Reptiles and Amphibians of Thailand

Thailand's Snakes, Lizards, Turtles, and Frogs

Martaban Water Snake

Homalopsis semizonata

This species is found in Thailand, but not within Bangkok itself
Martaban Water Snake mud snake Homalopsis semizonata phuket งูหัวกะโหลกระนอง
Subadult Martaban Water Snake in Phuket (© Montri Sumontha)

English name: Martaban Water Snake (aka “Martaban Mud Snake”, “Puff-faced Water Snake”)
Scientific name: Homalopsis semizonata
Thai name: งูหัวกะโหลกระนอง (Ngu Hua-kra-lok Ranong)

Description: To 120cm long. Robust, somewhat flattened body is brown with grey-to-beige saddle-shaped blotches outlined in black. Notable broad, grayish-brown head with dark eyestripes, a “Y” marking on top of the head and an inverted “Y” on the snout. Underside is beige with a highly broken black stripe down each side.

Relevant scale counts: 39-43 midbody scale rows, which are keeled. Typically 3 prefrontals (though sometimes 2 or 4), frontal scale usually broken into 2-7 smaller scales and pushes in between the parietals. 1-2 preoculars / 1 presubocular. 153-164 ventrals.

Similar Species: Jack’s Water Snake is more clearly banded rather than having saddle-blotches, has a single frontal and usually 165+ ventrals.
Puff-faced Water Snake is more clearly banded rather than having saddle-blotches, has a single frontal and 40 or fewer midbody scale rows.
Dog-faced Water Snake has black bars that are narrower than the light background and dorsolaterally protruding eyes
Bocourt’s Water Snake is thicker and darker in color, lacks a dark facemask, and has black markings interspersed with the brown.

Range: Southern/coastal Myanmar and the western coast of southern Thailand.

Habitat: Near sea level in rivers, lakes, ponds, swamps, rice paddies, drainage ditches, and any other lowland habitat with water, including brackish water. Can be found in the water or on the banks. During the day it hides in burrows and crab holes.

Place in the ecosystem: The Martaban Water Snake eats primarily fish, though it may also take crustaceans and frogs. Juveniles of the species are eaten by larger snakes, large fish, monitors, and wading birds.

Danger to humans: Can bite, but rarely does so and is not dangerous to humans.

Conservation status and threats: Little is known about the conservation status of this species due to the lack of records and its uncertain distribution.

Interesting facts: The constantly updated research into taxonomy can sometimes make snake names confusing to keep up with. The Puff-faced Water Snake, Homalopsis buccata, was once considered to occupy a huge range throughout southeast Asia. However, scientists studying the Homalopsis genus have found that it is actually comprised of five different species. These species are now:

Puff-faced Water Snake (Homalopsis buccata): Found in Indonesia, Singapore, Malaysia, and south Thailand
Martaban Water Snake (Homalopsis semizonata): Found in southern Myanmar and the western coast of south Thailand
Jack’s Water Snake (Homalopsis mereljcoxi): Found in most of Thailand as well as Cambodia and Vietnam
Deuve’s Water Snake (Homalopsis nigroventralis): Found in the Mekong River Valley in Laos, east Thailand, Cambodia, and Vietnam
Hardwick’s Water Snake (Homalopsis hardwickii): Found in northeast India, Bangladesh and Nepal

The five species are difficult to distinguish unless you are an expert, and may require scale counts to be certain. More information on the species and the rest of the Asian Water Snakes can be found in A Checklist and Key to the Homalopsid Snakes (Reptilia, Squamata, Serpentes), with the Description of New Genera, by John Murphy and Harold Voris. Further clarification on Homalopsis semizonata in Thailand can be seen in Taxonomic identity of two enigmatic aquatic snake populations from southern Thailand, by Olivier Pauwels and Montri Sumontha.

References:
Thai National Parks: Martaban Mud Snake
Taxonomic identity of two enigmatic aquatic snake populations from southern Thailand
A Checklist and Key to the Homalopsid Snakes
pers. comm. John Murphy
A Photographic Guide to Snakes and Other Reptiles of Peninsular Malaysia, Singapore and Thailand
A Field Guide to the Reptiles of South-East Asia

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