Enhydris subtaeniata
This species is found in Thailand, but not within Bangkok itself
Udon Thani (© Howard Cunningham) 
Udon Thani (© Howard Cunningham) 
Udon Thani (© Howard Cunningham) 
Nakhon Sawan (© John Murphy)
English name: Mekong Mud Snake
Scientific name: Enhydris subtaeniata
Thai name: งูสายรุ้งลาย (Ngu Sai Rung Lai)
Description: To 90cm long. A moderately thick-bodied snake with head only slightly thicker than the neck. Body is brownish or grayish, often darker on the top than on the sides, with rows of indistinct black markings on both the top and sides. There is a pink/red line on the lowest part of the sides below the dark side markings, some specimens also have a reddish line between the dark upper markings and dark side markings. Dorsal scales have striations. Belly is cream-colored, sometimes with a pair of zig-zag reddish lines on each side.
Relevant scale counts: 21 midbody scale rows, scales have striations. The underside of the head has 2-3 chin shields which are long rather than flared; when there are 2 shields the first is longer than the second. There are 136-153 ventral scales.
Similar Species: Chanard’s Mud Snake has no striations on the scales, has a flared first chin shield and the 2nd chin shield is longer than the 1st. It has 116-125 ventrals.
Rainbow Water Snake lacks dark markings and has 154 or more ventral scales.
Jagor’s Water Snake is thicker, has larger black blotches, and lacks the reddish lines. It has 117-127 ventral scales.
Range: The Mekong Mud Snake is found in the Mekong drainage including southern Laos, eastern Thailand, Cambodia, and Vietnam. There are some populations in central Thailand.
Habitat: Slow-moving water bodies including ponds, ditches, rice paddies and canals. Is not known to leave the water.
Place in the ecosystem: Eats fish and frogs. Is eaten by larger snakes, large fish, monitors, and wading birds.
Danger to humans: Is a rear-fanged species and will bite when threatened but is not dangerous to humans.
Conservation status and threats: The Mekong Mud Snake appears to be common within its range. However, it is one of many snakes that is being harvested unsustainably in several regions, including Cambodia and Vietnam.
Interesting facts: The Mekong Mud Snake is almost entirely limited to the lower Mekong River Basin. For example, one study found the species to be incredibly common inside the Khorat Basin which feeds into the Mekong, yet entirely absent just outside of it. Snakes can often have strict range boundaries due to minor habitat differences, competition from other species, and historical patterns in how the species spread. In this case the Mekong Mud Snake likely has never spread north due to the more mountainous terrain in that direction, though it is not known why it is not found further to the west like other water snakes. Competition with Jagor’s Water Snake and Chanard’s Mud Snake in the past when both speices were more abundant may have kept it from establishing itself in central Thailand.
References:
Thai National Parks: Mekong Mud Snake
IUCN Redlist: Enhydris subtaeniata
Comparison of Semiaquatic Snake Communities Associated with the Khorat Basin, Thailand
A Checklist and Key to the Homalopsid Snakes with the Description of New Genera
Evolution in the Mud
