Vipera
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Description
Members of the genus Vipera tend to be stout and small in size. The largest of them, V. ammodytes, can reach a maximum total length (including tail) of 95 cm (37 in), and the smallest, V. monticola, reaches a maximum total length of 40 cm (16 in).
The head of the members of this genus is clearly separated from the body, triangular in shape, and in most species covered in small scales. However, some species, notably V. berus, have small plates on the top of the head. Most species have large supraocular scales that tend to extend beyond the posterior margin of the eye. Some species also have some sort of "horn" on the head, either right behind the nasal scale, or behind the supraocular scales.
The color scheme and camouflage of the members of this genus vary widely, from a grayish ground color with dark brown transverse bands to browner colors with grey transverse bands edged with black in the case of V. ammodytes.
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Geographic range
Vipera species can be found all around the Old World, hence the common name of the genus, "Old World vipers". They can be found most notably in Europe, from Portugal to Turkey. They can also be found on some islands in the Mediterranean Sea (Sicily, Elba and Montecristo), and the United Kingdom. They can also be found in the Maghreb region of Africa with species living in Morocco (V. monticola) and northern parts of Algeria and Tunisia in the case of V. latastei. Many species can also be found in the Caucasus Mountains, parts of Iraq, Jordan, Israel and Syria. Only one species (V. berus) discovered so far lives in East Asia, most notably North Korea, northern China and northern Mongolia.
Habitat
Most Vipera species prefer cooler environments. Those found at lower latitudes tend to prefer higher altitudes and dryer, rocky habitats, while the species that occur at more northern latitudes prefer lower elevations and environments that have more vegetation and moisture.
Behavior
All species of the genus Vipera are terrestrial.
Reproduction
All Vipera species are viviparous, giving birth to live young.
Venom
Most Vipera species have venom that contains both neurotoxic and haemotoxic components. Bites vary widely in severity.
V. ammodytes is most likely the species with the most toxic venom. In a study solely involving mice, John Haynes Brown (1973) showed that the LD50 is about 1.2/mg/kg through an IV, 1.5 mg/Kg when injected in the peritoneum (IP), and 2.0 mg/kg when administered subcutaneously (SC).
V. berus venom is considered to be on the lower end of the scale when it comes to toxicity. Minton (1974) suggests that the LD50 values for mice are about 0.55 mg/kg IV, 0.80 mg/kg IP, and 6.45 mg SC. Venom yield tends to be lower in this species with Minton citing 10–18 mg per bite in specimens 48–62 cm (19–24 in), while Brown suggest only 6 mg for the same sized specimens.
However, bites from Vipera species are rarely as severe as those from larger Macrovipera or Daboia.
Fossil record
The oldest species of the genus Vipera is the Early Miocene V. antiqua from Southern Germany. The earliest known V. antiqua fossil has been dated to 22.5 million years ago. A very large indeterminate Vipera was found in the Early Pliocene deposits of Mallorca. This species surpassed in size all modern relatives, with a length of nearly 2 m (6 ft 7 in), and was one of the biggest predators of its ecosystem.
Species
* Not including the nominate subspecies. T: type species
Nota bene: A taxon author in parentheses indicates that the species was originally described in a genus other than Vipera.