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Dog-faced Watersnake
Cerberus rynchops

close up of headThese snakes got their name for their distinctive head shape with large scales (shield), small eyes positioned close to top of the head and nostrils, with well defined "lips". They are found mostly in slow-moving waters in mangroves and brackish rivers, but sometimes also in freshwater far inland, such as rice fields.
Mangrove and wetland wildlife at
Sungei Buloh Nature Park
Main features: Variously greyish, brownish. in the water, from above
or olive sometimes with dark spots or bars. Average 75-90cm, up to 1.2m.

Status in Singapore: Common.

World distribution: Tropical Asia from India across to the Philippines, down the Malay peninsula. Also on the Andaman and Nicobar Islands.

Classification: Family Colubridae. Subfamily Homalopsinae (rear-fanged water snakes).
At Sungei Buloh, they may sometimes be seen at low tide near the main bridge, well camouflaged among the tangle of mangrove roots.

on mudDog-faced Watersnakes feed mainly on fish. Small ones hunt smaller fishes, but larger ones can take mudskippers, eels, catfish and mullet. They may also eat crabs. They hunt by a sit-and-wait approach, or pursuing their prey. They may also bait fish with their tails and slither into mudskippers burrows to catch them. Strong swimmers, they are most active in the evenings. But they are sluggish on land. They have valved nostrils which they close when under water and have long lungs to help them float. To move across mudflats, they may sidewind in the same way that desert vipers move across soft sands.

close-up in the waterDog-faced Watersnakes have a very mild venom which rarely affect humans. Their fangs are small and found at the back of the mouth. The venom drips down grooves in the fangs. They are not aggressive in water, usually lethargic and docile, even allowing humans to handle them. However, on land, their first response to threats is to flee. When cornered, they emit a foul smell and may bite.

Breeding: The Dog-faced Watersnake gives birth to live young, 8-26 in a litter. Newborns look like miniature adults and measure 17-25cm. They reach maturity at 60cm which they usually attain in 2-3 years.

Role in the habitat: Like other predators, they control the populations of their prey. They are in turn eaten by other animals higher up the food chain.

Status and threats: CITES Appendix III. They are threatened by pesticide use which affects prey availability and the snakes' reproduction.

LINKS REFERENCES
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  • Merel J. Cox, Peter Paul van Dijk, Jarujin Nabhitabhata and Kumthorn Thirakhupt, "A Photographic Guide to Snakes and Other Reptiles of Peninsular Malaysia, Singapore and Thailand", New Holland, 1998 (p. 39: habits, habitat, photo).
  • Kelvin K P Lim and Francis L K Lim, "A Guide to The Amphibians and Reptiles of Singapore", BP Science Centre, 1992 (p. 76: habits, habitat, photo).
 
By Ria Tan, 2001