Reptiles and Amphibians of Thailand

Thailand's Snakes, Lizards, Turtles, and Frogs

White-spotted Slug Snake

Pareas margaritophorus

This species is found in Thailand, but not within Bangkok itself
Pareas margaritophorus, White-spotted slug snake kaeng krachen national park thailand งูกินทากจุดขาว Ngu Gin Thaag Jud Khao
White-spotted Slug Snake in Kaeng Krachen NP (Thai National Parks / CC BY-SA)

English name: White-spotted Slug Snake (aka “White-spotted Slug-eating Snake”)
Scientific name: Pareas margaritophorus
Thai name: งูกินทากจุดขาว (Ngu Gin Thaag Jud Khao)

Description: To 47 cm. Slightly vertically compressed body is purplish-brown to slate grey with prominent black-and-white spots that form something like broken crossbars. There is a white, cream, yellowish, or orange collar on the neck that is sometimes complete and sometimes reduced to large dots. Scales are completely smooth even on top.

Similar Species: Spotted Slug Snake is larger, has slightly keeled scales on top, and has a W-shaped collar which is rarely colored or no collar at all.

Range: Recorded from throughout Thailand as well as west through Myanmar to northeast India and Bangladesh, north to Laos and southern China, east to Cambodia and Vietnam and south to northwest Malaysia. However, due to previous confusion with P. macularius it is not certain that all of those localities are reliable.

Habitat: Wet areas in forest. Sjon Hauser has found that in northern Thailand the species appears to primarily be found in deciduous forest at elevations below 900m, though in cleared areas it can sometimes be found as high as 1100m.

Place in the ecosystem: Like most other slug snakes it feeds primarily on snails, as well as slugs at times. It may be eaten by larger snakes, nocturnal birds and carnivorous mammals such as civets.

Danger to humans: The White-spotted Slug Snake is no danger to humans.

Conservation status and threats: It appears to be common and widespread, though its forest habitat is threatened in some areas.

Interesting facts: In 2004 a researcher determined that White-spotted Slug Snakes were the same species as Spotted Slug Snakes, and declared the Spotted Slug Snake to be invalid. He based this determination on an inability to distinguish records of the species in China. However, several other researchers felt that this lumping was invalid, and since then both genetic and morphological studies show the species to be separate, although they indeed may have been confused often in the past.

Slug snakes have a specialized hook-like jaw with more teeth on the right-hand side than on the left. This rare “non-symmetric” feature came about because the snails they prey on tend to have right-handed twisting shells, therefore making it easier for the snake to get the right side of its mouth into the shell than the left side. In fact, studies have shown that the snakes are far more successful at extracting snails out of those right-handed shells than they are when faced with a snail in a left-handed twisting shell.

References:
IUCN Red List: White-spotted Slug Snake
Ecology Asia: White-spotted Slug Snake
On the validity of Pareas macularius
Sjon Hauser pers. comm.
Asymmetrical Snakes
Serpents of Thailand

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