Wednesday, August 15, 2012

Chek Jawa Wetlands at Pulau Ubin

Chek Jawa Wetlands is a 100-hectare protected nature area managed by the National Parks Board of Singapore. It is located at Tanjong Chek Jawa at the eastern coast of Pulau Ubin, an island off the northeastern coast of Singapore.

"Chek" can be short for "Encik", which means "uncle" or "sir" in Malay, or "macik" which means "madam" or "auntie". "Jawa" refers to "Java", an Indonesian island. Hence, it is believed that Chek Jawa was named after a person from Java who used to live in the area.

The area is home to a wide variety of coastal life, but was virtually unknown to scientists until late 2000. And ironically, it was partly due to the reclamation plans that the area's rich biodiversity got discovered. The reason being that there used to be a Chinese village occupying the area (and before that a Malay kampong), and since the area was private property, outsiders could not easily access the area. In the late 1990s, the villagers were relocated to other parts of the island or mainland Singapore as the government planned to develop and reclaim the area, and hence it became easier for members of the public to access the area. In December 2000, field botanist, Joseph Lai, brought a group of students there for a nature outing, and after seeing the rich biodiversity of the area, decided to bring it the attention of other nature lovers and biologists.

News travelled fast, and soon more nature lovers visited the area, and scientists from the National University of Singapore and volunteers from various nature groups did a survey of the flora and fauna of Chek Jawa. Several requests from various groups to postpone the reclamation plans were submitted to the government, and eventually in December 2001, the government surprised many when they acceded to the requests. On 7 July 2007, the visitor centre and boardwalk were officially opened, and the area was renamed as Chek Jawa Wetlands.

To visit Chek Jawa, you will need to take a bumboat from Changi Point Ferry Terminal to reach Pulau Ubin, and then either walk, cycle or take a van to reach Chek Jawa Wetlands. More details and the map of the island can be found at National Parks Board Website.

Dos & Don'ts
  1. If you intend to go down to the sand bar to look at the marine life, you will need to join the walks organised by NParks. Please do not go onto the shore on your own, as you may end up trampling on the fragile marine life. Without joining the walk, however, you can still walk on the boardwalk and check out the exhibits at the visitor centre.
  6. Bring water and some light snacks. There are vending machines at the visitor counter, but to play safe it is best to come prepared in case there is no power or breakdowns.
  12. Do not ride your bicycles onto the boardwalk, as you will be causing damages to it, and may also accidentally run over the wildlife.
  13. If you are joining an NParks guided walk, take note of the following:
    1. Please wear covered shoes, such as diving booties, water shoes, school shoes or old sport shoes for the shore exploration. No slippers or sandals will be allowed on the shore, as there could be sharp rocks, muddy ground and poisonous organisms.
    2. Be prepared to get your shoes wet and muddy, as there will be puddles of water along the trail and the ground may be soft.
    3. Bring an extra pair of shoes/sandals to change into after the shore exploration, as your original footwear will be wet by then.

What to Expect at Chek Jawa Wetlands

This is just a quick introduction to some of the things that you can expect to see at Chek Jawa. Definitely, you can expect to see a lot more on your trip there, preferably with a guide who can point out and tell you more about the things found here!

The gate to Chek Jawa Wetlands is located near Punai Hut, and even before you enter the gate there are several interesting things to see.

The area used to be a rubber plantation, and hence there are still many Rubber Trees (Hevea brasiliensis) there. If you are lucky, these deciduous trees may be shedding their leaves, and you can see the leaves in pretty colours of yellow or orange. The latex of these plants is still used to be made into erasers, rubber bands, toy balloons and tires.

Wild boars (Sus scrofa) can also be easily seen here. They are omnivores, feeding on young plants, roots, fruits, worms and grubs. Do remember that these are wild animals, and must be treated with respect - do not attempt to try to touch them, as they may feel threatened and get aggressive. Also, do not feed them, as they have enough food in the forest, and feeding them will "train" them to rely on human for food.

Sometimes, you may also see the Long-tailed Macaques (Macaca fascicularis). Please do not feed these monkeys as well if you see them. Once they have become more dependent on human for food, they may become more aggressive and even snatch food from people or attack them for food. If we leave them alone, they will leave you alone too.

On the trees, the Common Flying Dragons (Draco sumatranus) are sometimes seen. Also known as gliding lizards, they have a flap of skin extending from each side of their bodies, supported by their long ribs. They are able to glide from place to place by spreading out its ribs (somewhat like opening a folding fan) to form a gliding surface.

Leaving Punai Hut and walking through the gate, you will enter a trail in the middle of a secondary forest.

By the sides of the forest trail are many Jarum Jarum (Ixora congesta). "Jarum jarum" means "many needles", refering to the bunches of flower buds before they bloom, which appear like balls of needles.

Fishtail Palm (Caryota mitis)

The Golden Orb Web Spider (Nephila pilipes) is also easily seen here when it is in season. This spider builds one of the biggest spider webs in the world up to several metres wide! It got its name from the yellowish coloured web that it builds.

Occasionally, you can see the Oriental Whip Snake (Ahaetulla prasina) on the trees or shrubs along the way to the wetlands. These snakes are mildly poisonous, but are harmless to humans.

On reaching the visitor counter, you can turn left into a kampong trail. As mentioned earlier, there used to be a Chinese village at Chek Jawa, but before that, there was a Malay kampong here, evident from the Malay cemetery along the trail. It is said that the tall tombstones are for adults while the short ones are for children. There are also several wells at Chak Jawa, left from the old kampong. The previous villagers planted many fruit trees, and some of them are still growing well here!

The King of Fruits, the Durians (Durio spp.), is one of them. If you come in the middle of the year or the beginning of the year, you may even see the fruits hanging from the branches!

Apart from the King of Fruits, you can find the Queen of Fruits - the Mangosteen (Garcinia mangostana) - here too! It is said that the number of "petals" of the flower-shaped structure seen at the base of the fruit is the same as the number of compartments of edible flesh within the fruit.

Another fruit tree found here would be the Rambutan (Nephelium lappaceum), which is critically endangered in the wild, but commonly planted in kampong areas. In Malay, "rambut" means "hair", and the fruit's name is derived from the fruit's hairy appearance.

A few Starfruit (Averrhoa carambola) trees can be seen here too. The name was derived from the fruit's star-shaped cross-section. The edible fruits are highly nutritious, containing several antioxidant, minerals and vitamins, but unfortunately also contains oxalic acid which is harmful to people with kidney problems.

Moving further down the trail, we will start encountering a few native plants.

This curious-looking plant is called the Serengan (Flemingia strobilifera). The brownish things you see above are neither the fruit nor flower. They are modified leaves called bracts. If you open up the bracts, you will be able to find the little flowers (in green bracts) or fruits (in dried brown bracts) in them. The dried bracts are somewhat bouncy and very light, and are used for stuffing pillows and cushions in some places. The Malay name is derived from the word "rengan", which means "light-weight", refering to the bracts.

Senduduk (Melastoma malabathricum)

Mata Ayam (Ardisia elliptica)
The Mata Ayam (Ardisia elliptica) can also be found here. "Mata" means "eye", while "ayam" means "chicken", refering to the fruits which are about the size of a chicken eye. Like many other coastal plants, the Mata Ayam has thick leathery leaves to retain water, since the coastal environment is usually very dry, being exposed to the land and sea breezes which increase the rate of evaporation.

You can turn left to head into the mangrove boardwalk, which is about 500m long.

Near the beginning of the boardwalk is Jejawi Tower. The tower is 20m tall and can take a maximum of 40 people. It was named after the Jejawi Tree, also known as the Malayan Banyan (Ficus microcarpa), growing nearby that is as tall as the tower. The Malayan Banyan is a fig tree. As fig trees produce figs very regularly, they are able to provide regular food supplies for all kinds of animals such as birds and monkeys, unlike other forest trees that fruit perhaps once a year or even once every few years. In fact, such large fig trees play a critical role in providing food and shelter, and studies suggest the number of such fig trees limit the number of animals found in a forest.

Nipah Palm (Nypa fruticans)

Buta-buta (Excoecaria agallocha)
Another common mangrove tree that can be seen here is the Blind-your-eyes (Excoecaria agallocha). The sap of this tree can cause blisters if it touches your skin, and may even cause blindness if it gets into your eyes.


Sea Holly (Acanthus spp.)
A plant that can be found growing on mud lobster mounds is the Sea Holly (Acanthus spp.). It gets its common name from the shape of its leaves, which resemble those of the holly.

An animal commonly seen on mud lobster mounds is the tree-climbing crab (Episesarma sp.), which usually dig burrows into the mounds or at the base of trees. During high tide, you may encounter many of them climbing up to trees to avoid the predatory fishes in the water. Tree-climbing crabs are primarily leaf-eaters. They are also called vinegar crabs, because the Teochews are known to pickle this crab in black sauce with vinegar. By the way, I'm a Teochew, and I've eaten this when I was young actually, but don't exactly like it.

And among the muddy areas between the mounds, animals like this Blue-spotted Mudskipper (Boleophthalmus boddarti) can be found. Mudskippers got their name because they have very muscular tails which allow them to skip over the mud. They are able to survive out of water by holding water in their mouths and gill chambers. They can breathe through their moist skin too. The Blue-spotted Mudskipper grazes on the algae and edible organic particles by moving its mouth sideways over the mud.

The Giant Mudskipper (Periophthalmodon schlosseri) can also be found here, and unlike the previous mudskipper, this is a predator that feeds on other small animals, such as crabs and insects. This is also the largest mudskipper in Singapore. You will noticed that all mudskippers are rather dull-coloured, so as to blend in better with the muddy surroundings. The eyes are on top of their heads so as to give them a good view of the surroundings.

It is likely that you come across one or two Malayan Water Monitor (Varanus salvator) as well. This is one of the top predators in the mangroves, and eats almost anything that it can fit into its mouth, alive or dead. While it has a weak venom, it is not known to be venomous enough to kill humans, but the bacteria in its mouth may cause serious infection if it ever manage to set its teeth on you. You don't have to be paranoid though. The usual rule of thumb with wild animals is as long as you leave them alone, they will leave you alone. So please respect these wild animals and do not disturb them.

Bakau Kurap (Rhizophora mucronata)
The mangrove is a very harsh environment to live in. The soil is very poor in oxygen and very unstable, which is why many of the trees have roots exposed to the air to take in more oxygen, and the roots often spread over a wide area to allow the trees to stabilise themselves on the soft mud. The Bakau trees (Rhizophora spp.) above have prop and stilt roots to serve the above functions. The wood from this tree can be made into charcoal or furniture.

Bakau Putih (Bruguiera cylindrica)
One of the most common mangrove trees in Singapore is the Bakau Putih (Bruguiera cylindrica). Like the other Bruguiera species, it has exposed kneed roots. Both the Rhizophora and Bruguiera mangrove trees demonstrate vivipary, a condition whereby the young plant within the seed grows first to break through the seed coat then out of the fruit wall while still attached to the parent plant. Since the mangrove habitat is a very harsh environment, these plants have adapted such that the parent plants prepare their young as much as possible to increase their chances of survival.

Perepat (Sonneratia alba)
The Perepat (Sonneratia alba) has cable roots radiating from the tree underground arise at various intervals to form conical protruding roots. Like the roots of the Bakau Trees, these roots help the plant breathe air, which is scarce in the waterlogged soil. The roots spread over a wide area to help stabilise the tree on the unstable ground. The fruits and leaves of this plant are edible, while the wood is used for various construction purposes, such as the construction of buildings, bridges, boats, wooden tools and furniture.

Another harsh condition faced by mangrove plants is that they will be soaked in salt water, which can remove water from the plant tissues through osmosis. To deal with this condition, plants like the Rhizophora, Bruguiera and the Perepet can selectively absorb only certain ions from the sea water through a process called ultrafiltration. But this process is not 100% effective, and some salt still gets into the trees, and will be removed by transpiration of the leaf surfaces or accumulated in old leaves.

Api-api Putih (Avicennia alba)
The Api-api (Avicennia spp.) above and the Sea Holly, on the other hand, use another method known as salt secretion. They excrete salt with the salt glands on the leaves as the plants were expending energy. "Api-api" means "fire-fire" or "firefly" in Malay, as some Avicennia species are noted to attract fireflies.

As the boardwalk winds and turns, you will eventually leave the mangrove and enter the seashore section, otherwise known as the coastal boardwalk (600m long).

Sea Hibiscus (Talipariti tiliaceum)
The Sea Hibiscus (Talipariti tiliaceum) can be found at the beginning of the coastal boardwalk. It is a common coastal tree with heart-shaped leaves. The flowers are yellow, turning orange or red towards the end of the day, and will be shed usually by the next day. The fibre from the bark is used to make ropes and caulk boats.

The Fiddler Crab (Uca spp.) can also be found here. A male fiddler crab has an enlarged claw, which it waves the claw to attract the females and to ward off other males. Fiddler crabs feed on detritus, which are basically tiny bits of organic particles, and the male can only feed with its small claw (the big one is too cumbersome) and as it is feeding, it looked like it's playing a fiddle, and hence the common name. The females have two small equal-sized claws, and thus can eat faster - for a good reason as they need to lay eggs.

As you head further onto the coastal boardwalk, you will start to notice some huge rocks to your right. They are granite, and basically much of the island is made up of granite. Even the name of the island, "Ubin", means "tile" or "squared stone", as refering to the granite on the island which was used to make floor tiles.

Lots of Oysters (family Ostreidae) can be seen growing on the rocks. Oysters stick themselves to rocks with a strong glue. Being filter feeders, they open their shells slightly during high tide to suck in water and collect edible particles. At low tide, they will shut their shells tightly.

There are usually lots of drills (Thais sp.) and sometimes, their egg capsules on the rocks as well. Drills normally feed on barnacles and other shells by secreting an acid to soften the victim’s shell before boring a hole through it with its radula (something like a tongue). Their egg capsules turn purple when the eggs hatch.

You may also find little purple climber crabs (Metopograpsus sp.) creeping over the rocks. This crab usually scavenges for dead animals on rocky shores, though they hunt small animals and feed on algae as well.

Meanwhile, on the left you will see a lush seagrass meadow. Seagrasses are flowering plants, and they are also the only plants that can survive entirely submerged in sea water. Seagrasses are very important as they provide lots of food and shelter for marine animals, and hence many marine animals also treat seagrass meadows as their nursery. Like the plants on land, they also help to return oxygen into the atmosphere as they photosynthesize, and acts as carbon sinks.

Many different types of seaweed can also be found here. Unlike seagrasses, they are algae and do not flower. Also, they do not have proper roots to absorb nutrients from the ground, but have simple structures call "holdfast" to hold onto rocks and other structures. Many animals also feed on seaweed, making them an important part of the ecosystem too.

Several Haddon's carpet anemones (Stichodactyla haddoni) can be found among the seagrasses and seaweed. These sea anemones have sticky tentacles which sting small animals that have gotten too close to them. The tentacles will then transport the prey, acting like a conveyor belt system, to bring it to the centre of the animals where the mouth is located.

Flower Crabs (Portunus pelagicus) are often sold at our local markets, but do you know they are quite common in our waters? This crab is a type of swimming crab, characterised by the paddle-like back legs, which allow them to swim and burrow rather quickly. Their spiky claws help them to have a good grip on their prey, which are usually small fishes.

Occasionally, the Mangrove Horseshoe Crab (Carcinoscorpius rotundicauda) can be found creeping among the soft and muddy areas among the seagrasses. Horseshoe crabs are very ancient animals, and are said to have been around for more than 400 million years! They have an interesting way of dealing of bacterial infection - their blood will the bacteria and become gel like. Scientists these days use a substance extracted from the blood to test for bacteria on surgical instruments and also some drugs. And scientists from NUS have developed a way to clone this substance, so that we do not have to harvest from the wild as much.

The Noble Volute (Cymbiola nobilis), a large sea snail, can also be found here, and sometimes, they can be seen laying eggs - a very good sign indicating that these snails were doing well here! This snail is a fierce predator of clams and other smaller snails. It will embrace its prey with its huge foot to attempt to suffocate it. When the prey eventually opens up to breathe, the volute will feed on it.


If you head towards the floating pontoon, you will reach a sand bar. Those who join the NParks guided walks will be able to get down onto the sand bar here to see the animals close up, and get to touch them too!

As you get onto the sand bar, you will notice lots of sand balls made by Sand Bubbler Crabs (Scopimera sp.). This crab feeds on tiny organic particles on the sand. As they extract the food particles, the processed sand was discarded in the form of small sand balls.

sand-sifting star (Archaster typicus)
The Sand-sifting Star (Archaster typicus) can also be found on the sand bar. This is possibly the most common sea star in Singapore, and hence many nature guides also call it the common sea star. It has many common names though, but I personally prefer to call it the Sand-sifting Star, as I thought the name itself tells the story of how the sea star behaves - it sifts among the sand to avoid predation and to forage for detritus to feed on.

thorny sea cucumber (Colochirus quadrangularis)
At the edge of the sand bar among the seagrass, soem sea cucumbers can be found. This Thorny Sea Cucumber (Colochirus quadrangularis) appears to be seasonally abundant. It is a suspension feeder which gathers tiny food particles from the water with its colourful tentacles.

sandfish sea cucumber (Holothuria scabra)
The Sandfish Sea Cucumber (Holothuria scabra), one of the most commercially valuable species found in local waters, is quite common here. Often eaten as a delicacy in Chinese restaurants, they are sometimes over-harvested in the areas where they can be found. This species burrows into the sand, using their oral tentacles to gather tiny food particles in the sand. Their sand-like coloration allows them to camouflage with the surrounding sand.

sand dollar (Arachnoides placenta)
There are usually lots of Sand Dollars (Arachnoides placenta), which are basically "compressed" sea urchins, on the sand bar. They feed on tiny algae or other organic matter among the sand. They are covered with hair-like. movable spines which help them to move around and burrow.

Further away from the sand bar along the boardwalk is the coral rubble area, with lots of dead corals and fragments. There is a beacon there, and if you look back, you may notice another beacon among the trees on the coastal hill. At night, when the boat captains see that the lights from both beacons are aligned, they will know that they can avoid the shallow waters by sailing perpendicular to the aligned beacons.

Lots of colourful sponges (Phylum Porifera) can be found here. Sponges are simple animals which has lots of tiny holes and a few bigger holes on them. To feed, they suck water through their tiny holes and they will pick out the edible particles. The filtered water will then be pushed out of the big holes. Do you know that bathroom sponges used to be made from certain species of sea sponges? Nowadays most sponges were made from petroleum though. Take note that most sea sponges are poisonous and contain tiny glass-like bits though, and are not suitable to be made into bathroom sponges.

The Knobbly Sea Star (Protoreaster nodosus) is one of the bigger sea stars found at Chek Jawa, and some can be more than 35 cm wide! This is perhaps also one of the prettier sea stars, as they occur in various colours, ranging from bright red, orange and pink to dull colours such as brown and beige. They have a hard, calcified body with large nodules on the top surface, which protects them from most predators except fish with sharp and powerful teeth, such as pufferfish and triggerfish. Indeed, every now and then I will see individuals with broken nodules or arms. Despite the big size, this sea star feeds mainly on microorganisms, although it has also been observed to feed on snails, clams, soft corals and sponges.

Several nudibranchs (clade Nudibranchia) can be found in the coral rubble area. The term "nudibranch" means "naked gills", refering to the exposed flower-like gills on the back of most species. They are sea slugs - sea slugs are basically snails with very reduced shells, internal shells or no shells at all. Many nudibranchs are toxic, deriving the toxins from their prey, such as sponges. Like other sea slugs, they are hermaphrodites with both male and female reproductive organs. To mate, they usually get into a "69" position side by side and fertilise each other. The reproductive organs are located behind the head on the right side.

Several species of Marine Flatworms (class Turbellaria) can also be found here. Being very flat, the flatworms can easily slide into small cracks and gaps among rocks to seek for food and hide from predators. Some of the bigger species can also swim by flapping the sides of their body.

If you are lucky, you may even see the Smooth Otters (Lutrogale perpicillata)! This otter species is the largest in Southeast Asia. They got their common name from the smooth coat of fur.

And in the distance, you can see Pulau Sekudu, also known as the Frog Island. According to local myth, a frog, a pig and an elephant had a swimming competition across the Johor Strait. The frog were drown first and formed Pulau Sekudu. The pig and the elephant didn't fare much better, and soon were drown together to form Pulau Ubin.

Towards the end of the boardwalk, a few big trees can be seen.

Penaga Laut (Calophyllum inophyllum)
Among them is the Penaga Laut (Calophyllum inophyllum). The genus name of this critically endangered tree, Calophyllum, means "beautiful leaf", refering to the nice and glossy leaves with very fine veins. The wood of this tree is very hard and is used in construction and making furniture. Oil extracted from the seed is used as hair grease and bio-fuel. Most part of this plant, including its fruit and sap, are poisonous. It is sometimes planted as a shade tree.

Seashore Nutmeg (Knema globularia)
There are also a few Seashore Nutmegs (Knema globularia), also a locally critically endangered tree. The fruit is eaten and the seeds dispersed by big birds with strong stomachs, such as hornbills or large pigeons. The oil from the seed is used to treat skin infections, for making medicinal soaps and cosmetics, and to counteract putrefaction.

Sea Almond (Terminalia catappa)
As you move onto the coastal forest trail, other plants, such as the Sea Almond (Terminalia catappa) can be found. This common coastal tree is commonly planted as a wayside tree in Singapore. It is deciduous, shedding its leaves twice a year. The leaves turn orange or red before they are shed. The branching is somewhat layered horizontally (hence they are also called pagoda tree). The kernel of the fruit is edible, and taste somewhat like almond, hence the common name.

Nparks has also put up a nest box for the Oriental Pied-hornbill (Anthracoceros albirostris) on one of the trees along this trail. The Oriental Pied-hornbill were believed to have gone extinct in the early 1900s in Singapore, and the existing population were thought to be the descendants of those which have flown over from Johor to settle down on Pulau Ubin in the 1990s. Breeding was first recorded in 1997 on Pulau Ubin, and since then, several of them have flown over to settle down in Changi.


The forest trail will lead you back to the visitor counter, and if you turn left, to the Chek Jawa Visitor Centre. This building is also call House No. 1, which is its postal address in Pulau Ubin. This unique building was built in the 1930s for Langdon Williams, the then Chief Surveyor, as a holiday retreat. It is made of masonry and emulates the style of an English cottage, first found in tea planters’ residences during the British colonial era. The building was awarded conservation status on 1 December 2003, and restoration work of the building was completed in 2006. The toilets and washing points are also here, and there are also some exhibits in the building. You can also go down to the long jetty beyond the visitor centre to get a closer look at Pulau Sekudu!

Conserving Chek Jawa

The development plans for Chek Jawa have been postponed, but should the day come when there is a shortage of land or there are strong reasons to develop the area, Chek Jawa will not be spared. As such, it is important that more Singaporeans visit and get to know this nature spot better, so that when the time comes they can feedback to the government to protect the area.

It is also important the visitors do not leave any rubbish behind, as animals may end up eating or getting trapped in them.

In addition, do share your experience with your friends so that more people get to know and visit Chek Jawa. And if you have the time, become a volunteer to help with conducting guided walks here!

1 comment:

L Lee said...

Wow what an informative post with great photos - you must have spent many days there to capture such good pictures of the flora and fauna. Thanks for sharing!