Adder

Vipera berus
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Reptilia
Order:	Squamata
Suborder:	Serpentes
Family:	Viperidae
Subfamily:	Viperinae
Genus:	Vipera
Species:	V. berus
Binomial name
Vipera berus Linnaeus, 1758

Vipera berus is a venomous viper species found throughout Europe and most of Asia. Besides the typical form, one other subspecies is known. Common names for it are northern viper, European adder and crossed viper.

Description

V. berus is found farther north than any other snake and is known for being remarkably resistant to low temperatures. It is also the most widespread species of snake in the world and is found from the British Isles in the west, to the Chinese coast and Sakhalin in the east, and well within the Arctic Circle in the north. It is very adaptive and can be found in nearly any type of terrain and in mountains up to 3000 meters above sea level.

The snake itself is quite small, adult females rarely grow beyond 70 centimeters and males rarely over 60, although most specimens encountered are much smaller. V. berus can reach 20-25 years of age. Their food consists mainly of rodents, amphibians and lizards, although birds and their eggs are sometimes consumed.

Two color variations of Vipera berus in Copenhagen Zoo.

Appearance

Adult females are often a rusty brown color, with the black pattern on its back and grows much larger than the males, which usually are grey instead of brown. Young individuals are sometimes dark brown and their correct coloring emerges only after a few years. Apart from their gender-specific coloring, there are also individuals that are very dark or almost black. This is caused by a pigment error, melanism, that is apparently not inherited by their young. Black vipers usually give birth to normal colored young, and normal colored vipers may give birth to black vipers. While their camouflage is not as good as the normal colored snakes, the black crossed vipers have an advantage by being able to raise their body temperature more rapidly, which is especially useful after hibernation or in cold climates. Melanism appears to be more common in the northern regions than elsewhere throughout its range. The common name crossed viper comes from the black crossed pattern on its back.

Behavior

V. berus is not an aggressive species and when approached by a human, it tends to rely on its camouflage for as long as possible, before trying to escape. Only when it is surprised or provoked will it try to bite. This is possibly due to the high amount of energy it needs to produce its venom and, because it lives mostly in a temperate climate, its need to conserve energy. Its reliance on camouflage has caused it to become an easy victim for humans, and it is now a protected species in most of Europe.

Reproduction

Their mating season is in May and the females give birth in August or September, depending on the climate. The crossed viper usually gives birth to 5-20 live young, depending on the size of the female. The snake is exceptional since it is known to both give birth and lay eggs, which usually hatch within minutes of being laid. When they are born, they are between 15-20 centimeters long and already venomous.

A common belief is that young and especially newborn vipers are more venomous than adult snakes, but this is untrue. Another belief is that they are so aggressive after they are born, that the female has to give birth hanging from a bush to avoid being bitten by its own offspring. This is also untrue, although vipers are known to give birth hanging in bushes, possibly since it aids them in pushing out the babies. After being born, the snakes usually shed their skins. Before they go into their first hibernation in October or November, the young snakes do not always feed, since they need to fully digest the meal before entering the hibernation state, to avoid complications resulting from the changes in its metabolism.

Subspecies

Subspecies	Authority	Geographic range
V. b. berus	Linnaeus, 1758	Norway, Sweden, Finland, France, Denmark, Germany, Austria, Switzerland, Northern Italy, Belgium, Netherlands, Great Britain, Poland, Czech Republic, Slovakia, Hungary, Romania, Bulgaria, Albania, the former Yugoslavia, the Baltic states, Russia, Mongolia, North Korea, NW China (N Xinjiang, Jilin)
V. b. bosniensis	Boettger, 1889	The former Yugoslavia, Northern Albania, Northern Greece

Venom

V. berus is venomous and the lethality of its venom is equal to that of rattlesnakes', but because it injects much smaller amounts of the venom, the animal is considered less dangerous. A bite from V. berus is only rarely lethal and even then it is usually due to an anaphylactic reaction. In fact, bees are considered more dangerous to humans and only small children, allergic adults and seniors in poor health are at risk. Nevertheless, if bitten by V. berus, one should immediately but calmly seek medical assistance.

Further reading

• Do aposematism and Batesian mimicry require bright colours? A test, using European viper markings by Wüster W, Allum CSE, Bjargardottir IB, Bailey KL, Dawson KJ, Guenioui J, Lewis J, McGurk J, Moore AG, Niskanen M, Pollard CP, 2004, Proceedings of the Royal Society of London Series B-biological Sciences Volume: 271 Pages: 2495-2499, published by the Royal Soc. London, Joe Dumars.