Somerset Wildlife Trust

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Reptiles-and-AmphibiansThe adder
Vipera berus

Britain’s only poisonous snake so do take care whilst out walking on Mendip. Relying more on camouflage than venom, their ability to avoid detection insures that most adders are passed by unnoticed. Ground vibrations caused by the approach of a possible threat provides them with an early warning system that allows them to avoid situations where they may be required to bite. Adders are, therefore, relatively unaggressive and unlikely to attack - most adder bites in the UK are the result of an attempt to handle the snake.

Found throughout the UK except in mainland Ireland; Scotland’s only native snake. Their ability to survive in much harsher climates than other snakes is entirely based on their long hibernation, stretching from October to spring, from which they only emerge if the weather is suitable.

The preferred habitat is open moor and grassland where there is abundant prey. During warm springs the males can be easily spotted as they move about in search of a mate, often basking on rocks in full sun. In warm climates the adder can reach 90cm but is smaller in cooler regions. Body colouration is olive green with a distinctive black zig zag pattern along the back; occasionally the snake can be completely black, females are generally lighter.

The 'adder dance' can be seen from April onwards, where male adders wrestle for supremacy. Young are born in the autumn and often go into hibernation without having a first meal; young adders are born live, 15cm long, venomous and ready to fend for themselves.

Prey includes small mammals, bird's, eggs and frogs. This adaptability regarding diet is another key to the adder's success as it ensures that wherever it lives, there is certain to be a food source nearby.

Adders are protected by law in Great Britain. It is illegal to deliberately kill, injure or sell wild adders. There is a Species Action Plan for adders for the Mendip Hills and the Quantock Hills.

The Somerset Reptile and Amphibian Group (further information at are a source of local expertise in adders and may be able to offer survey training.


Photograph copyright of K.Palmer