Checkered keelback

Checkered keelback
File:Checkered Keelback Xenochrophis piscator Schneider, 1799 Assam by Dr Raju Kasambe DSC 0477 (2).JPG
in Assam
Conservation status
Least Concern Least Concern  (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Colubridae
Genus:	Fowlea
Species:	F. piscator
Binomial name
Fowlea piscator (Schneider, 1799)
Synonyms
List Hydrus piscator Schneider, 1799 Natrix piscator — Merrem, 1820 Tropidonotus quincunciatus Schlegel, 1837 Tropidonotus piscator — Boulenger, 1893 Nerodia piscator — Wall, 1921 Xenochrophis piscator — Cox et al., 1998

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

File:Fowlea piscator 86567565.jpg

Eating a fish, in Karnataka

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 (5.7 ft).

Defensive behavior

Aggressive when threatened or cornered. 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.

Checkered Keelback at Khulna

A checkered keelback (locally known as "Joldhora") swimming at Beel Dakatia, Khulna, Bangladesh

File:Checkered keelback at Taudaha, kathmandu.jpg

With catfish kill, Kathmandu

File:Xenochrophis piscator - Checkered Keelback at Palappuzha (5).jpg

In Kerala

Habitat

Active by day and night. The preferred habitat of F. piscator is in or near freshwater bodies and paddy fields.

Diet

F. piscator feeds mainly on fish, amphibians and arthropods, occasionally on rodents and amphibian eggs, and rarely on birds and juvenile Indian peacock softshell turtles.

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 (0.59–1.57 in) long. The female guards the eggs until they hatch in 60–70 days. Each hatchling is about 11 cm (4.3 in) 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, and Indonesia (Sumatra, Java, Borneo, Celebes = Sulawesi).

type locality: "East Indies", restricted by geographic inference to the northern coastal areas of Andhra Pradesh State, eastern India.

Taxonomy

The subspecies F. p. melanzostus was raised to species status, as Fowlea melanzostus, by Indraneil Das in 1996. There is no subspecies known.

Gallery for identification characteristics

• Chart 1 - Nostrils directed slightly upwards
  Chart 1 - Nostrils directed slightly upwards
• Chart 2 - Frontal constricted in the middle, twice as long as broad
  Chart 2 - Frontal constricted in the middle, twice as long as broad
• Chart 3 - Internasals much narrowed anteriorly, nearly as long as the prefrontals
  Chart 3 - Internasals much narrowed anteriorly, nearly as long as the prefrontals
• Chart 4 - One preocular scale only
  Chart 4 - One preocular scale only
• Chart 5 - Temporals are 2+2 or 2+3
  Chart 5 - Temporals are 2+2 or 2+3
• Chart 6 - 9 supralabials, 4th and 5th touching the eye, the 6th excluded by the lowest postocular
  Chart 6 - 9 supralabials, 4th and 5th touching the eye, the 6th excluded by the lowest postocular
• Chart 7 - Body rather stout
  Chart 7 - Body rather stout
• Chart 8 - Small tail
  Chart 8 - Small tail
• Chart 9 - Scales in 19 distinct rows
  Chart 9 - Scales in 19 distinct rows
• Body of checkered keelback
  Body of checkered keelback
• File:Checkered-keelback in IIT Bombay.JPG
• Checkered keelback basking
  Checkered keelback basking
• Scale pattern
  Scale pattern

Further reading

• Boulenger GA (1893). Catalogue of the Snakes in the .Volume I., Containing the Families ... Colubridæ Aglyphæ, part. London: Trustees of the British Museum (Natural History). (Taylor and Francis, printers). xiii + 448 pp. + Plates I-XXVIII. (Tropidonotus piscator, pp. 230–232).
• Dutt, Kalma (1970). "Chromosome Variation in Two Populations of Xenochrophis piscator Schn. from North and South India (Serpentes, Colubridae)". Cytologia 35: 455–464.
• Schneider JG (1799). Historiae Amphibiorum naturalis et literariae. Fasciculus Primus, continens Ranas, Calamitas, Bufones, Salamandras et Hydros. Jena: F. Frommann. xiii + 264 pp. + corrigenda + Plate I. (Hydrus piscator, new species, pp. 247–248). (in Latin).
• Smith MA (1943). The Fauna of British India, Ceylon and Burma, Including the Whole of the Indo-Chinese Sub-region. Amphibia and Reptilia. Vol. III.—Serpentes. London: Secretary of State for India. (Taylor and Francis, printers). xii + 583 pp. (Tropidonotus piscator, pp. 293–296, Figures 95–96).