Achalinus niger

Black Odd-Scaled Snake

標蛇 (biao1she2)

Status: Protected (Cat.II)


Colubridae, subfamily Xenoderminae
Max. length
80 cm
Occurrence in Taiwan
Throughout Taiwan, above 1000-2000 m altitude.
Global Distribution
Endemic to Taiwan.
Small snake; total length up to 80 cm. Whole body is iridescent under light. There are 21-25 (mostly 25 at mid-body) rows of scales, which are smooth in anterior part of body and keeled in posterior one. The scales of an outermost row in upper face of postcloacal region are distinctly enlarged when compared with adjacent scales. Head is small, oval and not distinct from neck; body is slender; tail is moderately short. Eye is small, bead-like; iris is black, indistinct since it blends with dark head and pupil is round, black, and blends with rest of eye. Tongue has reddish stem and diffuse gray fork tips with dark brown base. The frontal scale is slightly broader than long; the parietal is nearly twice as long as broad and contacted posterolaterally by an enlarged paraparietal. Upper head, body and tail is uniform olive (dark-edged in anterior part of scale), grayish tan, or black. There is a dark longitudinal line on mid-dorsal row of scales on body and tail. Ventral surface is olive-yellow (dark-edged in anterior part of scale) or dark gray; the color is slightly darker on tail than on body. Whole body is usually black in the young. Anal scale is entire, and subcaudals are not divided.
Biology & Ecology
This nocturnal and terrestrial snake inhabits humid environments, such as montane forest floors, stone cracks or decayed plants. Earthworms, slugs, or frogs may be its staple food. Females produce about 7 long eggs of approximately 2x1 cm per clutch in spring. It is not aggressive, and reports of bites by this snake are rare.
The Greek origin of Achalinus seem unclear. Stejneger's "Herpetology of Japan and Adjacent Territory" explains "From a, without; chalinos, poison fang." However, chalinos actually means "bridle".
niger is Latin for "black".
The origin of the character in the Chinese name used in Taiwan (標蛇, biao1she2) is unclear. 台灣 means "Taiwan", means "snake", but can mean many things, among them "mark" and "branch". These two are the most likely candidates for an explanation, as the snake can resemble a dead branch on the forest floor, but also has a dark stripe along the spine, which resembles a mark.
Further Info