Reptiles and Amphibians of Thailand

Thailand's Snakes, Lizards, Turtles, and Frogs

Boomsong's Stream Snake

Isanophis boonsongi

This species is found in Thailand, but not within Bangkok itself
Boomsong's Stream Snake Boonsong's Keelback Isanophis boonsongi Parahelicops boonsongi งูลายสอหมอบุญส่ง
Boomsong’s Stream Snake in Loei Province (© Merel “Jack” Cox)

English name: Boomsong’s Stream Snake (aka: “Boonsong’s Stream Snake, Boomsong’s Keelback”)
Scientific name: Isanophis boonsongi (formerly Parahelicops boonsongi)
Thai name: งูลายสอหมอบุญส่ง (Ngu Lai Sor Mor Boonsong)

Description: To at least 1m long. A large snake with moderately heavy body and very distinct head. Eye is large and nostrils face upwards. Dark chestnut brown on top fading to reddish-brown on the sides. Pale yellowish-brown on belly. Tail is rather long.

Relevant scale counts: 19 strongly keeled dorsal scale rows. 136–140 ventrals and 60 subcaudals. Single prefrontal scale, 8-9 supralabial scales, 2 anterior temporals, and 1 pair of chin shields.

Similar Species: Angel’s Stream Snake has small eyes, relatively smooth dorsal scales, and indistinct light inverted V-shapes on its sides.
Yunnan Water Snake has less keeled dorsal scales and distinct dark X-marks on the body.

Range: Only known from two localities in Loei Province, Thailand.

Habitat: Steams in mountain forest around 700-1800m elevation.

Place in the ecosystem: Likely feeds on frogs and fish. May be eaten by larger snakes and monitors.

Danger to humans: Is a rear-fanged snake but its venom properties and potential danger are unknown.

Conservation status and threats: This species is only known from three specimens, the first found in 1955 and the next two in the early 1990s. Its habitat is protected but the current status of the species is unknown.

Interesting facts: It is fascinating that a large, fairly conspicuous snake like Boomsong’s Stream Snake has been so rarely seen. There are several potential reasons for this. One is its aquatic and nocturnal habits, thus only being active at a time when few people are looking. Its presence in mountain streams makes habitat more different to access. The snake lives in a portion of the country not as regularly frequented by naturalists as the south, center, and north. And it may have a very limited range or low population density which simply means there aren’t very many of the snakes to come across.

IUCN Red List: Boomsong’s Stream Snake
Thai National Parks: Boonsong’s Stream Snake
Reptile Database: Isanophis boonsongi
On the taxonomic status of the Thai endemic freshwater snake Parahelicops boonsongi, with the erection of a new genus
Contribution to the Herpetology of Thailand: University of Kansas Science Bulletin

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