01 March 2009

Pulau Semakau: winged wonders, mudskippers and more

Another glorious sunny day out to Pulau Semakau with the enthusiastic Dragonfly and Butterfly Teams, plus John the one-man Wasp Team and of course the usual Book Team.While the Butterfly Team and John went off to do the sunlit terrestrial areas, the Dragonfly Team and the rest of us troop off to check out the back mangroves.
Not among my favourite shore ecosystems, but I was excited to try to find new stuff. While Tang and Robin came to look for the mystery damselfly that I saw the last time I was there. Totally oblivious to things terrestrial, I didn't realise what I saw was something special to the Dragonfly Team.

While we left the experts to do the necessary, Eric, Chay Hoon and I struggled through the back mangroves. Among the first things we saw were these special Nerite snails (Family Neritidae).
Though they look boring from the top, the underside of these snails reveals more about their identity. I'm not sure if both are the Violet nerite (Neritina violacea), or only the one with the orange mouth, while the one with the dark mouth might be Neritina cornucopia. It's my first time seeing these snails! More about these snails in the paper by Tan Siong Kia & Ruben Clements, (2008) Taxonomy and distribution of the Neritidae (Mollusca: Gastropoda) on Singapore. Zoological Studies 47(4): 481 – 494 (PDF file).

There were also lots of tree climbing crabs (Episesarma sp.).
Some were in the trees.Others on the mudlobster mounds, where they are very well camouflaged.And some were in holes in the mounds. This one seems to be stuck in a hole too small for it.

Among the scuttling creatures were many Sesarmine crabs (Family Sesarmidae).
Some had a bright blue 'face band' with colourful pincers.Here's a closer look at one.

Chay Hoon and I were earnestly looking for the Hairy foot mangrove spider (Idioctis littoralis) that builds a tunnel in mudlobster mounds and seals the opening with a trapdoor. As Chay Hoon put it, we were looking "for a door to knock on".

As we looked for the elusive spider, every now and then, a tiny many-legged animal would creep by. They are the amazing shore cricket that is sometimes seen on our shores.

Alas, we didn't find the Idioctis. But there were lots of other spiders among the trees.
They make pretty webs and are sometimes difficult to spot because they hide in some leaf stuck in the middle of the web, or off the web.Or like this one, hold their legs in such a way that they practically disappear from view. Throughout the trip, Chay Hoon and I also learnt lots from Eric about photography.

The most lively animal in the back mangroves are mudskippers. And they are really hard to shoot as they skitter away merrily out of range as soon as I slip, slide, sink through the soft, root-riddled mud.This was the only one I managed to sneak up to.

Out of the back mangroves, back on the main shore, the tide was coming in fast. And I finally got lots of mudskipper shots.As the tide came in, the little mudskippers hung on to the mangrove roots. This one is an elegant Silver-lined mudskipper (Periophthalmus argentilineatus). Very aptly named for the fine white bars on the sides of its body.
Here's a closer look at one, clasping the root with its arm-like pectoral fins, and its pelvic fins on the underside of the body which act like a sucker.
And a pretty Gold-spotted mudskipper (Periophthalmus chrysospilos) was swimming about in the water.While another one was clinging to a mangrove root.

With the incoming tide, all the little snails were frantically creeping up the roots to keep above the water line.
There were lots of little Periwinkle snails (Family Littorinidae) on the slow trek up. Most of them are difficult to identify in the field. But the delicate Black-mouth mangrove periwinkle snail (Littoraria melanostoma) in the photo on the right is easy to distinguish. In a submerged portion of a mangrove root were a Striped hermit crab (Clibanarius sp.) with blue legs, and a tiny little Dubious nerite (Clithon oualaniensis)!

It was disturbing to see large amounts of Tape seagrass (Enhalus acoroides) washed up on the shore.The leaves seemed unharmed (not 'burnt' or diseased) but broken off in long strands.I also saw one with its roots still attached. I hope this doesn't mean something has happened to affect the vast seagrass meadows on Pulau Semakau. Thankfully, TeamSeagrass regularly monitors this shore and the data gathered by the Team should help better understand what is going on.

Other encounters with questions was this boat off the Bukom beacon.
I'm not sure what the person is up to.

All too soon, it was time to go home. We finally meet up with all the other Teams. John had a particularly good day!He shares some his finds including sand wasps and some other really ferocious looking insects. He says they don't hurt much if they sting. Well...as long as the sentence includes the word 'hurt' I think I don't want to mess with the creature.The highlight was this particular wasp which he says he has not seen in Singapore and is infact usually restricted to more temperate climates. Wow!

Tang has just shared photos and information of their finds.They have found the mangrove dragonfly Raphismia bispina, which is the only mangrove species in Singapore. This is the female. And this is the male. Read more about this fascinating dragonfly on Robin's Creatures Big and Small blog.

They also found the female of the mystery damselfly.
Tang shares that it is suspected to be Mortonagrion falcatum, but he still has his doubts. The Team will need to secure a male specimen to be sure. Tang shares that Mortonagrion falcatum is listed as a critically endangered species in the Singapore Red Data Book. He saw it on the mainland in Tuas Marshland last year. Unfortunately, Tuas Marshland has now been destroyed for development. Tang adds that if the species seen in Semakau is not Mortonagrion falcatum, then it would be interesting. WOW!

While the Butterfly Team have come up with yet MORE species. I am in awe!

It was another fabulous day, with glorious weather (which I attribute to the Butterfly Circle offsetting Eric's wet weather effect) and great company as usual. On the boat trip home, we learnt a lot of about dragonflies from Tang too!

Thank you everyone!


  1. Wow, a very fruitful day indeed, especially for John and Tang. Pity that I could not join in the fun.

  2. Managed to hit 31 species of butts for Semakau after yesterday. Not bad for a little island in the middle of nowhere! :p

  3. Butterfly Circle is just amazing! Thank you for bringing light not only the butterflies of Semakau, but also to our trips. With BC, our days are full of sunshine!

    We missed you Federick!



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