European Adder (Vipera berus)
The Adder Vipera berus is the only venomous snake in Britain. It is easily recognised by the dark zigzag stripe running down the length of the spine. There is also a row of dark spots along each side and a V or X shape on the back of the head. It has red eyes and is the only native reptile with a vertically split pupil. Background colours vary from grey-white in the male to various shades of brown or copper in the female. On occasion, completely black specimens are described. Males grow to around 60cm in length and the females to around 75cm. Both sexes tend to have a rather stocky appearance.
V. berus is found throughout Britain right up to the north of Scotland. In Scandinavia its range extends into the Arctic Circle. It is not, however, found in Ireland. It likes open habitats such as heathland, moorland, open woodland and sea cliffs, and rarely strays into gardens.
The best time to see V. berus is during early spring when they emerge from their hibernation sites. By mid April, the males have shed their dull winter skin and are ready to mate. On warm humid days there is a lot of frenzied behaviour, with males looking for females and occasionally dueling with other males for territorial supremacy. The males writhe around each other in an impressive way, often covering the ground at great speed. It is an impressive site if you are fortunate to witness it.