Pseudoxenodon stejnegeri stejnegeri
(Stejneger's) Mountain Keelback
Status: Not protected
Colubridae, subfamily Natricinae
Occurrence in Taiwan
Throughout Taiwan, at altitudes of 1000-2500 m. Not very common.
Endemic to Taiwan.
Small snake; total length up to 90 cm. There are 15-21 (17 at mid-body) rows of keeled scales; anteriorly dorso-lateral scales are oblique. Head is oval, triangular and distinct from neck; body is slightly stout; tail is long. Eye is medium to large size; iris is light flesh-colored with flecks of black, and darkened in lower two-thirds; pupil is round, black, surrounded by narrow ring of light flesh. Tongue is maroon, fork tips may be gray. It has enlarged rear fangs. The color of upper surface is extensively varied among individuals, including grey, green, yellow, orange, brown, and purple. A dark stripe extends from eye to base of jaw, and usually a reddish or black chevron sits on the nape, with its apex pointing toward the head. There are light bands along the vertebral ridge and dark squares on the sides of the bands; a light mid-dorsal stripe runs along the tail. Ventral surface is whitish anteriorly, gradually tinted with pinkish and may be mottled with black or white pigment in following part of body; the black spots aggregating on sides of the ventrals usually form a longitudinal stripe. The ventrals in anterior body may also have scattered quadrangular marks of black pigment which are irregularly arranged on sides. Anal scale is divided and subcaudals are paired.
Biology & Ecology
This cathemeral (diurnal and nocturnal), opistoglyphous (= rear-fanged, see footnote (1)) snake inhabits humid mountain areas, in particular the forest floor close to rivers and creeks, where it preys on frogs and salamanders. P. stejnegeri is oviparous, but little else is known about its reproduction processes. When threatened, the snake may rear its head and neck, and expand its neck laterally, similar to a cobra, but not as wide.The snake's dorsal coloration is extensively varied among individuals, including grey, green, yellow, orange, brown, and purple.
Pseudoxenodon: Greek; pseudo means "fake" ; xenodon (lit. "alien tooth") is a family of South American snakes also known as "false pitvipers".
stejnegeri: after Leonhard Hess Stejneger, (1851-1943), a Norwegian-born herpetologist who moved to the US in 1881 and became curator of reptiles at the Smithsonian Institution in 1889.The Chinese name 史丹吉氏斜鱗蛇 (shi3dan1ji2shi4xie2lin2she2) means "Stejneger's (史丹吉氏) keel-scale (斜鱗) snake (蛇).
(1) "Opisthoglyphous snakes are similar to aglyphous (fangless) snakes, but possess weak venom, which is injected by means of a pair of enlarged teeth at the back of the maxillae (upper jaw). These "fangs" typically point backwards rather than straight down, possess a groove which channels venom into the prey, and are located roughly halfway back in the mouth, which has led to the vernacular name of "rear-fanged snakes". (Source)