Buff Striped Keelback

The buff striped keelback (Amphiesma stolatum) is a widespread non-venomous colubrid snake native to South and Southeast Asia. Known for its distinctive longitudinal stripes and generally docile disposition, it is commonly found in well-watered landscapes and often encountered near human habitation, though it is seldom seen owing to its secretive nature. The species is placed within the subfamily Natricinae, making it closely related to Nerodia and the Eurasian grass snakes, and it is frequently compared to the American garter snakes in its ecological habits and appearance.

Taxonomic History

Over time, the species has been described under several different genera, reflecting shifts in taxonomic understanding:

• Elaps bilineatus – Johann Gottlob Theaenus Schneider, 1801
• Natrix stolatus – Blasius Merrem, 1820
• Tropidonotus stolatus – Friedrich Boie, 1827
• Rhabdophis stolatus – Frank Wall, 1921
• Amphiesma stolatum – later revisions by various authors

These reclassifications underscore the complex evolutionary relationships within Natricinae.

Anatomy and Morphology

The buff striped keelback is a slender snake with an olive-brown to grey dorsal colouration. The head and body share the same overall tone, while the tail is notably long and tapering, comprising nearly one quarter of the snake’s total length. The most defining feature is the pair of pale yellow stripes running longitudinally along the body on either side of the spine. These stripes are muted near the head and become brightest toward the rear half of the body.
Other morphological features include:

• Irregular blackish crossbars, prominent near the head and fading posteriorly
• Yellow sides of the head and a distinctly narrow neck
• Red nape during the breeding season
• White or occasionally orange chin and throat
• Black vertical markings around the large golden-flecked eyes
• A black forked tongue
• Cream-coloured underside with fine black lateral speckling
• Strongly keeled dorsal scales except for the smooth outer row

Morphs and Colour Variants

Two main colour varieties occur:

• Typical variety – widespread, with greyish-blue interscale colour
• Variety erythrostictus – common in coastal regions, noted for bright vermilion interscale colour

These interscale hues become visible when the snake inflates its body in agitation.

Identifying Characteristics

Key diagnostic features include:

• Nasal shield not touching the second supralabial
• Rostral contacting six shields: two internasals, two nasals, and the first supralabial on each side
• Single temporal shield
• Nineteen rows of strongly keeled costal scales (outermost row smooth)
• Distinct longitudinal stripes
• Ventrals: 125–161
• Divided anal plate
• Subcaudals: 50–85

Size

Most individuals measure between 40 and 50 cm in total length. Females are consistently larger, while males rarely reach the maximum lengths occasionally recorded in females.

Distribution

The buff striped keelback is widespread across:

• Pakistan (Sindh)
• India, including the Andaman Islands and Sri Lanka
• Bangladesh
• Nepal
• Bhutan
• Myanmar
• Thailand, Laos, Cambodia, Vietnam
• Indonesia (including Borneo and Sabah)
• Taiwan
• China (Hainan, Hong Kong, Fujian, Jiangxi)

In India, the species occurs from lowland plains up to moderate hill elevations.

Conservation Status

The species is common throughout its extensive range and is not considered to be of conservation concern at international levels.

Ecology and Life History

Habitat

The keelback is terrestrial and diurnal, favouring moist lowland plains, agricultural areas, and foothills. It adapts easily to human-modified landscapes.

Feeding Ecology

Adults primarily consume frogs and toads, but they also prey on fish, earthworms, small lizards such as geckos, and other small invertebrates.

Reproduction

The species is oviparous. Mating is believed to coincide with the aestivation period. Gravid females are typically observed between April and August, and egg-laying occurs from May to September. Clutches usually contain 5–10 white eggs, deposited in concealed underground chambers. Females remain with their eggs until hatching. Hatchlings measure 13–17 cm and feed on small amphibians, fish, earthworms, tadpoles, and insects.

Behaviour

A diurnal species, the buff striped keelback spends most of its time on land but readily enters water when necessary. It possesses enlarged rear teeth that assist in gripping slippery amphibian prey. It is completely non-venomous and harmless to humans.
When threatened, the snake inflates its body, exposing the bright interscale colours, and may flatten its head to mimic a hood. This display can lead to mistaken identification as a juvenile cobra. The species aestivates in extreme heat and becomes abundant during the monsoon season. In northern India, individuals hibernate in soil or among grass roots at depths of 25–45 cm.

Local Names

Numerous vernacular names exist across South Asia, reflecting the snake’s wide distribution:

• Assamese/Odia regions: Bamuni saap, Halahalia saapa, Mati biradi saapa
• Bengali: Bamuni dhora shap, Hele shap, Ghorkuno shap, Ghenti shap
• Gujarati/Marathi dialect areas: Kankasiyukekariyu, Naneti wasya
• Tamil/Malayalam: Wannapam, Nirkatan pambu
• Telugu/Kannada: Pageley, Hullu haavu
• Hindi: Bamhani
• Nepali: Seetaalat, Harhare
• Punjabi: Gulera

These names highlight the cultural familiarity of the species throughout its range.

Cultural and Scientific Context

Although common, the buff striped keelback is often overlooked due to its elusive behaviour. It plays an important ecological role in regulating amphibian populations, and its striking defensive display has contributed to folklore and misidentification across rural regions. The species has been extensively referenced in South Asian herpetological literature since the eighteenth century, with detailed treatments appearing in colonial and post-colonial field guides.