Most species of snake are nonvenomous and those that have venom use it primarily to kill and subdue prey rather than for self-defense. Some possess venom that is potent enough to cause painful injury or death to humans. Nonvenomous snakes either swallow prey alive or kill by constriction.

Venomous snakes

Venomous snakes are species of the suborder Serpentes that are capable of producing venom which they use for killing prey, for defense, and to assist with digestion of their prey. The venom is typically delivered by injection using hollow or grooved fangs, although some venomous snakes lack well-developed fangs. Common venomous snakes include the families Elapidae, Viperidae, Atractaspididae, and some of the Colubridae. The toxicity of venom is mainly indicated by murine LD₅₀, while multiple factors are considered to judge the potential danger to humans. Other important factors for risk assessment include the likelihood that a snake will bite, the quantity of venom delivered with the bite, the efficiency of the delivery mechanism, and the location of a bite on the body of the victim. Snake venom may have both neurotoxic and hemotoxic properties.

The Viperidae (vipers) are a family of venomous snakes found in most parts of the world, with the exception of Antarctica, Australia, Hawaii, Madagascar, as well as various other isolated islands, and north of the Arctic Circle. All have long (relative to non-vipers), hinged fangs that permit deep penetration and injection of snake venom. Four subfamilies are currently recognized. They are also known as viperids. The name "viper" is derived from the Latin word vipera, -ae, also meaning viper, possibly from vivus ("living") and parere ("to beget"), referring to the trait viviparity (giving live birth) common in vipers but not in snakes at large.

Europe is generally not the favored destination for snake enthusiasts and herpetologists where the venomous species are not so numerous and far from being the most dangerous in the world. There is, for instance, only one venomous species in the United Kingdom, and no snake at all in Ireland (thanks to St Patrick!).

Yet, Europe does host a very nice variety of snake species. Many of them belong to the large and varied Colubrid group, and are either non-venomous or only slightly venomous and by no means a danger to humans. The only truly venomous snakes in Europe therefore all belong to the Viper family and, unlike their American counterparts, are all true vipers - as opposed to pit vipers.

European adders live 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, stone quarries, and on farms and cultivated lands. They will venture into wetlands if the dry ground is available nearby and thus may be found on the banks of streams, lakes, and ponds.

The Common Adder's color is variable: males are light brown to steel gray, and female are more colorful, ranging from yellow to brown or even brick red. Some individuals are completely black, while most have the striking dark zigzag stripe pattern running the length of their bodies above a line of oval spots. The Common Adder also bears a distinctive "X" or "V" black marking on its head.

The Common Adder is reputed for its irritable disposition and can strike without warning when startled or handled. Its venom haemotoxic, destroying blood cells and causing tissue damage. Most bites are inflicted on campers, hikers, and field workers..

Asp Viper or Asp, Aspic viper, European Asp, European Viper, Jura viper (Vipera aspis)

The Aspic Viper, which name - "aspis" means "viper" in Greek, is found in south-western Europe: northeastern Spain, Andorra, most of France (including in the Ile de Re and Oleron islands), Monaco, Italy, the islands of Elba, Montecristo and Sicily, San Marino, Switzerland; north-western Slovenia and extreme southwestern Germany (southern Black Forest).

In 2006, a number of individuals were discovered in a wooded area south of Rotterdam, in the Netherlands. It is likely that one or more escaped or were set loose in the area since the Asp Viper is not native in this country.

The Asp Viper likes warm areas that are exposed to the sun, with some plant cover and comparatively dry soils. In Italy and France, it is often found in areas with low mountains or hills, notably in limestone regions, though it sometimes occurs in lower plains. It can be found in scrublands, glades, mountain meadows, forest clearings, in areas bordering woods, in mesic chestnut/oak woodlands, near streams or even in rubbish dumps and stone quarries. Though not specifically a snake of high altitudes, the Asp Viper has been found in the Pyrenees mountains as high as 2,100 m - 6,500 feet - above sea level.

This 60 to 65 cm long (roughly 25 inches) viper has a distinctive very short tail and a broad, triangular head with a slightly upturned snout. The dorsal markings are highly variable, but only rarely take the form of a clear zigzag, as in the Common Adder.

Bites from this species can be more severe than those from the Common Adder (Vipera berus); not only can they be very painful, but they are fatal, if untreated, in about 4% of all cases. It is considered the most dangerous snake in France and it is responsible for 90% of all cases of snakebite in Italy.

Envenomation symptoms include rapidly spreading acute pain, followed by edema and discoloration. Severe haemorrhagic necrosis sometimes occurs after a few hours. Vision may also be severely impaired, probably because of the degradation of blood and blood vessels in the eyes. The venom has both coagulant and anticoagulant effects and may also affect glomerular structure, which can lead to death due to renal failure. In some cases, the victims develop neurotoxic symptoms, including difficulty in breathing and swallowing, as well as paralysis of the bitten limbs.

Five subspecies are currently recognized.

Long-nosed Adder, Nose-horned Viper, or Horned Viper (vipera ammodytes)

Occurs in south-eastern Europe, from Hungary and Austria to Italy, Romania, former Yugoslavia, and northern Albania.

This small viper - 45 to 90 cm (18 to 36 inches) - is commonly found in much of its range in habitats varying from farms, open fields and cultivated land to rocky slopes.

The name "long-nosed" or "nose-horned" comes from the projection of tiny scales it has on the tip of its nose. This gray to reddish viper also bears a distinctive dark brown or black zigzag pattern running the length of its back.

The Long-nosed Adder is responsible for many bites which can be fatal, though chances of survival are good with medical aid. Its venom is haemotoxic, causing severe pain, paralysis and massive tissue damage. However, while it is the most venomous among the European species, it is timid and shows little aggressiveness.

Pallas' Viper (Akistrodon halys)

This gray to yellow snake is a close relative of the American copperhead, which it resembles. The Palls' Viper occurs throughout southeastern Europe where it is found in farming regions, open fields or hillsides.

It is a shy snake which seldom strikes. It has a haemotoxic venom that is rarely fatal to humans.

Ursini's Viper, or Orsini's Viper, or Meadow Viper (Vipera ursinii) 

The Meadow viper is a very rare venomous snake, that is in danger of extinction. The smallest viper in Europe, it inhabits meadows, grassy fields, farmlands or rocky hillsides and can be found in south-eastern France, central Italy, west Balkans (former Yugoslavia), northern Greece, Albania, Bulgaria, Romania, Hungary, and Germany.

Its body is thick, its head narrow, and its appearance rough. The snout is not upturned. There are always several large scales or plates on the top of the head. The prominently keeled dorsal scales are in only 19 rows, and often dark skin shows between them. It is gray, tan, or yellowish with a dark undulating dorsal stripe, which is edged with black. Females of this species are larger than males.

Ursini's Viper has the same coloration and dorsal zigzag pattern as the Common Adder and Long-nosed Adder. This little snake - 45 to 90 cm (or 18 to 36 inches) - is known to have an irritable disposition. It will readily strike when approached. It has an haemotoxic venom which is quite potent and has caused human deaths, though on rare occasions.

Lataste's Viper or Snub-nosed Viper, Snub-nosed Adder (Vipera latastei)

This viper occurs in the extreme southwestern Europe - France, Portugal and Spain- and northwestern Africa - the Mediterranean region of Morocco, Algeria and Tunisia-.

It grows to a maximum length of about 72 cm (29 inches), but is usually shorter.

Lataste's Viper had the specificity of being classsified as "Near Threatened" on the IUCN Red List of Threatened Species (2001). Indeed, it is believed to be in significant decline mostly because widespread habitat loss - but also persecution - throughout much of its range. As further population declines are likely, this species could locally become extinct, notably in Tunisia.

Seoane's Viper or Baskian Viper, Iberian Cross Adder, Portuguese Viper (Vipera seoanei)

This venomous viper species is found in extreme southwestern France and the northern regions of Spain and Portugal (Basque country, mountains of Galicia and Cantabrici).

The Seoane's Viper is normally shorter than 75 cm (30 inches) and has very variable colorations. It can have well-developed, brown zigzag pattern down the back set against a beige or light-gray to brownish ground color;

The pattern can alternatively be a fragmented zigzag, a roughly twin-striped, or it can have no back marking at all.

Ottoman viper or Turkish Viper, Rock Viper, Coastal Viper, Near East Viper, Mountain Viper (Vipera xanthina)

The Ottoman Viper is a widely distributed species which occurs in northeastern Greece and European Turkey, as well as in some Aegean Sea islands (Simi, Kos, Kalimnos, Leros, Lipsos, Patmos, Samos, Chios and Lesbos). Its population is presumed to be quite large.

This snake is light in color, varying from gray to white with a black zig-zag pattern running along its back. It is a fairly big viper usually measuring some 70 to 95 cm (28 to 38 inches), but reaching up to 130 cm (52 inches) on some Greek islands.

Nikolsky's Adder or Forest-steppe Adder (Vipera nikolskii)

This venomous viper is endemic to central Ukraine.

Adults are short and thick-bodied, growing to a maximum length of 68 cm (27 inches).

Milos viper (Macrovipera schweizeri)

This Greek viper is limited to the islands of Milos, Kimolos, Polyaigos, and Sifnos.

Sources:

• https://sites.google.com/site/venomousdangerous/snakes/europe-s-most-venomous-snakes;
• https://animalia.bio/meadow-viper.]
• https://www.monaconatureencyclopedia.com/vipera-ammodytes/?lang=en
• Wikipedia.org