Enhydris jagorii
Uttaradit (© John Murphy) 
Uttaradit (© John Murphy) 
Head scale features (© John Murphy) 
Side of Chanard and Jagor (© John Murphy)
English name: Jagor’s Water Snake (aka: “Bangkok Mud Snake”)
Scientific name: Enhydris jagorii
Thai name: งูสายรุงลายขวาง (Ngu Sai-rung Lai Kwan)
Description: To 68cm long. A short, thick snake with moderate head. Body is grayish-brown to dark brown with large black blotches in a line down the sides and smaller blotches along the top. Underbelly is pale.
Relevant scale counts: 21 midbody scale rows with 23-25 scale rows at the neck. No striations on scales. “Flared” first pair of chin shields longer than the second pair. 117-127 ventral scales.
Similar Species: Mekong Delta Water Snake is similar but has 106-117 ventral scales and is only found in the Mekong Delta.
Long-tailed Water Snake is also similar but has 122-136 ventral scales and is only found in Tonlé Sap Lake in Cambodia.
Chanard’s Mud Snake has a pale line below a row of small dark spots rather than larger dark blotches, 2nd pair of chin shields longer than the first, and 21 scale rows at the neck.
Mekong Mud Snake has light lines along its sides and much smaller dark blotches. It has 136-153 ventral scales.
Bocourt’s Water Snake is larger and has narrow yellow banding on black/brown background coloration.
Range: Limited to central Thailand. There may only be one surviving population.
Habitat: Found in floodplains, freshwater swamps and shallow marshes, including artificial wetlands and rice paddies.
Place in the ecosystem: Studies suggest that it feeds entirely on fish. Is eaten by larger snakes, large fish, monitors, and wading birds.
Danger to humans: Is an aggressive rear-fanged species and will bite when threatened but is not dangerous to humans.
Conservation status and threats: This species was only found in Thailand’s Central Plain, and in fact only one population is currently known to persist. It is locally abundant there, but human encroachment and the possible draining or pollution of its wetlands are a threat to its current habitat and thus its continued existence. Fishing with gill nets also kills a large number of the snakes. Protection of the snakes in this wetland may be critical to keep the species from extinction.
Interesting facts: References to the current distribution of Jagor’s Water Snake vary widely. Some sources state that it is only found in a single location in Thailand’s Central Plain, others state that it is found broadly in the Central Plain and Southeastern Basin, and still others state that it is a wide-ranging species that can be found in most of Thailand and beyond. Why the discrepancy? It’s likely due to taxonomic confusion. New species are discovered every year in Thailand, and often what was previously thought to a be a single species turns out to be 2, 3, or even 10 or more different species. At the same time, different species discovered in different areas sometimes turn out to have been the same species all along. As these things get sorted out, different references will update their records at different times (or sometimes even refuse to accept the same explanation), and thus such discrepancies arise.
In this case, one problem is likely that a species called the Mekong Delta Water Snake is extremely similar to Jagor’s Water Snake but found in other areas, primarily the Mekong River drainage. Jagor’s Water Snake has also been confused with Chanard’s Mud Snake.
References:
Diet, female reproduction and conservation of Jagor’s water snake, Enhydris jagorii in Bung Ka Loh wetland
A New Thai Enhydris
IUCN Redlist: Enhydris jagorii
IUCN Redlist: Enhydris subtaeniata
Reptile Database: Enhydris jagorii
John C. Murphy, personal communication
Michael Cota, personal communication
A Checklist and Key to the Homalopsid Snakes with the Description of New Genera
A Photographic Guide to Snakes and Other Reptiles of Peninsular Malaysia, Singapore and Thailand
A Field Guide to the Reptiles of South-East Asia
Snakes of Thailand and their Husbandry
Reptiles and Amphibians of Thailand 