The adder (Vipera berus), also known as the common adder and the common European viper, is a species of venomous snake in the viper family, Viperidae. It occurs across much of Europe (where it is the most widespread snake species) and northern Asia, including Great Britain, Scandinavia, and parts of Russia and China. In several European countries, the adder is the only extant venomous snake. Usually growing to around 60 cm (24 in) in length, it has a dark zigzag stripe along the back, though colour varies considerably, including completely black melanistic forms. The adder inhabits a wide range of environments such as heathland, woodland edges, moors, and wetlands. It feeds mainly on small mammals, amphibians, and lizards, and is ovoviviparous, giving birth to live young. Although its bite can be painful, fatalities are extremely rare. The species is protected in several countries because of habitat loss and population declines. This female adder was photographed by the Grajcarek river in Szczawnica, Poland.

Photograph credit: Charles J. Sharp