Reptiles and Amphibians of Thailand

Thailand's Snakes, Lizards, Turtles, and Frogs

Blunt-headed Slug Snake

Aplopeltura boa

This species is found in Thailand, but not within Bangkok itself
Blunt-headed Slug Snake Blunthead Tree Snake aplopeltura boa malaysia งูกินทากหัวโหนก (Ngu Gin Taag Hua Nog)
Blunt-headed Slug Snake in Malaysia (© Chien C. Lee)

English name: Blunt-headed Slug Snake (aka “Blunthead Slug Snake”, “Blunt-headed Tree Snake”)
Scientific name: Aplopeltura boa
Thai name: งูกินทากหัวโหนก (Ngu Gin Taag Hua Nog)

Description: To 75 cm. Immediately recognizable due to the short thick head with large round eyes on an extremely slender body. Body is vertically flattened and can be grey to yellowish-gray or brown with various grayish-green or reddish-brown markings in a blotched, mottled, or clouded pattern and black flecks or bars. Head is often (though not always) lighter than the body and there is a prominent white or cream space below the eye which is split in half by an unusual vertical eye-stripe.

Relevant scale counts: 13 midbody rows of smooth scales.

Similar Species: Has a stouter head and more slender body than other slug snakes, and the vertical eye stripe and general pattern are also unique.
White-spotted Cat Snake is much larger with a longer head, vertical pupils, and 19 midbody rows.

Range: Southern Thailand, Myanmar, Malaysia, Indonesia, and the Philippines

Habitat: Low vegetation in moist forests in the lowlands and hills.

Place in the ecosystem: Eats lizards, slugs and snails. It may be eaten by larger snakes, nocturnal birds and carnivorous mammals such as civets.

Danger to humans: The Blunt-headed Slug Snake is no danger to humans.

Conservation status and threats: This species is noted as uncommon and difficult to find but it has a wide range. Large-scale deforestation could seriously threaten the species in the near future.

Interesting facts: The striking appearance of the Blunt-headed Slug Snake is unique among Asian Snakes, and is part of the reason it is placed as the sole member of its own genus. However, there is a snake in Latin America which is also known as the “Blunt-headed Tree Snake” and which shares a similar external appearance to the Asian version. That Latin American species, Imantodes cenchoa, is not at all related to Aplopeltura boa. Instead this is an example of “convergent evolution”, where two unrelated species which occupy the same habitat (trees in tropical forest) and behavior (nocturnal hunting of mostly stationary prey) adopt the same characteristics via natural selection over time.

One unique aspect of the evolution of slug snakes is that they have a specialized hook-like jaw with more teeth on the right-hand side than on the left. This rare “non-symmetric” feature came about because the snails they prey on tend to have right-handed twisting shells, making it easier for the snake to get the right side of its mouth into the shell than the left side. However, the Blunt-headed Slug Snake only has slightly asymmetrical jaw features. Scientists believe this may be because it preys on lizards as well as slugs and snails and thus no longer specializes in snail extraction. This also may explain the blunt head, which would appear unhelpful when getting inside of snail shells.

References:
IUCN Red List: Aplopeltura boa
Reptile Database: Aplopeltura boa
Thin like a (small) snake
Life is short, but snakes are long: Asymmetrical snakes
Right-handed snakes: convergent evolution of asymmetry for functional specialization
Serpents of Thailand

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