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Vipera berus, commonly known as the common European adder, , (2003). True Vipers: Natural History and Toxinology of Old World Vipers. Malabar, Florida: Krieger Publishing Company. . and the common European viper, (1974). Snakes of the World. New York: Grosset & Dunlap Inc. 160 pp. . is a species of venomous snake in the family Viperidae. The species is extremely widespread and can be found throughout much of Europe, and as far as East Asia. There are three recognised subspecies.
Known by a host of common names including common adder and common viper, the adder has been the subject of much folklore in Britain and other European countries. It is not regarded as especially dangerous; the snake is not aggressive and usually bites only when really provoked, stepped on, or picked up. Bites can be very painful, but are rarely fatal. The specific name, berus, is Neo-Latin and was at one time used to refer to a snake, possibly the grass snake, Natrix natrix.Gotch, Arthur Frederick (1986). Reptiles: Their Latin Names Explained. Poole, UK: Blandford Press. 176 pp. .
The common adder is found in different terrains, habitat complexity being essential for different aspects of its behaviour. It feeds on small , , , and , and in some cases on , , and . The common adder, like most other vipers, is Ovoviviparity. Females breed once every two or three years, with litters usually being born in late summer to early autumn in the Northern Hemisphere. Litters range in size from three to 20 with young staying with their mothers for a few days. Adults grow to a total length (including tail) of and a mass of . Three subspecies are recognised, including the nominate subspecies, Vipera berus berus, described here. The snake is not considered to be threatened, though it is protected in some countries.
| V. b. berus | (Carl Linnaeus, 1758) | Common European adder | Norway, Sweden, Bulgaria, Finland, Latvia, Estonia, Lithuania, France, Denmark, Germany, Austria, Switzerland, Northern Italy, Belgium, Netherlands, Great Britain, Poland, Croatia, Czech Republic, Slovakia, Slovenia, Hungary, Romania, Russia, Ukraine, Mongolia, Northwest China (north Xinjiang) |
| V. b. bosniensis | Oskar Boettger, 1889 | Balkan cross adder | Balkan Peninsula |
| V. b. sachalinensis | , 1917 | Sakhalin adder | Russian Far East (Amur Oblast, Primorsky Krai, Khabarovsk Krai, Sakhalin), North Korea, Northeast China (Jilin) |
The subspecies V. b. bosniensis and V. b. sachalinensis have been regarded as full species in some recent publications.
The name 'adder' is derived from nædre, an Old English word that meant snake in the older forms of many Germanic languages. It was commonly used in the Old English version of the Christianity Scriptures for the devil and the serpent in the Book of Genesis. In the 14th century, 'a nadder' in Middle English was Juncture loss to 'an adder' (just as 'a napron' became 'an apron' and 'a nompere changed into 'an umpire').
In keeping with its wide distribution and familiarity through the ages, Vipera berus has a large number of common names in English, which include:
In Welsh, it is called gwiber, a name derived from Latin vīpera. In Denmark, Norway and Sweden, the snake is known as hugorm, hoggorm and huggorm, roughly translated as 'striking snake'. In Finland, it is known as kyykäärme or simply kyy, in Estonia it is known as rästik, while in Lithuania it is known as angis. In Poland the snake is called żmija zygzakowata, which translates as 'zigzag viper', due to the pattern on its back.
Dorsally, there are usually five large plates: a squarish Frontal scale (longer than wide, sometimes rectangular), two Parietal scales (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). There are 10–12 sublabials and six to 10 (usually eight or 9) supralabials. Of these, numbers 3 and 4 are the largest, while numbers 4 and 5 (rarely 3 and 4) are separated from the eye by a single row of small scales (sometimes two rows in alpine specimens).
There are 21 rows of dorsal scales midbody (rarely 19, 20, 22, or 23). They are strongly keeled scales, except for those bordering the ventral scales. The scales appear to be loosely attached to the skin, with the lower rows becoming increasingly wider. Those closest to the ventral scales are twice as long as those along the midline. The number of ventral scales is 132–150 in males and 132–158 in females. The anal plate is single. The Subcaudal scales are paired and number 32–46 in males and 23–38 in females.
This species exhibits significant variation in colouration. Light-coloured specimens are characterised by small, incomplete, dark crossbars on their backs, while darker specimens display faint or clear, darker brown markings. Melanistic individuals are completely black and lack any apparent dorsal pattern. However, most specimens have a zigzag pattern on their backs that extends along their entire bodies and tails. A distinctive dark V or X marking is usually present on the dorsal surface of the head. A dark streak runs from the eye to the neck and continues as a series of longitudinal spots along the flanks.
Unlike most snakes, the sexes of this species can often be distinguished by colour. Females are typically brown with dark brown markings, whereas males are a uniform grey with black markings. The base colour of males is often slightly lighter than that of females, which makes the black zigzag pattern stand out more. Melanistic individuals are often female.
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. It is found in a variety of habitats, including: chalky downs, rocky hillsides, moors, sandy heaths, meadows, rough commons, woodland edges, sunny glades and clearings, scrubby slopes and hedgerows, rubbish tips, coastal dunes, and stone quarries. If dry ground is available nearby, it will venture into wetlands and may therefore be found on the banks of streams, lakes, and ponds.Street, Donald (1979). The Reptiles of Northern and Central Europe. London: B.T. Batsford Ltd. 272 pp. .
In much of southern Europe, such as southern France and northern Italy, it is found in either low-lying wetlands or at high altitudes. In the Swiss Alps, it may ascend to about . In Hungary and Russia, it avoids open steppeland; a habitat in which Vipera ursinii is more likely to occur. In Russia, however, it does occur in the forest steppe zone.
This species is listed as protected (Appendix III) under the Berne Convention.
The International Union for Conservation of Nature Red List of Threatened Species describes the conservation status as of 'least concern' in view of its wide distribution, presumed large population, broad range of habitats, and likely slow rate of decline though it acknowledges the population to be decreasing. Reduction in habitat for a variety of reasons, fragmentation of populations in Europe due to intense agriculture practices, and collection for the pet trade or for venom extraction have been recorded as major contributing factors for its decline. A citizen science based survey in the UK found evidence of extensive population declines in the UK, especially affecting smaller populations. A combination of public pressure and disturbance, habitat fragmentation and poor habitat management were considered the most likely causes of the decline. The release of 47 million non-native pheasants and 10 million partridges each year by countryside estates has also been suggested to have a significant impact on adder populations across the UK, with the possibility the reptile could be extinct by 2032.
Adders are not usually aggressive and tend to be rather timid, only biting only when they are cornered or alarmed. They will generally only bite if are 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 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 Hibernation 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.
Juveniles will eat nestling mammals, small lizards and frogs as well as worms and spiders. One important dietary source for young adders is the alpine salamander ( Salamadra atra). Because both species live at higher altitudes, S. atra could be a prevalent food source for adders, since there may be few other animals. One study suggests that alpine salamanders could consist of almost half of the adders' diets in some locations. They have been witnessed swallowing these salamanders in the early morning hours. Once they reach about in length, their diet begins to resemble that of the adults.
Females usually give birth in August or September, but sometimes as early as July, or as late as early October. Litters can range in size from three to 20. The young are usually born encased in a transparent sac, and must free themselves from it. Occasionally, they manage to break free from this membrane while still inside the mother.
Neonates measure in total length (including tail), with an average total length of . They are born with a fully functional venom apparatus and a reserve supply of yolk within their bodies. They shed their skin for the first time within a day or two. Females do not appear to take much interest in their offspring, but the young have been observed to remain near their mothers for several days after birth.
Mallow et al. (2003) describe the toxicity of the venom as being relatively low compared to that of other viper species. They cite Minton (1974) who reported the values for mice to be 0.55 mg/kg IV, 0.80 mg/kg IP and 6.45 mg/kg Subcutis. For comparison, one test found that the minimum lethal dose of venom for a guinea pig was 40–67 mg, whereas only 1.7 mg was necessary when Daboia russelii venom was used. Brown (1973) gives a higher subcutaneous LD50 range of 1.0–4.0 mg/kg. All agree that the venom yield is low. Minton (1974) mentions 10–18 mg for specimens in length, while Brown (1973) lists only 6 mg.
Relatively speaking, bites from this species are not highly dangerous. In Great Britain, there were only 14 known fatalities between 1876 and 2005—the last of which was a five-year-old child in 1975—and one near-fatal bite on a 39-year-old woman in Essex in 1998. An 82-year-old woman died following a bite in Germany in 2004, although it is unclear whether her death was due to the effects of the venom., and a 52-year-old male died in Sweden after failing to seek treatment in 2023. A 44-year-old British man was left seriously ill after he was bitten by an adder in the Dalby Forest, Yorkshire, in 2014. Even so, professional medical help should always be sought as soon as possible after any bite. Very occasionally bites can be life-threatening, particularly in small children, while adults may experience discomfort and disability long after the bite. The length of recovery varies, but may take up to a year.
Local symptoms include severe and immediate pain, followed by swelling and tingling after a few minutes, although this may take up to 30 minutes. Blisters containing blood are uncommon. The pain may then spread within a few hours, accompanied by tenderness and inflammation. Red Lymphangitis lines and bruising may appear, and the entire whole limb can become swollen and bruised within 24 hours. The swelling may also spread to the trunk and, in children, the whole body. Necrosis and intracompartmental syndromes are very rare.
Systemic symptoms arising from anaphylaxis can be severe. These may manifest within five minutes of the bite, or can be delayed for several hours. These symptoms may include nausea, retching and vomiting, abdominal colic and diarrhoea, incontinence of urine and faeces, sweating, fever, vasoconstriction, tachycardia, lightheadedness, loss of consciousness, and even blindness, shock, angioedema of the face, lips, gums, tongue, throat and epiglottis, urticaria and bronchospasm. If left untreated, these symptoms may persist or fluctuate for up to 48 hours. In severe cases, cardiovascular failure may occur.
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.
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