Reptiles and Amphibians of Thailand

Thailand's Snakes, Lizards, Turtles, and Frogs

Cantor’s Water Snake

Cantoria violacea

This species is found in Thailand, but not within Bangkok itself
Cantor's Water Snake Yellow-banded Mangrove Snake Cantoria violacea งูปากกวางลาย singapore
Cantor’s Water Snake in Singapore (© Noel Thomas)

English name: Cantor’s Water Snake (aka “Cantor’s Mangrove Snake”, “Yellow-banded Mangrove Snake”, “Cantor’s Mud Snake”)
Scientific name: Cantoria violacea
Thai name: งูปากกวางลาย ( Ngu Pak Kwang Lai)

Description: To 150 cm. The longest and most slender of the water snakes, with small head barely discernible from the neck. Striking black or dark violet color is ribbed with many thinner white or yellow bands. Belly is white in at least some mainland populations but is generally the same color as the rest of the body in the Andaman Islands population.

Relevant scale counts: 19 midbody scale rows of typical smooth scales. Over 234 ventral scales (more than any other water snake).

Similar Species: Keel-bellied Water Snake is not as long and slender, has very different body scales, and has a light background color with much narrower black bands.
Sea Snakes have a paddle-shaped tail.

Range: Andaman Islands and the Andaman Sea coasts of Myanmar, Thailand, and Malaysia down to Singapore and likely further east into Indonesia.

Habitat: Mangrove mudflats, occasionally moving up into the forest itself and sometimes even into fresh water. Utilizes the mud burrows of crustaceans.

Place in the ecosystem: Feeds on crustaceans, including snapping prawns and crabs. May be eaten by larger snakes, monitor lizards, wading birds, civets, and large fish.

Danger to humans: Cantor’s Water Snake is rear-fanged but its venom is not likely to be a threat to humans, though there are unconfirmed reports of serious adverse affects so it is best to treat it like a venomous species.

Conservation status and threats: This snake is rarely encountered and its conservation status is unknown. It appears to be quite common in the Andaman Islands and rare everywhere else, though that may simply be due to difficulty locating it in its habitat. There are no known threats to the species.

Interesting facts: Cantor’s Water Snake is the only snake known to focus its diet on Alpheus shrimp, known as snapping prawns. As these shrimp have a unique defensive behavior (producing an incredible burst of sound by collapsing a cavitation bubble in their large pincher), the Asian Water Snake expert John Murphy has suggested that Canton’s Water Snake may uniquely use this behavior to find its prey, potentially following the sound, light, or chemical effects from the water stream produced to track the shrimp’s location.

In the Middle Andaman Islands these snakes have been found to prey on Orange Signaler Crabs, using the mouth to subdue the crab, pulling off the claws and legs by pressing down on the appendages with its coils and then pulling away until they come off. It then swallows the head/body whole.

References:
Andaman & Nicobar Snakes: Cantoria violacea
IUCN Red List: Cantoria violacea
Yellow-banded Mangrove Snakes consume hard-shelled Orange Signaler Crabs
A Checklist and key to the Homolopsid snakes
Evolution in the Mud

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