Saturday, May 31, 2008
On 2nd June (Monday), Vyna and I will be guests on the radio talkshow "The Living Room" on 938LIVE from 10.30 to 11 a.m., to talk about what we do as members of the Naked Hermit Crabs. Tune in and listen to us share about our work as volunteers, raising awareness of our fragile shores.
Information on The Living Room and host Stanley Leong
Stanley's been fronting the popular weekday talkshow "The Living Room" on 938LIVE (formerly NewsRadio 93.8FM) since July 2002. His investigative and inquisitive approach coupled with quick wit, composure and his cordial ways have won the hearts of his studio guests. Among them, 'live' discussions with MPs, Ambassadors, High Commissioners, CEOs, medical and legal practitioners and international speakers.
Listeners have come to love the casual and edu-taining banter synonymous with the programme. The talkshow which broadcasts live from 10am to noon on weekdays, makes 938LIVE the third most-listened-to English station during those hours.
The profile of the Naked Hermit Crabs is certainly being raised; we've appeared on television, have been invited to the National Youth Environment Forum, and we're now getting sponsorship from Transitions Optical. Let's hope that with this media feature, the message gets spread further, that our shores are indeed very much alive, and definitely worth protecting.
Thursday, May 22, 2008
Update: Check out Ria's post on the things she discovered at the wildfilms blog.
I woke up early this morning to join Ria on a trip to explore the sandy shores of East Coast. Not many people know that although the beaches of East Coast Park are artificial, there is still quite a lot of marine life to be found in the inter-tidal zone.
Unfortunately, the tide was a bit too high for our liking, so we did not manage to find a lot of things, such as the sea fans that have been seen recently. Still, we did see quite a fair amount of marine critters, as I'll show later.
But today really brought home a message about the information that can be gained from examining the flotsam and jetsam that gets washed up on the shores. Although much of what you find on East Coast Park is man-made rubbish, there are plenty of signs that point to the existence of a variety of marine life.
First find of the morning was this sand dollar (Arachnoides placenta). These used to be very common on our sandy shores, but are unfortunately quite rare nowadays, being restricted to places such as Chek Jawa and Cyrene Reef. Believe it or not, sand dollars actually belong to the same group as the spiny sea urchins.
Here's a relatively common inhabitant of our northern shores - an orange striped hermit crab (Clibanarius infraspinatus).
I turned over a rock, and was thrilled to find a pair of tiny creatures that I'd seen before only in books - chitons!
Most people would be familiar with 3 main groups of molluscs, namely the Gastropoda (abalone, limpets, snails, slugs, sea butterflies and nudibranchs), Bivalvia (clams, scallops, oysters and mussels), and Cephalopoda (nautilus, cuttlefish, squid and octopus), when in fact there are 8 living groups of molluscs. One of these lesser-known groups is the Polyplacophora, known as chitons.
Chitons are quite similar to snails, in that they have a muscular foot, with a mouth on the bottom. Like many of the snails found on rocky shores, most species of chiton live on or under rocks, scraping off algae and other tiny organisms with their radula ('tongue'). However, unlike gastropods, their shell is very different; it's made up of eight separate overlapping plates which give it some flexibility. Some species can actually curl up into a ball when dislodged!
The rocks here are a shelter for many other creatures, such as these tiny glass shrimp.
Here's a little game: How many shrimp can you find in this photo? I see 9. How about you?
We were a little surprised to bump into this fellow. It's a gold-spotted mudskipper (Periophthalmus chrysospilos). These adaptable guys can sometimes be found even on sandy and rocky shores. I've personally seen them in the artificial lagoons created along Siloso Beach.
Mudskippers seem to be less skittish at night.
We managed to spot a swimming crab which isn't seen very often, but it vanished beneath a rock before I could snap a photo. It's possibly Charybdis annulata.
A great way to see what species of snails inhabit the area is to examine the local hermit crabs. Because hermit crabs have to continually upgrade to larger shells as they grow, they depend on a constant supply of shells.
Here we have 4 different hermit crabs of the same species, occupying the shells of 4 species of snail. Upper left: spiral melongena (Pugilina cochlidium). Upper right: dwarf turban shell (Turbo bruneus). Lower left: drill (Thais sp.). Lower right: pearl conch (Laevistrombus turturella) (I know it looks empty, but there was a hermit crab hiding inside, I swear).
We saw glimpses of the tips of a red sea fan, but the tide was too high, and the water was too murky, so we gave up and decided to head further down to another section of beach.
This is the shell of a huge Arabian cowrie (Cypraea arabica). Cowries are now rather rare due to overcollection for their beautiful shells, so it's fascinating to find evidence that such large cowries still exist in our waters.
Countless oyster shells are being washed up onto the shore. What could explain the presence of so many oyster shells?
The granite breakwaters have become a home for many of the creatures that live on rocky shores, such as barnacles and limpets.
Nerites (Nerita chamaeleon?) can be found as well. Remind me to take photos of the underside of the shells - shell colour can be highly variable, so sometimes looking at the columellar shelf (the flat region on the underside of the shell next to the aperture) is the only way to tell the various species apart.
Here's another game: Spot the onch (Onchidium sp.)!
Near the water's edge, a well-camouflaged topshell (Trochus maculatus).
There are huge masses of drills on the breakwaters. Are they feeding? Fornicating? Or just hanging around because they like each other's company?
Discovery of the day - seagrasses! This is the tape seagrass (Enhalus acoroides). It really raises the question - are there seagrasses growing in the waters off East Coast? Or is there some seagrass bed nearby that's being ripped up by development of some sort, resulting in all these little bits washing up on shore?
Large round burrows high up on the beach are commonly seen on our sandy shores. These are the burrows of ghost crabs (Ocypode spp.), which are very shy nocturnal scavengers. I've seen their burrows countless times, but so far the only time I've actually seen a ghost crab was at Bintan in September 2006.
If you look carefully on the high shore, you can find lots of pretty little button shells (Umbonium vestiarum)!
There's such a wide variety of colours and patterns.
Here's the half-eroded shell of a predator of button shells - a moon snail (Polinices didyma)
And the shell of an unidentified snail.
I realise that it's quite easy to find cuttlebone along the beach. The larger one is as long as my hand.
There are many animals on the beach which make a living out of scavenging. From large animals like birds and monitor lizards, to crabs, snails, and worms, to tiny critters such as springtails, amphipods, and isopods.
Here's another challenge for you: Please see this photo at full size. If you look very closely, you might be able to spot a couple of extremely tiny isopods. They make small burrows among the sand grains, and come out searching for dead animal matter washed up on the shore.
Give up? Here they are!
Are these little tracks in the sand made by ghost crabs? Or maybe even land hermit crabs (Coenobita spp.)?
It's a beautiful morning.
But being out here early in the morning means that one gets to see an ugly side of East Coast - the pollution that comes about from all the litter and trash.
The cleaners are already out and about before dawn, and this is what they have to deal with every morning:
True, quite a bit of the rubbish that's washed up is organic in nature, but there's a depressingly huge amount of plastic.
And it's not difficult to see the source of some of this garbage:
I simply cannot understand why people leave their trash behind, especially when the bin is just several metres away.
Along certain parts of the beach, the shore has been colonised by plants, which help providing a free service in stabilising the ground and minimising the impacts of erosion.
Such as this sea hibiscus (Hibiscus tiliaceus).
And this coconut palm (Cocos nucifera).
There's a small bunch of young sea almonds (Terminalia catappa).
Seashore morning glory (Ipomoea pes-caprae) have colonised the beach in numbers, and many of these plants were in flower. Ria shares more details about this adaptable plant here.
Beautiful, aren't they?
It's nice to see a different side of East Coast, rich in marine life. Sometimes the only evidence you find comes from the remains that you find washed up on the beach. Empty shells, bits of leaves, and other remains often provide valuable clues that hint at unsurveyed marine ecosystems found further offshore.
Unfortunately, in this modern day, one has to sift through a lot of man-made trash in order to find these clues.
Wednesday, May 21, 2008
No matter which shore you explore, one is sure to find the dead remains of some sort of animal to examine. Most common of course, are the empty shells of molluscs such as snails and clams, or pieces of dead coral. Dead flower crabs (Portunus pelagicus) can be seen quite often, although chances are that many of these are actually moults.
There were quite a few interesting dead things to look at along this stretch of Changi. And as we'll see later, for some of these animals, there is a very high likelihood that human activity can be implicated in these deaths.
I was wondering why this thunder crab (Myomenippe hardwickii) wasn't reacting to my presence, then I realised that it was quite dead.
As we slowly made our way back to wash up, I came upon the opisthosoma of a coastal horseshoe crab (Tachypleus gigas). Sigh. I seem to have more luck finding dead horseshoe crabs, when I'm more interested in seeing live ones.
I soon lagged behind, while the others went on ahead. Documenting death can be valuable, as a record of the organisms living in the area.
Cuttlebone. Among extant cephalopods, only the nautilus retain an external shell; in cuttlefish and squid, the shell is reduced to a thin internal strip, while the octopus have lost the shell entirely.
The discovery of the day, however, came when I stumbled upon these two large crabs, very dead, very smelly, and covered with flies.
These weren't flower crabs; I flipped them over with my boot, and realised that I was staring at two mud crabs, possibly the green mud crab (Scylla paramamosain)*, and the size of those you'd find for sale in markets and seafood restaurants.
Maybe these were some fisherman's discarded catch, I thought to myself. Further down though, I stumbled upon yet more dead mud crabs.
Three of them this time, and based on the coloration, these are purple mud crabs (Scylla tranquebarica)*.
The smell is seriously overwhelming, and the buzzing flies aren't too pleased at having their meal interrupted. The disgusting things I do in the pursuit of my passion for nature.
Further down, I found yet more dead crabs!
Some of them have a small bright pink mark on the carapace, that looks like it's been painted on. This one is possibly an orange mud crab (Scylla olivacea)*.
It's like a mud crab graveyard over here!
Take note of the pink markings on the two purple mud crabs. And I didn't notice the disembodied pincer on the top left corner of the photo, until I was home and processing the photos.
In all, I found 12 dead mud crabs along a 50 metre stretch of rocky shore! All were good-sized specimens, just like those you can buy at the market.
What could have happened here? Did some fisherman discard his catch? Did a shipment of crabs fall overboard? Is some disease or pollutant killing only mud crabs and nothing else?
When I caught up with Ria, she had a hypothesis of her own to account for this bizarre phenomenon. She thinks that it's very likely that these were released by devotees on Vesak Day, and I agree with her.
Religious merit-making in the form of release of captive animals is often practised on Vesak Day, as a symbolic act of liberation, compassion, and respect for all life. In Singapore and in many other countries in Asia, birds and fish are often released by Buddhist devotees, while turtles and frogs are also popular subjects. Yet, as they say, the road to hell is paved with good intentions.
Releasing of Animals - Good or Bad? by the Nature Society (Singapore)
Unfortunately, the people who carry out such practices do not often realise the harm that they cause, in terms of ecological damage from suddenly overwhelming the ecosystem with an influx of released animals, or from introduction of non-native species, such as American bullfrog (Lithobates catesbeianus), red-eared slider (Trachemys scripta elegans), and Chinese softshell turtle (Pelodiscus sinensis), or unwanted aquarium fish.
Not to mention the outright cruelty of not doing any background research, and releasing animals into the wrong habitats! Marcus mentions in this thread:
Some of the dumber cases recently have involved: star tortoises being dumped into the pond at East Coast Park, and freshwater fish like snakeheads being released into the sea.
Good intentions + wilful ignorance = disaster!
Andy has encountered people who tried to release Chinese softshell turtles (which live in freshwater) into the sea at Labrador Park. (I cannot believe that the couple he encountered believed that they were releasing sea turtles! Are people really that ignorant?)
While black-headed munias (Lonchura atricapilla), which are birds of open grassy areas, have been spotted in the forest at Upper Peirce Reservoir, as recorded in this post at the Bird Ecology Study Group, just before Vesak Day.
And often, the animals that are released are in no condition to survive suddenly being thrust into the wild; a sad example is shown here. Unfortunately, if you read the comments in the link provided, you will see a perfect example of how some people still don't understand the cruelty and ecological consequences of such a practice.
Is this the same thing that happened to our mud crabs? There are several pieces of evidence that point to the likelihood that these are the casualties of an ignorant and misguided attempt to give these animals a better life. Most of them point to these crabs being of captive origin, rather than having lived naturally along this shore:
- Mud crabs (Scylla spp.) are native to mangrove and muddy habitats. I've never encountered live mud crabs in the wild before, but I don't think they are found naturally in rocky shore habitats.
- The pink markings found on the carapace of some of these crabs are definitely artificial; it's not as if some pink algae or sponge was encrusting the shells of the crabs. I've seen similar marks on crabs in markets and restaurants, but don't know what they're for. In any case, it's likely that these crabs were captives only until recently, since the pink markings would have been lost the next time the crab moulted.
- The only dead animals visible along this stretch were mud crabs. Pollution would be killing off a much wider variety of creatures.
- These are all crabs of market size. If disease or pollution was killing specifically mud crabs, one would expect a wider range of sizes, from babies to huge adults.
And considering the fact that Vesak Day was just 2 days ago, I think the facts pretty much speak for themselves.
But why mud crabs? Many of the animals released are those destined for the table, so it's no surprise that somebody probably tried to rescue these crabs from the cooking pot, only to condemn them to dying in a habitat they could not survive in. Besides, the other species of crab commonly found in the markets, the flower crab, does not survive for long out of water. The mud crab, being a much hardier species, would be more likely to survive the trip.
I can imagine these crabs having been deprived of food and water for some time in the market, then disoriented from the journey, and then suddenly thrown into the sea in an unfamiliar environment. I doubt they would be in any condition to scuttle off, ready to take on the challenges of surviving in the wild.
Even worse, what if they had been tossed onto the shore at low tide? The crabs hitting the rocks won't exactly improve their chances of survival.
Of course, there is the possibility that this is all just idle speculation, that someone was simply trapping crabs and tossed the unwanted ones. But the fact that the crabs are of captive origin (evidenced from the pink markings, and consistently being of market size), and the proximity to Vesak Day, is just too tantalising to ignore.
Most times, dead animals on the shore provide evidence of the creatures that can be found in the area. Sometimes, however, dead animals can say a lot about the actions of people.
*: These are only tentative identifications, based on the photos of the various Scylla species in A Guide to the Mangroves of Singapore.
This is part 4 of a 4-part series on a trip to Changi on 21st May, 2008.
Part 1: Changi's Hidden Wonders
Part 2: Echinoderm Hangout
Part 3: Do not touch!
Part 4: Death on the shores (this post)