11 May 2009

Otter at Changi!

The highlight of this morning's trip to Changi was an amusing encounter with an otter!
We were about to end our exploration as the tide was coming in and sun about to rise. I decided, as usual, to check out the coastal plants on the high shore. There was a rustle and rattle in the undergrowth and something shot out towards the shore. I just ignored it, thinking it was another monitor lizard (we saw a lizard earlier). Until Kok Sheng shouted "Otter!"

It was still dark as we scanned the waters. The otter popped up here and there along the shoreline before it seemed to disappear for good. We dejectedly continued homeward but stopped to take a look at a humungous jellyfish in the water.It didn't look very healthy and was probably dying. As Kok Sheng and some of the rest stood on a big rock on the shore to look at the jellyfish, I noticed a little head nearby poking out of the water near them.It was the otter! It was taking a look at us as we looked at the jellyfish! It seemed to scold us by chattering and showing its teeth, before disappearing once again into the water! I had one shot at it, and it's a miracle anything showed up in the photo.

It's a good thing the otter showed up at the end of the trip. Or we wouldn't have been as excited about the other stuff that we saw on the shore earlier.

One of the other highlights of the trip was this large and beautiful feather star (Class Crinodea).
It was at the same location that we had seen a feather star on our last trip here with Dr Reimer nearly a year ago in July 08.
In the above photo is the one we saw in July 2008 in the same spot. Is it the same animal? Or is this just a good spot for a feather star to be? A post in the Echinoblog featured a study which suggests that feather stars remain at the same spot for a long time, some for 2-5 years! There's so much more to learn about our shores!

The shore we went to today is probably the last natural rocky shore left on Changi. Rocks may appear barren and devoid of life, especially during the day. But in the cool and dark of the night, they teem with life.
Here's a whole bunch of creatures in just a small spot on a boulder. A layer of tiny algae and other encrusting lifeforms coat the rock surface. On these miniature meadows graze placid Onch slugs (Family Onchididae).With rotund bodies and long tentacles, I find them quite endearing. Some like the one on the left are big and pimply, and others (usually found in shadier spots) are small and smoother.

At night, the rocks are also crawling with crabs and other critters with many legs.
There are lots of little Purple climber crabs (Metopograpsus sp.), and even insects such as the shore cricket! (photo on the right).The larger Stone crab (Myomenippe hardwicki) squeezes into crevices. It is identified by its red eyes with a green centre.

The rocks are also a great place to stick egg capsules on. And these drills (Family Muricidae) seemed to be having a party laying eggs in groups.Each bright yellow egg capsule may contain 20-40 eggs. The egg capsules turn purple when the free-swimming larvae hatch.

There are lots and lots of Banded bead anemones, that often jam together in cracks and crevices on the rocks. But the tiny sea anemones below are often overlooked.
On Changi especially, it is common to see them tucked into the empty shells of dead barnacles. The Lined bead anemone (Diadumene lineata) reminds me of blown glass ornaments! They are considered one of the most widely distributed sea anemones in the world and were probably distributed by ships.

On cool, dark spots of large boulders grow other kinds of encrusting animals such as sponges.
And often, we might see the Rock star of the rocks there too! The Crown sea star (Asterina coronota) is commonly seen on our northern rocky shores.
Here's more of the stars I saw today!

I don't know why, but hard surfaces on our Northern shores are often festooned with colourful hydroids (Class Hydrozoa).
These bright orange hydroids are colonial animals, each polyp found in the tiny capsules that are arranged on the 'branches'.Another kind of hydroid forms a fluffy colony when submerged. Some hydroids can sting very powerfully so it's best not to touch them.

There are even hard corals growing on the rocks of Changi!
Well, OK, one kind mainly. It's the tough and sturdy Zebra coral (Oulastrea crispata). This encrusting hard coral doesn't form huge colonies or fancy shapes. It's not too particular about where it settles and almost any kind of hard surface will do. So it's not surprising to find out that they can be found on almost all our shores. However, on Changi, they seem to do especially well. Perhaps because other corals can't tolerate the water conditions there?

Kok Sheng also noticed the tough little Cave corals (Tubastrea sp.) were still found in darker spots of this shore. As well as the colourful sea fans (Order Gorgoniacea) that are found in deeper waters. Kok Sheng took some great photos of them today and shared them on his wonderful creations blog.

One of the best places to be on a rocky shore is UNDER a stone or rock.
Here it is cool and wet, a great place for marine creatures to wait out the low tide and be safe from predators.

Among the animals that hide there include flatworms like this Blue-spotted flatworm (cf Pseudoceros indicus) which was seen several times during this trip.Cowries (Family Cypraeidae) are also commonly seen under stones. But please don't pull them off the rock as mama cowries lay their eggs under stones and remain over their eggs protecting them with her broad foot. If you remove her, her eggs will be in danger especially if she can't find her way back to them.

The team also found several Hoof shield limpets (Scutus sp.) which are not often seen on our shores.

If you do look under a rock, be very gentle when turning it so as to avoid crushing the animals found on TOP of the rock. After having a look, turn it back gently to the original position to avoid crushing animals under the rock. Don't turn over every rock on a shore.

In rocky pools which remain submerged even at low tide, were lots of other swimming creatures.
Such as this small Carpet eel-blenny (Congrogadus subducens). This fish is NOT an eel although it sure does look similar to one.
There are also lots of gobies, such as this very beautiful Ornate goby (Istigobius ornatus).
Other swimmers include the Swimming crabs (Family Portunidae). These predators snag all kinds of prey including, it seems, other swimming crabs. This Charybdis crab (Charybdis sp.) is eating a Flower crab (Portunus pelagicus).
Not confined to the water, the mudskippers hop about on top of the rocks. They are a lot easier to photograph at night as you can creep up real close to them before they skip away. This one is possibly the Dusky-gilled mudskipper (Periophthalmus novemradiatus).
Another creature that can move about out of water for a short while is the octopus. I saw this Smooth seagrass octopus foraging half in and half out of water among the piles of dead and living 'See ham' cockles (Anandara sp.).Eventually it squeezed among the shells and disappeared into the pile before I could call the others to have a look at it. Sorry guys.

The team saw lots of interesting marinelife such as colourful nudibranchs, sponges, zoanthids, sea urchin, sea cucumbers and more. See below for links to their blog posts and photos.

Unfortunately, this rich and living shore is impacted marine litter. This is what the incoming tide brought in today.
There was also the persistent smell of benzene in the air throughout our trip, and here and there, patches of oil floating in the water.
Many of the large oysters on the shores had also obviously been pried open by tool-wielding animals. I doubt if an otter could have done this. Our oysters do NOT contain pearls and they take a long time to grow large. Oysters filter feed and together with other filter feeders on the shores help keep the water clean. More about our oysters.

We also saw a large number of dead Mud crabs (Scylla sp.) today.
They were obviously dead (not moults) and recently too. From the smell, and clouds of flies and bugs around them.Body parts were also seen scattered along the shore.
I saw one half dead Mud crab trying to find shelter among the rocks. Mud crabs, as their name suggests, live in muddy places such as mangroves where they dig out a burrow to hide in. On a rocky shore, they are unable to do so and will remain exposed to predators and eventually die.

How did so many Mud crabs end up in the wrong place? Could this be related to an Animal Release event?

More blog posts about this trip


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