Exploring Chek Jawa on Nparks Volunteer Appreciation Day

It was NParks Volunteer Appreciation Day last Sunday, and this time round, the event was hosted on Pulau Ubin.

Initially, I was hoping to reach Ubin earlier and explore a bit, but the queue for the bumboat was surprisingly long, and I ended up reaching just half an hour before the meeting time, and hence only had time to look around the volunteers' hub.


As usual, the Kemunting (Rhodomyrtus tomentosa) planted near the volunteers' hub was blooming with pretty pink flowers. This shrub is rather uncommon in Singapore, but interesting is an invasive species in some countries where it was introduced.


Here are the fruits.


After the award presentation and lunch, we moved on to Chek Jawa for a walk. At the entrance, we were greeted by a rather tamed Wild Boar (Sus scrofa). Guess the visitors were really feeding it too much, and it was obviously sniffing around us for food!


I managed to take a look at the Pemphis (Pemphis acidula). There were lots of fruits.


Most of the flowers looked like they were withering though.


I also took a look at the Lenggadai (Bruguiera parviflora) near the mangrove boardwalk, which I noticed was flowering when I was guiding here two weeks back, but didn't have the time to take photos.


There was even a crab spider which climbed onto one of the flowers.


And I also spotted an interesting-looking caterpillar.


Also near mangrove boardwalk, I noticed a Dungun (Heritiera littoralis) fruiting! Wow! My first time having decent photos of the fruits! Previously when I saw them fruiting, they were always too high up, or I did not have my camera with me. Some of my friends call it the ultraman fruit, as the fruit has this ridge-like structure running across the middle of the fruit, making it appear like the head of the TV character, Ultraman.


The Sea Almond (Terminalia catappa) trees appeared to have just shed their leaves and were growing ones.


When we reached the intertidal area, many volunteers were already down on the sandflat!


The top find of the day must be this Honeycomb Stingray (Himantura uarnak). Adults are reported to be able to grow to more than 2m long! The one we found was probably just about 1m long.


There were lots of Noble Volutes (Cymbiola nobilis) laying eggs that day! I saw at least 15 of them, and at one spot, 3 of them within a 1m radius!


There were lots of Glassy Bubble Shells (Haminoea sp.) on the soft sand. Like other headshield slugs (Order Cephalaspidea), they have well-developed headshield, which is a broadening at the head used to plow beneath the sand surface and help prevents the sand entering the mantle cavity.


We also found another headshield slug, a Philinopsis sp. Members from this genus generally feed on other headshield slugs, such as the Glassy Bubble Shells!


There were several Sandfish Sea Cucumbers (Holothuria scabra). These sea cucumbers are the same species that are usually served in restaurants, but must be treated to remove toxins in them before they can be eaten.


There were also several of this smooth and slimy sea cucumber which I am not sure of the exact ID.


Our hunter-seekers also found us a few Sand-sifting Sea Stars (Archaster typicus)! They feed on tiny organic particles among the sand, and digestion is done externally. And to do that, they have to push out their stomachs through their mouths located on their undersides, and lay the stomachs over the sand to digest the edible bits.


The Sand Star (Astropecten sp.), on the other hand, swallows its food and digest it internally. It feeds on small snails and clams.


We saw a Pencil Sea Urchin (Prionocidaris sp.) too! Unlike most other sea urchins, the spines of this sea urchin were thick like pencils (with some imagination), hence giving it its common name.


The animal above is a Pygmy Squid (Idiosepius sp.), and is only about 1cm long!


Several juvenile Mangrove Horseshoe Crabs (Carcinoscorpius rotundicauda) were spotted too, burrowing just beneath the sand surface, probably searching for little worms to feed on?

All too soon, tide was rising and we had to end the walk. We were really luck that the weather was fine throughout the entire event. Thanks to NParks for organising this! :)

Chek Jawa on 22 Nov 2010

I had initially thought that I won't be able to make it in time for the guided walk at Chek Jawa, but luckily, I managed to finish my work and rushed down to Pulau Ubin.

The group that I guided was from Shell, and they were apparently volunteering at Sungei Buloh. We took a quick walk around the Mangrove Boardwalk at Chek Jawa, before heading down the intertidal area about 5pm.


Among the first things we saw was this little Thunder Crab hiding in a dead oyster's shell! There was a myth saying that if you are pinched by a Thunder Crab, it will not let go unless there is thunder. This, of course, is not true. You just have to put it in water, and it will usually let go.


The hunter-seekers found us a few Mangrove Horseshoe Crabs, and these animals quickly burrowed into the sand when we place them on the ground. Note that they are actually not crabs (they lack the 2 big claws and has no antennae), but more closely related to spiders and scorpions. They are very ancient animals that have hardly changed for over 400 million years, and hence are called "living fossils" by some.


The Orange Striped Hermit Crab is also not a crab. Unlike true crabs which have a hard exoskeleton covering the entire body, hermit crabs have a soft abdomen. Hence, they have to hide in dead snail shells for protection.


This animal here, however, is a true crab. It is called a Leaf-porter Crab, and are usually since carrying a leaf to hide itself from predators. This one was turned upside down.

Indeed, in order to survive well in the natural environment, many animals have evolved in various manners to better protect themselves. Many of them took to hiding like the Leaf-porter Crab.


The Estuarine Seahorse is one such example. It is often found coated with sediment and this allows it to blend in nicely into the seagrass environment. This seahorse is a male, and to differentiate it from the female, you will be able to find a brood pouch on its belly. This pouch is used to carry its eggs until they hatch. Sounds strange to hear the male carry eggs, but that is the case among seahorses and their relatives. The females will deposit their eggs into the males' brood pouches, and hence both genders share the burden of reproduction.


The Carpet Eel-blenny is another animal that tries to blend into its surrounding. The greenish colour and patterns on its body camouflage it so well with the seagrass that it can be really hard to spot this animal sometimes.


This Brittle Star also lives among the seagrass, and similarly, it blends into its surrounding with its dull colours. It got its name from the fact that it breaks its arms to escape from predators sometimes. It is able to regenerate the lost arm though.


Looking rather similar to the Brittle Star will be the Sea Stars, such as the Sand-sifting Sea Star above. Brittle Stars swing their arms to move though, while Sea Stars using little tube feet located under each arm to slide around. This Sand-sifting Sea Star is often found on sandy substrates. Not only is it sandy coloured for camouflaging, it can burrow into the sand to escape predation as well. It feeds on tiny organic matter on the sand by pushing its stomach out of its mouth on the underside and digest its meal externally. Since digestion is external, it has little waste matter, which it will excrete through the anus on the topside.


Another Sea Star that burrows in the sandy area is this Sand Star. Unlike the previous one, it swallows it food (usually small snails and clams) into its stomach. The Sand Star, however, lacks an anus, and so it just expels undigested waste out of its mouth.


The Chek Jawa guided walk was conducted mainly on a sand bar surrounded by seagrass, and hence we came across many burrowing animals. The Sand Dollar above is yet another one. It has lots of little spines on its body to help it moving around and burrow into the sand.


This Sandfish Sea Cucumber also protects itself by burrowing into the sand. It also bears similar coloration with its surrounding. However, it has an additional protection - like most other sea cucumbers, it contains toxins. This is the sea cucumber that can be found in many Chinese restaurants. They must be properly processed to remove the toxins in them before they can be eaten.


Most sea cucumbers contain toxins, and the Pink Thorny Sea Cucumbers above advertised their toxins with their bright colours. The thorny structures on their bodies also make them distasteful.


Similarly, this Hypselodoris nudibranch has bright colours to advertise its toxicity. The name "nudibranch" means "naked gills", refering to the flower-like gills on the back of most species. This sea slug feeds on sponges, and is able to harness chemicals from the latter for its own defense.


One of the most well-known poisonous marine animal, however, will be the pufferfish, and we were quite fortunate today to see this Spotted Green puffer! In fact, this was my first time seeing this species of puffer at Chek Jawa! Previously, I had only seen them at Pasir Ris and Sungei Buloh. Pufferfish are poisonous enough to kill humans, and hence they must be properly prepared by licensed chefs before they can be consumed.


Sea anemones, such as the Haddon's Carpet Anemone above, use toxins in a different manner. Armed with venomous stinging tentacles, they can sting both prey and would-be predators and inject paralysing venom into them. The toxins are hence not just used for defense, but for obtaining food as well.


Related to the sea anemone is the Tube Anemone, which also has stinging tentacles. It lives in a tube it made from its own mucus and sand, and hence the common name.


The various adaptations are obviously to ensure that the animals can survive and reproduce, and we are lucky enough to witness reproduction in action during the walk - a Noble Volute laying eggs! Noble Volutes are one of the bigger snails found in Singapore. It feeds on smaller snails and clams by holding them in its pretty foot (the orange and black part) to suffocate them.


All too soon, we had to end the walk. But not before we had a quick group photo! Glad to have an enthusiastic group of nature lovers with me during this walk! And if any of you are here, just click on the group photo above to get the bigger version for downloading! :)

Back Guiding at Chek Jawa

It's been a while since I last went to help out at Chek Jawa, so I was quite glad that I finally managed to find time to do so.


When I reached the Ubin Volunteers' Hub, I was surprised to see the area next to the hub covered with Rattlebox plants (Crotalaria sp.). Guess that shows I really have not been here for a while. And on the flowers, I found a number of these pretty moths.


I have not seen these kind of day-flying moths before. Two of them here.


And here are three of them. Didn't realised the plants were Rattlebox plants until KS Wong told me. The usual ones I saw came with compound leaves with three leaflets. Apparently there were quite a few species of Rattlebox plants in Singapore.


There were a few Pea Blue (Lampides boeticus) butterflies resting on the Rattlebox plant, which was supposed to be their host plant. I saw a number of caterpillars feeding on the leaves, which I assumed should be Pea Blue caterpillars.


There were also a few Blue Glassy Tiger (Ideopsis vulgaris macrina).

Soon, all the volunteers arrived, and we made our way to Chek Jawa.


And greeting us was the resident Wild Boar (Sus scrofa).


Thanks to Terry, who decided to guide on my behalf, I got to do hunting-seeking, something which I have not done for quite sometime at Chek Jawa. While heading to the intertidal area, I noticed that the Mata Ayam (Ardisia elliptica) were fruiting! "Mata" means "eye" and "ayam" means "chicken", and this plant was so named supposedly because the fruits appeared like chicken eyes.


The first animal I spotted was this female Flower Crab (Portunus pelagicus) among the seagrass. Seagrass meadows are very important habitats for many marine animals, many of which can be eaten by human, such as this Flower Crab. This crab is a type of swimming crab, characterised by the paddle-like back legs, which allow them to swim rather quickly.


Also in the seagrass meadow, I found this Crenate Swimming Crab (Thalamita crenata). Related to the flower crab, it also has paddle-like back legs, and is also edible. I have seen fishermen collecting them when I was in Bali. It was quite aggressive, and kept flashing its claws whenever I got near to it.


But the top swimming crab I found must be this Orange Mud Crab (Scylla olivacea) that was initially half-buried in the sand in the seagrass meadow. It was humongous! I found two of them but only took one to show the visitors.

So I guess you can imagine that without seagrass meadows, many of the seafood we love will be gone too.


While seeking for interesting animals, I came across this Orange Striped Hermit Crab (Clibanarius infraspinatus), which has climbed out of its shell. Not sure why it climbed out of the shell though. Unlike true crabs which have a hard exoskeleton all over, hermit crabs have a soft abdomen and hence they hide in the shells of dead snails, such as the Noble Volute above, for protection.


Here's a living Noble Volute (Cymbiola nobilis). Found 3 of them during this trip. This huge snail hunts for other smaller snails or clams to feed on. They will wrap their muscular foot around the prey to attempt to suffocate them. When the snail or clam emerge to breathe, the volute will feed on them.


Yet another predator of smaller snails and clams is this Pear-shaped Moon Snail (Polinices mammilla). Note only can it wrap its prey with its huge foot, it can also secrete an acid to soften the prey's shell, and using its radula (something like a tongue) to slowly create a hole through the shell to feed on the animals inside.


There were a few Haddon's Carpet Anemones (Stichodactyla haddoni) on the sand bar. This one was quite big, more than 30cm wide. Like other sea anemones, it uses its stinging tentacles to sting and capture prey.


It's definitely a Sandfish (Holothuria scabra) day, as I saw so many of them! This is the sea cucumber that we normally find in Chinese restaurants. Note that they must be properly treated by people who are trained to remove the toxins in them before they can be consumed.


We saw a few other types of sea cucumber, but one of the prettier ones must be this one which we called the Pink Thorny Sea Cucumbers (Colochirus quadrangularis). It's also seasonally abundant, and sometimes we can see hundreds of them!


As usual, there were lots of Sand Dollars (Arachnoides placenta) at the sand bank. They feed on tiny algae or other organic matter among the sand.


The only star of the day was the Sand Star (Astropecten sp.). It used to be very abundant here, but possibly because nowadays we are seeing less button shells and small clams here that they feed on, and hence their population here appeared to be going down as well.


After my hunting-seeking duties, I managed to run over to take a look at the Pemphis (Pemphis acidula), a mangrove plant that is critically endangered in Singapore.


Here's a look at both the fruits and the flowers. This plant is commonly used as a bonsai plant in the region, and in some places, are over-collected because of that. The seeds are dispersed by water.

Sure hope that I will soon see more of this plant around, since it appeared to be fruiting quite well! :)