Yamakagashi

Rhabdophis tigrinus

SUBFAMILY

Natricinae

TAXONOMY

Tropidonotus tigrinus Boie, 1826. Two subspecies are recognized.

OTHER COMMON NAMES

English: Tiger watersnake.

PHYSICAL CHARACTERISTICS

This is a rather slender snake that attains a length of about 40 in (1 m). Color varies, but most specimens are drab green to yellow, with red skin between the scales of the neck. Young have a bright light ring around the neck. The dorsal scales are keeled, and enlarged scales on the neck overlie special nuchal glands.

DISTRIBUTION

Widely distributed in eastern Asia, including much of China, Korea, and Japan.

HABITAT

This snake is terrestrial but is generally found in association with water, including rice paddies.

BEHAVIOR

The defensive behavior of this snake is very unusual. When threatened by a predator, the snake arches its neck toward the attacker and releases the contents of paired nuchal glands that lie in the dorsal skin. The product of those glands is distasteful and irritating to the eyes and contains compounds similar to those found in the skin glands of toads.

FEEDING ECOLOGY AND DIET

This species feeds almost entirely on frogs and toads, although it occasionally eats fishes.

REPRODUCTIVE BIOLOGY

This snake is oviparous, laying about a dozen eggs per clutch.

CONSERVATION STATUS

Not listed by the IUCN. At one site in Japan, this species is reported to have declined due to changes in agricultural practices, including the use of pesticides and chemical fertilizers, which may have reduced the numbers of frogs.

SIGNIFICANCE TO HUMANS

Although this snake is reluctant to bite defensively, the bite has been known to cause fatalities in humans. The venom acts very slowly, inhibiting the ability of the blood to clot and causing death by hemorrhage. ♦

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