Kreuzotter (Vipera berus) CC BY-SA 2.5 Piet Spaans (

European adder


The European adder reaches an average length of between 50 and 70 cm, but can grow to about 90 cm in extreme cases. Females are typically much longer than males, which do not usually exceed a body length of 60 cm. The tail length, on the other hand, is greater in males than in females in proportion to body length. The weight of the animals averages 100 to 200 g with maximum values up to about 300 g in pregnant females.

The body of the snake is stoutly built, the head comparatively little distinctly set off from the body for a viper. The snout is rounded in front and merges into a flat top of the head, the canthus rostralis is also rounded. The head is oval when viewed from the top and slightly broadened at the back of the head due to the venom glands. As an adaptation to cool habitats, it is able to widen its body by actively spreading its ribs to provide a larger surface area for heat absorption while basking, thus making more effective use of smaller amounts of radiant heat.

The basic coloration of the adder is highly variable, ranging from silver-gray and yellow to light and dark gray, brown, blue-gray, orange, reddish-brown, copper-red, and black. Coloration is highly variable within the species, and different colorations may appear even within the same population. In much of the range, the animals exhibit sexual dichromatism. Males usually have different shades of gray from whitish gray to almost black, moreover the contrast between the ground color and the markings is usually more pronounced in them than in females. In females, various shades of brown, red, or beige predominate, and the contrast between light ground color and dark zigzag band is usually somewhat less.

The most conspicuous feature of the pattern is a dark zigzag band on the back. Like the ground color, the dorsal pattern can be very variable. The variations range from broad or narrow zigzag lines to wavy and rhombic bands to single transverse bands, as they are especially developed in the subspecies V. b. bosniensis. Especially in Austria and Slovenia there are populations with a dark ground color with light or light bordered markings. On the flanks there is also a row of dark, round spots. Not infrequently, smooth snakes are mistaken for European adder snakes.

In addition to the marked color varieties, monochromatic specimens of the adder also exist. The black adder, also known as the mountain viper in the Alpine region, is a melanistic colored European adder. Just like the black adder, the "copper adder", a pure copper color variant, was once thought to be a separate species. Most specimens of the black (mountain) viper or "copper viper" are not black or red from birth, but darken or redden gradually in the first two years of life. The black coloration seems to occur more frequently in cooler areas, for example in northern Europe, in moor areas or in mountains, than in warmer areas. Locally, more than 50% or even 70 to 95% of the population may be melanistically colored. Partially melanistic and also albinotic animals are very rare, however, also documented.

The head usually shows the same basic color as the body, especially in females the rostral and Canthus rostralis can be slightly yellowish brown. On the back of the head, the animals have an x-shaped or a v-shaped marking with the tip pointing to the head, which is separated from the zigzag band of the back. A broad temporal band extends over the eyes to the neck. Typical for vipers are the vertically slit pupils, which are surrounded by a rust-red iris. The ventral side is grayish brown, blackish brown or black in color and often has lighter spots, especially on the throat and in the chin region. The underside of the tail tip may be yellow, orange, or brick red.


The European adder prefers habitats with strong day-night temperature variation and high humidity. It inhabits dwarf-shrub-rich forest aisles and forest edges, bogs, moors, wet lowlands, alpine scree fields and mountain meadows near the tree line. In the mountains, the snake can be found up to altitudes of 2500 to 3000 m.

The text is a translation of an excerpt from Wikipedia ( On wikipedia the text is available under a „Creative Commons Attribution/Share Alike“ licence. Status: 24 June 2021