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 .

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. Ananjeva NB, Orlov NL (1994). "Caudal Autotomy in Colubrid Snake ''Xenochrophis piscator'' From Vietnam"
''Russian Journal of Herpetology'' 1 (2): 169-171.

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 long. The female guards the eggs until they hatch. Each hatchling is about long. Das I (2002). ''A Photographic Guide to Snakes and other Reptiles of India''. Sanibel Island, Florida: Ralph Curtis Books. 144 pp. . (''Xenochrophis piscator'', p. 48).

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'' – Indonesia (Borneo Java, Sulawesi Sumatra), India (Andaman and Nicobar Islands)
*''F. p. piscator'' – 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.

Gallery for identification characteristics

File:Char1 Nostril.JPG, Chart 1 - Nostrils directed slightly upwards
File:Char2 Frontal.JPG, Chart 2 - Frontal constricted in the middle, twice as long as broad
File:Char3 Internasals.JPG, Chart 3 - Internasals much narrowed anteriorly, nearly as long as the prefrontals
File:Char4 Preocular.JPG, Chart 4 - One preocular scale only
File:Char5 Temporals.JPG, Chart 5 - Temporals are 2+2 or 2+3
File:Char6 Supralabials.JPG, Chart 6 - 9 supralabials, 4th and 5th touching the eye, the 6th excluded by the lowest postocular
File:Char7 Stout body.JPG, Chart 7 - Body rather stout
File:Char8 Small tail.JPG, Chart 8 - Small tail
File:Char9 19scales.JPG, Chart 9 - Scales in 19 distinct rows
File:Body Xenochrophis piscator.JPG, Body of checkered keelback
File:Checkered-keelback in IIT Bombay.JPG
File:Checkered Keelback.jpg, Checkered keelback basking
Xenophis piscator gab fbi.png, Scale pattern

References

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).

External links

{{Taxonbar, from=Q2717987

Fowlea
Reptiles of Afghanistan
Reptiles of Bangladesh
Reptiles of Myanmar
Reptiles of India
Reptiles of Indonesia
Reptiles of Laos
Reptiles of Malaysia
Reptiles of Pakistan
Reptiles of Sri Lanka
Reptiles of Taiwan
Reptiles of Thailand
Reptiles described in 1799
Taxa named by Johann Gottlob Theaenus Schneider
Snakes of China
Snakes of Vietnam
Reptiles of Borneo