Thai National Parks

Snakes of Thailand

Species of Thailand

Javan dragonsnake

In Thai: งูขอนท้องขาว, ngu khon thong khao

Binomial name: Xenodermus javanicus, Johan Reinhardt, 1836

Xenodermus is a genus of caenophidian snakes. It is a monotypic genus, containing only Xenodermus javanicus, and is also known as the dragon snake, Javan tubercle snake, Javan mudsnake, or rough-backed litter snake. Xenodermus javanicus demonstrates unique external morphology, e.g. characteristic dorsal scales, among xenodermatid snakes, which facilitates their distinguishing from different species. The snake is fully nocturnal and subsists on a diet of frogs, tadpoles and small fish. Xenodermus javanicus is a small non-venomous, semi-fossorial reptile. Dragon Snakes lay several clutches of 2–4 eggs each year in the rainy season (October–February).

Distribution and habitat

Xenodermus javanicus is found in the Malay Peninsula (Malaysia, Thailand, and one old record from the southermost tip of Myanmar) and parts of the Greater Sunda Islands (Sumatra, Java, and Borneo, as well as some smaller islands). It inhabits damp areas near water, including forests, swamps, marshes, and rice fields, at elevations below 1300 m, but most commonly between 500 – 1100 m above sea level.

Description

Xenodermus javanicus has distinct head and long tail. The body is slender and compressed. The total length is about 50 cm. Males can be distinguished from females by examining the overall size, tail thickness, tail length and cloacal vent for the presence of a hemipenial bulge. Females will be larger than males and have thinner, shorter tails while lacking a hemipenial bulge. Conversely, males will be smaller in comparison, have thicker, longer tails and exhibit a hemipenial bulge.

Differentiation of sex chromosomes and karyotype characterization

Xenodermus javanicus has an unusual chromosol number of 2n=32, contrasting with the most typical snake karyotype with a stable chromosomal number of 2n=36. The karyotype includes heteromorphic ZZ/ZW sex chromosomes with a heterochromatic W.

Breeding

Xenodermus javanicus undergo reproduction by egg and have low fecundity (2–4 eggs).

Sleep

Xenodermus javanicus are nocturnal.

Diet

Xenodermus javanicus subsist mainly on frogs, tadpoles and small fish.

Human interaction

Xenodermus javanicus exhibit a peculiar property when encountering perceived threats. This action involves stiffening its entire body. Xenodermus javanicus are known to die when placed into captivity, but some herpetoculturists have been successful in keeping them.

One particular difficulty people have caring for these snakes is getting them to eat. Xenodermus javanicus is an extremely picky eater. Some herpetoculturists have had success feeding fish, tadpoles and frogs but most people struggle to get these snakes to eat.

Conservation status

Xenodermus javanicus is rare in the northern parts of its range, but it is common in Java. There seem to be no major threats to it, and it can persist in wet agricultural lands such as rice fields. It could be potentially threatened by agricultural pollutants.

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Scientific classification

Kingdom
Animalia
Phylum
Chordata
Subphylum
Vertebrata
Class
Reptilia
Order
Squamata
Suborder
Serpentes
Family
Xenodermatidae
Genus
Xenodermus
Species
Xenodermus javanicus

Common names

  • German: Java Höckernatter
  • English:
    • Javan dragonsnake
    • Rough-backed litter snake
    • Java tubercle snake
    • Xenodermine snake
    • Dragon snake
    • Rough-bodied draogon snake
  • Thai: งูขอนท้องขาว, ngu khon thong khao

Synonyms

  • Xenodermus javanicus, Van Stanley Bartholomew Wallach et al. (2014)
  • Xenodermus javanicus, David J. Gower et al. (2012)
  • Xenodermus javanicus, Robert Stuebing & Robert Frederick Inger (1999)
  • Xenodermus javanicus, Ulrich Manthey & Wolfgang Grossmann (1997)
  • Xenodermus javanicus, Malcolm Arthur Smith (1943)
  • Xenodermus javanicus, George Albert Boulenger (1893)
  • Xenoderma javanicum, Salomon Müller (1887)
  • Xenodermus javanica, Giorgio Jan (1863)
  • Xenodermus javanicus, André Marie Constant Duméril & Gabriel Bibron (1854)
  • Gonionotus plumbeus, John Edward Gray (1846)
  • Xenodermus javanicus, Johannes Theodor Reinhardt (1836)

Conservation status

Least Concern (IUCN3.1)

Least Concern (IUCN3.1)

Range Map

Distribution map of Javan dragonsnake, Xenodermus javanicus in Thailand
  • Betong District, Yala
  • Namtok Sai Khao National Park
Range map of Xenodermus javanicus in Thailand