Reptiles and Amphibians of Thailand

Thailand's Snakes, Lizards, Turtles, and Frogs

Glossy Marsh Snake

Gerarda prevostiana

This species is found in Thailand, but not within Bangkok itself
Glossy Marsh Snake Cat-eyed Fishing Snake Gerarda prevostiana งูปลาตาแมว
Glossy Marsh Snake in Bangladesh (Jon Hakim / CC BY-NC-SA)

English name: Glossy Marsh Snake (aka “Gerard’s Water Snake”, “Cat-eyed Fishing Snake”, “Gerard’s Water Snake”)
Scientific name: Gerarda prevostiana
Thai name: งูปลาตาแมว (Ngu Pla Ta Maeo)

Description: To 52 cm. A small slender water snake. Color is a plain olive-brown to gray or black with a white belly. Head is somewhat distinct from the body and the same color as the body with white/cream lips.

Relevant scale counts: 17 midbody scale rows. The loreal scale is present, nasal scales are separated by an internasal, and the second pair of chin shields is separated by small scales.

Similar Species: Crab-eating Water Snake has a heftier, stronger body, a less distinct head, 23-27 midbody scales, usually lacks the loreal scale, and has its second pair of chin scales in contact with each other.
Yellow-bellied Water Snake usually (but not always) has a yellow belly, has 19 midbody scales rows, its nasal scales are in contact, and it is only found in fresh-water environments.

Range: Coastal areas from the Philippines across southeast Asia to India.

Habitat: This species is found in mangrove mudflats and the surrounding mangrove forests. It sometimes will appear in other aquatic habitats near the coastline.

Place in the ecosystem: Focuses on eating soft crabs that have recently shed their shells. May be eaten by larger snakes, large fish, monitors, and wading birds.

Danger to humans: The Glossy Marsh Snake is rear-fanged but its venom is not a threat to humans.

Conservation status and threats: It is considered to be widespread and common, there are no known threats.

Interesting facts: The Glossy Marsh Snake and its close relative the Crab-eating Water Snake are fascinating in that they both eat crabs but have completely different techniques for dealing with this unusual prey. The Glossy Marsh Snake is unable to attack the crabs when they are fully shelled, instead hunting for crabs that have recently shed their shells and preying on them during the short vulnerable period when they are soft. After initially striking and subduing the crab, it tears it apart by looping its coils around the crab and using its mouth to pull the crab through the too-small loop until the body structure collapses into a more easily swallowable piece.

Ecology Asia: Gerard’s Water Snake
IUCN Red List: Gerard’s Water Snake
A Checklist and key to the Homolopsid snakes
Evolution in the Mud

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