Frogs were croaking, crickets were chirping and nightjars were keening a jub-jub-jub call. We had to contend with mosquitoes and wet, muddy terrain. This did not deter the group of 30 odd kids and parents who had gathered at Pasir Ris mangrove boardwalk on 6 April 2013 at the dinner hour of 7 pm. Under the cover of darkness, we were here to search for nocturnal water snakes. Excitedly, we set off with flashlights, insect repellent and long-sleeved clothing.
|A mudskipper in the spot light. Mudskippers propel themselves forward by curling their muscular body sideways, then pushing against the mud to move in skips.|
At night, the mangrove swamp still teems with life. We spotted a handful of Giant Mudskippers (Periophthalmodon schlosseri) in their little territorial pools on the mudlfats. Mudskippers are fish that breathe through gills. Like amphibians, they can also obtain air through their skin and throat. When the tide is low, mudskippers adapt by storing air bubbles in their gills, much like a diver’s oxygen tank. Their eyes are perched on the top of their heads for a 360o view.
|The intricately patterned Violet Vinegar Crab (Episesarma versicolor) was well-camouflaged against the mossy mangrove trunk.|
Our torchlights also picked up numerous Vinegar Crabs, also known as Tree Climbing Crabs (Episesarma spp). There are three species found in Singapore. These crabs climb up mangrove trees during high tide to avoid predators such as fish, kingfishers and monitor lizards. They can scale heights as high as 6 m. They are given the moniker of ‘Vinegar Crabs’ as Teochews traditionally eat them pickled in vinegar and black sauce. Tiny semaphore crabs, less than 1 cm long, are easily missed. They communicate their territorial rights by waving their pincers like flags. By using our binoculars, we could still pick them out. To our dismay, we did not see the fiddler crab. The male fiddler crab has an enlarged claw for mating and fighting while its smaller pincer is used for feeding itself.
|The kids had satisfying close up views of an adult Dog-faced Water Snake.|
As we moved along the boardwalk, Uncle Ding Li, Auntie Gloria and Auntie Lena pointed out the unique landscape of mangrove trees with their air-breathing roots interspersed with numerous Mud Lobster mounds. On the mudflats were Nerites, mangrove snails known as Belongkeng, Mangrove Hermit Crabs as well as flatworms.
We focused our torches on the tiny brackish streams that flowed seaward, the hunting domain of the water snakes. Finally, Auntie Gloria spotted the first Dog-faced Water Snake (Cerberus schneiderii) of the night, a 50-cm long sub-adult named for its protruding eyes. This individual was just 10-m from the boardwalk. It lingered in the shallow stream for a good five minutes, its wavy body swaying with the flowing water. Then it disappeared under a root.
|Empty shells that could become home for the Mangrove Hermit Crab.|
Although we waved our flashlights at the trees and scanned the vegetation, we did not catch a glimpse of the elusive Shore Pit Viper, a venomous snake. You can be sure that the NSS Kids will be back to look for it, along with three other Water Snakes that inhabit Singapore’s mangroves, namely the Crab-eating, Gerard’s and the rare Cantor Water Snake!