Mamushi: curiosities and legends around this Japanese snake

The mamushi is not on the IUCN Red List, but the high human-induced mortality of adults, especially pregnant females, raises concern for the survival of this species

by Lorenzo Ciotti
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Mamushi: curiosities and legends around this Japanese snake

The mamushi is the most venomous snake species in Japan. Between 2,000 and 3,000 people are bitten by this species each year in this country. The mamushi is not on the IUCN Red List, but the high human-induced mortality of adults, especially pregnant females, raises concern for the survival of this species.

The mamushi lives on all the main islands of Japan, in Korea, in a large area of China and on the island of Kunasir, the southernmost of the Kurils. It is a particularly adaptable species, present in different habitats. It lives in swamps, wet pastures, meadows, woods, mountain forests, rocky hills and shrubs.

Mamushi venom is moderately potent, with an LD50 of 18.29 mg/kg. The quantity of venom that this reptile is capable of injecting is around 15 mg. It is mainly haemolytic, that is, it destroys red blood cells. This venom also contains two neurotoxins that act on the nervous system, as well as anticoagulants that cause massive bleeding.

An average of 10 to 50 people die each year from the bite of this snake. Among the local symptoms that occur after poisoning are pain, swelling, bruising, blisters and, in some cases, necrosis. This is followed by headache, dizziness, visual disturbances, abdominal pain, nausea, vomiting, diarrhea, neck stiffness, muscle pain, paralysis, bleeding, coagulopathy, convulsions, collapse, and acute renal failure.

In pregnant women, the bite causes miscarriage. Death can occur due to severe kidney damage. Against mamushi venom, however, there are two monovalent antidotes. The mamushi leads a mainly nocturnal existence, but is also active during the day when the temperatures are not too high.

It is usually a terrestrial species, but it is an excellent climber and tends to climb trees often and willingly, especially for hunting. Its hunting technique consists of stalking. Thanks to its colouration, it camouflages itself easily among the vegetation and waits motionless for its preys.

In addition to sight and an excellent sense of smell, the mamushi is equipped with heat sensors positioned between the eyes and nostrils which allow it to identify even in the dark prey that are not moving. This snake, when provoked, is quite aggressive and does not hesitate to bite.

When attacking, it is able to jump forward at least 30 cm. With an average length of 45 cm and a maximum recorded length of 91, the mamushi is a small reptile. The body, with an average weight of about 60 g, has a thick and massive appearance; the tail is short.

The background color is extremely variable, as it can be light gray, brown, reddish or pale yellow. The pattern is inverted U-shaped spots on the sides of the body. These are often bordered by black borders, with a lighter center.

The head, well distinct from the body, is flattened, triangular in shape and dark brown or black in colour. The sides of it, light gray or beige, are crossed by a dark line. The eyes are of medium size, with elliptical and vertical pupils. The venom teeth are positioned in the anterior part of the mandible and fold back when the animal closes its mouth.