Reptiles and Amphibians of Thailand

Thailand's Snakes, Lizards, Turtles, and Frogs

Deuve's Water Snake

Homalopsis nigroventralis

This species is found in Thailand, but not within Bangkok itself
Deuve's Water Snake Homalopsis nigroventralis mekong masked water snake thailand
Deuve’s Water Snake (© John Murphy)

These four pictures are a specimen found dead on the road. All photos © nopcoeur on iNaturalist.

English name: Deuve’s Water Snake (aka “Deuve’s Mud Snake”, “Mekong Masked Water Snake”)
Scientific name: Homalopsis nigroventralis
Thai name: งูหัวกะโหลกท้องดำ ( Ngu Hua-kra-lok Thong Damm)

Description: To 120cm long. Robust, somewhat flattened body. Notable broad, brown head with dark eyestripes, a “Y” marking on top of the head and an inverted “Y” on the snout. Body is dark brown to olive-grey with narrow tan bands that darken in old age. Underside is dark with pale markings, the opposite of other Homalopsis species.

Relevant scale counts: 35-39 midbody scale rows with keeled dorsal scales, single loreal, 1-2 postoculars/1 postsubocular, and 159-167 ventral scales.

Similar Species: Jack’s Water Snake is lighter in color with high contrast dark bands, 40+ midbody scale rows, and a pale venter with dark spots.
Bocourt’s Water Snake is bulkier, lacks a black facemask, and has black markings interspersed within the brown.
Puff-faced Water Snake is lighter in color, has a pale venter with dark spots, and is only known from southern Thailand and countries to the south.

Range: The Mekong River drainage in Laos, eastern Thailand, Cambodia and Vietnam.

Habitat: Found in a variety of water bodies, including streams, rivers, and lakes. Unlike other Homalopsis species which seem to prefer stagnant water with muddy substrate, Deuve’s Water Snake can be found in streams with a moderate current and sand or gravel substrate.

Place in the ecosystem: Deuve’s Water Snakes 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. Similar species are collected in large numbers for their skin and meat in nearby localities.

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 northeast Thailand, Laos, Cambodia and Vietnam
Hardwick’s Water Snake (Homalopsis hardwickii): Found in northeast India, Bangladesh and Nepal

The five species are difficult to distinguish 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.

References:
Thai National Parks: Deuve’s Mud Snake
A Checklist and Key to the Homalopsid Snakes
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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