Checkered keelback

The checkered keelback (Fowlea piscator), also known commonly as the Asiatic water snake, is a common species in the subfamily Natricinae of the family Colubridae. The species is endemic to Asia. It is non-venomous.

Description
The eye of F. piscator is rather small and shorter than its distance from the nostril in the adult. Its rostral scale is visible from above. The internasal scales are much narrowed anteriorly and subtriangular, with the anterior angle truncated and as long as the prefrontal scales. The frontal scale is longer than its distance from the end of the snout, and as long as the parietals or a little shorter. The loreal is nearly as long as it is deep. There are one preocular and three (rarely four) post-oculars. Its temporals are 2+2 or 2+3. There are normally nine upper labials, with the fourth and fifth entering the eye; and five lower labials in contact with the anterior chin-shields, which are shorter than the posterior. The dorsal scales are arranged in 19 rows, strongly keeled, with outer rows smooth. The ventrals number 125–158, the anal is divided, and the subcaudals number 64–90. Coloration is very variable, consisting of dark spots arranged quincuncially and often separated by a whitish network, or of black longitudinal bands on a pale ground, or of dark crossbands, with or without whitish spots. Two oblique black streaks, one below and the other behind the eye, are nearly constant. The lower parts are white, with or without black margins to the shields.

The checkered keelback is a medium-sized snake, but may grow to be large. Adults may attain a snout-to-vent length (SVL) of 1.75 m.

Defensive behavior
Most of the time this snake tries to raise its head as much as possible and expand its neck skin mimicking a cobra hood and intimidate the threat. Though it is non-venomous to humans, it can deliver a painful bite which is inflammatory.

F. piscator may lose its tail as an escape mechanism. A rare case of such autotomy is reported from Vietnam.

Habitat
The preferred habitat of F. piscator is in or near freshwater lakes or rivers.

Diet
F. piscator feeds mainly on small fish and water frogs.

Reproduction
F. piscator is oviparous. Clutch size is usually 30-70 eggs, but may be as few as 4 or as many as 100. Egg size is also variable. Each egg may be 1.5 - 4.0 cm long. The female guards the eggs until they hatch. Each hatchling is about 11 cm long.

Geographic range
F. piscator is found in Afghanistan, Bangladesh, Pakistan, Sri Lanka, India, Myanmar, Nepal, Thailand, Laos, Cambodia, Vietnam, West Malaysia, China (Zhejiang, Jiangxi, Fujian, Guangdong, Hainan, Guangxi, Yunnan), Taiwan, Australia and Indonesia (Sumatra, Java, Borneo, Celebes = Sulawesi)

type locality: "East Indies".

Subspecies

 * F. p. melanzostus (Gravenhorst, 1807) – Indonesia (Borneo [?], Java, Sulawesi [?]; Sumatra), India (Andaman and Nicobar Islands)
 * F. p. piscator (Schneider, 1799) – Bangladesh, Bhutan, India, Myanmar, Pakistan, People's Republic of China (including Hainan), Sri Lanka, Taiwan, and Thailand

Nota bene: A trinomial authority in parentheses indicates that the subspecies was originally described in a genus other than Fowlea.

Taxonomy
The subspecies F. p. melanzostus was raised to species status, as Fowlea melanzostus, by Indraneil Das in 1996.