Wednesday, February 13, 2013

Snakes (Phylum Chordata: Suborder Serpentes) of Singapore

Snakes (phylum Chordata, subphylum Vertebrata, superclass Tetrapoda, class Reptilia, order Squamata, suborder Serpentes) are legless reptiles with a long and somewhat cylindrical body. They resemble legless lizards, but lack the eyelids and external ears that most lizards possess.

Snakes and lizards are from the same order, Squamata, and they can be distinguished from other reptiles by their relatively slender bodies that are covered by scales; extremely movable upper jaws which allows them to swallow relatively large prey; and the males possessing penises that that in pairs (each called a hemipenis).

Like most other reptiles, they have limited physiological means to maintain the body temperature within a narrow range, and are more reliant on external heat sources. They are descended from four-limbed ancestors (hence the superclass Tetrepoda which means "four legs"), and have a backbone with a spinal cord (a hollow tube of nervous tissue).

Depending on the species, snakes may lay eggs (oviparous), bear live young (viviparous), or bear live young from eggs brood within the body (ovoviviparous).

Many people (including myself at one time) fear snakes, but most snakes are actually not aggressive unless provoked. If you keep a good distance and do not attempt to disturb them, they can be admired and observed. However, if the snake hisses or raises the front part of its body, it is probably disturbed and you should back off.

I still have not seen most of the snakes that are recorded from Singapore, and hope to eventually see more during my future trips so that I can update this blog post. Here are just some of those that I managed to photograph:

Family Typhlopidae

Typhlopids, also known as blind snakes, usually have very reduced eyes, a blunt and rounded snout, and a head that is indistinct from a cylindrical body. They also have a very short blunt tail, which ends in a spine for some species.

Brahminy Blind Snake (Ramphotyphlops braminus)
The Brahminy Blind Snake (Ramphotyphlops braminus) is a small blind snake (up to 18cm long) that has a black and smooth cylindrical body. It is often overlooked as it resembles a black earthworm, but it moves a lot faster. The snout and the tip of the tail (which ends in a spine) are usually of a paler colour. It burrows, and can be found under rocks and logs in the forest or even in gardens. It feeds on small soil-dwelling invertebrates. It is believed to be an all-female species that lay eggs.

Family Pythonidae

The pythons are usually large, muscular and non-venomous with heat-sensory pits along their upper lips to help them to detect warm-blooded prey. They kill their prey by wrapping their body around them and gradually constricting them until they suffocate. Some pythons have a pair of spurs on their pelvic region which are remnants of degenerate limbs.

Reticulated Python (Broghammerus reticulatus)
The Reticulated Python (Broghammerus reticulatus) can grow to almost 10m, though those seen in Singapore are seldom more than 5m. It is one of the biggest snakes in the world. The body is greyish brown with networks of irregular black and yellow patterns. It is mostly nocturnal, and feed on small mammals and birds. It can be found on the ground or on trees in the forest, and is also a good swimmer. It can sometimes be found in urban areas too, such as in monsoon drains. It is oviparous.

Family Acrochordidae

The acrohordid snakes are mostly aquatic. They have rough, baggy skin, small eyes on smallish heads. They give birth to live young.

Banded File Snake (Acrochordus granulatus)
The Banded File Snake (Acrochordus granulatus) is usually black or dark grey with light grey, white or cream-coloured bands. It has very rough scales, and the skin appears to be hanging loose. It usually does not exceed 1m in length. This non-venomous snake can be found in coastal areas and river mouths, feeding on small fish and other marine animals.

Family Colubridae

Colubrid snakes have large forehead scales and lateral nostrils. They are generally rather diverse, and more studies need to be done on the group. They can be non-venomous or venomous.

Oriental Whip Snake (Ahaetulla prasina)
The Oriental Whip Snake (Ahaetulla prasina) has a very slender body and a distinct head with a pointed snout (in side profile). The pupils of the eyes are horizontally elongated, compared to the the similar-looking Big-eye Whip Snake. Adult Oriental Whip Snakes are fluorescent green above, with a pair of yellow stripes, one on each side of the belly. Juvenile snakes may have paler colours or darker patches on the body. They are mostly found on trees and bushes in secondary forests or forest edges. Being mildly venomous, they hunt for small vertebrates such as lizards and frogs, usually in the day. They give birth to live young, and can grow to about 1.9m long.

Big-eye Whip Snake (Ahaetulla mycterizans)
The Big-eye Whip Snake (Ahaetulla mycterizans) appears very similar to the previous species, but has a pair of white (instead of yellow) stripes on its belly (one on each side). The pupils of the eyes often appear bigger than those of the previous species as well. Like the previous species, it is mildly venomous. This species gets to a maximum length of about 1m.

Paradise Tree Snake (Chrysopelea paradisi)
The Paradise Tree Snake (Chrysopelea paradisi) is black above with yellowish spots, sometimes with red patterns. Growing to about 1.3m, this snake is commonly seen in a variety of habitats, including mangrove forests, secondary forests, and even gardens and parks. It is mildly venomous, and usually hunts for small animals among trees and bushes in the day. One amazing characteristic of this snake is its ability to glide from tree to tree by launching itself into the air and flattening its body (much like a long kite). It is oviparous.

Twin-barred Tree Snake (Chrysopelea pelias)
The Twin-barred Tree Snake (Chrysopelea pelias) is mostly seen on trees and bushes in the day. It has broad red saddles on its back which are separated by narrow black-edged whitish bands. This small snake (usually not more than 74cm long) is mildly venomous. Like the previous related species, it is oviparous and can glide by launching itself into the air and flattening its body.

Painted Bronzeback (Dendrelaphis pictus)
The Painted Bronzeback (Dendrelaphis pictus) is commonly seen in back mangroves, secondary forests and even gardens and parks. Growing to about 1m long, it is bronze brown above, with a black stripe on each side of its head starting from the snout, passing through the eye towards the tail. There is usually a yellowish stripe on each side of the body. Believed to be non-venomous, it hunts for small vertebrates both on the trees and on the ground in the day. It is oviparous.

Haas's Bronzeback (Dendrelaphis haasi)
The Haas's Bronzeback (Dendrelaphis haasi) is usually found in mature forest. It has a very slender body, growing to about 95cm. Compared to the previous species, it has broader scales on its back, and has a faint cream stripe along its sides. It also has a narrow black stripe behind the eye that breaks into blotches on the side of the neck. This species was only described in 2008, and confirmed to occur in Singapore in 2011.

Elegant Bronzeback (Dendrelaphis formosus)
The Elegant Bronzeback (Dendrelaphis formosus) is mostly found on trees in mature forests. They are more active in the day, feeding on small lizards on the trees. Growing to about 1.4m long, it is bronze brown above with a broad black stripe on each side of the head and neck. The belly is yellowish green. It is oviparous.

Orange-bellied Ringneck (Gongylosoma baliodeirum)
The Orange-bellied Ringneck (Gongylosoma baliodeirum) is a small snake that can only grow to about 35cm long. It is usually found in mature forest, and can be recognised by the yellowish spots on the dark brown body. The underside is orange. It appears to be non-venomous.

House Wolf Snake (Lycodon capucinus)
The House Wolf Snake (Lycodon capucinus) is commonly seen in forested areas, gardens and even among human habitation. This small snake (up to about 75cm long) is usually chocolaty brown above with numerous cream-coloured bands, spots and patches. It feeds on small vertebrates such as geckos, and can be found on the ground as well as on trees at night. It is oviparous, and not known to be venomous.

Gold-ringed Cat Snake (Boiga dendrophila)
The Gold-ringed Cat Snake (Boiga dendrophila) is very distinctive with its shiny black body marked with narrow, bright yellow bands. It can grow to 2.5m long, and is nocturnal. Usually found on trees and low bushes, it can sometimes be seen slithering on the ground or swimming in water at night as well, hunting for small vertebrates. This oviparous snake is mildly venomous

Dog-toothed Cat Snake (Boiga cynodon)
The Dog-toothed Cat Snake (Boiga cynodon) is mostly seen on trees and bushes, and occasionally on the ground. It can grow to about 2.7m, with a laterally compressed body and distinctive head. The body is yellowish or brown with irregular dark brown to black (mostly) cross bars. This oviparous snake is nocturnal and mildly venomous, usually feeding on birds and eggs.

Pink-headed Reed Snake (Calamaria schlegeli)
The Pink-headed Reed Snake (Calamaria schlegeli) resembles the very venomous Blue Malayan Coral Snake, but lacks the bright blue stripes on the sides of the belly found on the latter. It is non-venomous, with a pinkish red head. It can grow to about 1.2m long. Like other reed snake, it is a burrower and feeds on small invertebrates. It is sometimes seen among the leaf litter, or on the forest floor at night.

Malayan Racer (Coelognathus flavolineatus)
The Malayan Racer (Coelognathus flavolineatus) is mostly terrestrial, and is sometimes encountered crossing the road in rural areas in the day. It can grow to about 1.8m long, with a dark brown body marked with black blotches and broken stripes. Sometimes, a pale stripe is present, running down the back of the animal. This oviparous snake appears to be non-venomous, and kill its prey (smaller vertebrates) by constriction.

Red-tailed Racer (Gonyosoma oxycephalum)
The Red-tailed Racer (Gonyosoma oxycephalum) is largely arboreal, being usually found on trees. It can reach a length of 2.4m, with thick-set, laterally compressed body that is bright green above and pale green below. The tail is rusty brown or reddish. This oviparous snake is non-venomous, and hunts for birds and small mammals, killing them by constriction.

Family Homalopsidae

Homalopsid snakes generally live partly or entirely in water. They usually have reduced eyes, probably an adaptation to having to live in murky waters, and nostrils which can be closed by valve-like structures to prevent water from getting in. They are mildly venomous, and are ovoviviparous (as explained earlier, bear live young from eggs brood within the body).

Dog-faced Water Snake (Cerberus schneiderii)
The Dog-faced Water Snake (Cerberus schneiderii), or Schneider's Bockadam, has an olive to brown body with irregular narrow blackish bars. The eyes are small, situated near the top of its head, which will be useful for peeping above the water. This ovoviviparous snake can grow to about one metre long. It is mostly nocturnal, though sometimes it can be seen in the day when it cloudy. It can be seen in the water in mangroves or adjacent shores, or on land exposed during low tide. Being mildly venomous, it feeds on fish. The common name is derived from the side profile of its head, which resembles a dog's head. In fact, the genus, Cerberus, is a multi-headed hound in Greek mythology (and is also featured in Harry Potter as a three-headed dog).

Family Elapidae

Elapid snakes are reputed and much-feared for their lethal venom. The venom glands are connected to a pair of short, rigid fangs in the front of their upper jaws. They are usually more aggressive when they perceive threat, and hence it is important not to provoke them by keeping a good distance. In fact, most of the time, they will stay away from human, and will quickly slither away when they sense someone getting near.

Blue Malayan Coral Snake (Calliophis bivirgata)
The Blue Malayan Coral Snake (Calliophis bivirgata) is highly venomous (possessing neurotoxins), and advertises this with its striking colours. The head and tail are bright red, while the back is navy blue. A powder blue stripe runs along each side of the body. This snake can grow to about 1.8m long, and is usually found in mature forest, usually on the forest floor. While it is mostly nocturnal, it is also occasionally seen in the morning. This oviparous snake feeds on other snake. A bite from this snake can result in death. Its venom glands occupy almost a third of its body length.

Equatorial Spitting Cobra (Naja sumatrana) feeding on an Asian Toad (Duttaphrynus melanostictus)
The Equatorial Spitting Cobra (Naja sumatrana), also called the Black Spitting Cobra locally, can spit venom over a distance of more than a metre away. The venom can cause temporary blindness if it gets into the eye, and hence it is important to keep a good distance from any black snake that you cannot immediately identify. This cobra can get to about 1.5m long, and has a hood (stretchable fold of skin on both sides of the neck) which can be spread out. It will usually do this, and also raise the front part of body when provoked. This oviparous snake feeds on small vertebrates, and can be found in a variety of habitats, ranging from mangrove forest to wooded areas and scrubland, even those near human habitation. The above photo features an Equatorial Spitting Cobra feeding on an Asian Toad (Duttaphrynus melanostictus).

Banded Krait (Bungarus fasciatus)
The Banded Krait (Bungarus fasciatus) is found in coastal and mangrove forests, inland forests and sometimes agricultural land, often close to water bodies. The body, which is triangular in cross-section, is marked with alternating black and yellow bands. It feeds on other snakes and lizards. While it is believed to be mostly nocturnal, it is sometimes seen slithering on the forest floor in the day. This oviparous snake is highly venomous, whose bite can be lethal.

Family Hydrophiidae

Hydrophiid snakes have short and flattened paddle-like tails, adapted for swimming in the sea. They are extremely venomous, possessing myotoxins that destroy muscle tissues, but are generally not aggressive.

Amphibious Sea Snake (Laticauda colubrina)
The Amphibious Sea Snake (Laticauda colubrina), also called the Yellow-lipped Sea Krait, is the only hydrophiid sea snake that comes ashore occasionally to rest and lay eggs. The other sea snakes give birth to live young. The body of the Amphibious Sea Snake is bluish grey with black bands, and the immediate area around the mouth is yellow in colour. Like other sea snakes, its tail is flattened and paddle-like. It feeds on fish, and can grow to about 1.4m long. While sea snakes usually appear rather docile, they should never be handled due to the extremely toxic venom.

Marbled Sea Snake (Aipysurus eydouxii)
The Marbled Sea Snake (Aipysurus eydouxii) is usually seen in shallow waters and coral reefs, though sometimes it can be found stranded on the beach by the receding tides. This is a true sea snake that gives birth to live young out in the sea. This species is believed to feeds mostly on fish eggs. Like other sea snakes, its tail is flattened and paddle-like. It grows to about 1m long and can be recognised by the broad dark brown and thinner pale bands on the body. This is a very venomous snake, and should never be handled.

Family Viperidae

Vipers can be recognised by their triangular heads and short, thick bodies. In Singapore, this family is represented by the pit-vipers, which have a heat-sensitive pit between the eyes and the nostrils for detecting warm-blooded prey. They are usually arboreal and have prehensile tails. They are mostly active at night, and rest on branches of trees in the day. They have a pair of long fangs on the upper jaw, which can deliver a haemotoxin that destroys red blood cells.

Shore Pit Viper (Cryptelytrops purpureomaculatus)
The Shore Pit Viper (Cryptelytrops purpureomaculatus) is usually found on trees coastal and mangrove forests, or sometimes among the rocks on rocky shores and sea walls. They have keeled scales, and the body is purplish black, grey or dark brown, often with irregular darker bands or patches. This venomous snake is nocturnal and live bearing. It is aggressive when provoked, and feed on small vertebrates. Adult snakes can be about 1m long.

Female Wagler's Pit Viper (Tropidolaemus wagleri)
The Wagler's Pit Viper (Tropidolaemus wagleri) is usually found in mature forests. The head is broadly triangular from top view, and like the previous species, it is covered with keeled scales. The females are black with greenish and yellow bands on its back, and yellow below.

Wagler's Pit Viper (Tropidolaemus wagleri)
The juvenile and male Wagler's Pit Vipers are green with pairs of green and red short bars sparsely spaced, running along the sides of their bodies. The bars tend to be longer on the adult males. Like other vipers, they are very venomous and hunt for small vertebrates at night. Like the previous species, they are live-bearing.



References
  • Baker, N. 2013. Ecology Asia. Retrieved Feb 12, 2013, from http://www.ecologyasia.com.
  • Baker, N. & K. Lim, (Vertebrate Study Group, Nature Society Singapore). 2008. Wild Animals Of Singapore. Draco Publishing and Distribution Pte. Ltd. 180 pp.
  • Das, I. 2010. A Field Guide to the Reptiles of South-east Asia. New Holland Publishers (UK) Ltd. 376 pp.
  • Lim, K.P. & L. K. Lim. 1992. A Guide to the Amphibians & Reptiles of Singapore. Singapore Science Centre. 160 pp.
  • Lim, K. K. P. & L. F. Cheong. 2011. Dendrelaphis haasi (Reptilia: Squamata: Colubridae), a new snake record for Singapore. Nature in Singapore, 4: 9–12.

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