Singapore: On the Boardwalk

After our brief tour in New Zealand, Eileen, Ryan and I flew back to Singapore for a few days with Eileen's cousin Chris Chang and his family. Chris very kindly agreed (on December 21, 2011 - I suspect this blog will never be up to date) to indulge my taste for nature and Ryan's newfound enthusiasm for wetland boardwalks by taking us to the mangrove boardwalk at Chek Jawa, on the offshore island of Pulau Ubin. Eileen, who is not as fascinated with mangroves as Ryan and I, decided to sit this one out, but we brought Chris's niece along instead.

Singapore is not awash in natural spectacles, but Chek Jawa has become a highly popular exception. Its chief visitor feature is its extensive boardwalk, allowing strollers access to an extensive cross-section of shore ecosystems and marine life.

On the shore edge of the mangroves are stands of Nipa palm (Nypa fruticosa), their gigantic leaves thrusting out of the mud like enormous feather dusters (their trunks are normally underground). Here are the odd-looking flowers (source of a local alcoholic beverage) and a cluster of fruit.

Chek Jawa has an extensive butterfly fauna, including some species no longer common elsewhere in Singapore. This is a Common Palmfly (Elymnias hypermnestra agina).

Here is a Malay Viscount (Tanaecia pelea pelea).

I was hoping that this would turn out to be one of the Chek Jawa specialties, the Black Veined Tiger (Danaus melanippus hegesippus), but I'm afraid it is the widespread (but still extremely handsome) Common Tiger (Danaus genutia).

As we set out on the boardwalk, strange structures cropped up from the mud beneath us. Are these sea anemones, their tentacles withdrawn as they wait for the returning tide? Are they, perhaps, tunicates (sea squirts), the fruiting structures of some sort of alga, or something else altogether?

Are these the mud-encrusted shells of some sort of oyster?

Well, there is certainly no question about what these are. Male fiddler crabs waving their enormous claws in display are a highlight of mangrove flats throughout the world. There are several species at Chek Jawa, and from the height of the boardwalk (and from my level of ignorance of crustacean taxonomy) I could not say which these were. I think, though, that these photos show two separate species.

As the males sat displaying near their burrows, other crabs circled near them (most, I presume, small-clawed female fiddlers checking out the talent).

This one, I thought, seemed to looking rather beseechingly up at me (though getting anthropomorphic about crabs is probably not zoologically useful).

Here is a crab that is not a fiddler: a Face-banded Sesarmine, with a electric-blue facial blaze and chunky, muscular-looking claws like a pair of boxing gloves. There are two species at Chek Jawa; I think this is Perisesarma indiarum, which is distinguished by a seond blue blaze, like an upside-down V, under the main one. You can just see that feature in the photo. Face-banded Sesarmines are largely sediment-eaters, feeding on bits of decaying mangrove leaf and other objects in the mud, and are abundant and important recycling agents in the mangrove ecosystem.

This is not a crab, though it is called one. It is, instead, a far more interesting creature, and one of most ancient of surviving animals: a horseshoe crab, a distant relative of spiders and scorpions that has been trundling about on shallow muddy shores for over 300 million years. There are only four species in the world today, one on the shores of eastern North America and the other three in Asia. At Chek Jawa I had the singular problem of trying to decide which of two local species I was looking at. Is this a Mangrove Horseshoe Crab (Carcinoscorpius rotundicauda) or a Coastal Horseshoe Crab (Tachypleus gigas)? I'm still not sure. The easiest way to tell them apart is he cross-sectional shape of the tail (rounded in the Coastal, triangular in the Mangrove) - hardly something I could check from my elevated position on the boardwalk. Its  rounded shape and lack of obvious large spines lining its broad rear segment suggests to me that this is a Mangrove, but I could certainly be wrong.

From Ryan's point of view (shared, no doubt, by many others) the most entertaining feature of Chek Jawa is a chance on get on close terms with a variety of mudskippers. A number of species of these goggle-eyed gobies flick themselves over the mudflats to the delight and amusement of human visitors, including small children like Ryan. This one, if I have identified it correctly, is a Blue-spotted Mudskipper (Boleophthalmus boddarti).

This is a Dusky-gilled Mudskipper (Periophthalmus novemradiatus).

Here is the most spectacular of the lot, the Gold-spotted Mudskipper (Periophthalmus chrysospilos). It may not look any more spectacular than the others, but that is because these individuals aren't displaying.

When one male strays over the border of a neighbor's mud patch, however, the stage is set for a squabble.  Owner and intruder face off side by side and head to head, raising bright orange dorsal fins and stretching them to their full extent as the tension increases.  In the bottom photo the upper mudskipper has raised the ante by elevating his second dorsal fin as well.

Eventually the winner, banner still raised, sees the abashed loser off.

Much smaller, and less strikingly marked is the elongate little Serpent Mudskipper (Parapocryptes serperaster). It has, though, its own striking method of calling attention to itself.

Every once in a while, one of the little fishes would leap straight up out of the water. I could not see exactly what motivated this activity, but I assume that it had something to do with either territory or sex, unless it was trying to catch a flying insect (something I don't think mudskippers do).

Less entertaining,though equally odd-looking, were small schools of Spot-tail Needlefish (Strongylura strongylura) swimming just under the surface where the boardwalk met the open sea.

On our return from the boardwalk, this young Wild Boar (Sus scrofa) stepped out to meet us.  Boars are increasing in Singapore's reserves, and the National Parks Department has had to reassure visitors about them.  This one, though, seemed, despite everything, quite harmless.  Well, it was only a little one.