It may be the only venomous snake throughout much of its range, including England, but the adder is not an aggressive species and avoids conflict.

The majority of members of the viper family are venomous, and the adder - or common viper - is no exception. However, it poses little threat to humans. Adders rarely bite humans, and, even when they do, the consequences are usually no more than a painful swelling around the area of the bite. Recovery is slow, however, and can take up to a year. These snakes are most dangerous when they first emerge from hibernation, although they may be less active, as the weather can still be relatively cold. Adders spend most of their day basking in the sunshine, and go out to hunt in the late afternoon. As winter closes in, adders prepare to hibernate, usually burrowing underground to sleep through the cold weather. The duration of hibernation varies with latitude. Adders often frequent heathland, but also occur in areas such as forest clearings.

The adder's predominantly grey-brown colour, with zigzag markings down the back, is very different from the coloration of the grass snake, yet people often confuse the two.

The active periods of adders can be divided into three distinct phases. The first phase occurs during spring, when they come out of hibernation and disperse. This is when the males, having shed their skins, go in search of females, and mating occurs. The second phase begins at the onset of summer, when adders migrate along hedgerows and ditches to prime feeding grounds, such as wet meadows. They stay in these areas until summer starts to draw to a close, at which time they head back to drier areas - the third phase. Female adders give birth to their young -they do not lay eggs - which immediately prepare to hibernate, too.

Distribution: Occurs throughout much of western Europe, although absent from Ireland, extending north to Sweden and eastwards across most of Asia.

Habitat: Open places such as heaths, meadows and woodland edges.

Weight: 50 - 100 g (1.75 - 3.5 oz); females larger.

Length: 60 - 75 cm (24 - 30 in) on average, but up to 104 cm (41 in) has been recorded.

Maturity: Females 3 years; males 5 years.

Gestation Period: 3 - 4 months; females only breed in alternate years.

Breeding: 3 - 20, but typically 8.

Food: Small mammals, especially mice and shrews; also birds, amphibians and lizards.

Lifespan: 10 - 25 years.

Status: Common.

Back markings

The black zig-zag stripe running down the centre of the back identifies this species.


Adders have slitlike rather than rounded pupils.

Head markings

Adders have a V-shaped (sometimes X-shaped) marking on the back of stheir heads.


Adders can be sexed their colouration. The brownish appearance here indicates a female.


These snakes seek out suitable retreats, often under tree roots. Scandinavian adders hibernate for up to nirffe months of the year.

Gallery of Adder