Saturday, October 25, 2008

Bukit Timah Nature Reserve

Established in 1883, Bukit Timah Nature Reserve is the oldest nature reserve in Singapore, and many Singaporeans visit it to hike, jog or stroll. The 163-hectare reserve also has the highest hill in Singapore - Bukit Timah Hill - at 163.63m.

Literally translated, 'bukit' means 'hill', and 'timah' means 'tin'. The origins of the name were not confirmed, though it is known that the hill does not have tin. Some claimed that the hill's original Malay name was Bukit Temak, named after the temak tree (Shorea roxburghii). However, this tree is not found in Singapore. There are also records that the name temak can be applied to Shorea macroptera and Shorea bracteolata, according to the book 'The Malayan Forest Records - No.5; Malayan Plant Names, J.G. Watson, 1928', which are both found at Bukit Timah (see Jo Lai's website for details). Others suggested that it could have been corrupted from the name of the medicinal herb Labisia pumila, also known as "Selusuh Fatimah" (literally Fatimah's childbirth medicine) and "Kacip Fatimah" (Fatimah's betel scissors) in Malay.

Bukit Timah Hill comprises largely of granite, and was once an active quarrying site in the mid-1900s. In fact, one of the used quarry was even developed into a park - Hindhede Nature Park.

The forest of Bukit Timah Nature Reserve has a rich variety of flora and fauna, with more than 840 flowering plants, almost 100 species of ferns, and over 240 species of vertebrates. In a 2-hectare study plot, more than 300 species of trees were recorded! And not to forget that since modern Singapore was founded for the past 200 years, many species of plants and animals were first obtained and described from here.

Dos & Don'ts
  1. Stay on the trail! Wandering off the trail may result in trampling of the flora and fauna.
  2. Bring water and some light snacks, but avoid eating or drinking when there are monkeys around.
  3. Do not feed any animals, as they may become very dependent on human to feed them, and forget how to find food on their own. Some animals, such as the macaques, may even learn to snatch food from human.
  4. Keep your volume down, or you may disturb the very animals you want to see, and they may hide away from you.
  5. Take nothing but photos, leave nothing but foot prints. Bring your litter out with you, and never take anything from the forest. Poaching has resulted in severe reduction in the population of much wildlife in many places.
  6. You may want to consider wearing long pants, e.g. light track pants etc. There could be mosquitoes.
  7. Please bring insect repellent. Mosquito pads are usually not very useful for such outdoor activities as the mosquitoes can be quite aggressive.
  8. Please bring a cap/hat in case of sunny weather, and raincoat/poncho in case of wet weather. I would also recommend bringing a few plastic bags to keep your electronic products in case it rains.
  9. Bring a camera along, but remember to have a plastic bag to keep it dry in case it rains.

Getting Started

As you enter Bukit Timah Nature Reserve, it is not hard to notice that it feels cooler, quieter and more humid than the urban areas. The shade provided by the trees keeps the air in the forest cool; the thick leaves screen the noise from the nearby roads; and the trees also help increase the humidity through transpiration. All these are typical conditions you will experience in a rainforest. Being a tropical dryland rainforest, the reserve also experiences high temperature throughout the year, with more than 100 mm of rain every month.

Bukit Timah Nature Reserve is one of the two last remaining places in Singapore which contains areas with primary dryland rainforests, the other place being the Central Catchment Nature Reserve. Unfortunately, much of Bukit Timah Nature Reserve is actually covered by secondary vegetation, and primary vegetation only occupies about 24 percent of the area.

In these patches of primary vegetation, you can usually see one of the common features of an Old World primary tropical rainforest - the lianas. Lianas are woody climbers. Climbing from tree to tree, they link up the various trees like highways for animals that live in the canopy. However, if one tree falls, the liana will drag the other trees along, thus creating a gap in the forest.

Like other tropical rainforests, the forest of Bukit Timah Nature Reserve consists of four layers, and here are some of the flora and fauna that you can found in the various layers.

The Forest Floor

The bottom layer is the forest floor, where little sunlight can reach, thus resulting in little undergrowth. The floor is usually covered with a thin layer of fallen leaves, branches, fruits and seeds, many of which quickly decompose.

As a result, decomposers such mushrooms can be commonly seen sprouting out of fallen branches or dead trees.

The soil in a tropical rainforest is usually very poor in nutrients, and most of the available nutrients are found in the living organisms. The remaining nutrients out in the open are usually in the top soil, which explains the shallow roots of trees to absorb the nutrients and also water near the surface. The soil is usually somewhat acidic, and as the acidity increases, the species variety usually decreases.

Leafy herbaceous plants, small shrubs, or young trees are found growing sparsely on the forest floor, except along forest trails, rivers or forest gaps created by fallen trees.

Hill Coconut, Curculigo sp.
On the sides of the foot path in Bukit Timah Nature Reserve, many of these plants which look like miniature palms can be found. Called the hill coconut (Curculigo sp.), they are not palms, but are actually herbs with pretty yellow flowers which grow at the base of the herb. The fruit contains a protein called curculin which has a taste-modifying activity converting sourness into sweetness, and at the same time, the protein itself elicits a sweet taste. Several studies have been conducted on plants from this genus to test whether the protein can be used as a replacement for sugar.

Bat lily (Tacca integrifolia)
Bat Lily (Tacca integrifolia), a herb which usually grow in moist shady spots, is also quite common in Bukit Timah Nature Reserve. This herb produces spectacular purplish black flowers with long whiskers.

This interesting fern, paku biawak (Tectaria singaporeana) is a native fern named after Singapore! Like other ferns, they don't produce flowers or fruits, but reproduce from spores found on the underside of mature fronds. Various species of ferns ca sometimes be found growing in the forest floor layer, especially when there is a gap in the canopy.

Zebra dove, Geopelia striata
In some of the more open areas, zebra dove (Geopelia striata) are sometimes spotted. Closely related to the peaceful dove (Geopelia placida) found in Australia and New Guinea, the zebra dove feeds on small grass and weed seeds, though at times it may feed on small invertebrates too. This bird is very popular as a song bird, resulting in many of them being trapped for the cage bird industry.

Clouded monitor lizard, Varanus bengalensis
Sometimes, if you look closely into the undergrowth, you may be lucky enough to spot the clouded monitor lizard (Varanus bengalensis). Monitor lizards are mildly venomous, but their bites are often still very dangerous due to the many bacteria found in their mouths, giving their victims a bad infection, sometimes leading to fatalities. They feed on smaller animals. The above monitor lizard was observed eating a centipede.

Damselfly, Vestalis amethystina
Dragonflies and damselflies such as this Vestalis amethystina are often seen near streams or other water bodies. They feed on other insects, catching them on the wing. The adults have big eyes containing as many as 30,000 individual lenses, thus giving them an excellent eyesight.

Jumping spider
Spiders such as this jumper (Family Salticidae) are very common, but they often require keen eyes to spot them, as they can be quite small and well camouflaged. Jumpers are able to jump from place to place, secured by a silk tether. They have good eyesight, allowing them to hunt for small insects efficiently.

Millipedes are usually found in the leaf litter, though sometimes you may find them on the little shrubs too. They generally feed on decaying plant matter. If you are confused about telling millipedes and centipedes apart, just look at the number of legs per segment - millipedes have 2 pairs, while centipedes only have 1 pair.

Crickets (Family Gryllidae) are often seen in the early morning when it is darker and cooler. The male crickets are often heard "singing". The left forewing of the male has a thick rib with many ridges, while the upper hind edge of the right forewing has a thick scraper, and thus a chirping sound is produced when the male cricket rubs its left forewing against the right forewing.

Giant forest ant, Camponotus gigas
The giant forest ant (Camponotus gigas) is another common animal often encountered on the forest floor. It is one of the largest ant species in the world. They live in colonies with territories up to 0.8 ha.

The Understorey

The understorey layer consists of taller shrubs, small trees, climbers and epiphytes. Many animals can also be spotted here, since they are not hidden by the thick foliage of the canopy. This layer also includes the shrub layer, which some people see as a separate layer.

mousedeer plant, Anisophyllea distichia
This interesting forest shrub is call a mousedeer plant (Anisophyllea distichia), and its fruits are thought to be dispersed by mousedeer. Also called kayu pachat or leech wood, this shrub has a unique leaf arrangment made up of two kinds of leaves in four rows.

bintangors or beautiful leaves, Calophyllum spp.
There are many species of bintangors or beautiful leaves (Calophyllum spp.) at Bukit Timah Nature Reserve. They got their name from their pretty glossy leaves with fine parallel veins. Some species of bintangors have been tested for their anti-aids properties.

Buttefly vine, Bauhinia sp.
The butterfly vine (Bauhinia sp.) is a very pretty vine with leaves resembling butterfly wings. This climber is a hitch-hiker on other trees, but it is not a parasite and does not steal nutrients from the tree.

Monkey, Long-tailed macaque, Macaca fascicularis
The most commonly seen mammal at Bukit Timah Nature Reserve must be the long-tailed macaque (Macaca fascicularis). They are often seen jumping from tree to tree, and more often than not, foraging on the ground. Irresponsible reserve visitors often feed these monkeys, and as a result, the macaques are "trained" to harass visitors for food, and some even attack and snatch food from visitors.

Malayan Colugo (Cynocephalus variegatus)
Another mammal that is sometimes seen in Bukit timah Nature Reserve is the colugo (Cynocephalus variegatus). This cute mammal which can glide from tree to tree is sometimes called flying lemur, which is an inaccurate description since it does not fly, and it is not a lemur, since true lemurs are only found in Madagascar.

Common posy, Drupudia ravindra moorei
The common posy (Drupudia ravindra moorei) is a common forest butterfly. It has a swift flight, and will often return to the same perch.

Yellow assasin bug, Cosmolestes picticeps
The yellow assasin bug (Cosmolestes picticeps) has a dagger-like beak which it uses to stab its victims, which are usually smaller insects. The beak injects a chemical to break down the prey's internal tissues into a partically digested fluid, which the bug will suck up.

Hopper, Ricanula stigmatica
Commonly found in the more opened areas in the reserve, this hopper (Ricanula stigmatica) are sometimes mistaken for moths due to its shape. It usually feeds on plant sap.

When you are in the forest, you can usually hear a shrilling whine made by the male cicadas. The cicadas sing for several purposes, and sound differently for each purpose. They may sing to lure females, and this song may change to a 'courtship song' when the female has arrived in the near vicinity, or give 'distress calls' when they are disturbed. They sing by rapidly vibrating 2 drum-like membranes at the base of their abdomens.

In the darker parts of the forest, moths (Order Lepidoptera) can be found perching on leaves and tree trunks.

Weird-looking caterpillars are often spotted on tree tunks or even on the pillars of the shelters in the reserve.

Stick insect
Sometimes, if you take a closer look, you can find insects sticking themselves to the unusual spots, such as this stick insect (Order Phasmatodea) on a sign board.

The Canopy

The layer above the understorey is the canopy which comprises most of the larger trees, forming a tight and continuous layer with their irregular crowns.

This pretty tree is related to jambu trees (Syzygium sp.). Trees from this family are characterised by having opposite leaves with marginal veins. Syzygium is among the most poorly known of the large (> 500 species) genera of vascular plants.

Baccaurea parviflora
The Baccaurea parviflora tree is another tree found in our forests. The female tree, as shown above, flowers at the base of the trunk, while the male tree flowers directly on the trunk.

Tampines Tree, Streblus elongatus
This is the tampines tree (Streblus elongatus) that gives Tampines Town its name! Supposed to come from the fig family (Moraceae), and has white sap. Streblus means crooked in Latin, while elongatus means elongated or lengthened - possibly refering to the flowers (see the longish flowers in the photo above). This is one of the most common trees in Bukit timah Nature Reserve.

Gutta percha, Palaquium gutta
From the chiku family, the Gutta percha (Palaquium gutta) has a sticky white sap which was previously used as a raw material for chewing gum and also used to make into linings for submarine cables. In the 19th century, the latex was destructively collected by felling wild trees, causing a lot of damage to the ecosystem. Nowadays, the latex is used as a raw material to make dental fillings. The leaves of this tree has a beautiful golden underside.

Cheng Tng (Scaphium macropodum)
These fruits belong to a Cheng Tng (Scaphium macropodum) tree. The seed, when soaked in cold water over night, or in hot water for a few hours, produces an edible jelly that is used in our local dessert, Cheng Tng.

Greater racket-tailed drongo, Dicrurus paradiseus
The canopy is home to many birds and insects, but they are more often heard than seen. The greater racket-tailed drongo (Dicrurus paradiseus) is probably the most commonly seen one, but even then it takes a pair of keen eyes to spot it. It resembles a crow except for two long rackets on the outer tail feathers. This bird is said to be a good mimic of other birds, and can produce various sounds.

The Emergent Layer

The emergent layer comprises giant trees taller than the canopy.

Red dhup, Parishia insignis
This red dhup (Parishia insignis) is one of the larger tree in Bukit Timah Nature Reserve, and it is also one of our heritage trees. The Heritage Tree Scheme was started by HSBC and NParks to protect some of our old and big trees. These tress will be given regular inspection and pruning, and will also be protected against potential lightning damages with lightning conductors.

keruing,  Dipterocarpus caudatus
Yet another forest giant was this keruing tree (Dipterocarpus caudatus) from the Dipterocarp family.

Keruing (Dipterocarpus caudatus) flowers
These are the flowers of the keruing.

Keruing (Dipterocarpus caudatus)
The keruing has seeds with 2 or 3 wings each, which germinate very quickly after they land.

Seraya, Shorea curtisii
One of the most important tree in Bukit Timah Nature Reserve must be the seraya (Shorea curtisii), since it is the dominant primary forest tree species.

Seraya (Shorea curtisii)
These are the fruits of the seraya. According to The Natural Heritage of Singapore by Hugh T.W. Tan, L.M. Chou, Darren C.J. Yeo and Peter K.L. Ng, the Bukit Timah Nature Reserve primary dryland forests are of the hill dipterocarp forest type, of which the large dipterocarp trees, which are members of the meranti family (Dipterocarpaceae), are the most common tree species. Since seraya trees are the dominant species in Bukit Timah Nature Reserve, the forest is thus further classified as seraya-ridge forests (a sub-type of hill dipterocarp forests).

Seraya-ridge forests in Peninsular Malaysia are typically found between 300-762m altitude, though on isolated mountains or coastal hills, they can occur almost to sea level. Seraya trees can grow to over 30m, and their crowns look like heads of cauliflowers when seen from afar.

The Central Catchment Nature Reserve, however, has a different type of forest called the red meranti-keruing forest, which is also a sub-type of lowland dipterocarp forests.

Natural Succession in the Primary Forest

Among the tall primary forest giants, several patches of secondary forest trees can be found, usually at the edge of the forest, along trails and roads, and also in gaps created by fallen trees. Trees in a forest may die from old age, lightning strikes, or diseases. And since the dying tree is usually linked to several other trees by wood climbers, it drags down several trees with it when it falls, thus creating a gap in the canopy, allowing sunlight to reach places where it hardly touched for hundreds of years. Grasses and shrubs will start colonising the gap, followed by sun-loving and fast growing pioneer tree species. These pioneer species are often secondary forest species. Eventually, the true primary forest species which are slow-growing will emerge and after many years, overtake the pioneer species, and the gap will be closed and the pioneer species will slowly die out.

The pulai tree (Alstonia sp.) is one of the common sun-loving plant found in forest gaps. It can be identified by its leaves with a whitish underside and parallel veins. Being fast-growing with soft and light wood, this tree is usually not highly valued for timber. Some pulai species, however, are harvested for making plywood or match sticks.

You may have noticed that the leaves above each has a pointed tip. This tip is called a "drip tip", and it allows excess moisture to run off to minimise fungal growth.

The terentang (Campnosperma auriculata) is also commonly found in gaps. The huge leaves are rather distinctive, and these trees can grow to majestic heights. However, the presence of this tree is often indicative of disturbance in the area a long time ago.

Tiup tiup, Adinandra dumosa
In the secondary forests of Bukit Timah Nature Reserve, several patches of tiup tiup (Adinandra dumosa) can be found. The tiup tiup of the tea family is a small tree bearing alternate leaves with leathery, elliptical leaf blades and almost indistinct veins. The flowers are cream-coloured with a long style each, and never open fully. The flowers are often pollinated by carpenter bees, while the fruits are eaten by fruit bats.

Interestingly, the tiny seeds eaten by the bats with the fruits are usually defecated and thus dispersed away from the parent plant about 10-15 minutes later when the bats are in flight, due to their short digestive tracts. Secondary forests dominated by tiup tiup are also called adinandra belukar, where "belukar" means forest in Malay.

Interactions and Relationships between Organisms

In many cases, relationships between organisms simply involve the passing of energy, i.e. the produer-consumer relationship or prey-predator relationships. Many plants, being at the bottom of the food chain, have thus developed various ways to protect themselves from herbivores.

For example, you may noticed that many young leaves in the forest are reddish in colour. This is due to the presence of anthocyanin pigments in the leaves, believed to serve as a warning sign to herbivores that the young leaves are toxic, since many animals prefer to eat softer young leaves to tougher old leaves. It is also believed that the red pigment may act as a sun block to prevent too much light from damaging the developing chorophyll in the young leaves.

Some other plants may lack the anthocyanin pigment, but they develop hairy structures to make them distasteful (e.g. hairy clidemia), or thorns to protect themselves (e.g. rattan).

Apart from the flow of energy, other forms of interactions between organisms occur.

benjamin's fig, Ficus benjamina
This benjamin's fig (Ficus benjamina) at the carpark near the entrance to Bukit Timah Nature Reserve harbours several good examples of interactions between forest organisms. Fig trees can be easily identified by their leaves, which have distinct lateral veins at the base forming a tighter angle with the midrib than the other lateral veins, a feature referred to as "tri-veined". All figs possess a whitish to yellowish sap, and their twigs possess paired stipules or a circular stipule scar if the stipules have fallen off.

Fig trees are very important in tropical forests as they flower and fruit frequently, thus providing the frugivorous animals with a year-round supply of food, i.e. the producer-consumer relationship. They are so important that it is believed that the number of fig trees in a forest will in turn determine the number of organisms that can be found in the forest. Some people thus call fig trees the keystone species in a forest, as they are just as important as the keystone on a bridge.

More often than not, you will find many other species of organisms on a fig tree. The one above has several bird nest ferns, staghorn fern, adder's tongue fern, other epiphytes and also several creepers and climbers on it. These plants establish a foothold on tall trees so as to make it easier for them to get the sunlight required for photosynthesis. They do not suck any nutrients off the host plant though.

Figs also share a special relationship with little insects known as fig wasps. Interestingly, the figs we see on the fig trees are actually not the fruits, but the synconia – a container for tiny fig flowers. Figs are pollinated by tiny little fig wasps. The female wasp which comes from another fig tree will force its way through a tiny hole at the base of the synconia. Inside the synconia, there are 3 types of flower - female flowers, male flowers, and gall flowers. The female wasp will pollinate the female flowers with the pollen it has collected from the previous fig tree, lay eggs in the gall flowers, and die. Little male wasp will hatch first, and they will feed on the gall flower then mate with the females, sometimes even before they are hatched. There were lots of studies on the fig wasps in recent years. Previously, it was thought that the male wasps die in the fig without seeing daylight, but recent studies on certain fig species showed that the male wasps will chew their way out of the fig, thus enlarging the exit for the females, and at the same time, act as decoy to distract any predators which outside the fig to allow the females to escape. As the females escape, they will pick up pollens as they brush against the male flowers located near the exit, and the next cycle begins as they fly to seek for another flowering fig tree. The symbiotic relationship between the fig and the fig wasp is termed "mutualism" since both parties benefit from this relationship - the fig gets pollinated, and the wasp gets food and shelter.

On the bark of the fig tree, you can also find lichen growing on it - another example of mutualism, but this time round between algae and fungus. The fungus provide the algae with water and minerals, while the algae can photosynthesize and pass on nutrients to the fungus.

Conserving Bukit Timah Nature Reserve

Our rainforests faces several serious problems, and unfortunately they are all caused by human.

Our forests are badly fragmented which makes it almost impossible for populations scattered around the various forest to exchange genes. For example, Bukit Timah Nature Reserve and Central Catchment Nature Reserve were unfortunately isolated from each other by the BKE. The expressway prevents movement of animals between the 2 reserves, and hence prevents seeds dispersal as well since many of the plants disperse their seeds through animals. Animals also won't get to exchange genes and may result in inbreeding, which can lead to animals suffering from genetic diseases and becoming extinct. Fortunately, a study is now being conducted on creating an ecological link between the 2 reserves to facilitate animal movement. Hopefully this study will result in concrete plans to build the ecological link, or else many of our plants and animals may just head down the the route to extinction in the near future.

Many people are also releasing non-native species in our forest, which compete with our native species for food and space. Most of the time, the non-native emerge as the winner, since their natural predator and diseases were not brought into Singapore with them.

Many of our native trees have also lost their dispersal agents, such as big pigeons and hornbills.

Our remaining forests are also too small to support many of our animals, and they are slowing dying out competing for the scarce resources available.

And even till this day, we still have poachers stealing fishes, birds, little animals and plants from our forests.

While several measures have been taken by the authorities to counter these problems, many Singaporeans, including some decision makers, remain ignorant of the impact that their actions could have on the fragile forest that we have. Perhaps a more extensive education programme need to be developed to educate Singaporeans to make them realise that we are all part of a bigger ecosystem, and it's not just about conserving nature, but conserving life.


Neil said...

Some more great photos, of some amazing animals. How big was the ant?

tHE tiDE cHAsER said...

The ant is about 3cm long.

EUNICEEESH(: said...

reli informative post. thankyou!

YiNG YiNG ♥ said...

Wow, what you provided certainly helped me with my Geography assigment.
Thanks for Sharing :)
Will credit you :)

Anonymous said...

Hey, you were a great help for my Bio project. I'll link you in my bibliography. Thanks so much!

Dale said...

Thanks for sharing! As an amateur botanist, I really enjoyed this informative article! I was wondering, how do you manage to identify the forest trees? Some of them are so tall that its impossible to examine their leaves.

tHE tiDE cHAsER said...

Hi Dale, I am not that good with plants actually, and so I can only identify the shorter ones that I can see the leaves and branching, or those with characteristic barks and trunks. Fallen leaves on the forest floor also help.

Dale said...

I'd say that you're really good, to be able to identify a tree based on its bark alone! Anyway, thanks for the response! I'm going to your suggestions out the next time i'm there!