Bungarus Andamanensis

The South Andaman krait (Bungarus andamanensis) is a venomous elapid snake endemic to the Andaman Archipelago of India. Recognised as a distinct species in the late twentieth century, it forms part of the genus Bungarus, a group known for potent neurotoxic venoms and distinct banded colouration. The species is a relatively rare and localised reptile with ecological adaptations suited to humid island environments. Its morphology, behaviour and habitat preferences contribute to its biological significance within the herpetofauna of the Andaman Islands.

Taxonomy and Discovery

The species was formally described in 1978 by the herpetologists S. Biswas and D. P. Sanyal following systematic surveys in the Andaman Islands. It is classified within the family Elapidae, which encompasses other venomous snakes such as cobras and sea snakes. Morphological comparisons undertaken in subsequent phylogenetic studies have placed it firmly within the Bungarus lineage, though it remains geographically and genetically isolated from mainland congeners.

Morphological Characteristics

The South Andaman krait is a medium-sized snake, generally attaining lengths of up to 1.3 metres. The body is cylindrical, with a head that is only slightly broader than the neck, giving it a characteristic slender appearance. The eyes are small, completely black and equipped with round pupils, traits associated with predominantly nocturnal species. The tail is blunt and thickened towards the tip, a feature shared with several other Bungarus species.

Scalation Features

Scalation plays a crucial role in identifying elapid snakes, and B. andamanensis exhibits several diagnostic traits:

• Dorsal scales: Smooth and arranged in a consistent 15–15–15 series; vertebral scales are noticeably enlarged.
• Head scales: Internasals are shorter than prefrontals; the species lacks a loreal scale. The preocular makes direct contact with the posterior nasal. Two postoculars are present, and the temporals follow a 1+2 arrangement.
• Labials: Seven supralabials are present, with the third and fourth touching the eye; the sixth supralabial is the largest. Seven infralabials exist, with the first three contacting the genials.
• Ventral and subcaudal scales: Characteristically, the species possesses between 192 and 200 ventral scales and 40–47 entire subcaudal scales. The anal plate is entire.

These features collectively assist in distinguishing the species from both continental and island elapids.

Colouration and Patterning

The colouration of the South Andaman krait is glossy and striking. Adults are typically black or brownish, often displaying a blue sheen when observed under natural light. The body is encircled by 39–47 thin, yellow or white crossbars of equal spacing, while the tail bears 9–13 similar bands that broaden slightly towards the ventral surface. The underside is yellowish-cream with irregular dark spotting, and the tail may show prominent brownish blotches. The lips are pale yellow. Juveniles appear more vividly marked, with brighter yellow crossbars and a distinctive head marking that fades with age.

Distribution and Habitat

The species is restricted to the Andaman Islands, including South Andaman, Middle Andaman, North Andaman, and Little Andaman Islands. As an island endemic, its distribution is shaped by ecological isolation and limited dispersal.
It occupies a broad variety of habitats, including:

• Paddy fields and agricultural margins
• Coastal vegetation and low mountain scrub
• Mangrove belts
• Freshwater stream banks
• Roadside areas following rainfall
• Vicinity of termite mounds

Populations are particularly abundant on Little Andaman Island, suggesting favourable ecological conditions there.

Ecology and Behaviour

The South Andaman krait is primarily nocturnal, emerging most frequently during or after heavy rains when prey availability increases. When alarmed, it flattens its body slightly and coils in a loose defensive posture, concealing the head beneath the body coils. A distinctive squeaking sound may be produced, which is presumed to act as a deterrent to predators. Juveniles are most commonly encountered in June, indicating a seasonal emergence linked with the region’s climatic patterns.

Feeding Ecology

As with other kraits, the species is predominantly ophiophagous. It preys extensively on other snakes, including aquatic species such as water snakes. Occasional predation on fish has also been observed. Adults are encountered less frequently than juveniles, with many adult sightings reported near freshwater streams where prey diversity is greater.

Reproductive Aspects

Detailed reproductive biology for B. andamanensis remains insufficiently documented. However, the consistent appearance of juveniles during early monsoon months suggests a seasonal breeding cycle, potentially aligned with increased humidity and prey abundance. Clutch size, egg morphology and incubation behaviours remain subjects for further herpetological investigation.

Conservation and Research Significance

Although no comprehensive conservation assessment has been finalised, the species’ restricted island range, habitat specificity and human-induced modifications to wetlands and coastal regions may pose future risks. Research efforts have emphasised its importance in understanding island biogeography, reptile diversification and the evolutionary pathways of Asian elapids. Studies on the venom composition and ecological role of B. andamanensis continue to be relevant for both public health and biodiversity management within the Andaman Islands.