The berg adder (Bitis atropos ) is a small, venomous viper species endemic to mountainous regions in southern Africa. No subspecies are currently recognized.
The typical adult size of B. atropos is 30–40 cm (about 12–16 in) in total length (body and tail), with some females reaching a maximum total length of 50 cm (20 in) in the wild and 60 cm (24 in) in captivity.
B. atropos is found in isolated populations of the mountainous regions of southern Africa. In South Africa, the species is known to occur in the Transvaal, along the Drakensberg escarpment of the eastern and northern Transvaal. Elsewhere in South Africa, it occurs in western Natal, Lesotho, and eastern Free State, and in the southern coastal mountains of western and eastern Cape Province. Spawls and Branch (1995) also mentioned, in Cape Province, its range extends into the Cape Peninsula. It also occurs in Eswatini, in higher altitudes of eastern Zimbabwe such as the Inyanga Highlands and Chimanimani Mountains, and in nearby Mozambique.
B. atropos occupies a number of different habitats, but prefers relatively cool environments with high levels of precipitation. In the northern part of its range, where the winters are cold and dry and the summers warm and wet, it is restricted to higher elevations, up to 3,000 m (9,800 ft). In Zimbabwe, it is not found below 1,500 m (4,900 ft), usually associated with mountain slopes and rocky hillsides, but also montane grassland with patches of bushes and shrubs.
In the southern part of its range (Cape Province, South Africa), where the winters are cold and wet and the summers warm and dry, it can be found in coastal and mountain heathland, as well as small rock outcrops at sea level and grassy areas with clumps of bushes and shrubs west of the Cape Peninsula.
B. atropos is viviparous. Young are born in late summer. Average litter size is seven, but may be as many as 15. Each neonate has a total length (including tail) of about 13 cm (5.1 in).