Enhydris chanardi
Head scales (© John Murphy) 
Side pattern comparison with Jagor’s Water Snake (© John Murphy)
English name: Chanard’s Mud Snake (aka “Sind River Snake”)
Scientific name: Enhydris chanardi
Thai name: งูสายรุ้งลายจั่นอาจ (Ngu Sai Rung Lai Chan-Ard)
Description: To 55cm long. A very short, thick water snake. Body is grayish-brown above with a pale stripe on the 3rd row of scales on each side and a row of small dark dots running just above it. Other rows of less distinct dark dots are found higher on the body. Underbelly is pale with a grayish zig-zag line on the edges. Head is broad and mottled yellow and grayish-brown.
Relevant scale counts: 21 midbody scale rows which remain 21 at the neck. Scales have no striations. Has two pairs of flared chin shields with with second pair equal or longer than the first. 116-125 ventral scales.
Similar Species: Jagor’s Water Snake lacks the pale stripe, has large dark blotches rather than small dark dots, a 1st pair of chin shields longer than the 2nd and 23-25 scale rows at the neck.
Mekong Mud Snake has striations on the scales and 2-3 longish chin shields with the first pair longer than the second when there are 2 pairs, as well as 136-153 ventral scales.
Rainbow Water Snake lacks the dark spots, often has additional light dorsolateral lines, has striations on the scales and 154+ ventrals.
Range: Recorded only in central Thailand from Bangkok area as well as Nakhon Nayok and Chantanburi provinces.
Habitat: This snake is found in freshwater bodies in the Chao Phraya drainage. Like other members of its family, it likely spends nearly all of its time in the water.
Place in the ecosystem: Living populations have not yet been studied, but it likely feeds on fish and frogs. Would be eaten by larger snakes, large fish, monitors, and wading birds.
Danger to humans: Is a rear-fanged snake like other members of its family, but is not dangerous to humans.
Conservation status and threats: This species was recently described from 15 museum specimens, all of which came from Metropolitan Bangkok or the surrounding area. The most recent of these records was about 20 years old. There are concerns that development in Bangkok may have destroyed much of its habitat and it may be extinct in Bangkok. The above photograph from Nakhon Nayok Province represents the most recently seen living specimen.
Interesting facts: New species are not always found out in the wild. This species was discovered in 2005 by two biologists who examined Jagor’s Water Snake specimens from many museums and discovered that a number of the records were actually mislabeled and represented a previously unknown species. The species was described from these museum specimens, the most recent of which was nearly twenty years old and some of which had been collected a hundred years earlier.
Unfortunately, the Chanard’s Mud Snake might be gone almost as soon as it was discovered. Nearly all of the museum specimens of the species come from Bangkok, which is a tough place for water snakes to live due to its high degree of development. It is possible that some Chanard’s Mud Snakes persist in Bangkok, but their status may be fragile. Hopefully the more rural surrounding provinces have enough of the species in less developed areas that it will be able to survive.
References:
A New Thai Enhydris
A Checklist and Key to the Homalopsid Snakes with the Description of New Genera
IUCN Redlist: Enhydris chanardi
Thai National Parks: Chan-ard’s Mud Snake
Michael Cota, personal communication
John C. Murphy, personal communication
Evolution in the Mud
A Field Guide to the Reptiles of South-East Asia
Reptiles and Amphibians of Thailand 