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The common adder is only to be found in the north and east of France and grows to a maximum of 90cm. It has a slightly flattened head and is round nosed, eyes with red iris and vertically slit oval pupils. Colouration varies regionally and also between the sexes, males are more varied in colour than females. Their backs can be almost any colour from pale grey to a dark olive green with darker bands which give a zig zag pattern, underneath they are a greyish blue with intense dark marks. They can also be entirely black; these are normally to be found in high regions above the tree line.
The common adder grows to lengths of 65 cm (25.5 in) and occasionally reaches 90 cm (35 in). Adult males are usually pale gray with a contrasting black pattern of dorsal zigzag stripes; adult females may be brown or reddish-brown with a dark brown pattern of zigzag stripes. Individuals from some populations may be entirely black. The common adder is mostly diurnal and preys heavily on small rodents, but it also eats lizards. It gives birth to live young. In the southern portion of the range, females may reproduce every year; in the north, females give birth only every two or three years.
Other vipers in the same genus as the common adder are sometimes referred to as adders, including, at one extreme, the Orsini viper of Europe, which lives largely on insects and appears to use its venom rarely, even when handled; and, at the other extreme, the daboia, or Russell's viper, of southeastern Asia, which has probably caused more human fatalities than any other species of viper.
In Africa many snakes of the viper family are sometimes also called adders, including the berg adder; the dwarf adder; the Gaboon adder; the horned adder; the many-horned adder; the mountain, or African Cape, adder; the puff adder; and the night adders.
Adders are relatively short and robust with large heads and a rounded snout. The red-brown eyes have vertical elliptical, rather then round, pupils - a feature of all venomous snakes. Males are usually a grey or buff colour with vivid black markings, although they can also vary from silver to yellow or green in colour. Females are brown with dark red-brown markings that are less prominent than in the males. Both sexes have a zigzag pattern running along the back with a / or X-shaped marking at the rear of the head, although this zigzag pattern may be replaced by a straight brown stripe with dark spots on either side. Adders have black undersides. Melanistic (black) individuals sometimes occur in mountainous regions.
Hunting And Diet
The diet of adders is very varied and includes voles and other small rodents, lizards, birds eggs, insects and snails. Like other reptiles, they hibernate under ground throughout the cold winter months, usually choosing the same place year after year.
Adders have several enemies including foxes, badgers and some of the larger owls. They begin their hunting for food at dusk and are most active during the first few hours of darkness, travelling up to 100 metres from their lair (which is often the hole made by another animal).
Reproduction & Behaviour
Adders are viviparous. The eggs develop and hatch in the body of the female adder. Typically ten baby adders, 16 - 18 cm long, are born in mid summer; they are able to reproduce when they are five years old. The life span of the adder is up to 15 years.
Adders are active during the day, spending time basking until their body temperature is high enough to hunt for food. In some of the hotter countries of their range, they may emerge at dawn and dusk to avoid the intense heat. Mating takes place between April and May, with males often fighting for females. They rear up at each other and try to push the head of their opponent onto the ground. Eventually, one male will give up and search for another mate. Adders hibernate from September to March when temperatures dip below nine degrees Celsius, often using deserted rabbit or rodent burrows, or settling under logs. They sometimes hibernate communally. Males emerge 2-5 weeks before the females and shed their skin before setting off in search of females.