Adder (Vipera berus)

Adder amongst heather


  • Name: Adder
  • Latin: Vipera berus
  • Classification: Reptile
  • Origin: Europe
  • Lifespan: 15 years
  • AKA: Common European adder, common viper


  • Kingdom: Animalia (animals)
  • Phylum: Chordata (vertebrates)
  • Class: Reptilia (reptiles)
  • Order: Squamata (scaled reptiles)
  • Family: Serpentes (snakes)
  • Genus: Vipendae (vipers)
  • Species: Vipera berus (adder)


  • Length: Male=60cm Female=75cm
  • Weight: Male=50-60gm Female=80-100gm

The adder has a distinct ‘V’ or ‘X’ marking on its head and have vertically slit pupils. They can be creamy white to rusty brown and have a long black diamond pattern running along their back.
The females tend to be larger than the males and have a brown, yellow or brick red background colouration, while the males are usually white or grey.

Male adder
Female adder


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  • Black asp (Vipera aspis atra) -VULNERABLE-
  • Desert viper (Macrovipera deserti) -NEAR THREATENED-
  • Palestine saw-scaled viper (Echis coloratus) -NOT EVALUATED-
  • Horned bush viper (Atheris ceratophora) -VULNERABLE-  

Habitat & Distribution

The adder prefers rough and open countryside and can often be seen in woodland edge habitats. They are the most frequently seen of the three British snakes as they are less likely to disappear into the undergrowth.

The adder is the most northerly distributed reptile and can even be found within the edges of the Arctic Circle. They live across Europe, as east as the mountains of Russia and as south as the Mediterranean. The UK is its westerly extreme, although they are absent from Ireland.

Map showing the distribution of the Adder taxa



The diet of the adder is very varied and can include voles and other small rodents, lizards, bird’s eggs, insects and snails. To hunt, they strike at the prey, injecting a lethal dose of venom, and then they wait patiently for it to die. It will then find the prey by following its scent and then begin the lengthy swallowing process.

Like other snakes, the adder will swallow its prey whole. The jaw bones can move independently as they are connected by extensible connective tissue, also the ribs are not joined at the bottom, allowing them to open right up. This allows the adder to eat prey much larger than the width of its head. The teeth are also designed to grip the prey while it is being swallowed. The adder also has a very powerful digestive fluid which can digest flesh and bones almost completely. Only the hair and teeth pass through intact.


In the north of their range, adders tend to be diurnal, and near the south, they are more crepuscular. They tend to be terrestrial but they will climb up banks and into low bushes to bask or search for prey.

They are the only venomous snake in Britain but will rarely attack. Instead, they rely on their camouflage to keep them hidden and will disappear into the undergrowth if they feel the vibrations of a threat approaching. The venom of the adder is quite strong, however, they do not inject a large amount at one time nor do they strike repeatedly which makes them less of a risk to humans.
In Britain, the males will hibernate for 150 days and the females for 180 days. On mild winter days, the adder will travel across the snow to patches where it has melted to bask. 15% of adults and 30-40% of juveniles will die during hibernation.


Courtship and mating of the adder takes place around April-May and are so preoccupied with such that they will often completely ignore the presence of a human. The males will circle the female in jerky movement and flicking his tongue all over her body. This allows the male to determine whether she is receptive. Mating takes place in dense undergrowth and can take up to two hours.

After mating, the male will ‘mate-guard’ the female, staying close to her side, this insures that no rival males mate with her. Intruding males will be challenged. They begin by sizing each other up, by moving parallel to each other. During combat, the males will intertwine their bodies, attempting to force the head of their opponent to the ground. This is known as the ‘Dance of the Adders’ and can often last several minutes. The defeated male will shoot away and the victor will return to the female.

Adders are viviparous, giving birth to live young, and the eggs develop and hatch within the body of the female. The young adders are born in mid-summer. Around 8-10 babies are born with an average length of 6-7 inches. The adder has a slow reproductive rate, only giving birth once every other year.

Immature female adder
Immature female adder



  • Like other snakes, the jaws of the adder can move independently of each other and the ribs are not connected at the bottom allowing it to open is mouth incredibly wide. This allows the adder to eat food many times the width of its head.
  • The adder has excellent camouflage. The dark diamond pattern running along its back keeps it invisible in the undergrowth. The adder uses this as its primary method of avoiding detection by predators.
  • Adders are almost deaf and would not be able to hear an approaching threat. They can however, feel vibrations in the earth. They will take off of they feel the vibrations of an approaching animal.
  • The adder has very powerful venom which it uses to kill its prey. It is not fatal to humans however medical help is given soon after an attack.


The adder has a few predators including birds of prey, such as the buzzard, and other adult snakes. Also, they can be killed and eaten by rodents during hibernation. They suffer habitat loss in a number of areas throughout Europe because of scrub encroachment, development, agriculture and afforestation.

Outside of Britain, they are collected for the pet trade and in Romania, they are killed for illegal collection of their venom.


  • IUCN Status: Least Concern

In the UK, the adder is protected under the Wildlife and Countryside Act 1981 which makes it illegal to kill, injure, harm or sell the adder. They are also classified as a priority species under the UK Biodiversity Action Plan, a proposed action being to educate the public in order to dispel fears and reduce deliberate persecution.

They are listed on Annex II of the Bern Convention which aims to conserve wild flora and fauna in their natural habitats. They occur in protected areas throughout their range and are protected by national legislation in many countries.

Fun Facts

  • Male: Male snake
  • Female: Female snake
  • Young: Hatchling
  • Group: Nest
  • Snakes do not have eyelids.
  • Snakes are found on every continent, except Antarctica.
  • Snakes can smell with their tongue.
  • There are 3,000 different species of snake.
  • Snake have flexible jaws, allowing them to eat prey much larger than themselves.

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