13 February 2009

Back to the back mangroves at Pulau Semakau

A quick but fun trip to the mosquito-infested back mangroves yesterday morning, with a great team from the Raffles Museum of Biodiversity Research who joined the Semakau Book Team for another trip to Pulau Semakau.

We were on the hunt for crabs, especially fiddler crabs. Amos gamely joined us too!

The tide was rather high when we got to the shore, but we still managed to see lots of fiddler crabs and other crabs. I learnt today the fiddler crabs that we know and love could actually be made up of several, similar-looking species! A closer look by experts is needed to find out for sure. The RMBR team is superb at this!
And here's an odd-looking crab. Is it a Sand bubbler crab (Scopimera sp.) or a Soldier crab (Dotilla sp.)? And look at the bright red markings on the legs. We often overlook these seemingly boring crabs. But thanks to the crab experts, we see them with new eyes!

Then it was time to unroll our sleeves and put on our best mosquito-proof gear and head off into the dense undergrowth of the Back Mangroves. Here, there were even more crabs!

The crabs are tiny and fast and look just like the mud. It was really hard to work with them, surrounded by clouds of blood-thirsty mosquitos, while trying not to fall down from slippery mudlobster mounds and negotiating tricky pnematophore covered pools while avoiding being strangled and tripped by vines and parts of trees.

But here's a pretty crab with blue markings near its mouth. These little crabs are probably Sesarmine crabs, which according to the "Guide to the Mangroves of Singapore" by Peter Ng and N. Sivasothi, are the dominant crabs in our mangroves, with almost 40 species. One of the reasons for their success is their ability to live in extreme environments. They are able to 'recycle' deoxygenated water by pumping this water through a dense mat of hairs on the face and/or carapace thereby aerating it before re-circulating it into their gill chamber! Read more about them on the online version of the guidebook.

For me, the special encounters was with Ellobid snails! These snails belong to Family Ellobidae and are only commonly seen in such tricky areas. On the shores, we often only see their empty shells. Since I'm quite lame and rarely struggle through back mangroves, I've not seen too many of these snails!

Here's one showing its white spotted body. It looks like an Ellobium snail (Ellobium sp.).

A view of the underside of this olive-shaped animal.

Another one with a more rounded shell, possibly a Cassidula snail (Cassidula sp.).

The underside looks different, rounded and slightly pink. And the shell also has a banded pattern.

The RMBR team show us much larger Ellobium snails!

If they remind you of the more commonly encountered land snails, you're not far off. Like land snails, the Ellobid snails also breathe air (instead of through gills like most other marine snails). All of them lack an operculum to seal the shell opening.

Here's the underside of the big snails.

Having just spent a day with the Dragonfly Team, I also start to notice these insects.

This pretty one was resting on a mangrove pneumatophore.

And here it is showing its delicate wings. I have, of course, no idea what it might be. Hopefully, the Dragonfly Team can help.

Alas, I failed to find the Hairy foot mangrove spider (Idioctis littoralis) which builds burrows in mudlobster mounds. It waits inside its burrow for passing prey, like a trapdoor spider. And also no fiddler crabs. What I thought was one, was not. It was also hard to figure out the tree species in the area as the growth was so dense that the leaves of the bigger trees were quite high up.

Though it isn't fun to explore such tricky areas, the company was great! And from the google map of Semakau, it looks like there are more of such places to get to and poke around. I should just find enough courage to do it again soon.

Meanwhile, Eric and the rest of the Book Team were out trying a tricky dive. I hope they are Ok and had a successful day.


  1. Not often we could shoot an open-winged damselfly. well done. Your macro shots on the winged insects are good too.

  2. It was blind luck Federick! Emphasis on the blind. I had no idea what I got until I got home and looked at the photos. It isn't easy at all taking the flying creatures. So I am really in awe of your photos.



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