Calloselasma rhodostoma – Malayan Pit Viper

Malayan Pit Viper (Calloselasma rhodostoma) in Yan Ta Khao district, Trang, Thailand

The Malayan Pit Viper, Calloselasma rhodostoma, is a well-camouflaged, terrestrial, brown, pit viper species that is found in most of the country where habitat is suitable. This species seems to prefer lowland areas, and seems to thrive in agricultural land. This combined with its camouflage and tendency to stay put, means the Malayan Pit Viper often comes in conflict with humans. And its potent venom can cause some serious injury when such accidents happen. It’s wise to wear boots in areas where these occur/ are common.

Hiding in plain sight on a forest trail lies a highly venomous Malayan Pit Viper (Calloselasma rhodostoma). Photographed in Yan Ta Khao district, Trang, Thailand

facts

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Malayan Pit Viper (Calloselasma rhodostoma) subadult in Yan Ta Khao district, Trang, Thailand

Description

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A nice looking red specimen of the Malayan Pit Viper (Calloselasma rhodostoma) in Kaeng Krachan district, Thailand

Similar-looking species

The coloration of the Malayan Pit Viper can vary quite a bit, so do not get fooled by this. It can be brown, grey, reddish or even pinkish.
Telling the Malayan Pit Viper, Calloselasma rhodostoma apart from the other brown viper species that occur in Thailand is generally quite easy. Different markings is the easiest way to recognize, but the Malayan Pit Viper is also the only viper species currently known in Thailand that has large head scales, whereas the other vipers have a lot of small scales on the top of their heads. Also it has a typical ambush position with the head/ nose protruding diagonally up from its body, normally not seen in the other viper species. Unless you are in some forested mountainous area, the Malayan Pit Viper is the most likely seen of all the brown vipers in Thailand.

• Psammodynastes pulverulentus – Mock Viper
  
  

  Common Mock Viper (Psammodynastes pulverulentus) in Kaeng Krachan national park, Thailand

  Probably, visually the most similar species to the Malayan Pit Viper of all snake species in the range. The Mock Viper is only mildly venomous, and as far as we know this has no serious effect on humans. The head is not quite as distict as in the real pit viper, and usually has a lined pattern on it. The body markings can be quite similar triangular shaped. However this Mock Viper is normally more slender in built. Recent research has even shown this species goes as far as mimicking the pupil shape of the pit viper, changing it from rounded to a vertical slit when it feels threatened.
• Oligodon fasciolatus – Banded Kukri Snake
  
  

  Banded Kukri Snake (Oligodon fasciolatus) in Kaeng Krachan district, Phetchaburi, Thailand. Common species in human dominated areas. Non-venomous.

  Another common and widespread species. We won’t mention all kukri snakes. Most can be similar in coloration, though all have different markings than the triangles appearing on the back of the Malayan Pit Viper. The head shape is very different, hardly distinct from its body, whereas it is highly distinct in the pit viper.
• Daboia siamensis – Siamese Russell’s Viper
  
  

  Siamese Russell’s Viper, Daboia siamensis

  Just like the Malayan Pit Viper, the Siamese Russell’s Viper is a brown terrestrial species with very potent venom. The Siamese Russell’s Viper grows quite a bit bigger, and appears more heavy built. It has rounded brown markings on its back edged with black and white instead of the more triangle shaped markings found on the Malayan Pit Viper. And it has three brown markings on the top of its head whereas the Malayan Pit Viper has no markings on the top of its head, only a light strip on both edges. The nose of the Siamese Russell’s Viper is more stump/ rounded, the Malayan Pit Viper has a more pointy nose.
• Protobothrops mucrosquamatus – Brown-spotted Pit Viper
  This long slender viper species with a more blotched pattern, is found in North Thailand, but for long has stayed under the radar so is not a species you likely encounter.

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Behaviour

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Malayan Pit Viper (Calloselasma rhodostoma) hiding in the leaf litter

Range & habitat

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Malayan Pit Viper (Calloselasma rhodostoma) subadult in Yan Ta Khao district, Trang, Thailand

Taxonomy

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Malayan Pit Viper (Calloselasma rhodostoma) subadult hiding in plain sight in Yan Ta Khao district, Trang, Thailand

How to find this species in Thailand?

This species can be locally common, yet hard to find in other regions. They are most often seen after the rain, when they often show up on the road and their camouflage is no longer helping them to remain unseen. The Thai peninsula seems to be the best spot to look for this species. It thrives in e.g. rubber, oil palm, and pineapple plantations. Herping at night will be your best bet. And road cruising most likely being the most successful in the right conditions. We are personally not a great fan of road cruising, as it is more exciting to find snakes in their natural habitat on foot. And in the right locations like the lowland dipterocarp forests in the South it is possible to find them on forest trails in the leaf litter. In many cases they seem to pick locations where they have either a log, tree, or a rock behind their back while coiled up in front of it and facing away from it. But dense vegetation bordering some open space will suit them as well.