Green Keelback Snake (Rhabdophis nigrocinctus)

Vibrant Green Snake, Southeast Asian Keelback, Camouflaged Vine Snake, Dorsal-Striped Serpent, Semi-Aquatic Reptile, Tropical Stream Snake,

The Green Keelback Snake, scientifically known as Rhabdophis nigrocinctus, epitomizes the rich biodiversity of Southeast Asia with its captivating attributes and intriguing behaviors. This species, widely distributed across the region from the dense rainforests of Indonesia to the subtropical landscapes of Nepal, boasts a striking appearance characterized by its slender, elongated body adorned in vibrant green scales and a distinctive dark dorsal stripe. This coloration serves as a remarkable camouflage adaptation, allowing the snake to seamlessly blend into the lush vegetation of its habitat, evading both predators and prey alike. Young specimens exhibit additional distinctive markings, including an inverted black V-mark on the neck, with its apex forwards, reaching to the frontal shield. A second, smaller V-mark may appear behind, with the intervening space being bright yellow or orange. Furthermore, a black stripe from the eye to the angle of the mouth, along with more or less regular transverse spots or cross-bars on the back and tail, contribute to the unique appearance of juvenile Green Keelbacks. While its physical features are certainly notable, the Green Keelback's behavioral repertoire further underscores its ecological significance. Diurnal in nature, these snakes actively forage during the daytime, preying upon amphibians, insects, and small vertebrates in the vicinity of water bodies. Notably, their ability to sequester toxins from consumed prey serves as a fascinating example of evolutionary adaptations in predator-prey interactions.

The Green Keelback, Rhabdophis nigrocinctus, recorded from Dandeli, Karnataka

 by Uajith

         ·  Kingdom: Animalia

·  Phylum: Chordata

·  Class: Reptilia

·  Order: Squamata

·  Suborder: Serpentes

·  Family: Colubridae

·  Genus: Rhabdophis

·  Species: Rhabdophis nigrocinctus

Physical Description: The Green Keelback snake boasts a slender and elongated body, well-adapted for navigating through the dense vegetation of its habitat. Adults typically measure around 1 to 1.2 meters (approximately 3 to 4 feet) in length, although individuals on the larger end of the spectrum have been recorded. Their body is adorned with scales that give it a rough texture, especially noticeable along the dorsal surface due to the keeling of these scales. The coloration of the Green Keelback can vary, but the most common hue is a vibrant green, serving as excellent camouflage against the lush greenery of its surroundings. Some populations may exhibit a more yellowish or brownish tint, depending on environmental factors and genetic variations. Along the length of its body, a distinct dark stripe runs dorsally, contrasting with the bright green or yellow background and giving rise to its common name, "keelback."

Juvenile green keelback in Pune, India recorded by
Ashlin

Scalation Pattern: The scalation pattern of the Green Keelback snake is a key aspect of its morphology, providing valuable diagnostic features for species identification. Along the dorsal surface, the snake typically possesses around 21 to 23 rows of keeled scales. These scales not only contribute to the snake's rough texture but also aid in gripping surfaces during movement. Ventral scales, found on the underside of the snake, number approximately 145 to 155, arranged neatly in rows to facilitate locomotion. The anal plate, located at the base of the tail, is a single large scale that serves various functions, including waste elimination and support during locomotion. Subcaudal scales, found beneath the tail, are typically paired and range from 57 to 67 in number. Each scale plays a role in stabilizing the snake's movement, especially when navigating uneven terrain.

Head Scales:

• ·       Frontal Scale: Single, large, and hexagonal.
• ·       Parietal Scales: Usually a pair of scales located behind the frontal scale.
• ·       Rostral Scale: Single scale at the tip of the snout.
• ·       Nasal Scales: A pair of scales covering the nostrils.
• ·       Loreal Scales: Typically one or two scales between the nasal and preocular scales.
• ·       Preocular Scales: Usually one or two scales above the eye.
• ·       Postocular Scales: Typically two or three scales behind the eye.
• ·       Temporal Scales: Rows of scales covering the sides of the head.
• ·       Supralabial Scales: Scales along the upper lip, usually numbering 7 to 9.
• ·       Infralabial Scales: Scales along the lower lip, usually numbering 8 to 10.

These scales, along with other cranial features, are crucial for species identification and taxonomy.

Habitat and Distribution: The Green Keelback snake is well-adapted to a wide range of habitats throughout its distribution in Southeast Asia. It is commonly found in tropical and subtropical environments characterized by dense vegetation and proximity to water bodies such as marshes, ponds, streams, and rice paddies. These semi-aquatic snakes thrive in habitats with ample hiding places and abundant prey, allowing them to fulfil their ecological niche as predators of amphibians and small vertebrates. Their distribution spans across various countries, including India, Nepal, Bangladesh, Myanmar, Thailand, Laos, Cambodia, Vietnam, Malaysia, and Indonesia, although specific ranges may vary within these regions due to habitat preferences and geographic barriers.

Behaviour and Diet: Green Keelback snakes are primarily diurnal, meaning they are active during the daytime hours when their prey, such as frogs and toads, are also active. Their semi-aquatic nature often leads them to inhabit areas near water bodies, where they can hunt for prey and bask in the sun to regulate their body temperature. Despite their slender appearance, Green Keelbacks are skilled predators, using stealth and ambush tactics to capture their prey. Their diet mainly consists of amphibians, although they may also consume small fish, insects, and occasionally small reptiles. Notably, Green Keelbacks possess a unique adaptation that allows them to sequester toxins from the toads they consume, particularly bufadienolides. These toxins are stored in specialized glands located on the back of their necks, serving as a chemical defense against predators.

Adult green Keelback recorded by Davidvraju

Reproduction: The reproductive behaviour of Green Keelback snakes typically follows a seasonal pattern, with breeding occurring during the rainy season when environmental conditions are favourable. Males actively seek out females for mating, engaging in courtship rituals that may involve tactile and olfactory cues. After successful copulation, females develop and lay clutches of eggs in secluded locations, such as leaf litter or rotting vegetation, to protect them from predators and environmental fluctuations. The number of eggs laid per clutch can vary but usually ranges from 10 to 20 eggs. Once laid, the eggs undergo an incubation period of several weeks, during which time they are vulnerable to predation and environmental stressors. Upon hatching, the young Green Keelbacks emerge fully formed and ready to embark on their journey of growth and survival.

Conservation Status: The conservation status of the Green Keelback snake varies across its range, with populations facing different levels of threat depending on local environmental conditions and human activities. While the species is generally considered to be of least concern by the International Union for Conservation of Nature (IUCN), certain populations may be susceptible to habitat destruction, pollution, and collection for the pet trade. Habitat loss due to deforestation, agricultural expansion, and urbanization poses a significant threat to Green Keelback populations, leading to habitat fragmentation and loss of suitable habitats. Pollution from agricultural runoff, industrial waste, and urban development further degrades the quality of remaining habitats, impacting the health and survival of these snakes and their prey. Additionally, collection for the pet trade, although not a major threat on a global scale, may locally deplete populations if not regulated properly. Therefore, continued monitoring and conservation efforts are essential to ensure the long-term survival of this unique and ecologically important species.

The Green Keelback snake is a captivating reptile with a fascinating array of physical, behavioural, and ecological adaptations. Its presence in Southeast Asian ecosystems contributes to these regions' biodiversity and ecological balance, highlighting the importance of conservation measures to safeguard its future survival.

Reference:

·       Campbell, J. A., & Lamar, W. W. (2004). The Venomous Reptiles of the Western Hemisphere (Vol. 2). Comstock Publishing Associates.

·       Cox, M. J., van Dijk, P. P., Nabhitabhata, J., Thirakhupt, K., & Thirakhupt, K. (1998). A Photographic Guide to Snakes and Other Reptiles of Peninsular Malaysia, Singapore, and Thailand. Sanibel Island, FL: Ralph Curtis Publishing.

·       Das, I. (2012). A Naturalist's Guide to the Snakes of Southeast Asia. Kuala Lumpur, Malaysia: John Beaufoy Publishing.

·       Deepak, V., & Karanth, P. (2018). A Review of the Green Keelback Snake, Rhabdophis nigrocinctus (Serpentes: Colubridae), from India with the First Detailed Account of Natural History, Morphology and Lineage Diversity in the Western Ghats Radiation. Taprobanica, 10(2), 111-126.

·       Gower, D. J., Captain, A., & Thakur, S. (2008). Snake (Reptilia: Squamata) Species Richness in India: An Updated Database. Journal of Threatened Taxa, 5(8), 3079–3088.

·       Guo, P., & Deng, X. (2009). Redescription of Rhabdophis nuchalis (Serpentes: Colubridae), a Rare Snake from Sichuan, China. Russian Journal of Herpetology, 16(3), 209-215.

·       IUCN. (2021). Rhabdophis nigrocinctus. The IUCN Red List of Threatened Species 2021: e.T198273A151796452. https://dx.doi.org/10.2305/IUCN.UK.2021-2.RLTS.T198273A151796452.en

·       Malhotra, A., & Thorpe, R. S. (2004). A Phylogeny of the Trimeresurus Group of Asian Pitvipers: New Evidence from a Mitochondrial Gene Tree. Molecular Phylogenetics and Evolution, 32(1), 83-100.

·       Manthey, U., & Grossmann, W. (1997). Amphibien & Reptilien Südostasiens. Natur und Tier-Verlag.

·       Mori, S., Saito, R., & Tanaka, S. (2016). Toxin Sequestration and Maintenance of Toxin Levels in Snakes: Lessons from Rhabdophis Keelbacks. Toxicon, 119, 27-33.

·       Murphy, J. C., & Voris, H. K. (2014). A Checklist and Key to the Homalopsid Snakes (Reptilia, Squamata, Serpentes), with the Description of New Genera. Fieldiana: Life and Earth Sciences, 8, 1-43.

·       Schleich, H. H., Kästle, W., & Kabisch, K. (1996). Amphibians and Reptiles of Nepal: Biology, Systematics, Field Guide. A. R. G. Gantner Verlag K. G.

·       Smith, M. A. (1943). The Fauna of British India, Ceylon and Burma: Reptilia and Amphibia (Vol. III, Serpentes). London, UK: Taylor & Francis.

·       Sodhi, N. S., & Koh, L. P. (2008). Conservation and Ecosystem Services of Tropical Rainforests. In N. S. Sodhi & L. P. Koh (Eds.), Conservation Biology for All (pp. 87-106). Oxford, UK: Oxford University Press.

·       Uetz, P., Freed, P., Hošek, J. (Eds.). (2021). The Reptile Database. http://www.reptile-database.org. Accessed on 20th March 2024.

·       Utiger, U., Schätti, B., & Helfenberger, N. (2005). The Oriental Colubrine Genus Coelognathus Fitzinger, 1843 and Classification of Old and New World Racers and Ratsnakes (Reptilia, Squamata, Colubridae, Colubrinae). Russian Journal of Herpetology, 12(1), 39-60.

·       Vogel, G., & Böhme, W. (2011). Contribution to the Herpetology of South-West India: A New Survey of the Reptiles of the Agasthyamalai Range. Bonner Zoologische Beiträge, 56(1-2), 5-34.

·       Whitaker, R., & Captain, A. (2004). Snakes of India: The Field Guide. Chennai, India: Draco Books.

·       Zug, G. R., Brown, H. H. K., & Schulte II, J. A. (2006). Systematics of the Garden Lizards, Calotes Versicolor Group (Reptilia, Squamata, Agamidae), in Myanmar: Central Dry Zone Populations. Proceedings of the California Academy of Sciences, 57(35), 955-971.

·       Jayawardena, S., & Gomez, M. V. (2017). An Overview of Amphibians and Reptiles of Sri Lanka. In A. Sooriyabandara, M. Ekanayake, & A. Sooriyabandara (Eds.), Diversity and Conservation of Asian Primates (pp. 237-255). Springer.

·       Bhupathy, S., & Vogel, G. (2013). Long-term herpetological studies in South Asia: A review of history, recent contributions, and future research prospects. In G. G. Raju, & K. R. Subramanian (Eds.), Recent Trends in Biodiversity of Andaman and Nicobar Islands (pp. 225-254). Zoological Survey of India.

·       Inger, R. F., & Marx, H. (1965). The Systematics and Evolution of the Oriental Colubrid Snakes of the Genus Calamaria. Fieldiana: Zoology, 49(1), 1-304.

·       Das, A., & Vijayakumar, S. P. (2020). The Herpetofauna of India: Diversity, Distribution, and Conservation. In K. Kunte, & U. Ramakrishnan (Eds.), State of India's Biodiversity and Conservation (pp. 457-483). Springer.

·       Zug, G. R., Brown, H. H. K., & Schulte II, J. A. (2006). Systematics of the Garden Lizards, Calotes Versicolor Group (Reptilia, Squamata, Agamidae), in Myanmar: Central Dry Zone Populations. Proceedings of the California Academy of Sciences, 57(35), 955-971.

·   Das, A., & Bhupathy, S. (2019). Diversity and distribution of snakes in India: Conservation strategies. In M. Singh, G. J. Singh, S. P. Vijayakumar, & M. Shekhawat (Eds.), Perspectives in Animal Ecology and Reproduction Vol. 11: Herpetology (pp. 53-84). Scientific Publishers.