A full-grown adult adder is typically 50 to 65 cm long, and occasionally females can grow to over a metre long; however, for the most part adders are shorter and invariably much thicker than grass snakes. The grey-brown background colour of the adder is quite different from the dark green of a grass snake, and yet many people have difficulty distinguishing the two. Adders have a dark zig-zag running along the back and a dark Vee on the back of the head. The point of the Vee is between the eyes.
The patterning and the background colour become duller just before the snake sheds (sloughs) a skin.
Adders - also known as common vipers - are found throughout the British Isles and are particularly common on heathland and on grassy cliff-tops and slopes, where they like to bask in open areas (including on footpaths). Unlike grass snakes, adders do not like wet places. They are Britain's only venomous snakes, and although very poisonous an adder's bite rarely proves fatal for an adult. Even so, if you go walking in adder habitat it is advisable to wear stout footwear that will protect your ankles.
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).
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.
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