Clyde Amphibian and Reptile Group


Life History

The ony snake found naturally within the Clyde catchment, the adder (Vipera berus) is also the only venomous snake in Britain. More likely to flee before you get close to them, adders pose little risk to people.

What do they look like?

The adder is Britain’s only venomous snake. Adders grow to measure around 90 centimetres in length and are relatively short and robust with large heads and a rounded snout. The red-brown eyes have vertical elliptical, rather then round, pupils - a feature of all venomous snakes. They are easily recognised by a dark 'zig-zag' stripe along their back. There is also a row of dark spots along each side and a ‘V’ or ‘X’ shape on the head. Background colours vary from grey-white in the male to shades of brown or copper in the female.

How do they reproduce?

Adders emerge from hibernation in March and mating takes place in April/May. Upon discovering a receptive female, a male begins a courtship display in which he flicks his tongue over the female’s body. The male and female may vibrate their tails briefly and bouts of body quivering may ensue. If the courtship is a success, copulation takes place, after which the pair may remain together for two hours or so. Female adders reproduce once every two years(or even once every three years if the seasons are short and the climate is severe) and are ‘viviparous’: they give birth to live young which are initially encased in a membrane. Towards the end of August or early September, the female will return to the site of hibernation, and give birth to 3-18 young. Those reach sexual maturity at 3-4 years of age.

How do they live?

Adders are active during the day, spending time basking until their body temperature is high enough to hunt for food. They use venom to immobilise prey such as lizards, amphibians, nestlings and small mammals. After striking their prey, adders will leave the venom to take effect before following the victim’s scent to find the body. Although adders are poisonous, they are not aggressive and rarely bite humans or domestic animals, preferring to retreat into thick vegetation instead.

Legal protection

In United Kingdom, it is illegal to kill, injure, harm, sell or trade adders (i.e. sale, barter, exchange, transporting for sale and advertising to sell or to buy) under sub-section 9(1) and all of sub-section 9(5) of the 1981 Wildlife and Countryside Act. This species is also listed as protected (Appendix III) under the Berne Convention.

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