- Coluber berus Linnaeus, 1758
Adder, Common European adder, Common European viper, Common adder, Common viper
Value of species
Vipera berus has a wide range. It can be found across the Eurasian land-mass; from northwestern Europe (Great Britain, Netherlands, Scandinavia, Germany, France) across southern Europe (Italy, Serbia, Albania, Croatia, Montenegro, Bosnia and Herzegovina, Republic of 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 further north than any other snake species. The type locality was originally listed as "Europa". Mertens and Müller (1940) proposed restricting the type locality to "Upsala, Schweden" (Uppsala, Sweden) and it was eventually restricted to Berthåga, Uppsala by designation of a neotype by Krecsák & Wahlgren (2008).
The species has three recognised subspecies: V. b. berus (Linnaeus, 1758) Common European adder, V. b. bosniensis Boettger, 1889 Balkan cross adder, V. b. sachalinensis Zarevskij, 1917 Sakhalin Island adder.
Sufficient habitat complexity is a crucial requirement for the presence of this species, in order to support its various behaviors—basking, foraging, and hibernation—as well as to offer some protection from predators and human harassment. It is found in a variety of habitats, including: chalky downs, rocky hillsides, moors, sandy heaths, meadows, rough commons, edges of woods, sunny glades and clearings, bushy slopes and hedgerows, dumps, coastal dunes, and stone quarries. It will venture into wetlands if dry ground is available nearby and thus may be found on the banks of streams, lakes, and ponds.
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 3,000 m (9,800 ft). In Hungary and Russia, it avoids open steppeland; a habitat in which V. ursinii is more likely to occur. In Russia, however, it does occur in the forest steppe zone.
In several European countries, it is notable as being the only native venomous snake. It is one of only three snake species native to Britain. The other two, the Grass snake and the Smooth snake are non-venomous.
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, although it has been known to climb up banks and into low bushes in order to bask or search for prey.
Adders are not usually aggressive, tending to be rather timid and biting only when cornered or alarmed. People are generally bitten only after stepping on them or attempting to pick them up. They will usually disappear into the undergrowth at a hint of any danger, but will return once all is quiet, often to the same spot. Occasionally, individual snakes will reveal their presence with a loud and sustained hissing, hoping to warn off potential aggressors. Often, these turn out to be pregnant females. When the adder is threatened, the front part of the body is drawn into an S-shape to prepare for a strike.
The species is cold-adapted and hibernates in the winter. In Great Britain, males and females hibernate for about 150 and 180 days respectively. In northern Sweden hibernation lasts 8–9 months. On mild winter days, they may emerge to bask where the snow has melted and will often travel across snow. About 15% of adults and 30–40% of juveniles die during hibernation.
Diet consists mainly of small mammals, such as mice, voles, and shrews, as well as lizards. Sometimes, slow worms are taken, and even weasels and moles. They feed on amphibians, such as frogs, newts, and salamanders. Birds are also reported to be consumed, especially nestlings and even eggs, for which they will climb into shrubbery and bushes. Generally, diet varies depending on locality. Juveniles will eat nestling mammals, small lizards and frogs as well as worms and spiders. Once they reach about 30 cm (0.98 ft) in length, their diet begins to resemble that of the adults.
In Hungary, mating takes place in the last week of April, while in the north it happens later in the second week of May. Matings have also been observed in June and even early October, but it is not known if the autumn matings result in any young. Females often breed once every two years, or even once every three years if the seasons are short and the climate is severe.
Males find females by following their scent trails, sometimes tracking them for hundreds of meters a day. If a female is found and flees, the male follows. Courtship involves side-by-side parallel "flowing" behavior, tongue flicking along the back and excited lashing of the tail. Pairs stay together for one or two days after mating. Males chase away their rivals and engage in combat. Often, this also starts with the aforementioned flowing behavior before culminating in the dramatic "adder dance." In this act, the males confront each other, raise up the front part of the body vertically, make swaying movements and attempt to push each other to the ground. This is repeated until one of the two becomes exhausted and crawls off to find another mate. Interestingly, Appleby (1971) notes that he has never seen an intruder win one of these contests, as if the frustrated defender is so aroused by courtship that he refuses to lose his chance to mate. There are no records of any biting taking place during these bouts.
Females usually give birth in August or September, but sometimes as early as July, or as late as early October. Litters range in size from 3 to 20. The young are usually born encased in a transparent sac from which they must free themselves. Sometimes, they succeed in freeing themselves from this membrane while still inside the female. The neonates measure 14 to 23 cm (5.5 to 9.1 in) in total length (including tail), with an average total length of 17 cm (6.7 in). They are born with a fully functional venom apparatus and a reserve supply of yolk within their bodies. They shed their skins 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.
- Літопис природи. Природний заповідник «Медобори». 2018, т.26. – Гримайлів, 2019. – 509 с.