Chek Jawa Walk on 15 April 2009

It's been a few months since I last guided at Chek Jawa, due to my tight schedule. The last time I signed up to help with the guiding, it rained very heavily and the walk was cancelled, and thus I was really glad that the weather was fine today.


I guided the group with JL, the man who brought Chek Jawa to the attention of scientists and volunteers, and I have certainly learned quite a few new things about guiding and the organisms found at Chek Jawa from him :)


One of the first few animals we saw was this Green-crested Lizard (Bronchocela cristatella). This stunning green lizard is a native animals, and blends into the surrounding very nicely. I'm always amazed by the way that it stretches its legs in all directions - it's definitely the "yoga master" in the animals world! :P


As we walk along the boardwalk, we saw lots of Orange Fiddler Crabs (Uca vocans). The above are male crabs, each with an enlarged claw. The big claw is used for hunting or attacking predators, but for attracting females.


We had to climb down the floating pontoon to get to the intertidal area.


The first thing which caught my attention when we got down was this Tube Anemone (Order Ceriantharia). This animal filters plankton and tiny organic particles from the water to feed on. They come in various colours, and thus they were sometimes also called Peacock Anemones.


A Sand Star (Astropecten sp.) was found just next to the ladder. This sea star can burrow, and feeds on small snails and clams. It is quite common on our northen shores, and I sometimes see hundreds of them during my trips.


The Orange-striped Hermit Crab (Clibanarius infraspinatus) is a huge hermit crab commonly found among seagrass habitats in Singapore. Like other hermit crabs, it has a soft and long abdomen, which is why it needs to hide it in an empty shell.


A few sea cucumbers were spotted, including the slimy sea cucumber above which we were still not sure of the ID, and also the Sandfish Sea Cucumber (Holothuria scabra).


On the sandbar, there were lots and lots of sand balls made by Sand Bubbler Crabs (Scopimera sp.). This crab feeds on tiny organic particles on the sand, and the processed sand was discard in the form of small sand balls. It usually will not venture to far from its burrow, in case there are predators so that it can quickly run and hide in side.


I was quite happy to see this Noble Volute (Cymbiola nobilis) laying eggs! This is a good sign that our shores are still very much alive and the conditions must be right - that's why the organisms are reproducing.


After making one round around the sand bar, we left the intertidal area for the Mangrove Boardwalk, and saw that the wild Delek Air (Memecylon edule) in the coastal forest are blooming with pretty bluish-purple flowers!


At the edge of the mangrove were the Nipah Palms (Nypa fruticans). I used to live in a kampong when I was young, and the house I lived in had roofs from Nipah leaves, otherwise also called Attap leaves. The fruit of this palm also gives us the attap chee we get in the ice kacang desert.


The Tumu Putih (Bruguiera sexangula) is very rare in Singapore, and Nparks have planted a few trees at Chek Jawa. The bigger seedling that I saw during my previous trip here was gone though, but I still see a few of the smaller ones.

We soon ended the guided walk, and fortunately, it only started raining then!


After the walk, RH and I took the bumboat back to Mainland Singapore.


On reaching Changi Point Ferry Terminal, we saw this huge prawn swimming near the water surface, and it appeared to be gathering the fallen stems of Casuarina Trees (Casuarina equisetifolia). Why is it doing this? Hmm...

The Other Side of St. John's Island

Due to the recent rockfall at the intertidal reef that we usually visit at St. John's Island, some of us RMBR Nature Guides decided to check out the shore on the other side of the island to see if it's possible to conduct a guided walk there.

It was mostly a rocky shore, with very few corals, and thus the diversity of marine life was somewhat not as rich as the usual shore that we visit.


Most of the hard corals we saw were really huge though - the one above probably close to a metre wide - indicating that they were probably very old colonies since most corals grow quite slowly.


Among the rocks and few corals, the many Black Sea Cucumbers (Holothuria leucospilota) were probably the most conspicuous.


SY found this Diamond Wrasse (Halichoeres dussumieri) which got itself stranded on some Bryopsis seaweed.


There were quite a number of Land Hermit Crabs (Coenobita cavipes) on the upper shore. These hermit crabs are very much adapted to living on land, and may in fact drown if kept underwater.


Several Branched Anemones (Phymanthus sp.) were spotted as well. Like other sea anemones, they have stinging cells in their tentacles to sting and capture small animals to feed on.


Seeing a Flatworm (Pseudobiceros uniarborensis) swimming always fascinates me, as it is so graceful as it flaps the sides of its mantle!


I found this small Black Long-spined Sea Urchin (Diadema setosum) in a tidal pool. This sea urchin feeds on algae, and its mouth is located underneath.


Since it was a rocky shore, I wasn't surprised to find several Giant Top Shells (Trochus niloticus). These huge shells are collected for food in the region, and also, the shells can be made into pretty glossy buttons when polished.


Another top shell spotted was this Thick Lipped Top Shell (Monodonta labio). Top shells generally feed on algae on the rocks.


Drills (Thais bitubercularis) were found on the rocks too, probably feeding on barnacles. They feed by secreting carbonic acid to soften the shell of the barnacle, and drill a hole through it with their radula.


I'm not entirely sure what snail this is. Could it be a limpet? Guess will have to check with SK again and update later. Update: This is indeed a limpet, Cellana radiata. It is moderately common among breakwater rocks.


Lightning Dove Snails (Pictocolumbella ocellata) were a common sight on most rocky shores of Singapore. These snails feed on algae.


SY found this Spotted-belly Crab (Ozius guttatus) which has very strong pincers, allowing it to crack snails shells to feed on the snail within.

Other than the animals, we found several interesting plants too!


The Beach Gardenia (Guettarda speciosa) was blooming with its pretty and fragrant white flowers.


The Sea Daisy (Wedelia biflora) is a native coastal plant related to the sunflower.


Several Geiger Trees (Cordia sebestena) were planted on the island, and most of them were blooming with bright orange trumpet-shaped flowers.


The fruits of the Geiger Tree turned white as they mature, and is said to be edible.


On one of the Geiger Trees, I found a Mistletoe (Dendrophthoe pentandra) growing on it. Mistletoes are hemi-parasitic plants which can photosynthesize, but at the same time, leech nutrients from the host plants they were growing on. D. pentandra is known to be a butterfly host plant to the Painted Jezebel (Delias hyparete metarete).

While the biodiversity of this shore may not be as high as the one which had the rockfall, it was a good trip nonetheless! :)