Pseudagkistrodon rudis rudis
False Viper, False Habu
擬 龜殼花 (ni3gui1ke3hua1)
Status: Not Protected
Colubridae, subfamily Natricinae
Occurrence in Taiwan
Low and medium elevations throughout Taiwan. Quite common.
South China (Fujian, Yunnan, Sichuan, Guizhou, Hunan, Jiangxi, Zhejiang, Guangxi, Guangdong, Anhui, Hunan), Taiwan.
Medium-sized snake; total length up to 120 cm. There are 19-25 (23 at mid-body) rows of scales, which are heavily keeled. Head is broad, moderately triangular and moderately separated from neck; body is stout, slightly compressed or flattened; tail is moderately long. Eye is medium to large; iris is light brown with scattered areas of black, while anterior and posterior quarters of eye are dark brown, pupil is slightly oval to round, black, surrounded by irregular ring of light tan. Tongue is large, dark gray blue, fork tips light gray. Upper head is dark dirty brown to chocolate, with a prominent line of demarcation where the brown of the upper head meets the light brown, orange tinged side of head, extending from tip of nose along side of head to neck. Dorsal shields of head are large, but not distinct due to coloration and poorly developed sutures. The nuchal scales are heavily keeled. Upper body is brown to gray brown, may be tinted with bronze, interrupted by dark designs, variable in size, disposition and intensity of pigmentation. The irregular designs crossing the vertebral line in anterior half of body tend to lose continuity in the following part of body where they are replaced by roughly circular, separated designs along vertebral line. Other spots involving two to four scales occur on the sides of the body, and the posterior ones may fuse to form longitudinal lateral band. Ventral head is dirty white to dull orange gray. Ventral body is variable, dull dirty orange at neck with scattered dark gray to brown black pigment, overall color progressively darker posteriorly with mottled or marbled appearance in posterior parts of body. Anal scale is divided and subcaudals are paired.
Biology & Ecology
This diurnal or nocturnal rear-fanged (= opistoglyphous, see footnote (1)) snake is found on mountainous forest floors, bush- and grassland, or near creeks. It feeds mainly on toads, but also on frogs, small snakes, lizards, insects and earthworms. Females give birth to 12-27 young per litter in late summer and fall; hatchlings measure 13-20 cm in total length. When irritated and excited, it may make every effort to act or appear as a venomous snake: the head and neck, or the entire body, may be flattened as the snake coils up in defense; when flattened, the oval head may take on a strong, definite triangular shape in an attempt to mimic vipers.
Many members of the family Colubridae that are considered venomous are essentially harmless to humans, because they either have small venom glands, relatively weak venom, or an inefficient system for venom delivery. The venom of P.rudis is not well studied but a transcriptomic study found that P. rudis contains toxin-encoding genes that are homologous to front-fanged snakes. (Source)
Pseudagkistrodon: from Greek "pseudes", "false", and "Agkistrodon", a genus of American pit vipers. The name Agkistrodon comes from the Greek words ankistron 'fishhook' and odon 'tooth' and is likely a reference to the fangs. (Source)
rudis is Latin for "rough, crude, unlearned".The Chinese name 擬龜殼花 (ni3gui1ke3hua1) means "False Taiwan Habu", referring to the sympatric pitviper Protobothrops mucrosquamatus which it appears to mimic.
(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 her 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)