| Monocled cobra | |
|---|---|
| A young monocled cobra | |
| Conservation status | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Elapidae |
| Genus: | Naja |
| Species: | N. kaouthia |
| Binomial name | |
| Naja kaouthia Lesson, 1831 |
|
The monocled cobra (Naja kaouthia) is a cobra species, which is widespread across central and southern Asia. It has been assessed as Least Concern by IUCN owing to its large distribution, tolerance of a broad range of habitats, including anthropogenically altered environments, and its reported abundance. No major threats have been reported, and the species is not thought to be undergoing a significant population decline.[1]
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The monocled cobra has an O-shaped, or monocellate hood pattern, unlike that of the Indian cobra. Coloration in young is more constant. They are olivaceous or brownish to black above with or without a yellow or orange-coloured O-shaped mark upon the hood. They have a black spot on the lower surface of the hood on either side, and one or two black cross-bars on the belly behind it. The rest of the belly is usually of the same colour as the back, but paler. As age advances, they become paler, and when adult are brownish or olivaceous. Adult monocled cobras reach a length of 135 to 150 cm (53 to 59 in) with a tail length of 23 cm (9.1 in). Many larger specimens have been recorded, but they are rare. They have 25 to 31 scales on the neck, 19 to 21, usually 21, on the body, and 17 or 15 on the front of the vent. They have 164 to 196 ventral scales and 43 to 58 subcaudal scales.[2]
The elongated nuchal ribs enable cobras to expand the anterior of the neck into a “hood”. A pair of fixed anterior fangs is present. Monocled cobras are non-spitting. Adults are a maximum of 2.3 metres (7 ft 7 in) in length. The dorsal surface may be yellow, brown, gray, or blackish and with or without ragged or clearly defined cross bands. The throat is usually immaculate and followed by a dark band. The ventral surface is the same color as the dorsal but the sub-caudals are light with dark edges.[3]
Monocled cobras tend to have more than one cuneate scale on each side. The shape of the frontal scale is short and square. Ventrals in males range from 170 to 192, in females from 178 to 197. Subcaudals in males range from 48 to 61, in females from 46 to 59. The largest fang recorded measured 6.78 mm (0.267 in). Fangs are moderately adapted for spitting.[4]
The median lethal dose is 0.28-0.33 mg per gram of mouse body weight.[3] The major toxic components in cobra venoms are postsynaptic neurotoxins, which block the nerve transmission by binding specifically to the nicotinic acetylcholine receptor, leading to flaccid paralysis and even death by respiratory failure. The major α-neurotoxin in Naja kaouthia venom is a long neurotoxin, α-cobratoxin; the minor α-neurotoxin is different from cobrotoxin in one residue.[5] The neurotoxins of this particular species are weak.[6] The venom of this species also contains myotoxins and cardiotoxins.[7][8]
In case of intravenous injection the LD50 tested in mice is 0.373 mg/kg, and 0.225 mg/kg in case of intraperitoneal injection.[9][10] The average venom yield per bite is approximately 263 mg dry weight.[11]
The monocled cobra causes the highest fatality due to snake venom poisoning in Thailand.[12] Envenomation usually presents predominately with extensive local necrosis and systemic manifestations to a lesser degree. Drowsiness, neurological and neuromuscular symptoms will usually manifest earliest; hypotension, flushing of the face, warm skin, and pain around bite site typically manifest within one to four hours following the bite; paralysis, ventilatory failure or death could ensue rapidly, possibly as early as 60 minutes. The presence of fang marks does not always imply that envenomation actually occurred.[13]
Monocled cobras are distributed from India in the west through to China, Vietnam and Cambodia, also occurs in the Malay Peninsula and is native to Bangladesh, Bhutan, Myanmar, Laos, Nepal, and Thailand. They are found up to elevations of 1,000 m (3,300 ft) above sea level, and prefer habitats associated with water, such as paddy fields, swamps, and mangroves, but are also found in grasslands, shrublands, and forests, in agricultural land and human settlements, including cities.[1]
Monocled cobras can adapt to a range of habitats, from natural to anthropogenically impacted environments. They prefer habitats associated with water, such as paddy fields, swamps, and mangroves, but can also be found in grasslands, shrublands, and forests. It also occurs in agricultural land and human settlements, including cities.[1] In rice-growing areas they live in rodent burrows in the dykes between the fields and have become semi-aquatic in some areas. Juveniles take mostly amphibians. Adults eat small mammals, and occassionally snakes and fish. They are most active at dusk and night, but are also found basking during daytime. If encountered, they will flee.[4]
When threatened, they will raise the anterior portions of their bodies, spread their hood, usually hiss loudly, and strike in an attempt to bite and defend themselves.[3]
Females lay between 16 and 33 eggs per clutch. Incubation periods range from 55 to 73 days.[14] Egg-laying takes place in January to March. The females usually stay with the eggs. Some collaboration between males and females has been reported in Naja naja x Naja kaouthia -hybrids.[4]
Monocled cobras are harvested for the skin trade, however, collection from the wild is minimal and not likely to be causing significant population declines.[1]
Naja kaouthia is listed on CITES Appendix II. In places the distribution of this species coincides with protected areas, probably providing small safeguards.[1]
In 1831, Lesson first described the monocled cobra as a beautiful snake that is well distinct from the spectacled cobra, with 188 ventral scales and 53 pairs of caudal scales.[15]
Since then, several monocled cobras were described under different scientific names:
Several varieties of monocled cobras were described under the binomial Naja tripudians between 1895 and 1913.
In 1940, Malcolm Arthur Smith classified the monocled cobra as a subspecies of the spectacled cobra under the trinomial Naja naja kaouthia.[18]