Monocled cobra

Identification

The monocled cobra is a smooth-scaled cobra that rears up and spreads a hood when alarmed^1,2. Most are medium to dark brown, grey-brown or blackish and many are plain, but snakes from Bengal and the Gangetic Plain often have pale bands that split into a net-like pattern towards the tail².

Its name comes from the single pale ring with a dark centre on the back of its hood, which looks like a monocle; this mark is almost always present, though it can be faint or shaped more like a mask². The throat is pale with a small dark spot on each side, usually followed by a dark band^1,2.

Most adults measure 1.1–1.5 m, and a typical total length is given as 1.5 m^1,2. The record is about 2.3 m².

Distribution

The monocled cobra ranges from north-eastern India, Bangladesh and Bhutan through Myanmar and southern China to Thailand, Laos, Cambodia, Vietnam and northern Peninsular Malaysia¹. In India it lives in the Gangetic Plain, Bengal, Odisha and the north-east, and it shares much of northern India with the Indian cobra². It also occurs in Nepal, where the World Health Organization lists it among the most medically important snakes^3,6.

In Bangladesh it is found throughout the country and is the only cobra in the south-east, including Chittagong and Cox’s Bazar³. Genetic studies suggest that one population may be a separate, still unnamed species¹.

Habitat

Where it lives alongside other cobras, the monocled cobra tends to occupy lower, wetter ground². It is common in rice-growing areas, where it shelters in rodent burrows in the banks between fields, and in some places it has become almost semi-aquatic². Plantations are another favourite haunt, and it adapts well to living near people unless it is heavily persecuted².

It is the commonest venomous snake around the Sundarbans in West Bengal, where wet paddy fields are a favoured habitat⁷.

Behaviour

The monocled cobra is most active at dusk and in the evening, but it can be met at other times². In a study of 70 bites in south-eastern Bangladesh, most happened in the early morning or evening, and only 12% of the victims were asleep⁴.

Like other cobras, it usually flees and faces an attacker only when cornered². It was long thought not to spit venom, but spitting has now been recorded in West Bengal and Assam in India and in Nepal^5,6.

Diet

Young monocled cobras eat mostly frogs and toads, while adults also take small mammals². Snakes and fish are eaten occasionally².

Reproduction

Like all cobras, the monocled cobra lays eggs, and the female generally stays with them². Egg-laying is often given as January to March, and incubation takes about 50 days⁷.

The season varies by region: near the Sundarbans, females have been seen guarding eggs in late July and August, and young cobras measuring 28–36 cm from snout to vent were rescued from October to early December⁷.

Venom and medical significance

The monocled cobra is highly venomous, and the World Health Organization places it in its highest category of medical importance in Bangladesh, Nepal, Myanmar, Thailand and eastern India³. In Bangladesh it causes most cobra bites³.

In a study of 70 people bitten in south-eastern Bangladesh, 58 developed severe paralysis, usually starting with drooping eyelids; 19 developed blistering and tissue death around the bite, 11 needed a breathing machine and two died in hospital⁴. The Indian polyvalent antivenom used there, which is not made with this cobra’s venom, reversed paralysis in most patients but did not prevent tissue damage, and most patients had reactions to it⁴.

WHO notes that Indian antivenoms may not neutralise this species, while the Thai Red Cross and Myanmar produce specific monocled cobra antivenoms³. Anyone bitten should go to hospital immediately.

Conservation

The monocled cobra is listed as Least Concern on the IUCN Red List (2012 assessment)⁸. It has a large range and adapts well to farmland and villages^1,2. In India, every species of the genus Naja is listed in Schedule I of the Wild Life (Protection) Act, as amended in 2022, which gives the highest level of legal protection⁹.

Similar species

The Indian cobra (Naja naja) overlaps with the monocled cobra in northern and north-eastern India and around and west of Dhaka in Bangladesh^2,3. Its hood mark is spectacle-shaped or missing, whereas the monocled cobra’s is a single ring or mask that is almost never absent, and its throat pattern is often indistinct².

The king cobra (Ophiophagus hannah) has a pair of large scales at the back of its head that true cobras lack³. The harmless Indian rat snake (Ptyas mucosa) has small loreal scales between the nostril and the eye; cobras and other elapids have none³. These differences are not a safe basis for handling any snake. Keep your distance from every snake you cannot identify.

In captivity

The monocled cobra is a dangerous venomous snake and is not suitable as a pet. In India it is protected under Schedule I of the Wild Life (Protection) Act, as amended in 2022⁹. It should never be caught or kept by private individuals.