Photo StoryPublished : Sep 10, 2021Updated : Oct 05, 2023
No other snake, except the king cobra, evokes as strong a sense of fear as the medically important krait does
Text by: Dr Seshadri KS
No other snake, except the king cobra, evokes as strong a sense of fear as the medically important krait does
Kraits are a group of highly venomous snakes found in parts of tropical Asia from Iran through the Indian subcontinent into the jungles of Borneo. There are 16 recognised species, with eight species from India and several more listed as subspecies.
Kraits are nocturnal and typically have a non-aggressive demeanour. Yet, they are among the most medically important snakes, particularly in India, as they have the most toxic venom among terrestrial snakes found on the Indian subcontinent. The common krait (Bungarus caeruleus) is listed among the “Big Four” of Indian venomous snakes, along with the spectacled cobra, saw-scaled viper and Russell’s viper. Together, these snakes are responsible for over 50,000 reported annual deaths from snakebites in India.
Kraits closest relatives are cobras, believed to have broken off from a common ancestor during the Miocene, about 10.2 million years ago. Fossil evidence was discovered in the Potwar Plateau in the Siwaliks in present-day Pakistan, as reported by Head et al. in 2016 in a paper in the journal Palaentologica Electronica.
Interestingly, both their evolutionary origin and their common and genus names are tied to India. The common name, krait, stems from the Hindi word “karait”, meaning black. The genus name, Bungarus, stems from the Telugu word, “Bungarum”, meaning gold. One would wonder how the two names for the same group can mean two distinct colours; the answer is that the names go back to the regions where the species were described. It turns out that the banded krait (Bungarus fasciatus) with its prominent gold bands was used to coin the genus name, while the word krait must have come from the Hindi heartland of Central India where the predominantly black common Indian krait (B. caeruleus) is encountered.
Kraits are medium to moderately large and often measure up to a meter in length. Nocturnal in habit, they forage slowly on the ground and among leaf litter. Adult kraits are known to feed on mice, snakes, and lizards, but we don’t know much about the diet of juveniles. All species lay eggs, often in a burrow. Despite being feared and of medical importance, we know very little about kraits, but here’s what we do know about our fascinating, feared, and fanged friends.
A distinguishing feature of kraits is the hexagonal scales on the spike. Seen here is a banded krait (Bungarus fasciatus) from Hooghly, West Bengal. Photo: Vishal Santra.
Cover photo: A coiled up banded krait. Photo: Girish Choure
As the name suggests, the Andamans krait (Bungarus andamanensis) is found only in the Andaman Islands and was described in 1978 by S Biswas and DP Sanyal of the Zoological Survey of India. It is the only krait species found on the islands, and interestingly, does not occur in the nearby Nicobar Islands. The snake is seen near roadside ditches during the monsoon. However, nothing is known about its venom, and no fatalities have been reported. Photo: Girish Choure
The Himalayan krait (Bungarus bungaroides), also known as the northeastern hill krait, is found in parts of Assam, Meghalaya, and Sikkim in India and in Myanmar, Bhutan, Vietnam, and China. It is a moderately long snake found at elevations of about 2,400 m. The snake was first described from Cherrapunji in Meghalaya by Theodore Cantor, a Danish naturalist working with the British East India company in 1839. Nearly all krait species have an iridescent sheen on their skin (above right). Photos: Vishal Santra
The common Indian krait (Bungarus caeruleus) in black morph (left) is widespread across India. It is one of the most feared snakes, responsible for many snakebite fatalities. It was first described in 1801 in Vishakapatnam, Andhra Pradesh, by the German naturalist Johann Schneider. The term caeruleus implies a dark colour, referring to the predominantly black colour of the snake. Typically active at night but relatively quiet during the day, they can be found in termite hills, burrows or even among garden pots and urban construction rubble. They are known to cannibalise and consume their own kind as well as other snakes, mice, lizards, and frogs. “Numerous reports exist of the snake biting sleeping humans in the dead of night. The fact that the bite from this snake is not painful, unlike that of the spectacled cobra or Russell’s viper, adds to the mortality rate as people may not rush to get medical attention,” says Rom Whitaker, renowned herpetologist and co-founder of the Madras Crocodile Bank Trust. Krait venom is neurotoxic and often causes paralysis of muscles, leading to respiratory failure. “People in parts of Rajasthan believe that the krait coils up on a sleeping person’s chest and sucks their breath out, killing them. While the snake does no such thing, this is an accurate description of what the victim goes through—chest tightness, the person cannot breathe, and dies of respiratory failure,” adds Rom. An albino morph of the common Indian krait (right). Photos: Vishal Santra (above left), Girish Choure (above right)
Banded kraits Bungarus fasciatus are rendered the genus Bungarus and the word fasciatus refers to the bands. This distinctive black-and-yellow banded snake is widespread along eastern India. The snake is rather mild-mannered, and bites are rare. Recalling an expedition to the remote villages in West Bengal, Rom said, “In the early 1970s, I would travel to remote parts of 24 Parganas district, to collect snakes for the first venom lab in Bombay. At the time, many tribal people kept snakes like banded kraits in boxes to sell to dealers, about 40 in a box, all large-sized. When I asked to see one, the seller put his hand right into the box and casually picked one up mid-body, saying that at night they were deadly, but during the day they would not bite at all!” It is still a mystery as to why the snakes chose not to bite during the day. “Back then, the Wildlife Protection Act was not in existence, and I suspect the snakes were sold to extract snake oil,” he added. Photo: Vishal Santra
Lesser black krait (Bungarus lividus) was first described by Theodore Cantor in 1839 with a specimen from Assam. The name lividus refers to the bluish lead metallic colour of the snake. Its bites are fatal. We know hardly anything else about this small, secretive snake. Photo: Avrajjal Ghosh
Greater black krait (Bungarus niger) is a south Asian endemic that is relatively rare. It can be found on the edges of villages and forests of the Eastern Himalayas. It was first described in 1908 by Frank Wall, a Ceylon-born herpetologist, with specimens from Darjeeling. The name niger refers to the overall black colour of this snake, which lacks bands. Photo: Girish Choure
