Adder

Relatively thick-bodied, adults usually grow to 60 cm (24 in) in total length (including tail), with an average of 55 cm (22 in). Maximum size varies by region. The largest, at over 90 cm (35 in), are found in Scandinavia; specimens of 104 cm (41 in) have been observed there on two occasions. In France and Great Britain, the maximum size is 80–87 cm (31–34 in). Mass ranges from 50 g (1.8 oz) to about 180 grams (6.3 oz).

The head is fairly large and distinct and its sides are almost flat and vertical. The edge of the snout is usually raised into a low ridge. Seen from above, the rostral scale is not visible, or only just. Immediately behind the rostral, there are two (rarely one) small scales. Dorsally, there are usually five large plates: a squarish frontal (longer than wide, sometimes rectangular), two parietals (sometimes with a tiny scale between the frontal and the parietals), and two long and narrow supraoculars. The latter are large and distinct, each separated from the frontal by one to four small scales. The nostril is situated in a shallow depression within a large nasal scale. The eye is relatively large, equal in size to or slightly larger than the nasal scale, but often smaller in females. Below the supraoculars, there are six to 13 small circumorbital scales, usually eight to 10. The temporal scales are smooth (rarely weakly keeled). …

Vipera berus has a wide range. It can be found across the Eurasian land-mass; from northwestern Europe (Great Britain, Belgium, Netherlands, Scandinavia, Germany, France) across southern Europe (Italy, Serbia, Albania, Croatia, Montenegro, Bosnia and Herzegovina, North Macedonia, Bulgaria, and northern Greece) and eastern Europe to north of the Arctic Circle, and Russia to the Pacific Ocean, Sakhalin Island, North Korea, northern Mongolia and northern China. It is found farther north than any other snake species. The type locality was originally listed as 'Europa'. Mertens and Müller (1940) proposed restricting the type locality to Uppsala, Sweden and it was eventually restricted to Berthåga, Uppsala by designation of a neotype by Krecsák & Wahlgren (2008). In several European countries, it is notable for being the only native venomous snake. It is also one of only three native British snake species. The other two, the barred grass snake and the smooth snake, are non-venomous. Sufficient habitat complexity is crucial for this species to be present, in order to support its various behaviours—basking, foraging, and hibernation—as well as to offer some protection from predators and human disturbance. …

This species is mainly diurnal, especially in the north of its range. Further south, it is said to be active in the evening, and it may even be active at night during the summer months. It is predominantly a terrestrial species, though it is known to climb up banks and into low bushes in order to bask or search for prey. Adders are not usually aggressive and tend to be rather timid, biting only when they are cornered, alarmed, stepped on, or picked up. They will usually disappear in the undergrowth at the slightest hint of danger, but will return once all is quiet, often to the same spot. Occasionally, individual snakes will reveal their presence with a loud, sustained hiss, presumably to warn off potential aggressors. These are often pregnant females. When threatened, the front part the adder's body is drawn into an S-shape in preparation for a strike. This cold-adapted species hibernates in winter. In Great Britain, males hibernate for around 150 days and females for around 180 days. In northern Sweden, hibernation lasts 8–9 months. On mild winter days, they may emerge to bask in areas where the snow has melted, often travelling across snow in the process. Approximately 15% of adults and 30–40% of juveniles die during hibernation.

It was once thought that adders were deaf, as referenced in Psalm 58 (v. 4), yet snake oil derived from adders was used as a cure for deafness and earaches. Females were also thought to swallow their young when threatened and regurgitate them unharmed later. It was further believed that they did not perish until sunset. Remedies for adder "stings" included killing the snake responsible and rubbing the corpse or its fat on the wound, also holding a pigeon or chicken on the bite, or jumping over water. Adders were thought to be attracted to hazel trees and repelled by ash trees. The Druids believed that large, frenzied gatherings of adders took place in spring, at the centre of which was a polished rock called an adder stone or Glain Neidr in the Welsh language. These stones were said to have held supernatural powers.