Jack’s Water Snake

Homalopsis mereljcoxi

Jack’s Water Snake in Nakhon Ratchasima Province (photo by Alex Heimerdinger)

Head shot of Jack’s Water Snake (photo by Alex Heimerdinger)

Jack’s Water Snake (photo by Alex Heimerdinger)

Jack’s Water Snake (photo by Alex Heimerdinger)

Jack’s Water Snake (photo by John Murphy)

Jack’s Water Snake (photo by John Murphy)

Older adult Jack’s Water Snake (photo by Michael Cota)

Jack’s Water Snake trapped in Vietnam (photo by Alex Krohn)

Jack’s Water Snake killed by car (photo by Alex Heimerdinger)

Jack’s Water Snake that had been released by tourist into Lumpani Park

English name: Jack’s Water Snake (aka “Jack’s Masked Water Snake”, “Puff-faced Water Snake”)
Scientific name: Homalopsis mereljcoxi (formerly Homalopsis buccata)
Thai name: Ngu Hua-kra-lok, Ngu Leuamao

Description: To 137cm long. Robust, somewhat flattened body. Notable broad, brown head with dark eyestripes, a “V” marking on top of the head and an inverted “V” on the snout. Has keeled scales. Body is dark brown to black with narrow light bands that fade in old age. Underside is white to yellow with small black dots.

Similar Species: Bocourt’s Water Snake has no face mask, is thicker and darker with black markings interspersed with the brown.
Red-tailed Pipe Snake has a small, dark head, smooth scales, and a barred underbelly.
Puff-faced Water Snake, which is not found in Bangkok, can only be distinguished by scale counts and range

Habitat: 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: Jack’s Water Snake eats fish, 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: Due to its broad distribution and ability to live in human-altered habitats, this snake is not considered at risk in Thailand. It is becoming popular in the pet trade, but that has only had an effect on populations at the local level. In nearby countries similar species are declining due to massive collection for food, skins and crocodile feed.

Interesting facts: In September 2010, I came upon a juvenile Jack’s Water Snake in Lumpani Park. Upon viewing and photographing the snake, an American tourist nearby got anxious and stated, “I ask only that you do not harm the snake.” Further inquiry found that he had bought the snake at a Bangkok market and “humanely” released it into the Lumpani Park lakes. He had no idea whether the snake was a native species or whether it was venomous.

Releasing a captive animal into the wild, even a native one, is not good for the local ecosystems. Non-native species, such as the red-eared sliders in the ponds, the Norway rats in the streets, and the English house sparrows in the trees, may prey on, outcompete, or spread disease among local species. And even native species that have spent time in captivity are highly at risk for transmitting disease into the wild populations. If you purchase a captive animal and can no longer care for it, please find a responsible person to take over care for the animal rather than releasing it into the wild.

References:
The IUCN Red List: Homalopsis buccata
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
A Field Guide to the Snakes of South Vietnam