Xenochrophis piscator

Chequered Keelback
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Colubridae
Genus:	Xenochrophis
Species:	X. piscator
Binomial name
Xenochrophis piscator (Schneider, 1799)

The Chequered Keelback or Asiatic Water Snake (Xenochrophis piscator) is a common species of non-venomous snake found in Asia.

Description

Scale pattern

This snake's eye 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 is 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. Scales are arranged in 19 rows, strongly keeled, with outer rows smooth. Ventrals are at 125–158, anal divided, with subcaudals at 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 cross bands, with or without whitish spots. Two oblique black streaks, one below and the other behind the eye, are nearly constant, lower parts white, with or without black margins to the shields.^[1]

A rare case of autotomy is reported from Vietnam.^[2]

Habitat

This snake is found in or near fresh water lakes or rivers. It feeds mainly on small fish and water frogs.

Distribution

The species is found in Afghanistan, Pakistan, Sri Lanka, India, Myanmar, Thailand, Laos, Vietnam, West Malaysia, China (Zhejiang, Jiangxi, Fujian, Guangdong, Hainan, Guangxi, Yunnan), Taiwan, Indonesia (Sumatra, Java, Borneo, Celebes = Sulawesi)

type locality: "East indies"

Races

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

Gallery for identification characteristics

• 

  Chart 1 - Nostrils directed slightly upwards

• 

  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 4 - One preocular scale only

• 

  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 7 - Body rather stout

• 

  Chart 8 - Small tail

• 

  Chart 9 - Scales in 19 distinct rows

• 

  Body of Chequered Keelback

References

1. ^ Boulenger, G.A. (1890) Fauna of British India. Reptilia and Batrachia.
2. ^ N. B. Ananjeva and N. L. Orlov 1994. "Caudal Autotomy in Colubrid Snake Xenochrophis piscator From Vietnam" Russian Journal of Herpetology 1(2)

Other references

• Dutt, Kalma 1970 Chromosome Variation in Two Populations of Xenochrophis piscator Schn. from North and South India (Serpentes, Colubridae). Cytologia 35: pp. 455–464
• Schneider, J. G., 1799 Historiae Amphibiorum narturalis et literariae. Fasciculus primus, continens Ranas. Calamitas, Bufones, Salamandras et Hydros. Jena, 266 S.