Species of Thailand

Malayan pit viper

Calloselasma rhodostoma, Heinrich Kuhl, 1824

(In Thai: งูกะปะ, ngu ga pha)

Calloselasma is a monotypic genus created for a venomous pit viper species, C. rhodostoma, which is endemic to Southeast Asia from Thailand to northern Malaysia and on the island of Java. No subspecies are currently recognized.


Attains an average total length of 76 cm, with females being slightly longer than males. Occasionally, they may grow as long as 91 cm.

A specimen with a total length of 81 cm has a tail 9 cm long.

Dorsally it is reddish, grayish, or pale brown, with two series of large, dark brown, black-edged triangular blotches, which are alternating or opposite. There is also a thin dark brown vertebral stripe, which may be interrupted or indistinct in some specimens. The upper labials are pink or yellowish, and powdered with brown. There is a broad, dark brown, black-edged diagonal stripe from the eye to the corner of the mouth, with a narrower light-colored stripe above it. Ventrally it is yellowish, uniform or powdered or spotted with grayish brown.

The smooth dorsal scales are arranged in 21 rows at midbody. Ventrals 138-157; anal plate entire; subcaudals 34-54 pairs.

Snout pointed and upturned. Rostral as deep as broad. Two internasals and two prefrontals. Frontal as long as or slightly longer than its distance from tip of snout, as long as or slightly shorter than the parietals. 7-9 upper labials. Loreal pit not in contact with the upper labials.

This is the only Asian pit viper with large crown scales and smooth dorsal scales.

Geographic range

Found in Nepal, Thailand, Cambodia, Laos, Vietnam, northern West Malaysia and on the Indonesian island of Java. The type locality is listed as "Java". There are unconfirmed, but credible reports from southern Myanmar (Burma), northern Sumatra and northern Borneo.

Habitat and diet

Prefers coastal forests, bamboo thickets, unused and overgrown farmland, orchards, plantations as well as forests around plantations, where it searches for rats and mice.


This species is oviparous and the eggs are guarded by the female after deposition.


This species has a reputation for being bad-tempered and quick to strike. In northern Malaysia it is responsible for some 700 incidents of snakebite annually with a mortality rate of about 2 percent. Remarkably sedentary, it has often been found in the same spot several hours after an incident involving humans. Its venom causes severe pain and local swelling and sometimes tissue necrosis, but deaths are not common. Many victims are left with dysfunctional or amputated limbs due to the lack of antivenom and early treatment. In a 2005 study of 225 Malayan pit viper (Calloselasma rhodostoma) bites in Thailand, most victims had mild to moderate symptoms, but 27 of 145 patients (18.6%) developed permanently swollen limbs. There were only two deaths (related to intracerebral hemorrhage) and no amputations. The antivenin manufactured in Thailand seemed effective in reversing the blood clotting caused by the venom. Most patients remained stable and did not require antivenin. The authors suggested that victims not use traditional healers and avoid overuse of tourniquets. In a prospective phase of the study, bites occurred throughout the year but mostly early in the monsoon season (May and June).

Venom and thrombosis treatment

The venom of this species is used to isolate a thrombin-like enzyme called ancrod. This enzyme is used clinically to break down and dissolve thrombi (blood clots) in patients and lower blood viscosity to help prevent heart attack and stroke.

This article uses material from Wikipedia released under the Creative Commons Attribution-Share-Alike Licence 3.0. Eventual photos shown in this page may or may not be from Wikipedia, please see the license details for photos in photo by-lines.

Scientific classification

Calloselasma rhodostoma

Common names

  • German: Malaiische Mokassin-Grubenotter
  • English:
    • Malayan pit viper
    • Malayan grond pit viper
    • Malayan ground snake
    • Malayan moccasin
  • Thai: งูกะปะ, ngu ga pha


  • Calloselasma rhodostoma annamensis, Fernand Angel, 1933

    Range: Southeast Cambodia and Vietnam

  • Calloselasma rhodostoma rhodostoma, Friedrich Boie, 1827

    Range: South Vietnam (Binh Thuan etc.), Cambodia, Thailand, Laos, West Malaysia and Indonesia (Java).


  • Calloselasma rhodostoma, Van Stanley Bartholomew Wallach et al. (2014)
  • Calloselasma rhodostoma, Nguyen Van Sang et al. (2009)
  • Calloselasma rhodostoma, Roy W. McDiarmid, Jonathan A. Campbell & T'Shaka A. Touré (1999)
  • Calloselasma rhodostoma, Merel J. Cox et al. (1998)
  • Calloselasma rhodostoma, Ulrich Manthey & Wolfgang Grossmann (1997)
  • Calloselasma rhodostoma, Kenneth Welsh (1994)
  • Calloselasma rhodostoma, Simon M Campden-Main (1970)
  • Ancistrodon rhodostoma, Malcolm Arthur Smith (1943)
  • Agkistrodon annamensis, René Léon Bourret (1936)
  • [Agkistrodon] annamensis, Clifford H. Pope (1935)

Conservation status

Least Concern (IUCN3.1)

Least Concern (IUCN3.1)


Calloselasma rhodostoma
Calloselasma rhodostoma
Calloselasma rhodostoma
Calloselasma rhodostoma - Hua Hin District
Calloselasma rhodostoma
Calloselasma rhodostoma
Calloselasma rhodostoma
Calloselasma rhodostoma

Range Map

Distribution map of Malayan pit viper, Calloselasma rhodostoma in Thailand
  • Ban Laem District, Phetchaburi
  • Ban Lat District, Phetchaburi
  • Bang Lamung District, Chonburi
  • Bang Saphan District, Prachuap Khiri Khan
  • Cha-Am District, Phetchaburi
  • Chaloem Phra Kiat District, Nan
  • Chiang Khan District, Loei
  • Hat Yai District, Songkhla
  • Hua Hin District, Prachuap Khiri Khan
  • Huai Kha Khaeng Wildlife Sanctuary
  • Kabin Buri District, Prachinburi
  • Kaeng Krachan District, Phetchaburi
  • Kaeng Tana National Park
  • Kanchanadit District, Surat Thani
  • Kantang District, Trang
  • Khanom District, Nakhon Si Thammarat
  • Khao Chamao - Khao Wong National Park
  • Khao Nam Khang National Park
  • Khao Nan National Park
  • Khao Phra - Bang Khram Wildlife Sanctuary
  • Khao Soi Dao Wildlife Sanctuary
  • Khao Sok National Park
  • Khao Yoi District, Phetchaburi
  • Khlong Hoi Khong District, Songkhla
  • Khun Nan National Park
  • Ko Lanta District, Krabi
  • Kumphawapi District, Udon Thani
  • Lan Sak District, Uthai Thani
  • Lom Sak District, Phetchabun
  • Mae Chaem District, Chiang Mai
  • Mae Suai District, Chiang Rai
  • Mae Taeng District, Chiang Mai
  • Mueang Chiang Mai District, Chiang Mai
  • Mueang Krabi District, Krabi
  • Mueang Nakhon Si Thammarat District, Nakhon Si Thammarat
  • Mueang Nongbua Lamphu District, Nong Bua Lamphu
  • Mueang Prachuap Khiri Khan District, Prachuap Khiri Khan
  • Nam Nao National Park
  • Nong Khae District, Saraburi
  • Nong Phok District, Roi Et
  • Nong Wua So District, Udon Thani
  • Nopphitam District, Nakhon Si Thammarat
  • Pak Phli District, Nakhon Nayok
  • Pang Sida National Park
  • Pathio District, Chumphon
  • Phu Khiao Wildlife Sanctuary
  • Phu Phan National Park
  • Phu Si Than Wildlife Sanctuary
  • Phu Wua Wildlife Sanctuary
  • Phunphin District, Surat Thani
  • Plai Phraya District, Krabi
  • Pran Buri District, Prachuap Khiri Khan
  • Pua District, Nan
  • Ron Phibun District, Nakhon Si Thammarat
  • Royal Chumphon Forest Park
  • Sadao District, Songkhla
  • Sakaerat Environmental Research Station
  • Sam Roi Yot District, Prachuap Khiri Khan
  • Sathing Phra District, Songkhla
  • Sattahip District, Chonburi
  • Sawi District, Chumphon
  • Si Racha District, Chonburi
  • Sri Nakarin Dam National Park
  • Sukhirin District, Narathiwat
  • Ta Phraya National Park
  • Tha Li District, Loei
  • Tha Mai District, Chanthaburi
  • Tha Sae District, Chumphon
  • Tha Takiap District, Chachoengsao
  • Tha Yang District, Phetchaburi
  • Thale Ban National Park
  • Thong Pha Phum District, Kanchanaburi
  • Thung Chang District, Nan
  • Thung Song District, Nakhon Si Thammarat
  • Thung Tako District, Chumphon
  • Ton Nga-Chang Wildlife Sanctuary
  • Yan Ta Khao District, Trang
  • Yod Dom Wildlife Sanctuary
Range map of Calloselasma rhodostoma in Thailand