Thai National Parks

Species of Thailand

Gerard's mud snake

Gerarda prevostiana, Joseph Fortuné Théodore Eydoux & Paul Gervais, 1822

(In Thai: งูปลาตาเล็ก, ngu plaa dta laek)

Gerarda prevostiana, commonly known as Gerard's water snake or the cat-eyed water snake, is a species of water snake endemic to Asia. It is the only species in the genus Gerarda.


The generic name, Gerarda, is in honor of someone named "Gerard". Unfortunately, Gray, who named the genus in 1849, did not specify whom he was honoring. Two possibilities are Adam Gerard or Rev. Gerard R. Smith, both of whom sent specimens of reptiles to Gray at the British Museum.

The specific name, prevostiana, is in honor of French naturalist and illustrator Florent Prévost.


G. prevostiana feed almost exclusively on crabs, which they tear into bite-sized pieces by pulling them through their coils, in contrast to most other snakes which swallow their prey whole.


Frontal a little longer than broad, shorter than its distance from the end of the snout, or than the parietals; loreal slightly longer than deep, a little smaller than the nasal; one preocular and two postoculars; temporals 1+2; upper labials 8, fourth entering the eye; 4 lower labials in contact with the anterior chin shields, which are much larger than the posterior. Dorsal scales in 17 rows at midbody. Ventrals 146–158; anal divided; subcaudals 31–34.

Uniform dark olive above; three outer rows of scales whitish; upper lip white, rostral dark olive; ventrals and subcaudals whitish, with dark edges.

Total length 41 cm (16 inches); tail 5 cm (2 inches).


G. prevostiana is found in India, Myanmar (= Burma), Sri Lanka, Thailand, Philippine Islands (Mindanao), Bangladesh, west Malaysia, and Singapore.

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Scientific classification

Gerarda prevostiana

Common names

  • German: Katzenaugen-Wassertrugnatter
  • English:
    • Gerard's mud snake
    • Cat-eyed water snake
    • Glossy marsh snake
    • Gerard's water snake
  • Thai:
    • งูปลาตาเล็ก, ngu plaa dta laek
    • งูปลาตาแมว, ngu plaa dta meow


  • Gerarda prevostiana, John C. Murphy & Harold Knight Voris (2014)
  • Gerardia prevostiana, R.C. Sharma (2004)
  • Gerarda prevostiana, Merel J. Cox et al. (1998)
  • Gerarda prevostiana, Ulrich Manthey & Wolfgang Grossmann (1997)
  • Gerardia prevostianus, Indraneil Das (1996)
  • Gerardia prevostiana, Malcolm Arthur Smith (1943)
  • Gerardia prevostiana, Frank Wall (1921)
  • Gerardia prevostiana, Frank Wall (1905)
  • Gerardia sic prevostiana, George Albert Boulenger (1890)
  • Helipophis flavescens, Fritz Müller (1884)

Conservation status

Least Concern (IUCN3.1)

Least Concern (IUCN3.1)


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Gerarda prevostiana - Kra Buri District, Ranong
Gerarda prevostiana - Kra Buri District, Ranong

Range Map

Distribution map of Gerard's mud snake, Gerarda prevostiana in Thailand
  • Chonburi Coast
  • Kra Buri District, Ranong
  • Prachuap Khiri Khan Coast
Range map of Gerarda prevostiana in Thailand