Tuesday, August 29, 2006

"Curse" of "The Devil-Eyed"

A Shore Pit Viper (Trimeresurus purpureomaculatus) was sighted by Charlene Yeong in Lim Chu Kang mangroves on 28 August 2006, at about 9 pm. This venomous snake, as in my previous sightings in Pasir Ris Park Mangrove Swamp on 7 May 2006 and 18 August 2006, was lying on the ground coiling its body around mangrove roots and branch twigs. So please watch where you step and do not kill the snake under your feet! Oh, of course this is for your own safety too.

Somehow, I found a strange and unproven correlation between the presence of Short Pit Viper and the absence of crustacean-eating homalopsines (Cantoria violacea, Fordonia leucobalia and Gerarda prevostiana), and vice versa. This is the trend for all 6 nights:

4 September 2005 (Cantoria violacea)
7 May 2006 (Trimeresurus purpureomaculatus)
18 August 2006 (Trimeresurus purpureomaculatus)
19 August 2006 (Cantoria violacea and Fordonia leucobalia)
27 August 2006 (Fordonia leucobalia and Gerarda prevostiana)
28 August 2006 (Trimeresurus purpureomaculatus)

Could environmental factors be the cause of this observations?

Gerard's Water Snake (Gerarda prevostiana)

A Gerard's Water Snake (Gerarda prevostiana) was spotted by Helen Wong and caught by Lim Weiling in a tidal pool at the base of a mud lobster mound in Pasir Ris Park Mangrove Swamp on 27 August 2006, 9 pm. This mildly-venomous snake seems to be rather rare nowadays.

Karns et al., (2002) investigated on the homalopsine snakes population in Pasir Ris Park Mangrove Swamp, and found Gerarda prevostiana to be the second most common of four species in Pasir Ris Park, after the fish-eating Cerberus rynchops. Results showed that this species is more commonly encountered on full and new moon nights compared to half moon nights.

John Murphy and Harold Voris (2002) called Gerarda prevostiana "a snake with a secret".

They also wrote:
"Gerald's water snake remained a mystery in virtually all aspects of its biology until recently. Few museum specimens were available before the 1990's."

This trend holds true for the other crustacean-eating homalopsines found in Singapore: Cantor's Water Snake (Cantoria violacea) and Crab-eating Water Snake (Fordonia leucobalia).

Studies by a team of American biologists (Harold Voris, Daryl Karns and Bruce Jayne) here in 2001 shed invaluable light on these mysterious creatures.

It has been suggested that Gerard's water snake, like most homalopsines, feeds on fishes (Cox et al., 1998; Murphy & Voris, 2002; Voris & Murphy, 2002). Examination of museum specimens proved this to be wrong, and revealed that this snake preys on grapsid crabs (Murphy & Voris, 2002; Voris & Murphy, 2002).

In the laboratory, Bruce Jayne found that captive snakes feed only on freshly moulted crabs. The video can be downloaded here.

The table manners of Gerarda prevostiana is so unusual that it has never been documented in other snakes. All snakes are known to swallow food whole, except this species which uses a 'loop and pull' technique to tear its food into bite-sized pieces before enjoying the meal (Jayne et al., 2002; Murphy & Voris, 2002). By doing this, the snake can feed on prey that are otherwise too large for its mouth (gape). This is also probably the reason why Gerard's Water Snake loves soft-shelled crabs.

Like Fordonia leucobalia, the distribution of Gerarda prevostiana is remarkably similar to that of the mud lobster (Thalissina anomala) (Murphy & Voris, 2002). This snake hides in the burrows of mud lobster mounds, swims in tidal pools formed in depressions around the bases of mud lobster mounds, and moves in and out of the water and crab burrows on the outer surface of the mounds when foraging (Murphy & Voris, 2002; Voris & Murphy, 2002).

Gerarda prevostiana has been recorded from India, Sri Lanka, Thailand, Singapore and the Philippines (Murphy & Voris, 2002; Voris & Murphy, 2002). Locally, this snake has been collected from Pasir Ris Park and Lim Chu Kang (Karns et al., 2002; Voris & Murphy, 2002).

From left to right: Dorsal side of head; Ventral side of head; Right side of head; Dorsal side of body; Ventral side of body; Dorsal side of tail; Ventral side of tail.

* All photographs by Mr Lim Swee Cheng.


Cox, M. J., van Dijk, P. P., Nabhitabhata, J. & Thirakhupt, K., 1998. A photographic guide to snakes and other reptiles of Peninsula Malaysia, Singapore and Thailand. New Holland Publishers (UK) Ltd, p. 42.

Jayne, B. C., Voris, H. K. & Ng, P. K. L., 2002. Snake circumvent constraints on prey size. Nature 418: 413.

Karns, D.R., Voris, H. K. & Goodwin, T. G., 2002. Ecology of Oriental-Australian rear-fanged water snakes (Colubridae: Homalpsinae) in the Pasir Ris Park Mangrove Forest, Singapore. The Raffles Bulletin of Zoology 50(2): 487-498.

Murphy, J. C. & Voris, H. K., 2002. Aquatic snakes with crustacean-eating habits elude herpetologists for two centuries. Litteratura Serpentium 22(3): 107-114.

Voris, H. K. & Murphy, J. C., 2002. The prey and predators of Homalopsine snakes. Journal of Natural History 36: 1621-1632.



Wednesday, August 23, 2006

Bad Publicity For Snakes

Poor snakes.

New blow to their reputation.

And you thought they have enough bad publicity.

"Snakes On A Plane" (a ridiculousss Hollywood movie about snakes terrorising humans on a plane) will be opening tomorrow (24 August 2006) in Singapore theatres.

Before you become too paranoid after watching the show and decide to kill every snakes you encounter, it is important to know that only a small percentage of the almost 3,000 species of snakes in the world are dangerous to people.

I cannot get any figures from the books I have, but through googling, I found websites consistently stating the percentage to be 10%.

I think there are about 25 species of venomous snakes in Singapore, 11 of which are considered mildly venomous (venom which is often too mild to have any serious effects on normal humans), 7 of which inhabits the sea, some rarely bite people, and most are very shy/elusive.

In fact, ALL snakes (maybe except a huge and hungry Reticulated Python) cannot be bothered with humans, unless you "suay suay" disturbed them (e.g. stepped on their tails).

Interesting articles:

Video of Ular Laut in Pulau Hantu

Debby Ng of Hantu Bloggers has a wonderful video of a Yellow-lipped Sea Krait (Laticauda colubrina) swimming along the sea bed of Pulau Hantu.

Check out earlier SLOG post on this beautiful snake.

Crab-eating Water Snake (Fordonia leucobalia)

Two Crab-eating Water Snakes (Fordonia leucobalia) were sighted in Pasir Ris Park Mangrove Swamp on 19 August 2006, 9 pm. One snake was lying on the mudflat while the other was found on a mud lobster mound. My first encounter with this species was when I was part of a volunteering team "Snakehunters" led by a group of American biologists (Daryl Karns, Harold Voris & Bruce Jayne) researching on the ecology of homalopsines (A group of snakes that includes Fordonia leucobalia, Cantoria violacea, Gerarda prevostiana, and Cerberus rynchops) in Pasir Ris Park Mangrove Swamp in 2001. This study was published in our local biodiversity journal Raffles Bulletin of Zoology in 2002 [pdf, 1390 kb].

Ten years after the description of Fordonia leucobalia in 1837, Theodore Cantor recognized that F. leucobalia ate crabs, thus its common name (Murphy & Voris, 2002). Alan Savitzky (1983) suggested that this snake uses its jaws to crush crabs. John Murphy and Harold Voris (2002), however, found that the carapace always remained intact when F. leucobalia consumed hard-shelled crabs. Richard Shine and Terry Schwaner (1985) observed this species using an unusual form of constriction while feeding on crabs and removing and eating each of the crab's legs. By using the same method, F. leucobalia teared apart carapaces of very large soft shelled crabs (Murphy & Voris, 2002).

John Murphy and Harold Voris (2002) described the unique feeding strategy of Fordonia leucobalia:
"Small crabs were simply seized and swallowed with the strike, but larger crabs were handled in a different manner. The snake struck at the crab with a closed mouth, but instead of grabbing the crab in its jaws it slapped the crab with its chin. The crab, apparently realized it was under attack, withdrew its legs and sunk into the substrate into a defensive posture. The snake then went to work swallowing the crab sideways. Large crabs that resist predation may end up having the snake chewing on one of its legs, and as the crab tires, it may eject the leg to escape, leaving only a small piece of itself as a morsel for the snake."

This midly-venomous snake possesses massive fangs that look like nail punches built to puncture the hard chitinous exoskeleton of crabs (Murphy & Voris, 2002).

Cox et al. (1998) claimed that this species not only preys on crabs, but also on small fish.

Litters of 6-15 young, each 18 cm long, are known (Cox et al., 1998). Adults can grow up to 94 cm (Cox et al., 1998).

This nocturnal snake inhabits tidal rivers and coastal areas (Cox et al., 1998). It made extensive use of mud lobster mounds, has been observed foraging on mud tidal flats, and also known to use crab burrows (Karns et al., 2002).

It occurs from Burma through southern Thailand, Malaysia, Singapore and New Guinea to northern Australia, a distribution remarkably similar to mud lobsters (Thalissina anomala) (Barrett, 1950; Cox et al., 1998; Murphy & Voris, 2002).

From left to right: Dorsal side of head; Right side of head; Dorsal side of body; Ventral side of body; Ventral side of tail.

* All photographs by Chan Kwok Wai


Barrett, C., 1950. Reptiles of Australia: crocodiles, snakes and lizards. Cassel & Company Limited, p. 113.

Cox, M. J., van Dijk, P. P., Nabhitabhata, J. & Thirakhupt, K., 1998. A photographic guide to snakes and other reptiles of Peninsula Malaysia, Singapore and Thailand. New Holland Publishers (UK) Ltd, p. 39.

Jayne, B. C., Voris, H. K. & Ng, P. K. L., 2002. Snake circumvent constraints on prey size. Nature 418: 413.

Murphy, J. C. & Voris, H. K., 2002. Aquatic snakes with crustacean-eating habits elude herpetologists for two centuries. Litteratura Serpentium 22(3): 107-114.

Savitzky, A. H., 1983. Coadapted character complexes among snakes: fossoriality, piscivory, and durophagy. American Zoologist 23: 397-409.

Shine, R. & Schwaner, T., 1985. Prey constriction by venomous snakes: a review and new data on Australian species. Copeia 1985(4): 1067-1071.

Sunday, August 20, 2006

Cantor Lost It's Golden Rings

Joe Ong spotted a Cantor's Water Snake (Cantoria violacea) on the mudflat in Pasir Ris Park Mangrove Swamp on 19 August 2006, 10pm. The scale pattern of this individual is slightly different from that of the other snake I found on 4 December 2005. The golden rings of the former are not present throughout the whole body and tail as in the latter. Chan Kwok Wai captured wonderful close-up shots of this beautiful snake.

From left to right: Dorsal side of head; Right side of head, Dorsal side of body, Ventral side of body; Cloaca; Ventral side of tail.

* All photographs by Mr Chan Kwok Wai.

Friday, August 18, 2006

Banded File Snake (Acrochordus granulatus)

Ria Tan seems to have lots of luck with Banded File Snakes (Acrochordus granulatus), having sighted them 3 times on the northern shores of Singapore:

Chek Jawa 21 October 2001
Chek Jawa 16 June 2003
Pulau Sekudu 10 July 2005

This nocturnal species inhabits various coastal habitats such as shallow seas, river mouths, estuaries and mangroves (Lim & Lee, 1989; Lim & Lim, 1992; Cox et al., 1998). It feeds on fishes, including eels (Lim & Lee, 1989; Lim & Lim, 1992; Cox et al., 1998).

These live-bearers produce a litter of 5-10 young, averaging 22 cm, after about six months' gestation (Cox et al., 1998). One individual was found to have 7 fully developed embryos in late April (Lim & Lee, 1989). This non-venomous species can grow to about 1 m in length (Lim & Lee, 1989; Lim & Lim, 1992; Cox et al., 1998).

It ranges from India to northern Australia and to Hainan (Cox et al., 1998).

From left to right: Dorsal side of head; Right side of head; Dorsal side of body; Ventral side of body; Dorsal side of tail.

* All photographs by Ms Ria Tan.


Cox, M. J., van Dijk, P. P., Nabhitabhata, J. & Thirakhupt, K., 1998. A photographic guide to snakes and other reptiles of Peninsula Malaysia, Singapore and Thailand. New Holland Publishers (UK) Ltd, p. 12.

Lim, F. L. K. & Lee, M. T. M., 1989. Fascinating Snakes of Southeast Asia – an Introduction. Tropical Press, Kuala Lumpur, p. 30.

Lim, K. K. P. & Lim, F. L. K., 1992. A Guide To The Amphibians & Reptiles Of Singapore. Singapore Science Centre, p. 147.

Thursday, August 17, 2006

What's Hisss Name?

Since we live in a multi-lingual society, I supposed it is useful to know the name of our beloved limbless friends in all five "National" languages:

English: Snake
Malay: Ular
Mandarin: She (pronounce "Sir")
Singlish (Hokkien in this case): Zua
Tamil: Pambu

Another Snake Roadkill

Another roadkill sighted by Norman Lim on The Singapore Offshore Island. This House Wolf Snake (Lycodon capucinus) was found lying on the side of the road on 10 August 2006. It was not flattened but has some scratches. Perhaps it was abandoned after being attacked by a predator (e.g. bird)? Nobody knows.

SLOG had already documented 6 other snake species from this locality, most of which are thanks (oh well ...) to roadkills:

Keel-bellied Whip Snake (Dryophiops rubescens) 20 May 2006
Banded Krait (Bungarus fasciatus) 21 May 2006
Common Malayan Racer (Coelognathus flavolineatus)27 June 2006
Painted Bronzeback (Dendrelaphis pictus)27 June 2006
Equatorial Spitting Cobra (Naja sumatrana) 27 June 2006
King Cobra (Ophiophagus hannah) 27 June 2006

I am sure there are many more out there ...

Wednesday, August 09, 2006

"Gor Yok" Uncle and His Gold-ringed Cat Snake

I chanced upon this uncle selling "gor yok" (膏药; medical oilment) in Jurong West today. On the table is this Gold-ringed Cat Snake (Boiga dendrophila) displayed in an opened red bag. I am not sure what the legless friend has got to do with the medicine the uncle is selling but it is definitely a crowd-puller!

People might have mistaken the snake for a highly venomous snake such as a cobra or a krait, and somehow formed an equation of "uncle not afraid of venomous snake" = "medicine is good" = "must buy!" Haha.

Monday, August 07, 2006

Blind snake MTV

Blind snake 1
Release from box, back to home sweet soil
4th July 06, approx. 5pm, Junyuan Primary School

Blind snake 2
Found another one 5m away! woo hoo!
4th July 06, approx. 5.30pm, Junyuan Primary School

Stalking Blindy who was so camera shy. Not sure if it's the same guy as the lucky one spotted on 4th July.
7th July 06, approx. 5pm, Junyuan Primary School

The secret location of where Blindy 2 stakes out - under the stone slab!
7th July 06, approx. 5.30pm, Junyuan Primary School
*Thanks to my very enthusiastic P6 Science Gym students who tirelessly lift up almost all the stone slabs in their ecogarden!

Wednesday, August 02, 2006

There used to be a lot of snakes in Singapore

I chanced upon this extremely illogical but hissslarious article by T. S. Daniel (19 May 2004, Singapore Can!), when I was googling on "Singapore Snakes".

There used to be a lot of snakes in Singapore

"There are not very many snakes slithering around the streets of Singapore, But there are a few. And they are very big. Usually about 30 metres long. It wasn’t always like this. Snakes used to be much smaller and there were thousands of them everywhere. What happened is that the stronger snakes started to eat the weaker snakes. This usually meant that the longer snakes were swallowing the shorter snakes. To cut a long story short, the reason there aren’t many snakes left and why those that are left are so big is because they have swallowed all the others. It has been calculated that within 5 years there will be only one snake left in Singapore. And that snake will be so big that when he gets hungry he will mistake the end of his tail for another snake and start eating it. This won’t hurt, of course, because his other end will be so far away. And snake pain doesn’t travel very fast. This, the mad hotness of the sun beating down and the lack of water will probably mean that he will gobble himself up in no time. Then there will be no snakes at all. This is what happened in Ireland."

A Snake-Charmed Life in Singapore

Michael Richardson wrote the article "A Snake-Charmed Life in Singapore" in International Herald Tribute on 07 Jan 1997.

The article might be old, but I think it is still good enough to share with you. N. Sivasothi of Habitatnews has kindly uploaded a pdf file of the article on his website.

Richardson was charmed by the snakes in Singapore. I am charmed by him, especially his change of perspective towards snakes.

Some interesting extracts from the article:

" As a boy who spent time on farms in Australia, I was taught that the best snake is a dead one."

" So when I arrived in Singapore — a small island-state where nearly all of the original tropical. jungle has been replaced by apartment and office blocks, factories, highways and manicured parks and gardens — I did not expect any further problems with snakes."

"I have lately discovered that one of the reasons Singaporeans are disinclined to rent such places (old British military quarters) — apart from their reputation as being haunted — is the prevalence of snakes."

" But it is hard to feel so affectionate about the snakes that seek sanctuary in the park where we live."

" I never try to harm these snakes as none of them is aggressive or seriously venomous."

"The snake was fully exposed on a bare embankment — a relatively easy target for my stick. But instead of striking, I hesitated, mesmerized by its slow, sinuous movement."
"It was true that I was still recovering from food poisoning. But that was only part of the truth."

Tuesday, August 01, 2006

Snake Roadkills in Singapore

Norman Lim sighted FOUR roadkills of different snake species on a single day (27 June 2006) on an offshore island of Singapore: Coelognathus flavolineatus (Common Malayan Racer), Dendrelaphis pictus (Painted Bronzeback), Naja sumatrana (Equatorial Spitting Cobra), and a Ophiophagus hannah (King Cobra) juvenile.

Snakes need to bask but these poor souls were probably enjoying a nice sun tan, when they were driven to their graves. Nobody knows how many snakes are killed this way in Singapore. Please drive safely, for the snakes.

Bad for snakes but good for scientists. Live snakes are hard to collect, thus dead specimens are extremely precious. Scientists can still collect loads of useful data from well-preserved specimens, without killing one. You can do your part for local conservation by reporting roadkills to the Raffles Museum of Biodiversity Research soon after your sighting.