species inhabiting these forests are increasingly being targeted as specimens for the illegal pet trade (WWF, 2010).
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