Monday, August 20, 2007

The Great Flood at Chek Jawa

NF#1: In January 2007, Singapore experience some of the heaviest rainfall in 75 years. The rain was just as severe in Johor, and the Johor River was bloated with rain water, which it eventually released into the Straits of Johor.

NF#2: On 18 January 2007, there was a public walk at Chek Jawa, and Adelle from Nparks informed the other regular guides that a lot of animals have died. We suspected that due to the heavy rainfall, Chek Jawa was flooded with freshwater, and it is known that most marine animals could not survive well in water with low salinity. Animals like the carpet anemone simply exploded from taking in too much freshwater, others like sea stars and sponges turned black and died, and many of the snails just died and decomposed into black liquid in their shells.

An exploded carpet anemone.

A dead knobbly seastar.

A decomposed noble volute.

NF#3: Kok Sheng from NUS is conducting a study on the mass mortality and recruitment of macrofauna for example like carpet anemones. This project also lays the foundation for the long-term monitoring and understanding of Chek Jawa.

More information at:
- 18th January
- Death Note from Chek Jawa
- First TeamSeagrass Field Orientation at Chek Jawa
- Chek Jawa Mortality and Recruitment Project

Chek Jawa Boardwalk

NF#1: The CJ boardwalk was constructed in about 18 months, but the impact on the rich seagrasses and sandflats was minimal. This is because the barge only brought in the construction material for the workers to do the piling during high tide, and when the tide got lower, it returned to deeper waters.

Interesting note: We started seeing oysters, mussels and barnacles on the pillars just weeks after they were placed! And we had seen healthy sea anemones growing just next to the pillars! The public walks were only suspended when the floods in January 2007 caused the massive mortality.

Question for Visitors: What material do you think the boardwalk is made of?

NF#2: While the boardwalk looks like it was made from wood, it was actually made from concrete and fibre glass! The mold used to make the boardwalk was made based on real wooden planks.

NF#3: The entire boardwalk is 1.1km long and has 2 sections - the coastal section (600m) and the mangrove section (500m).

Friday, August 17, 2007

Legend of Ubin and Pulau Sekudu

Naked Fact #1:
Three animals from Singapore -- a pig, an elephant and a frog -- had a challenge to see who would reach the shore of Johor first. Whichever animal that failed to reach the shore would be turned into rock. All three creatures had difficulties swimming the Straits and the frog turned into Pulau Sekudu, while both the pig and the elephant changed into one big rocky island - Ubin.

Naked Fact #2:
Pulau Ubin is originally bisected down the middle by the river Sungei Jelutong. However, due to prawn farming over the decades, the island has been joined together by the mud bunds across the river that form the prawn ponds. Perhaps that would explain why 2 animals form the bulk of Ubin.

Naked Fact #3:
The islet off Ubin that can be seen from Chek Jawa is named Pulau Sekudu which means Frog Island. There is a rock on Pulau Sekudu that resembles a frog. In fact, a smiley face has been painted on the "face" of the rock. However, it looks most like a frog from its side profile.

CARE Message:
Understand and respect the tides.
Pulau Sekudu, like much of the inter-tidal areas of Chek Jawa, is only accessible at low tide. However, the tides can be unpredictable and dangerous especially when the tide is rushing in. The water level can suddenly increase and you can be trapped on the fast-submerging islet before you know it. Accidents have been known to happen so it's always important to check tide tables before going out to shore areas. Safety first!

Jejawi Viewing tower

NF#1: The tower is 20m tall and allows visitors to get a good view of Chek Jawa and the surrounding areas. Due to it's height, the tower is also a great place to spot birds on nearby trees. This tower can take a maximum of 40 people.

NF#2: The Jejawi Tower is named after the Malayan Banyan (Ficus microcarpa) growing nearby that was 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.

Interesting Note: To connect visitors to figs, guides who understand Chinese can ask the visitors if they know the popular oldies "榕树下"(pronounced as Rong Shu Xia), which means "Under the Banyan Tree". Or has anyone eaten "无花果"(pronounced as Wu Hua Guo), which is also a fig. Do explain to the visitors that "无花果" actually do flower, just that the flowers are concealed within the fig. And what they are eating is not really the fruit, but a natural container for the flowers and seeds!

Too Much Information:

Figs are pollinated by tiny fig wasp that are mostly smaller than the head of a pin!

The female wasp somehow finds the correct fig tree in bloom, and sometimes, she must fly a long long way!

To get to the flowers, she squeezes through a tiny little hole in the fig. In the process she loses her wings and most of her antennae.

Usually, there are 3 types of flowers inside the fig:
1. Male flowers near the tiny hole
2. Female flowers with short styles
3. Female flowers with long styles

The male flowers are still immature without pollen. As the female wasp moves around in the fig, she transfers pollen she collected from her previous fig to the female flowers.

She will lay eggs in the female flowers with short styles. After laying the eggs, she dies.

After some time, the baby wasps hatch and feed on the plant tissue surrounding them. The males will hatch first. They are wingless but have strong mouth parts.

Meanwhile, the female flowers with the long styles develop seeds.

Once the male wasps become adults, they will seek out the female wasps and mate with them. After mating, the male wasps will chew and enlarge the tiny hole to create a wider tunnel so that the females can depart without losing their wings. The males usually die soon after they enlarged the tunnel.

As the females leave the fig, they pick up pollen from the male flowers that are now mature.

After they leave, the fig ripens and the walls become yummy to eat. Animals eat the fig and disperse the seeds.

Meanwhile, the brave little female wasp flies on to start the whole cycle then starts all over again.

Additional info on fig and fig wasp:
- The Fib Web
- The Last Stand of the Male Fig Wasp
- One Fig, One Wasp? Not Always!

Wednesday, August 15, 2007

House No. 1 - Chek Jawa Visitor Centre

NF#1: The Chek Jawa Visitor Centre 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.

NF#2: House No. 1 is also the home to rare 2 species of rare bats! The fireplace, which is among the last few working ones left in Singapore, is the home to a colony of rare Pouched Tomb bats. The nearby water tower was retained as another rare species of Malayan False Vampire bats currently resides in it.

NF#3: There used to be another smaller outbuilding. Although newer than the main house, it had to be pulled down as it was no longer structurally sound. Some of its wall facades have been salvaged and incorporated into the toilet block.

Tuesday, August 14, 2007

Slithery Snakes

Naked Facts (General information about snakes):
  • All snakes are carnivorous or you can say they only eat meat.
    • Some snakes have a venomous bite, which they use to kill their prey before eating it.
    • Other snakes kill their prey by constriction or called 'wrapping you up and then squeezing you to death'.
    • Still others swallow their prey whole and alive.
  • Snakes are covered in scales. Most snakes use specialized belly scales to travel, gripping surfaces.
  • They shed their skin periodically. The primary purpose of shedding is to grow; shedding also removes external parasites.
  • Venom VS poison: The term poisonous snake is mostly false - poison is inhaled or ingested whereas venom is injected. A venomous snake is a snake that uses modified saliva, venom, delivered through fangs in its mouth, to immobilize or kill its prey.
Too Much Information:
  • Unlike other reptiles, shedding for snakes is usually done in one piece, like pulling off a sock, with the snake rubbing its nose against something rough, like a rock, for instance, creating a rip in the skin around the nose and the mouth until the skin is completely removed.
  • It is a common misconception that snakes actually dislocate their lower jaw to consume large prey. Actually as snakes do not chew their food and have a very flexible lower jaw, the two halves of which are not rigidly attached, and numerous other joints in their skull, allowing them to open their mouths wide enough to swallow their prey whole, even if it is larger in diameter than the snake itself.

Fabulous four (Mangrove) snakes:

Common Characteristics:

  • All of them are aquatic.
  • Their eyes are positioned on the top of their heads so that they can remain with their body submerged in water and yet are able to see above the surface.
  • All of them have poisonous fangs on the back of their jaws, but their venom is not known to have any serious effects on humans.
  • All of them give birth to living young, and appear to be largely nocturnal in habits.

Dog-faced Water snake or Bockadam, Cerberus rynchops feeds largely on fish trapped in mud puddles during the low tide.

Yellow-lipped Water snake, Gerarda prevostiana, is less common. It specialises in feeding on newly-moulted crabs.

Cantor’s Water snake, Cantoria violacea, is a rarely seen and extremely long species with markings similar to that of the venomous sea snakes (family Elapidae, or Hydrophiidae). It feeds on snapping shrimps.

Crab-eating Water snake, Fordonia leucobalia, is believed to live mainly in mud-lobster mounds and feeds on hard-shelled crabs.

Monitor Lizards: Cleaner of the Mangroves

Naked Facts:
  • Monitor lizards are the “cleaners” of the mangrove habitat as they eat anything that they can swallow therefore helping to make sure there is no too much of any living things in the mangrove.
  • Their long list of 'diet' consists of (here goes): tiny insects, crabs, molluscs, snakes, eggs (of birds and crocodiles), fishes (including eels up to 1m long), rodents, small mouse deer, other monitor lizards and even human faeces. But they are particularly fond of dead bodies.
  • They have known to eat prey almost as big as themselves: a 1.2m long monitor lizard ate a snake 1.3m long.
  • Corny Joke: As long you try not to look ‘delicious’, they are not known to consume humans.
  • Message behind joke: Observe but not disturb them.
  • The Water Monitor's main hunting technique is to run after prey that it has spotted, rather than stalking and ambushing.
  • Like snakes, they have a forked tongue that they stick in and out regularly to "smell" their prey and other tasty titbits.
  • Water Monitor Lizards are highly mobile. They can swim, run faster than most of us can run and even climb trees.
  • Monitors can survive in habitats (such as the mangrove forests) that wouldn't be able to support other large carnivores as they are cold blooded (If you need to drag time, you might want to explain the difference between warm and cold blooded).
Did you know?
  • Komodo Dragons are a member of the monitor lizard family, Varanidae.
Too Much Information:
  • They have been seen swimming far out at sea and can remain underwater for up to half an hour.
  • They climb to search for food as well as to escape predators. The young usually stay in trees for safety. If cornered up a tree, they will jump into the safety of a stream or river.
  • As scavengers, Water Monitors keep the habitat neat and tidy, and also control populations of their prey. They in turn provide food for larger carnivores such as crocodiles and birds of prey. Small young Water Monitors are particularly vulnerable even to large birds such as herons.
More about the Monitor Lizard.

R(A) link (Watch how two monitor lizards mate):

Vinegar Crabs aka Tree Climbing Crabs

Name the Creature Activity (Something you can try with kids if a Vinegar Crab is spotted on a tree):

Guide: "Hey, we have a crab on a tree here (point to crab)."

Guide: "Let's say we want to name this crab, what name would you give it?"

Kid A: "Tree crab?"

Guide: "But how did it get up there?"

Kid A: "Climb! Oh, Tree-climbing crab!"

Disclaimer: Might not work every time.

Naked Facts:
  • During low tides, you can find them on the forest/mangrove floor feeding on leaves.
  • During high tides, you can usually find them at a height high enough to clear the water level and they will remain motionless on tree-trunks, leaves or boardwalk legs.
  • This is probably a predator-avoidance behaviour, especially with the many predatory species of fish and crabs that hunt with the incoming tide. Out of the water, they remain motionless to avoid other predators like kingfishers, monitor lizards and otters.
  • At night time or dusk, they have been seen climbing up trees to heights of more than six meters to graze on algae as well as eating leaves.
  • Food fact (1): The Teochew are known to pickle this crab in black sauce with vinegar, and take it with porridge. That’s why they are also called vinegar crabs.
  • Food fact (2): The Thais like it salted, with the roe or simply fried whole.
  • National Education: There is a tree climbing crab named the Singapore vinegar crab (E. singaporense), it is a common species of the tree climbing crab (Episesarma) and has entirely red claws. It is commonly sighted in or near mud lobster mounds.
Too Much Information:
  • They are usually burrowing crabs, digging holes at the base of trees and mud lobster mounds.
  • They are considered pests of mangrove plantations for their habit of attacking propagules (seeds of the Lenggadai, a threaten species of mangrove).
  • Tree Climbing Crabs are known to scavenge meat like many other crabs.
Reference and more about Tree Climbing Crabs