Gloydius shedaoensis
Encyclopedia
- Common names: Shedao island pitviper, Shedao pit-viper.
Gloydius shedaoensis is a venomous
Venomous snake
"Poisonous snake" redirects here. For true poisonous snakes, see Rhabdophis.Venomous snakes are snakes which have venom glands and specialized teeth for the injection of venom...
pitviper
Crotalinae
The Crotalinae, commonly known as "pit vipers" or crotaline snakes, are a subfamily of venomous vipers found in Asia and the Americas. They are distinguished by the presence of a heat-sensing pit organ located between the eye and the nostril on either side of the head...
species
Species
In biology, a species is one of the basic units of biological classification and a taxonomic rank. A species is often defined as a group of organisms capable of interbreeding and producing fertile offspring. While in many cases this definition is adequate, more precise or differing measures are...
found only on Shedao Island in China
China
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. Although very small, this island is home to an extraordinarily large population of these snakes. No subspecies
Subspecies
Subspecies in biological classification, is either a taxonomic rank subordinate to species, ora taxonomic unit in that rank . A subspecies cannot be recognized in isolation: a species will either be recognized as having no subspecies at all or two or more, never just one...
are currently recognized.
Description
Adults grow to an average snout-vent length of 65–70 cm. Scalation includes 23 rows of dorsal scalesDorsal scales
In snakes, the dorsal scales are the longitudinal series of plates that encircle the body, but do not include the ventral scales.When counting dorsal scales, numbers are often given for three points along the body, for example 19:21:17...
at midbody, an average of 57 ventral scales
Ventral scales
In snakes, the ventral scales are the enlarged and transversely elongated scales that extend down the underside of the body from the neck to the anal scale. When counting them, the first is the anteriormost ventral scale that contacts the paraventral row of dorsal scales on either side...
and an average of 41 paired subcaudal scales
Subcaudal scales
In snakes, the subcaudal scales are the enlarged plates on the underside of the tail. These scales may be either single or divided and are preceded by the anal scale....
. Also, the second supralabial scale is low and does not form the anterior margin of the pit. The color pattern consists of a grayish brown ground color overlaid with a series of dark brown X-shaped markings. A postocular stripe is present that is very narrow and very dark in color.
Geographic range
Found only on Shedao Island off the coast of Liaotung in northeastern ChinaChina
Chinese civilization may refer to:* China for more general discussion of the country.* Chinese culture* Greater China, the transnational community of ethnic Chinese.* History of China* Sinosphere, the area historically affected by Chinese culture...
. The type locality given is "Shedao (Snake Island), situated about 24 nautical miles (44.4 km) from and to the north-west of Lüshun (Port Arther [sic]), Liaoning Province, altitude below 215 m" (China).
Shedao Island lies 7 nautical miles (about 13 km) from the nearest mainland and has an area of 0.63 km² (or 0.73 km²). However, despite its small size, the population density of these snakes on the island has long been know to be extremely high. Koba (1938) estimated that, on the southeastern part of the island, there was about one snake for every square meter, while Huang (1984) calculated that there were about 9,100-11,500 snakes on the island during the spring and fall of 1982 when the snakes were active.
Feeding
The diet consists of small passerinePasserine
A passerine is a bird of the order Passeriformes, which includes more than half of all bird species. Sometimes known as perching birds or, less accurately, as songbirds, the passerines form one of the most diverse terrestrial vertebrate orders: with over 5,000 identified species, it has roughly...
birds of various species. These birds migrate to and from their breeding grounds in Siberia
Siberia
Siberia is an extensive region constituting almost all of Northern Asia. Comprising the central and eastern portion of the Russian Federation, it was part of the Soviet Union from its beginning, as its predecessor states, the Tsardom of Russia and the Russian Empire, conquered it during the 16th...
and visit the island in May and September. The snakes prey on the birds during these months and are inactive for the rest of the year.
Prey is ambushed either on the ground or from tree branches, the snake waiting with its forbody in a concertina shape. Researchers have found specimens in this position containing two or three freshly ingested birds already. Larger snakes on the ground also scavenge birds that have been struck and killed by other snakes too small to eat them.