133506 Adder Vipera berus Length 45-60cm Venomous snake. Hibernates October-March and sunbathes regularly in spring. Males perform wrestling ‘dances’ to determine access to females for mating. Sexes are similar but females are larger than males. Adult ground colour ranges from reddish brown, greenish yellow or grey to creamy buff. Almost all have a blackish zigzag line along back, anterior end of which looks arrowheaded and framed by inverted ‘V’ marking on head. Melanic ‘Black Adders’ also occur; commonest in N. Juvenile is similar but slender and usually reddish brown. Widespread but local, found on heaths, moors, open woodlands, rough grassland and coastal dunes. Easiest to see in early spring when basking.