The Enigmatic Beauty of Herpetoreas sieboldii: Unveiling the Wonders of Siebold's Smooth Snake

Herpetoreas sieboldii, commonly known as Siebold's Keelback, emerges as a mesmerizing serpent within the realms of Asian herpetology.


Herpetoreas sieboldii, commonly known as Siebold's Keelback, emerges as a mesmerizing serpent within the realms of Asian herpetology. This non-venomous snake belongs to the Natricidae family, showcasing a distinctive array of features that contribute to its unique identity. In this exploration, we unravel the physiological intricacies, behavioral traits, distribution, and scientific classification of this captivating species.

Higher Taxa and Synonymy:

Siebold's Keelback finds its taxonomic placement within Colubridae (Natricinae), Colubroidea, Caenophidia, Alethinophidia, Serpentes, Squamata. It is synonymous with Herpetoreas sieboldii, as classified by Günther (1860), Theobald (1868, 1876), Das (1996), David et al. (2005), Wallach et al. (2014), Guo et al. (2014), and Lalremsanga et al. (2022).

Distribution: This enigmatic serpent gracefully navigates specific regions across Asia, including Pakistan, India (Uttar Pradesh, Sikkim, Punjab, Jammu, Himachal), Nepal, Myanmar (= Burma), Bangladesh, and Bhutan. The snake's adaptability allows it to thrive in diverse habitats within these territories, showcasing its ecological resilience.

Scientific Classification:

  • ·        Kingdom: Animalia
  • ·        Phylum: Chordata
  • ·        Class: Reptilia
  • ·        Order: Squamata
  • ·        Suborder: Serpentes
  • ·        Family: Natricidae
  • ·        Genus: Herpetoreas
  • ·        Species: sieboldii
  • ·        Binomial name: Herpetoreas sieboldii

Morphology and Size: Siebold's Keelback exhibits a slender and elongated body, with distinctive keeled dorsal scales contributing to its semi-aquatic nature. The species attains a moderate size, typically ranging from  two to three feet. The coloration is a harmonious blend of olive-brown dorsally, complemented by a yellowish ventral side with darker lateral stripes.

Behavioral Traits: Known for its docile disposition, Siebold's Keelback tends to avoid confrontations and adopts a retreat strategy when encountered. This behavior aligns with its survival instincts, allowing it to navigate various terrains with efficiency.

Reproduction and Types: Siebold's Keelback is oviparous, with the holotype designated as BMNH 1946.1.13.16, a 917 mm male collected by Hermann, Adolphe, and R. von Schlagintweit between 1854-1858.

Diagnosis and Original Description: The diagnosis of the genus Herpetoreas includes semi-aquatic snakes with keeled dorsal scales. The original description by Günther (1860) highlights the distinctive features of Siebold's Keelback, emphasizing its unique scale characteristics, coloration, and head morphology.

Morphological and Scalation Characters:

Head: Elongated, rounded in front, and flat above.

Rostral Shield: Broader than high, rounded superiorly.

Frontal Shields: Pentagonal, anterior ones one-half the size of posterior ones.

Vertical Shield: Five-sided, with lateral margins nearly parallel, posterior sides very short.

Nostril: Between two plates, one loreal, one anterior, and two posterior oculars.

Labials: Eight upper labials, third, fourth, and fifth entering the orbit; ten lower labials.

Chin-shields: Two pairs, anterior smaller than posterior.

Dorsal Scales: Nineteen rows, slightly keeled.

Ventrals: 216; anal bifid; subcaudals 90.

Conservation Status: While specific conservation assessments for Siebold's Keelback might vary, monitoring potential threats such as habitat loss, pollution, and human encroachment is crucial. Conservation efforts and research initiatives are warranted to ensure the sustained existence of this captivating species.

In conclusion, Siebold's Keelback, with its captivating features and intriguing behaviors, stands as a testament to the biodiversity of Asian snakes. Conservation endeavors and continued research are pivotal in ensuring the sustained existence of this enigmatic serpent, allowing future generations to marvel at its unique place in the intricate tapestry of nature.

Literature Cited:

  • 1.  Das, A., Gower, D. J., & Deepak, V. (2020). Lost and found: rediscovery and systematics of the Northeast Indian snake Hebius pealii (Sclater, 1891). Vertebrate Zoology 70 (3): 305–318 - Link
  • 2. Das, I. (2012). A Naturalist's Guide to the Snakes of South-East Asia: Malaysia, Singapore, Thailand, Myanmar, Borneo, Sumatra, Java and Bali. Oxford John Beaufoy Publishing.
  • 3. David, P.; Vogel, G. & Pauwels, O.S.G. (2005). On the occurrence of Amphiesma bitaeniatum (WALL, 1925) in Vietnam, with preliminary remarks on the group of Amphiesma parallelum (BOULENGER, 1890) (Serpentes, Colubridae, Natriciniae). Salamandra 41 (4): 167-178 - Link
  • 4. David, Patrick; Ishan Agarwal, Ramana Athreya, Rosamma Mathew, Gernot Vogel & Viral K. Mistry (2015). Revalidation of Natrix clerki Wall, 1925, an overlooked species in the genus Amphiesma Duméril, Bibron & Duméril, 1854 (Squamata: Natricidae). Zootaxa 3919 (2): 375–395 - Link
  • 5. Günther, A. (1864). The Reptiles of British India. London (Taylor & Francis), xxvii + 452 pp.
  • 6. Günther, A. (1860). Contributions to a knowledge of the reptiles of the Himalaya mountains. - I. Descriptions of the new species. II. List of Himalayan reptiles, with remarks on their horizontal distribution. Proc. Zool. Soc. London 1860: 148-175 - Link
  • 7. Günther, A. (1860). Reptiles of Siam. Proc. Zool. Soc. London 1860: 113-117 - Link
  • 8. Guo, Peng; Fei Zhu, Qin Liu, Liang Zhang, Jian X. Li, Yu Y. Huang & R. Alexander Pyron (2014). A taxonomic revision of the Asian keelback snakes, genus Amphiesma (Serpentes: Colubridae: Natricinae), with description of a new species. Zootaxa 3873 (4): 425–440 - Link
  • 9. Khan, M.S. (2002). Die Schlangen Pakistans [English edition as “A Guide to the snakes of Pakistan”]. Edition Chimaira (Frankfurt am Main), 265 pp.
  • 10. Kramer, E. (1977). Zur Schlangenfauna Nepals. Revue Suisse de Zoologie 84 (3): 721-761.
  • 11. Lalremsanga, H. T., Bal, A. K., Vogel, G., & Biakzuala, L. (2022). Molecular phylogenetic analyses of lesser known colubrid snakes reveal a new species of Herpetoreas (Squamata: Colubridae: Natricinae), and new insights into the systematics of Gongylosoma scriptum and its allies from northeastern India. SALAMANDRA, 58(2): 101-115 - Link
  • 12. Malnate, E. V. (1966). Amphiesma platyceps (BLYTH) and Amphiesma sieboldii (GÜNTHER): sibling species (Reptilia: Serpentes). J. Bombay Nat. Hist. Soc. 63 (1): 1-17 - Link
  • 13. Theobald, WILLIAM (1868). Catalogue of reptiles in the Museum of the Asiatic Society of Bengal. J. Asiatic Soc. Bengal, Calcutta, 37 (extra number 146): (2), vi, 7-88 - Link
  • 14. Theobald,W. (1876). Descriptive catalogue of the reptiles of British India. Thacker, Spink & Co., Calcutta: xiii + 238 pp.
  • 15. Tillack, F. (2003). Über die Verbreitung und Biologie der Himalaya-Gebirgswassernatter Amphiesma platyceps (BLYTH 1854) und einen Fall von Amphigonia retardata (Serpentes: Colubridae: Natricinae). Sauria 25 (1): 21-27 - Link
  • 16. Wallach, Van; Kenneth L. Williams, Jeff Boundy (2014). Snakes of the World: A Catalogue of Living and Extinct Species. [type catalogue] Taylor and Francis, CRC Press, 1237 pp.
  • 17. Wangyal, Jigme Tshelthrim (2019). The status of herpetofauna of Bhutan. District Forest Office, District Administration, Trashigang, Bhutan, 20-39 - [Link](
  • 18. Ziegler, T., and Quyet, L.K. 2006. A new natricine snake of the genus Amphiesma (Squamata: Colubridae: Natricinae) from the central Truong Son, Vietnam. Zootaxa 1225: 39-56 - get paper here



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Herps Of Doda: The Enigmatic Beauty of Herpetoreas sieboldii: Unveiling the Wonders of Siebold's Smooth Snake
The Enigmatic Beauty of Herpetoreas sieboldii: Unveiling the Wonders of Siebold's Smooth Snake
Herpetoreas sieboldii, commonly known as Siebold's Keelback, emerges as a mesmerizing serpent within the realms of Asian herpetology.
Herps Of Doda
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